diff --git a/.github/workflows/python-builds.yml b/.github/workflows/python-builds.yml
index 296ea28..7c60cb9 100644
--- a/.github/workflows/python-builds.yml
+++ b/.github/workflows/python-builds.yml
@@ -11,48 +11,76 @@ jobs:
   linux:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - name: Checkout current repository
+      uses: actions/checkout@v3
+
+    - name: Clone remote repository
+      run: |
+        git clone https://github.com/david-bouyssie/mzcore.git ../mzcore
+        ls /home/runner/work/mzio/mzcore
+
     - uses: PyO3/maturin-action@v1
       with:
-        manylinux: auto
+        manylinux: off # auto
         command: build
-        args: --release --sdist -o dist --find-interpreter
+        args: -o dist --strip --find-interpreter
         working-directory: mzio-py
+
     - name: Upload wheels to artifact
       uses: actions/upload-artifact@v3
       with:
         name: wheels
-        path: dist
+        path: mzio-py/dist
+
+    - name: Setup tmate session
+      if: ${{ failure() }}
+      uses: mxschmitt/action-tmate@v3
 
   windows:
     runs-on: windows-latest
     steps:
-    - uses: actions/checkout@v3
+    - name: Checkout current repository
+      uses: actions/checkout@v3
+
+    - name: Clone remote repository
+      run: |
+        git clone https://github.com/david-bouyssie/mzcore.git ../mzcore
+        ls ../mzcore
+
     - uses: PyO3/maturin-action@v1
       with:
         command: build
-        args: --release -o dist --find-interpreter
+        args: -o dist --strip --find-interpreter
         working-directory: mzio-py
-    - name: Upload wheels
+
+    - name: Upload wheels to artifact
       uses: actions/upload-artifact@v3
       with:
         name: wheels
-        path: dist
+        path: mzio-py/dist
 
   macos:
     runs-on: macos-latest
     steps:
-    - uses: actions/checkout@v3
+    - name: Checkout current repository
+      uses: actions/checkout@v3
+
+    - name: Clone remote repository
+      run: |
+        git clone https://github.com/david-bouyssie/mzcore.git ../mzcore
+        ls ../mzcore
+
     - uses: PyO3/maturin-action@v1
       with:
         command: build
-        args: --release -o dist --universal2 --find-interpreter
+        args: -o dist --strip --find-interpreter --target universal2-apple-darwin
         working-directory: mzio-py
-    - name: Upload wheels
+
+    - name: Upload wheels to artifact
       uses: actions/upload-artifact@v3
       with:
         name: wheels
-        path: dist
+        path: mzio-py/dist
 
   # release:
   #   name: Release
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..e6479ef
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,6 @@
+[workspace]
+
+members = [
+    "mzio-rs",
+    "mzio-py"
+]
diff --git a/mzio-py/Cargo.toml b/mzio-py/Cargo.toml
index 3fa289c..6bbf82e 100755
--- a/mzio-py/Cargo.toml
+++ b/mzio-py/Cargo.toml
@@ -10,7 +10,7 @@ name = "mzio_py"
 crate-type = ["cdylib"]
 
 [dependencies]
-anyhow = "1.0.68"
+anyhow = "1.0.75"
 fallible-iterator = "0.2.0"
-mzio = { path = "../mzio-rs" }
-pyo3 = { version = "0.17.3", features = ["extension-module", "anyhow"] }
+pyo3 = { version = "0.20.0", features = ["extension-module", "anyhow"] }
+mzio = { path = "../mzio-rs", features = ["fasta", "mgf"] }
diff --git a/mzio-py/pyproject.toml b/mzio-py/pyproject.toml
index 07c3332..98238c3 100755
--- a/mzio-py/pyproject.toml
+++ b/mzio-py/pyproject.toml
@@ -35,5 +35,5 @@ doc = [
 ]
 
 [build-system]
-requires = ["maturin>=0.14,<0.15"]
+requires = ["maturin>=1.0.0,<1.3.0"]
 build-backend = "maturin"
diff --git a/mzio-py/src/fasta/entry.rs b/mzio-py/src/fasta/entry.rs
index 01031fc..7e75637 100644
--- a/mzio-py/src/fasta/entry.rs
+++ b/mzio-py/src/fasta/entry.rs
@@ -2,8 +2,9 @@
 use std::collections::HashMap;
 
 // 3rd party imports
+use anyhow::Result;
 use pyo3::prelude::*;
-use mzio::fasta::entry::Entry as BaseEntry;
+use mzio::fasta::entry::FastaEntry as BaseEntry;
 
 /// Wrapper for the rust implementation entry
 /// 
@@ -35,7 +36,8 @@ impl Entry {
                 entry_name,
                 protein_name,
                 keyword_attributes,
-                sequence
+                sequence,
+                None
             )
         }
     }
@@ -43,29 +45,29 @@ impl Entry {
     /// Returns the database type
     ///
     #[getter]
-    pub fn database(&self) -> PyResult<&str> {
-        Ok(&self.base_entry.get_database())
+    pub fn database(&self) -> Result<&String> {
+        Ok(self.base_entry.get_database())
     }
 
     /// Returns the accession
     ///
     #[getter]
-    pub fn accession(&self) -> PyResult<&str> {
-        Ok(&self.base_entry.get_accession())
+    pub fn accession(&self) -> Result<&String> {
+        Ok(self.base_entry.get_accession())
     }
 
     /// Entry name
     ///
     #[getter]
-    pub fn entry_name(&self) -> PyResult<&str> {
-        Ok(&self.base_entry.get_entry_name())
+    pub fn entry_name(&self) -> Result<&String> {
+        Ok(self.base_entry.get_entry_name())
     }
 
     /// Returns the protein name
     ///
     #[getter]
-    pub fn protein_name(&self) -> PyResult<&str> {
-        Ok(&self.base_entry.get_protein_name())
+    pub fn protein_name(&self) -> Result<&String> {
+        Ok(self.base_entry.get_protein_name())
     }
 
     /// Returns additional keyword attributes, e.g
@@ -74,7 +76,7 @@ impl Entry {
     ///
     // !!! TODO Reference to HasMap is no convertible to PyResult by default.
     #[getter]
-    pub fn keyword_attributes(&self) -> PyResult<HashMap<String, String>> {
+    pub fn keyword_attributes(&self) -> Result<HashMap<String, String>> {
         // TODO: avoid clone?
         Ok(self.base_entry.get_keyword_attributes().clone())
     }
@@ -82,8 +84,15 @@ impl Entry {
     /// Returns the amino acid sequence
     ///
     #[getter]
-    pub fn sequence(&self) -> PyResult<&str> {
-        Ok(&self.base_entry.get_sequence())
+    pub fn sequence(&self) -> Result<&String> {
+        Ok(self.base_entry.get_sequence())
+    }
+
+    /// Returns the plain header (before parsing)
+    ///
+    #[getter]
+    pub fn plain_header(&self) -> Result<&String> {
+        Ok(self.base_entry.get_sequence())
     }
 }
 
diff --git a/mzio-py/src/fasta/reader.rs b/mzio-py/src/fasta/reader.rs
index 6dad5be..a057786 100644
--- a/mzio-py/src/fasta/reader.rs
+++ b/mzio-py/src/fasta/reader.rs
@@ -1,10 +1,10 @@
 // std imports
 use std::path::PathBuf;
 
-// 3rd party modules
-use pyo3::prelude::*;
+// 3rd party imports
 use anyhow::Result;
-use mzio::fasta::reader::Reader as BaseReader;
+use pyo3::prelude::*;
+use mzio::fasta::reader::FastaReader as BaseReader;
 
 // internal imports
 use crate::fasta::entry::Entry;
@@ -17,8 +17,9 @@ pub struct Reader {
 #[pymethods]
 impl Reader {
     #[new]
-    fn new(fasta_file_path: PathBuf, buffer_size: usize) -> Result<Self> {
-        match BaseReader::new(&fasta_file_path, buffer_size) {
+    fn new(fasta_file_path: PathBuf, buffer_size: usize, keep_plain_header: bool) -> Result<Self> {
+        match BaseReader::new(&fasta_file_path, buffer_size, keep_plain_header
+        ) {
             Ok(base_reader) => Ok(Self{base_reader}),
             Err(err) => Err(err)
         }
diff --git a/mzio-py/src/fasta/writer.rs b/mzio-py/src/fasta/writer.rs
index 92cd91c..02183cf 100644
--- a/mzio-py/src/fasta/writer.rs
+++ b/mzio-py/src/fasta/writer.rs
@@ -1,15 +1,14 @@
 // std imports
 use std::path::PathBuf;
 
-// 3rd party modules
+// 3rd party imports
 use anyhow::Result;
 use pyo3::prelude::*;
-use mzio::fasta::writer::Writer as BaseWriter;
+use mzio::fasta::writer::FastaWriter as BaseWriter;
 
 // internal imports
 use crate::fasta::entry::Entry;
 
-
 #[pyclass]
 pub struct Writer {
     base_writer: BaseWriter
@@ -24,15 +23,15 @@ impl Writer {
     /// * `fasta_file_path` - Path to FASTA file
     /// 
     #[new]
-    pub fn new(fasta_file_path: PathBuf) -> PyResult<Self> {
-        match BaseWriter::new(&fasta_file_path) {
+    pub fn new(fasta_file_path: PathBuf, sort_keyword_attributes: bool) -> PyResult<Self> {
+        match BaseWriter::new_with_default_seq_formatting(&fasta_file_path, sort_keyword_attributes) {
             Ok(base_writer) => Ok(Self{base_writer}),
             Err(err) => Err(err.into())
         }
     }
 
-    pub fn write_entry(&mut self, entry: &Entry, sort_keyword_attributes: bool) -> Result<usize> {
-        match self.base_writer.write_entry(entry.into(), sort_keyword_attributes) {
+    pub fn write_entry(&mut self, entry: &Entry) -> Result<usize> {
+        match self.base_writer.write_entry(entry.into()) {
             Ok(written_bytes) => Ok(written_bytes),
             Err(err) => Err(err)
         }
diff --git a/mzio-py/src/lib.rs b/mzio-py/src/lib.rs
index ae30b19..02dfcfe 100755
--- a/mzio-py/src/lib.rs
+++ b/mzio-py/src/lib.rs
@@ -34,9 +34,9 @@ fn register_fasta_module(py: Python, parent_module: &PyModule) -> PyResult<()> {
 /// `parent_module` - Parent module of the mgf module
 fn register_mgf_module(py: Python, parent_module: &PyModule) -> PyResult<()> {
     let child_module = PyModule::new(py, "mgf")?;
-    child_module.add_class::<mgf::spectrum::Spectrum>()?;
-    child_module.add_class::<mgf::reader::Reader>()?;
-    child_module.add_class::<mgf::writer::Writer>()?;
+    child_module.add_class::<mgf::spectrum::MgfSpectrum>()?;
+    child_module.add_class::<mgf::reader::MgfReader>()?;
+    child_module.add_class::<mgf::writer::MgfWriter>()?;
     parent_module.add_submodule(child_module)?;
     Ok(())
 }
diff --git a/mzio-py/src/mgf/reader.rs b/mzio-py/src/mgf/reader.rs
index 1d12e08..d5be93b 100644
--- a/mzio-py/src/mgf/reader.rs
+++ b/mzio-py/src/mgf/reader.rs
@@ -1,39 +1,40 @@
 // std imports
 use std::path::PathBuf;
 
-// 3rd party modules
+// 3rd party imports
 use pyo3::prelude::*;
 use anyhow::Result;
-use mzio::mgf::reader::Reader as BaseReader;
-
 use fallible_iterator::FallibleIterator;
+use mzio::mgf::reader::MgfReader as BaseMgfReader;
 
 // internal imports
-use crate::mgf::spectrum::Spectrum;
+use crate::mgf::spectrum::MgfSpectrum;
 
 #[pyclass]
-pub struct Reader {
-    base_reader: BaseReader
+pub struct MgfReader {
+    base_reader: BaseMgfReader
 }
 
 #[pymethods]
-impl Reader {
+impl MgfReader {
     #[new]
-    #[args(buffer_size=4096)]
+    #[pyo3(signature = (mgf_file_path, buffer_size=4096))]
     fn new(mgf_file_path: PathBuf, buffer_size: usize) -> Result<Self> {
-        match BaseReader::new(&mgf_file_path, buffer_size) {
+        let base_reader = BaseMgfReader::new(&mgf_file_path, buffer_size)?;
+        Ok(Self{base_reader})
+        /*match BaseReader::new(&mgf_file_path, buffer_size) {
             Ok(base_reader) => Ok(Self{base_reader}),
             Err(err) => Err(err)
-        }
+        }*/
     }
 
     fn __iter__(slf: PyRef<'_, Self>) -> PyRef<'_, Self> {
         slf
     }
 
-    fn __next__(mut slf: PyRefMut<'_, Self>) -> Option<Spectrum> {
+    fn __next__(mut slf: PyRefMut<'_, Self>) -> Option<MgfSpectrum> {
         match slf.base_reader.next().ok()? {
-            Some(base_spectrum) => Some(Spectrum::from(base_spectrum)),
+            Some(base_spectrum) => Some(MgfSpectrum::from(base_spectrum)),
             None => None
         }
     }
diff --git a/mzio-py/src/mgf/spectrum.rs b/mzio-py/src/mgf/spectrum.rs
index 129c383..82deb6a 100644
--- a/mzio-py/src/mgf/spectrum.rs
+++ b/mzio-py/src/mgf/spectrum.rs
@@ -1,17 +1,17 @@
 // 3rd party imports
 use pyo3::prelude::*;
-use mzio::mgf::spectrum::Spectrum as BaseSpectrum;
-
+use mzio::mgf::spectrum::MgfSpectrum as BaseMgfSpectrum;
 
 /// Wrapper for the rust implementation spectrum
 /// 
 #[pyclass]
-pub struct Spectrum {
-    base_spectrum: BaseSpectrum
+#[derive(Clone, Debug)]
+pub struct MgfSpectrum {
+    base_spectrum: BaseMgfSpectrum
 }
 
 #[pymethods]
-impl Spectrum {
+impl MgfSpectrum {
     /// Python constructor
     /// 
     /// # Arguments
@@ -24,10 +24,16 @@ impl Spectrum {
     /// * `intensity_list` -  Intensity list
     /// 
     #[new]
-    fn new(title: String, precursor_mz: f64, precursor_charge: Option<i8>,
-        retention_time: Option<f64>, mz_list: Vec<f64>, intensity_list: Vec<f32>) -> Self {
+    fn new(
+        mz_list: Vec<f64>,
+        intensity_list: Vec<f32>,
+        title: String,
+        precursor_mz: f64,
+        precursor_charge: Option<i8>,
+        retention_time: Option<f64>
+    ) -> Self {
         Self {
-            base_spectrum: BaseSpectrum::new(
+            base_spectrum: BaseMgfSpectrum::new(
                 title,
                 precursor_mz,
                 precursor_charge,
@@ -41,62 +47,62 @@ impl Spectrum {
     /// Returns the spectrum title
     ///
     #[getter]
-    pub fn title(&self) -> PyResult<&str> {
-        Ok(&self.base_spectrum.get_title())
+    pub fn title(&self) -> String {
+        self.base_spectrum.header.get_title().to_owned()
     }
 
     /// Returns the precursor mz
     ///
     #[getter]
-    pub fn precursor_mz(&self) -> PyResult<f64> {
-        Ok(self.base_spectrum.get_precursor_mz())
+    pub fn precursor_mz(&self) -> f64 {
+        self.base_spectrum.header.get_precursor_mz()
     }
 
     /// Returns the precursor charge
     ///
     #[getter]
-    pub fn precursor_charge(&self) -> PyResult<Option<i8>> {
-        Ok(*self.base_spectrum.get_precursor_charge())
+    pub fn precursor_charge(&self) -> Option<i8> {
+        self.base_spectrum.header.get_precursor_charge()
     }
 
     /// Returns the retention time
     ///
     #[getter]
-    pub fn retention_time(&self) -> PyResult<Option<f64>> {
-        Ok(*self.base_spectrum.get_retention_time())
+    pub fn retention_time(&self) -> Option<f64> {
+        self.base_spectrum.header.get_retention_time()
     }
 
     /// Returns the mzs
     ///
     #[getter]
-    pub fn mzs(&self) -> PyResult<Vec<f64>> {
-        Ok(self.base_spectrum.get_mz_list().to_vec())
+    pub fn mzs(&self) -> Vec<f64> {
+        self.base_spectrum.get_mz_list().to_owned()
     }
 
     /// Returns the intensities
     ///
     #[getter]
-    pub fn intensities(&self) -> PyResult<Vec<f32>> {
-        Ok(self.base_spectrum.get_intensity_list().to_vec())
+    pub fn intensities(&self) -> Vec<f32> {
+        self.base_spectrum.get_intensity_list().to_owned()
     }
 }
 
 
-impl From<BaseSpectrum> for Spectrum {
+impl From<BaseMgfSpectrum> for MgfSpectrum {
     /// Convert entry from the Rust implementation to the python wrapper.
     /// 
     /// # Arguments
     /// 
     /// * `base_spectrum` - Spectrum from rust implementation
-    fn from(base_spectrum: BaseSpectrum) -> Self {
+    fn from(base_spectrum: BaseMgfSpectrum) -> Self {
         Self {
             base_spectrum
         }
     }
 }
 
-impl<'a> Into<&'a BaseSpectrum> for &'a Spectrum {
-    fn into(self) -> &'a BaseSpectrum {
+impl<'a> Into<&'a BaseMgfSpectrum> for &'a MgfSpectrum {
+    fn into(self) -> &'a BaseMgfSpectrum {
         &self.base_spectrum
     }
 }
diff --git a/mzio-py/src/mgf/writer.rs b/mzio-py/src/mgf/writer.rs
index a1f1244..681f799 100644
--- a/mzio-py/src/mgf/writer.rs
+++ b/mzio-py/src/mgf/writer.rs
@@ -1,22 +1,21 @@
 // std imports
 use std::path::PathBuf;
 
-// 3rd party modules
+// 3rd party imports
 use anyhow::Result;
 use pyo3::prelude::*;
-use mzio::mgf::writer::Writer as BaseWriter;
+use crate::mgf::spectrum::MgfSpectrum;
 
 // internal imports
-use crate::mgf::spectrum::Spectrum;
-
+use mzio::mgf::writer::MgfWriter as BaseMgfWriter;
 
 #[pyclass]
-pub struct Writer {
-    base_writer: BaseWriter
+pub struct MgfWriter {
+    base_writer: BaseMgfWriter
 }
 
 #[pymethods]
-impl Writer {
+impl MgfWriter {
     /// Creates a new Writer
     /// 
     /// # Arguments
@@ -24,25 +23,25 @@ impl Writer {
     /// * `mgf_file_path` - Path to MGF file
     /// 
     #[new]
-    pub fn new(mgf_file_path: PathBuf) -> PyResult<Self> {
-        match BaseWriter::new(&mgf_file_path) {
-            Ok(base_writer) => Ok(Self{base_writer}),
-            Err(err) => Err(err.into())
-        }
+    pub fn new(mgf_file_path: PathBuf) -> Result<Self> {
+        let base_writer = BaseMgfWriter::new(&mgf_file_path)?;
+        Ok(Self {base_writer})
     }
 
-    pub fn write_spectrum(&mut self, spectrum: &Spectrum) -> Result<usize> {
-        match self.base_writer.write_spectrum(spectrum.into()) {
+    pub fn write_spectrum(&mut self, spectrum: &MgfSpectrum) -> Result<usize> {
+        self.base_writer.write_spectrum(spectrum.into())
+        /*match self.base_writer.write_spectrum(spectrum.into()) {
             Ok(written_bytes) => Ok(written_bytes),
             Err(err) => Err(err)
-        }
+        }*/
     }
 
 
     pub fn flush(&mut self) -> Result<()> {
-        match self.base_writer.flush() {
+        self.base_writer.flush()
+        /*match self.base_writer.flush() {
             Ok(_) => Ok(()),
             Err(err) => Err(err)
-        }
+        }*/
     }
 }
diff --git a/mzio-rs/Cargo.toml b/mzio-rs/Cargo.toml
index 65a96f9..ebe8f9d 100755
--- a/mzio-rs/Cargo.toml
+++ b/mzio-rs/Cargo.toml
@@ -10,11 +10,17 @@ keywords = ["bioinformatics", "mass spectrometry", "proteomics", "eubic-ms"]
 categories = ["science"]
 publish = false
 
-# [lib]
-# name = "mzio"
+[lib]
+name = "mzio"
 # crate-type = ["cdylib"]
 
 [dependencies]
-anyhow = "1.0.68"
+anyhow = "1.0.75"
 fallible-iterator = "0.2.0"
-fast-float = "0.2.0"
+fast-float = { version = "0.2.0" , optional = true }
+serde = "*"
+mzcore = { path = "../../mzcore/mzcore-rs" }
+
+[features]
+fasta = []
+mgf = ["dep:fast-float"]
\ No newline at end of file
diff --git a/mzio-rs/src/fasta/entry.rs b/mzio-rs/src/fasta/entry.rs
index de4230f..24354f1 100755
--- a/mzio-rs/src/fasta/entry.rs
+++ b/mzio-rs/src/fasta/entry.rs
@@ -1,16 +1,17 @@
 use std::collections::HashMap;
 
 /// Keeps all information of FASTA entry
-pub struct Entry {
+pub struct FastaEntry {
     database: String,
     accession: String,
     entry_name: String,
     protein_name: String,
     keyword_attributes: HashMap<String, String>,
-    sequence: String
+    sequence: String,
+    plain_header: Option<String>
 }
 
-impl Entry {
+impl FastaEntry {
     /// Creates a new FASTA entry
     /// # Arguments
     ///
@@ -22,38 +23,39 @@ impl Entry {
     /// * `sequence` - Amino acid sequence
     /// 
     pub fn new(database: String, accession: String, entry_name: String, protein_name: String,
-        keyword_attributes: HashMap<String, String>, sequence: String) -> Self {
+        keyword_attributes: HashMap<String, String>, sequence: String, plain_header: Option<String>) -> Self {
             Self {
                 database,
                 accession,
                 entry_name,
                 protein_name,
                 keyword_attributes,
-                sequence
+                sequence,
+                plain_header,
             }
         }
 
         /// Returns the database type
         ///
-        pub fn get_database(&self) -> &str {
-            &self.database.as_str()
+        pub fn get_database(&self) -> &String {
+            &self.database
         }
 
         /// Returns the accession
         ///
-        pub fn get_accession(&self) -> &str {
+        pub fn get_accession(&self) -> &String {
             &self.accession
         }
 
         /// Entry name
         ///
-        pub fn get_entry_name(&self) -> &str {
+        pub fn get_entry_name(&self) -> &String {
             &self.entry_name
         }
 
         /// Returns the protein name
         ///
-        pub fn get_protein_name(&self) -> &str {
+        pub fn get_protein_name(&self) -> &String {
             &self.protein_name
         }
 
@@ -67,7 +69,13 @@ impl Entry {
 
         /// Returns the amino acid sequence
         /// 
-        pub fn get_sequence(&self) -> &str {
+        pub fn get_sequence(&self) -> &String {
             &self.sequence
         }
+
+        /// Returns the plain header (before parsing)
+        ///
+        pub fn get_plain_header(&self) -> &Option<String> {
+            &self.plain_header
+        }
 }
\ No newline at end of file
diff --git a/mzio-rs/src/fasta/mod.rs b/mzio-rs/src/fasta/mod.rs
index 561dbd7..6dd730f 100755
--- a/mzio-rs/src/fasta/mod.rs
+++ b/mzio-rs/src/fasta/mod.rs
@@ -1,6 +1,9 @@
 pub mod entry;
 pub mod reader;
 pub mod writer;
+pub mod prelude;
+
+pub use prelude::*;
 
 #[cfg(test)]
 mod test {
@@ -9,9 +12,9 @@ mod test {
     use std::fs;
     use std::path::Path;
 
-    const FASTA_FILE_PATH_STR: &'static str = "./test_files/fasta/partial_mouse.fasta";
+    const FASTA_FILE_PATH_STR: &'static str = "../test_files/fasta/partial_mouse.fasta";
     const EXPECTED_NUM_PROTEINS: usize = 10;
-    const TEMP_FASTA_PATH_STR: &'static str = "./test_files/fasta/partial_mouse.fasta.tmp";
+    const TEMP_FASTA_PATH_STR: &'static str = "../test_files/fasta/partial_mouse.fasta.tmp";
 
     #[test]
     /// Reads a FASTA file, parses the proteins,
@@ -20,26 +23,43 @@ mod test {
         let fasta_file_path = Path::new(FASTA_FILE_PATH_STR);
         let tmp_fasta_file_path = Path::new(TEMP_FASTA_PATH_STR);
 
-        let reader = reader::Reader::new(
+        assert!(fasta_file_path.exists(), "FASTA file not found at path: {}", FASTA_FILE_PATH_STR);
+
+        let reader = FastaReader::new(
             fasta_file_path,
-            1024
+            1024,
+            true
         ).unwrap();
 
-        let entries: Vec<entry::Entry> = reader.into_iter().collect();
+        let mut entries = Vec::with_capacity(1000);
+
+        for entry in reader {
+
+            let entry_as_string = FastaWriter::stringify_entry(&entry, true, None);
+
+            assert_eq!(
+                [entry.get_plain_header().to_owned().unwrap(), entry.get_sequence().to_owned()].join("\n"),
+                entry_as_string,
+                "the formatted entries are not matching"
+            );
+
+            entries.push(entry);
+        }
         assert_eq!(entries.len(), EXPECTED_NUM_PROTEINS);
 
-        let mut writer = writer::Writer::new(
-            tmp_fasta_file_path
+        let mut writer = FastaWriter::new_with_default_seq_formatting(
+            tmp_fasta_file_path,
+            true
         ).unwrap();
 
-        writer.write_all(entries.iter(), true).unwrap();
+        writer.write_all(entries.iter()).unwrap();
         writer.flush().unwrap();
 
         let tmp_fasta_content  = fs::read_to_string(tmp_fasta_file_path).unwrap().trim().to_string();
         fs::remove_file(tmp_fasta_file_path).unwrap();
 
         assert_eq!(
-            fs::read_to_string(fasta_file_path).unwrap().trim(),
+            fs::read_to_string(fasta_file_path).unwrap().trim().replace("\r\n", "\n"),
             tmp_fasta_content.as_str()
         );
     }
diff --git a/mzio-rs/src/fasta/prelude.rs b/mzio-rs/src/fasta/prelude.rs
new file mode 100644
index 0000000..21f39e0
--- /dev/null
+++ b/mzio-rs/src/fasta/prelude.rs
@@ -0,0 +1,3 @@
+pub use crate::fasta::entry::FastaEntry;
+pub use crate::fasta::reader::FastaReader;
+pub use crate::fasta::writer::FastaWriter;
\ No newline at end of file
diff --git a/mzio-rs/src/fasta/reader.rs b/mzio-rs/src/fasta/reader.rs
index 5ddc133..8bc32c6 100755
--- a/mzio-rs/src/fasta/reader.rs
+++ b/mzio-rs/src/fasta/reader.rs
@@ -1,30 +1,38 @@
+// std imports
 use std::collections::HashMap;
 use std::fs::File;
 use std::io::BufReader;
 use std::io::prelude::*;
 use std::path::Path;
 
-use crate::fasta::entry::Entry;
+// 3rd party imports
 use anyhow::Result;
 
+// internal imports
+use crate::fasta::entry::FastaEntry;
+
 /// Reader for common FASTA files as distributed by UniProt (https://uniprot.org)
-pub struct Reader {
+pub struct FastaReader {
     internal_reader: BufReader<File>,
+    keep_plain_header: bool,
     is_eof: bool,
     header: String,
     sequence: String
 }
 
-impl Reader {
+impl FastaReader {
     /// Creates a new Reader
     /// # Arguments
     ///
     /// * `fasta_file_path` - Path to FASTA file
+    /// * `buffer_size` - Buffer size to use when loading bytes from disk.
+    /// * `keep_plain_header` - Whether to keep or not the plain read header in the generated FastaEntry.
     /// 
-    pub fn new(fasta_file_path: &Path, buffer_size: usize) -> Result<Self> {
+    pub fn new(fasta_file_path: &Path, buffer_size: usize, keep_plain_header: bool) -> Result<Self> {
         let fasta_file: File = File::open(fasta_file_path)?;
         Ok(Self {
             internal_reader: BufReader::with_capacity(buffer_size, fasta_file),
+            keep_plain_header,
             is_eof: false,
             header: String::new(),
             sequence: String::new()
@@ -49,14 +57,15 @@ impl Reader {
         }
     }
 
-    /// Creates a new Entry from the given header and sequence.
+    /// Creates a new FastaEntry from the given header and sequence.
     /// 
     /// # Arguments
     ///
     /// * `header` - A FASTA header
     /// * `sequence` - Amino acid sequence
+    /// * `keep_plain_header` - Whether to keep or not the plain read header in the generated FastaEntry.
     /// 
-    pub fn create_entry(header: &str, sequence: &str) -> Option<Entry> {
+    pub fn create_entry(header: &str, sequence: &str, keep_plain_header: bool) -> Option<FastaEntry> {
         // Split by '|' and extract database and accession 
         let mut header_split = header.split("|").collect::<Vec<&str>>();
         let mut database: String = header_split.remove(0).to_string();
@@ -93,7 +102,7 @@ impl Reader {
                         current_attr.push_str(" ");
                         current_attr.push_str(header_split.remove(0));
                     } else {
-                        Reader::prep_and_add_attribute_to_keyword_attributes(
+                        FastaReader::prep_and_add_attribute_to_keyword_attributes(
                             &current_attr, 
                             &mut keyword_attributes
                         );
@@ -104,25 +113,28 @@ impl Reader {
                 }
             }
             // Process the remaining attribute
-            Reader::prep_and_add_attribute_to_keyword_attributes(
+            FastaReader::prep_and_add_attribute_to_keyword_attributes(
                 &current_attr, 
                 &mut keyword_attributes
             );
         }
-        return Some(Entry::new(
+        let plain_header_opt = if keep_plain_header {Some(header.to_string())} else {None};
+
+        return Some(FastaEntry::new(
             database,   // database
             accession,   // accession
             entry_name,
             protein_name,
             keyword_attributes,
-            sequence.replace("\n", "")
+            sequence.replace("\n", ""),
+            plain_header_opt
         ));
     }
 }
 
 
-impl Iterator for Reader {
-    type Item = Entry;
+impl Iterator for FastaReader {
+    type Item = FastaEntry;
 
     fn next(&mut self) -> Option<Self::Item> {
         if self.is_eof {
@@ -134,15 +146,15 @@ impl Iterator for Reader {
             if let Ok(num_bytes) = self.internal_reader.read_line(&mut line) {
                 if num_bytes == 0 {
                     self.is_eof = true;
-                    return Reader::create_entry(&self.header, &self.sequence);
+                    return FastaReader::create_entry(&self.header, &self.sequence, self.keep_plain_header);
                 }
                 line = line.as_mut_str().trim().to_string();
                 if !line.starts_with(">") && num_bytes > 0 {
                     self.sequence.push_str(&line)
                 } else {
                     if self.header.len() > 0 {
-                        let entry = Reader::create_entry(&self.header, &self.sequence);
-                        self.header = line; // safe newly read header
+                        let entry = FastaReader::create_entry(&self.header, &self.sequence, self.keep_plain_header);
+                        self.header = line; // save newly read header
                         return entry;
                     } else  {
                         self.header = line; 
@@ -154,7 +166,6 @@ impl Iterator for Reader {
     }
 }
 
-
 #[cfg(test)]
 mod test {
     use super::*;
@@ -188,7 +199,7 @@ QRSGIVALDGERELAFGPDDEVTVTLHDHAFRSIDVAACMRHAGRHHLMRSLPQPAAVG";
     /// Tests the creation of a FASTA entry from a header and a sequence.
     ///
     fn test_entry_creation() {
-        let entry = Reader::create_entry(TEST_HEADER, TEST_SEQUENCE).unwrap();
+        let entry = FastaReader::create_entry(TEST_HEADER, TEST_SEQUENCE, false).unwrap();
         assert_eq!(entry.get_database(), EXPECTED_DATABASE);
         assert_eq!(entry.get_accession(), EXPECTED_ACCESSION);
         assert_eq!(entry.get_entry_name(), EXPECTED_ENTRY_NAME);
diff --git a/mzio-rs/src/fasta/writer.rs b/mzio-rs/src/fasta/writer.rs
index 02bb567..1a2f501 100755
--- a/mzio-rs/src/fasta/writer.rs
+++ b/mzio-rs/src/fasta/writer.rs
@@ -1,30 +1,76 @@
+// std imports
 use std::fs::File;
 use std::io::BufWriter;
 use std::io::prelude::*;
 use std::path::Path;
 
-use crate::fasta::entry::Entry;
+// 3rd party imports
 use anyhow::Result;
 
-/// Max amino acids per sequence line.
-const MAX_AMINO_ACIDS_PER_LINE: usize = 60;
+// internal imports
+use crate::fasta::entry::FastaEntry;
+
+/// DEFAULT max amino acids per sequence line.
+const DEFAULT_MAX_AMINO_ACIDS_PER_LINE: usize = 60;
 
 /// Writer for common FASTA files as distributed by UniProt (https://uniprot.org)
 /// Use flush() to mak ensure the buffer is written completely.
-pub struct Writer {
+pub struct FastaWriter {
+    /// Max amino acids per sequence line.
+    max_amino_acids_per_line: Option<usize>,
+    sort_keyword_attributes: bool,
     internal_writer: BufWriter<File>
 }
 
-impl Writer {
+impl FastaWriter {
     /// Creates a new Writer
     /// 
     /// # Arguments
     ///
     /// * `fasta_file_path` - Path to FASTA file
+    /// * `sort_keyword_attributes` - If true the keyword attributes will be sorted (for testing and readability reasons)
+    /// * `max_amino_acids_per_line` - If Some(), will format the sequence line to not exceed the given length.
     /// 
-    pub fn new(fasta_file_path: &Path) -> Result<Self> {
+    pub fn new(fasta_file_path: &Path, sort_keyword_attributes: bool, max_amino_acids_per_line: Option<usize>) -> Result<Self> {
         let fasta_file: File = File::create(fasta_file_path)?;
+
         Ok(Self {
+            max_amino_acids_per_line,
+            sort_keyword_attributes,
+            internal_writer: BufWriter::new(fasta_file),
+        })
+    }
+
+    /// Creates a new Writer
+    ///
+    /// # Arguments
+    ///
+    /// * `fasta_file_path` - Path to FASTA file
+    /// * `sort_keyword_attributes` - If true the keyword attributes will be sorted (for testing and readability reasons)
+    ///
+    pub fn new_with_default_seq_formatting(fasta_file_path: &Path, sort_keyword_attributes: bool) -> Result<Self> {
+        let fasta_file: File = File::create(fasta_file_path)?;
+
+        Ok(Self {
+            max_amino_acids_per_line: Some(DEFAULT_MAX_AMINO_ACIDS_PER_LINE),
+            sort_keyword_attributes,
+            internal_writer: BufWriter::new(fasta_file)
+        })
+    }
+
+    /// Creates a new Writer
+    ///
+    /// # Arguments
+    ///
+    /// * `fasta_file_path` - Path to FASTA file
+    /// * `sort_keyword_attributes` - If true the keyword attributes will be sorted (for testing and readability reasons)
+    ///
+    pub fn new_without_seq_formatting(fasta_file_path: &Path, sort_keyword_attributes: bool) -> Result<Self> {
+        let fasta_file: File = File::create(fasta_file_path)?;
+
+        Ok(Self {
+            max_amino_acids_per_line: None,
+            sort_keyword_attributes,
             internal_writer: BufWriter::new(fasta_file)
         })
     }
@@ -36,7 +82,7 @@ impl Writer {
     /// * `entry` - FASTA entry
     /// * `sort_keyword_attributes` - If true the keyword attributes will be sorted (for testing and readability reasons)
     /// 
-    fn create_header(entry: &Entry, sort_keyword_attributes: bool) -> String {
+    fn create_header(entry: &FastaEntry, sort_keyword_attributes: bool) -> String {
         let mut header = ">".to_string();
         header.push_str(entry.get_database());
         header.push_str("|");
@@ -63,29 +109,50 @@ impl Writer {
     /// # Arguments
     ///
     /// * `sequence` - Amino acid sequence
+    /// * `max_amino_acids_per_line` - Maximum length of each line containing sequence amino acids.
     /// 
-    fn format_sequence(sequence: &str) -> String {
+    fn format_sequence(sequence: &str, max_amino_acids_per_line: usize) -> String {
         return sequence.chars()
             .collect::<Vec<char>>()
-            .chunks(MAX_AMINO_ACIDS_PER_LINE)
+            .chunks(max_amino_acids_per_line)
             .map(|c| c.iter().collect::<String>())
             .collect::<Vec<String>>()
             .join("\n");
     }
 
     /// Writes entry into the FASTA file.
-    /// 
+    ///
     /// # Arguments
     ///
     /// * `entry` - FASTA entry
     /// * `sort_keyword_attributes` - If true the keyword attributes will be sorted (for testing and readability reasons)
+    /// * `max_amino_acids_per_line` - If Some(), will format the sequence line to not exceed the given length.
+    ///
+    pub fn stringify_entry(entry: &FastaEntry, sort_keyword_attributes: bool, max_amino_acids_per_line: Option<usize>) -> String {
+
+        let header_as_string = Self::create_header(entry, sort_keyword_attributes);
+
+        let seq_as_string = if max_amino_acids_per_line.is_some() {
+            Self::format_sequence(entry.get_sequence(), max_amino_acids_per_line.unwrap())
+        } else {
+            entry.get_sequence().to_string()
+        };
+
+        [header_as_string, seq_as_string].join("\n")
+    }
+
+    /// Writes entry into the FASTA file.
     /// 
-    pub fn write_entry(&mut self, entry: &Entry, sort_keyword_attributes: bool) -> Result<usize> {
-        let mut written_bytes: usize = 0;
-        written_bytes += self.internal_writer.write(Self::create_header(entry, sort_keyword_attributes).as_bytes())?;
-        written_bytes += self.internal_writer.write(b"\n")?;
-        written_bytes += self.internal_writer.write(Self::format_sequence(entry.get_sequence()).as_bytes())?;
-        written_bytes += self.internal_writer.write(b"\n")?;
+    /// # Arguments
+    ///
+    /// * `entry` - FASTA entry
+    ///
+    pub fn write_entry(&mut self, entry: &FastaEntry) -> Result<usize> {
+        let mut entry_as_string = Self::stringify_entry(entry, self.sort_keyword_attributes, self.max_amino_acids_per_line);
+        entry_as_string.push_str("\n");
+
+        let written_bytes = self.internal_writer.write(entry_as_string.as_bytes())?;
+
         return Ok(written_bytes);
     }
 
@@ -93,16 +160,15 @@ impl Writer {
     /// 
     /// # Arguments
     ///
-    /// * `entires` - Iterator of FASTA entries
-    /// * `sort_keyword_attributes` - If true the keyword attributes will be sorted (for testing and readability reasons)
-    /// 
-    pub fn write_all<'b, I>(&mut self, entries: I, sort_keyword_attributes: bool) -> Result<usize>
+    /// * `entried` - Iterator of FASTA entries
+    ///
+    pub fn write_all<'b, I>(&mut self, entries: I) -> Result<usize>
     where
-        I: Iterator<Item = &'b Entry>,
+        I: Iterator<Item = &'b FastaEntry>,
     {
         let mut written_bytes: usize = 0;
         for entry in entries {
-            written_bytes += self.write_entry(entry, sort_keyword_attributes)?;
+            written_bytes += self.write_entry(entry)?;
         }
         return Ok(written_bytes);
     }
@@ -149,23 +215,24 @@ QRSGIVALDGERELAFGPDDEVTVTLHDHAFRSIDVAACMRHAGRHHLMRSLPQPAAVG";
     #[test]
     /// Tests the creation of a FASTA entry from a header and a sequence.
     ///
-    fn test_seqeunce_formatting() {
-        let formatted_sequence  = Writer::format_sequence(TEST_SEQUENCE);
+    fn test_sequence_formatting() {
+        let formatted_sequence  = FastaWriter::format_sequence(TEST_SEQUENCE, DEFAULT_MAX_AMINO_ACIDS_PER_LINE);
         assert_eq!(formatted_sequence, EXPECTED_SEQUENCE)
     }
 
     #[test]
     /// Reads a FASTA file, parses the proteins and counts protein
     fn test_header_creation() {
-        let entry = Entry::new(
+        let entry = FastaEntry::new(
             TEST_DATABASE.to_string(),
             TEST_ACCESSION.to_string(),
             TEST_ENTRY_NAME.to_string(),
             TEST_PROTEIN_NAME.to_string(),
             TEST_KEYWORD_ATTRIBUTES.into_iter().map(|elem| (elem.0.to_string(), elem.1.to_string())).collect::<HashMap<String, String>>(),
-            TEST_SEQUENCE.to_string()
+            TEST_SEQUENCE.to_string(),
+            None
         );
-        let header = Writer::create_header(&entry, true);
+        let header = FastaWriter::create_header(&entry, true);
         assert_eq!(header, EXPECTED_HEADER);
     }
 }
diff --git a/mzio-rs/src/lib.rs b/mzio-rs/src/lib.rs
index df1277f..ed81f4c 100755
--- a/mzio-rs/src/lib.rs
+++ b/mzio-rs/src/lib.rs
@@ -1,2 +1,4 @@
+#[cfg(feature = "fasta")]
 pub mod fasta;
+#[cfg(feature = "mgf")]
 pub mod mgf;
diff --git a/mzio-rs/src/mgf/mod.rs b/mzio-rs/src/mgf/mod.rs
index 6f32af8..9ff4088 100644
--- a/mzio-rs/src/mgf/mod.rs
+++ b/mzio-rs/src/mgf/mod.rs
@@ -3,7 +3,9 @@
 pub mod reader;
 pub mod spectrum;
 pub mod writer;
+pub mod prelude;
 
+pub use prelude::*;
 
 #[cfg(test)]
 mod test {
@@ -13,8 +15,8 @@ mod test {
     use std::iter::zip;
     use std::path::Path;
 
-    use fallible_iterator::IntoFallibleIterator;
-    use fallible_iterator::FallibleIterator;
+    //use fallible_iterator::IntoFallibleIterator;
+    //use fallible_iterator::FallibleIterator;
 
     const MGF_FILE_PATH_STR: &'static str = "../test_files/mgf/Velos005137.mgf";
     const EXPECTED_NUM_SPECTRA: usize = 100;
@@ -27,20 +29,20 @@ mod test {
         let mgf_file_path = Path::new(MGF_FILE_PATH_STR);
         let tmp_mgf_file_path = Path::new(TEMP_MGF_PATH_STR);
 
-        let reader = reader::Reader::new(
+        let mgf_reader = MgfReader::new(
             mgf_file_path,
             1024
         ).unwrap();
 
-        let entries: Vec<spectrum::Spectrum> = reader.into_fallible_iter().collect().unwrap();
+        let entries: Vec<MgfSpectrum> = mgf_reader.into_fallible_iter().collect().unwrap();
         assert_eq!(entries.len(), EXPECTED_NUM_SPECTRA);
 
-        let mut writer = writer::Writer::new(
+        let mut mgf_writer = MgfWriter::new(
             tmp_mgf_file_path
         ).unwrap();
 
-        writer.write_all(entries.iter()).unwrap();
-        writer.flush().unwrap();
+        mgf_writer.write_all(entries.iter()).unwrap();
+        mgf_writer.flush().unwrap();
 
         let tmp_mgf_content  = fs::read_to_string(tmp_mgf_file_path).unwrap().trim().to_string();
         fs::remove_file(tmp_mgf_file_path).unwrap();
diff --git a/mzio-rs/src/mgf/prelude.rs b/mzio-rs/src/mgf/prelude.rs
new file mode 100644
index 0000000..67f51b5
--- /dev/null
+++ b/mzio-rs/src/mgf/prelude.rs
@@ -0,0 +1,5 @@
+pub use fallible_iterator::IntoFallibleIterator;
+pub use fallible_iterator::FallibleIterator;
+pub use crate::mgf::spectrum::MgfSpectrum;
+pub use crate::mgf::reader::MgfReader;
+pub use crate::mgf::writer::MgfWriter;
\ No newline at end of file
diff --git a/mzio-rs/src/mgf/reader.rs b/mzio-rs/src/mgf/reader.rs
index 9260ee6..1bdd2ee 100644
--- a/mzio-rs/src/mgf/reader.rs
+++ b/mzio-rs/src/mgf/reader.rs
@@ -10,14 +10,14 @@ use anyhow::{Result, bail};
 use fallible_iterator::FallibleIterator;
 
 // internal imports
-use crate::mgf::spectrum::Spectrum;
+use crate::mgf::spectrum::MgfSpectrum;
 
 /// Reader for MGF
-pub struct Reader {
+pub struct MgfReader {
     internal_reader: BufReader<File>
 }
 
-impl Reader {
+impl MgfReader {
     /// Creates a new Reader
     /// 
     /// # Arguments
@@ -32,8 +32,8 @@ impl Reader {
     }
 }
 
-impl FallibleIterator for Reader {
-    type Item = Spectrum;
+impl FallibleIterator for MgfReader {
+    type Item = MgfSpectrum;
     type Error = anyhow::Error;
 
     fn next(&mut self) -> Result<Option<Self::Item>> {
@@ -55,36 +55,21 @@ impl FallibleIterator for Reader {
                     }
                     return Ok(None);
                 }
+
                 line = line.as_mut_str().trim().to_string();
                 if line.is_empty() {
                     continue
                 }
 
-                if line.chars().nth(0).unwrap().is_numeric() {
-                    let mut split = line.split_ascii_whitespace();
-
-                    match split.next() {
-                        Some(mz) => mz_list.push(fast_float::parse(mz)?),
-                        None => bail!("mz value is missing")
-                    };
-
-                    match split.next() {
-                        Some(intens) => intensity_list.push(fast_float::parse(intens)?),
-                        None => bail!("intensity value is missing")
-                    };
-
-                } else if line.starts_with("TITLE=") {
-                    title = line[6..].to_owned();
-                } else if line.starts_with("PEPMASS=") {
-                    precursor_mz = fast_float::parse(&line[8..])?;
-                } else if line.starts_with("RTINSECONDS=") {
-                    retention_time = Some(fast_float::parse(&line[12..])?);
-                } else if line.starts_with("CHARGE=") {
-                    precursor_charge = Some(line[7..].parse()?);
-                } else if line == "BEGIN IONS" {
+                let first_char = line.chars().next().unwrap();
+
+                if first_char == 'B' && line.starts_with("BEGIN IONS") {
                     in_spectrum = true;
-                } else if line == "END IONS" {
-                    return Ok(Some(Spectrum::new(
+                } else if first_char == 'E' && line.starts_with("END IONS") {
+
+                    //in_spectrum = false;
+
+                    return Ok(Some(MgfSpectrum::new(
                         title,
                         precursor_mz,
                         precursor_charge,
@@ -92,8 +77,50 @@ impl FallibleIterator for Reader {
                         mz_list,
                         intensity_list
                     )));
-                }
-            }
-        }
+                } else if in_spectrum {
+                    // if line contains a peak
+                    if first_char.is_numeric() {
+                        let mut split = line.split_ascii_whitespace();
+
+                        match split.next() {
+                            Some(mz) => mz_list.push(fast_float::parse(mz)?),
+                            None => bail!("m/z value is missing")
+                        };
+
+                        match split.next() {
+                            Some(intens) => intensity_list.push(fast_float::parse(intens)?),
+                            None => bail!("intensity value is missing")
+                        };
+
+                    } else {
+                        if line.starts_with("TITLE=") {
+                            title = line[6..].to_owned();
+                        } else if line.starts_with("PEPMASS=") {
+                            let prec_mz_str_opt = &line[8..].split_ascii_whitespace().next();
+                            precursor_mz = fast_float::parse(prec_mz_str_opt.unwrap_or_else(|| "0.0"))?;
+                        } else if line.starts_with("RTINSECONDS=") {
+                            retention_time = Some(fast_float::parse(&line[12..])?);
+                        } else if line.starts_with("CHARGE=") {
+                            // Locate the value and its sign within the string
+                            let value = &line[7..];
+                            let mut chars = value.chars();
+                            let charge_sign_idx = chars.position(|c| !c.is_numeric()).unwrap_or(value.len());
+
+                            // Parse the charge value
+                            let charge_str = &value[0..charge_sign_idx];
+                            let mut charge = charge_str.parse()?;
+
+                            // Parse the charge sign and update the value accordingly
+                            let sign = chars.nth(charge_sign_idx).unwrap_or('+');
+                            if sign == '-' {
+                                charge *= -1;
+                            }
+
+                            precursor_charge = Some(charge);
+                        }
+                    }
+                } // ends else if in_spectrum
+            } // ends read_line
+        } // ends loop
     }
-}
+}
\ No newline at end of file
diff --git a/mzio-rs/src/mgf/spectrum.rs b/mzio-rs/src/mgf/spectrum.rs
index 8a0af7b..00893bd 100644
--- a/mzio-rs/src/mgf/spectrum.rs
+++ b/mzio-rs/src/mgf/spectrum.rs
@@ -1,14 +1,22 @@
+
+// 3rd party imports
+use serde::{Serialize, Deserialize};
+
+// internal imports
+use mzcore::ms::spectrum::SpectrumData;
+use mzcore::ms::utils::mz_to_mass;
+
 /// Spectrum representation for MGF files.
-pub struct Spectrum {
-    title: String,
-    precursor_mz: f64,
-    precursor_charge: Option<i8>,
-    retention_time: Option<f64>,
-    mz_list: Vec<f64>,
-    intensity_list: Vec<f32>
+#[derive(Clone, Debug, PartialEq, PartialOrd, Serialize, Deserialize)]
+pub struct MgfSpectrumHeader {
+    pub title: String,
+    pub precursor_mz: f64,
+    pub precursor_charge: Option<i8>,
+    pub precursor_mass: Option<f64>, // Not in the header (for post-processing convenience)
+    pub retention_time: Option<f64>,
 }
 
-impl Spectrum {
+impl MgfSpectrumHeader {
     /// Creates a new spectrum
     /// 
     /// # Arguments
@@ -20,21 +28,24 @@ impl Spectrum {
     /// * `mz_list` - M/Z list
     /// * `intensity_list` -  Intensity list
     /// 
-    pub fn new(title: String, precursor_mz: f64, precursor_charge: Option<i8>,
-        retention_time: Option<f64>, mz_list: Vec<f64>, intensity_list: Vec<f32>) -> Self {
+    pub fn new(
+        title: String,
+        precursor_mz: f64,
+        precursor_charge: Option<i8>,
+        retention_time: Option<f64>
+    ) -> Self {
         Self {
             title,
             precursor_mz,
             precursor_charge,
+            precursor_mass: None,
             retention_time,
-            mz_list,
-            intensity_list,
         }
     }
 
     /// Returns the spectrum title
     /// 
-    pub fn get_title(&self) -> &str {
+    pub fn get_title(&self) -> &String {
         &self.title
     }
 
@@ -46,26 +57,90 @@ impl Spectrum {
 
     /// Returns precursor charge
     /// 
-    pub fn get_precursor_charge(&self) -> &Option<i8> {
-        &self.precursor_charge
+    pub fn get_precursor_charge(&self) -> Option<i8> {
+        self.precursor_charge
+    }
+
+    /// Returns precursor mass
+    ///
+    pub fn get_precursor_mass(&self) -> Option<f64> {
+        self.precursor_mass
+    }
+
+    /// Sets precursor mass
+    ///
+    pub fn set_precursor_mass(&mut self, precursor_mass: f64) -> &MgfSpectrumHeader {
+        self.precursor_mass = Some(precursor_mass);
+        self
+    }
+
+    /// Calculates and sets precursor mass
+    ///
+    pub fn calc_precursor_mass(&mut self) -> &MgfSpectrumHeader {
+        self.precursor_mass = self.precursor_charge.map(|z| mz_to_mass(self.precursor_mz, z as i32));
+        self
     }
 
     /// Returns retention time
     /// 
-    pub fn get_retention_time(&self) -> &Option<f64>  {
-        &self.retention_time
+    pub fn get_retention_time(&self) -> Option<f64>  {
+        self.retention_time
+    }
+
+}
+
+#[derive(Clone, Debug, PartialEq, PartialOrd, Serialize, Deserialize)]
+pub struct MgfSpectrum {
+    pub header: MgfSpectrumHeader,
+    pub data: SpectrumData,
+}
+
+impl MgfSpectrum {
+    /// Creates a new spectrum
+    ///
+    /// # Arguments
+    ///
+    /// * `title` - Specturm title
+    /// * `precursor_mz` -  Precursor mass
+    /// * `precursor_charge` -  Precursor charge
+    /// * `retention_time` -  Retention time
+    /// * `mz_list` - M/Z list
+    /// * `intensity_list` -  Intensity list
+    ///
+    pub fn new(
+        title: String,
+        precursor_mz: f64,
+        precursor_charge: Option<i8>,
+        retention_time: Option<f64>,
+        mz_list: Vec<f64>,
+        intensity_list: Vec<f32>
+    ) -> Self {
+
+        let mgf_header =  MgfSpectrumHeader::new(title, precursor_mz, precursor_charge, retention_time);
+
+        let data = SpectrumData {
+            mz_list,
+            intensity_list,
+        };
+
+        Self {
+            header: mgf_header,
+            data: data,
+        }
     }
 
     /// Returns M/Z list
-    /// 
+    ///
     pub fn get_mz_list(&self) -> &Vec<f64> {
-        &self.mz_list
+        &self.data.mz_list
     }
 
     /// Returns intensity list
-    /// 
+    ///
     pub fn get_intensity_list(&self) -> &Vec<f32> {
-        &self.intensity_list
+        &self.data.intensity_list
     }
 
-}
\ No newline at end of file
+}
+
+
diff --git a/mzio-rs/src/mgf/writer.rs b/mzio-rs/src/mgf/writer.rs
index 19540bf..02292ec 100644
--- a/mzio-rs/src/mgf/writer.rs
+++ b/mzio-rs/src/mgf/writer.rs
@@ -8,15 +8,15 @@ use std::path::Path;
 use anyhow::Result;
 
 // internal imports 
-use crate::mgf::spectrum::Spectrum;
+use crate::mgf::spectrum::MgfSpectrum;
 
 /// Writer for MGF files
 /// Use flush() to make ensure the buffer is written completely.
-pub struct Writer {
+pub struct MgfWriter {
     internal_writer: BufWriter<File>
 }
 
-impl Writer {
+impl MgfWriter {
     /// Creates a new Writer
     /// 
     /// # Arguments
@@ -36,22 +36,38 @@ impl Writer {
     ///
     /// * `spectrum` - Spectrum
     /// 
-    pub fn write_spectrum(&mut self, spectrum: &Spectrum,) -> Result<usize> {
+    pub fn write_spectrum(&mut self, spectrum: &MgfSpectrum) -> Result<usize> {
+        let spec_header = &spectrum.header;
+
         let mut written_bytes: usize = 0;
-        written_bytes += self.internal_writer.write("BEGIN IONS\n".as_bytes())?;
-        written_bytes += self.internal_writer.write(format!("TITLE={}\n", spectrum.get_title()).as_bytes())?;
-        written_bytes += self.internal_writer.write(format!("PEPMASS={}", spectrum.get_precursor_mz()).as_bytes())?;
-        if let Some(retention_time) = spectrum.get_retention_time() {
-            written_bytes += self.internal_writer.write(format!("\nRTINSECONDS={}", retention_time).as_bytes())?;
+
+        written_bytes += self._write_str("BEGIN IONS\n")?;
+        written_bytes += self._write_string(format!("TITLE={}\n", spec_header.get_title()))?;
+        written_bytes += self._write_string(format!("PEPMASS={}", spec_header.get_precursor_mz()))?;
+
+        if let Some(retention_time) = spec_header.get_retention_time() {
+            written_bytes += self._write_string(format!("\nRTINSECONDS={}", retention_time))?;
         }
-        if let Some(charge) = spectrum.get_precursor_charge() {
-            written_bytes += self.internal_writer.write(format!("\nCHARGE={}", charge).as_bytes())?;
+        if let Some(charge) = spec_header.get_precursor_charge() {
+            let charge_sign = if charge < 0 { '-'} else { '+' };
+            written_bytes += self._write_string(format!("\nCHARGE={}{}", charge, charge_sign))?;
         }
         for (mz, intensity) in zip(spectrum.get_mz_list(), spectrum.get_intensity_list()) {
-            written_bytes += self.internal_writer.write(format!("\n{mz} {intensity}").as_bytes())?;
+            written_bytes += self._write_string(format!("\n{mz} {intensity}"))?;
         }
-        written_bytes += self.internal_writer.write("\nEND IONS\n".as_bytes())?;
-        return Ok(written_bytes);
+        written_bytes += self._write_str("\nEND IONS\n")?;
+
+        Ok(written_bytes)
+    }
+
+    #[inline(always)]
+    fn _write_str(&mut self, str: &str) -> Result<usize> {
+        Ok(self.internal_writer.write(str.as_bytes())?)
+    }
+
+    #[inline(always)]
+    fn _write_string(&mut self, string: String) -> Result<usize> {
+        Ok(self.internal_writer.write(string.as_bytes())?)
     }
 
     /// Writes multiple spectra to file.
@@ -62,7 +78,7 @@ impl Writer {
     /// 
     pub fn write_all<'b, I>(&mut self, spectra: I) -> Result<usize>
     where
-        I: Iterator<Item = &'b Spectrum>,
+        I: Iterator<Item = &'b MgfSpectrum>,
     {
         let mut written_bytes: usize = 0;
         for spectrum in spectra {
diff --git a/mzio-rs/test_files/fasta/partial_mouse.fasta b/mzio-rs/test_files/fasta/partial_mouse.fasta
deleted file mode 100644
index 462f2f6..0000000
--- a/mzio-rs/test_files/fasta/partial_mouse.fasta
+++ /dev/null
@@ -1,134 +0,0 @@
->sp|A0A024B7W1|POLG_ZIKVF Genome polyprotein OS=Zika virus (isolate ZIKV/Human/French Polynesia/10087PF/2013) OX=2043570 PE=1 SV=1
-MKNPKKKSGGFRIVNMLKRGVARVSPFGGLKRLPAGLLLGHGPIRMVLAILAFLRFTAIK
-PSLGLINRWGSVGKKEAMEIIKKFKKDLAAMLRIINARKEKKRRGADTSVGIVGLLLTTA
-MAAEVTRRGSAYYMYLDRNDAGEAISFPTTLGMNKCYIQIMDLGHMCDATMSYECPMLDE
-GVEPDDVDCWCNTTSTWVVYGTCHHKKGEARRSRRAVTLPSHSTRKLQTRSQTWLESREY
-TKHLIRVENWIFRNPGFALAAAAIAWLLGSSTSQKVIYLVMILLIAPAYSIRCIGVSNRD
-FVEGMSGGTWVDVVLEHGGCVTVMAQDKPTVDIELVTTTVSNMAEVRSYCYEASISDMAS
-DSRCPTQGEAYLDKQSDTQYVCKRTLVDRGWGNGCGLFGKGSLVTCAKFACSKKMTGKSI
-QPENLEYRIMLSVHGSQHSGMIVNDTGHETDENRAKVEITPNSPRAEATLGGFGSLGLDC
-EPRTGLDFSDLYYLTMNNKHWLVHKEWFHDIPLPWHAGADTGTPHWNNKEALVEFKDAHA
-KRQTVVVLGSQEGAVHTALAGALEAEMDGAKGRLSSGHLKCRLKMDKLRLKGVSYSLCTA
-AFTFTKIPAETLHGTVTVEVQYAGTDGPCKVPAQMAVDMQTLTPVGRLITANPVITESTE
-NSKMMLELDPPFGDSYIVIGVGEKKITHHWHRSGSTIGKAFEATVRGAKRMAVLGDTAWD
-FGSVGGALNSLGKGIHQIFGAAFKSLFGGMSWFSQILIGTLLMWLGLNTKNGSISLMCLA
-LGGVLIFLSTAVSADVGCSVDFSKKETRCGTGVFVYNDVEAWRDRYKYHPDSPRRLAAAV
-KQAWEDGICGISSVSRMENIMWRSVEGELNAILEENGVQLTVVVGSVKNPMWRGPQRLPV
-PVNELPHGWKAWGKSYFVRAAKTNNSFVVDGDTLKECPLKHRAWNSFLVEDHGFGVFHTS
-VWLKVREDYSLECDPAVIGTAVKGKEAVHSDLGYWIESEKNDTWRLKRAHLIEMKTCEWP
-KSHTLWTDGIEESDLIIPKSLAGPLSHHNTREGYRTQMKGPWHSEELEIRFEECPGTKVH
-VEETCGTRGPSLRSTTASGRVIEEWCCRECTMPPLSFRAKDGCWYGMEIRPRKEPESNLV
-RSMVTAGSTDHMDHFSLGVLVILLMVQEGLKKRMTTKIIISTSMAVLVAMILGGFSMSDL
-AKLAILMGATFAEMNTGGDVAHLALIAAFKVRPALLVSFIFRANWTPRESMLLALASCLL
-QTAISALEGDLMVLINGFALAWLAIRAMVVPRTDNITLAILAALTPLARGTLLVAWRAGL
-ATCGGFMLLSLKGKGSVKKNLPFVMALGLTAVRLVDPINVVGLLLLTRSGKRSWPPSEVL
-TAVGLICALAGGFAKADIEMAGPMAAVGLLIVSYVVSGKSVDMYIERAGDITWEKDAEVT
-GNSPRLDVALDESGDFSLVEDDGPPMREIILKVVLMTICGMNPIAIPFAAGAWYVYVKTG
-KRSGALWDVPAPKEVKKGETTDGVYRVMTRRLLGSTQVGVGVMQEGVFHTMWHVTKGSAL
-RSGEGRLDPYWGDVKQDLVSYCGPWKLDAAWDGHSEVQLLAVPPGERARNIQTLPGIFKT
-KDGDIGAVALDYPAGTSGSPILDKCGRVIGLYGNGVVIKNGSYVSAITQGRREEETPVEC
-FEPSMLKKKQLTVLDLHPGAGKTRRVLPEIVREAIKTRLRTVILAPTRVVAAEMEEALRG
-LPVRYMTTAVNVTHSGTEIVDLMCHATFTSRLLQPIRVPNYNLYIMDEAHFTDPSSIAAR
-GYISTRVEMGEAAAIFMTATPPGTRDAFPDSNSPIMDTEVEVPERAWSSGFDWVTDHSGK
-TVWFVPSVRNGNEIAACLTKAGKRVIQLSRKTFETEFQKTKHQEWDFVVTTDISEMGANF
-KADRVIDSRRCLKPVILDGERVILAGPMPVTHASAAQRRGRIGRNPNKPGDEYLYGGGCA
-ETDEDHAHWLEARMLLDNIYLQDGLIASLYRPEADKVAAIEGEFKLRTEQRKTFVELMKR
-GDLPVWLAYQVASAGITYTDRRWCFDGTTNNTIMEDSVPAEVWTRHGEKRVLKPRWMDAR
-VCSDHAALKSFKEFAAGKRGAAFGVMEALGTLPGHMTERFQEAIDNLAVLMRAETGSRPY
-KAAAAQLPETLETIMLLGLLGTVSLGIFFVLMRNKGIGKMGFGMVTLGASAWLMWLSEIE
-PARIACVLIVVFLLLVVLIPEPEKQRSPQDNQMAIIIMVAVGLLGLITANELGWLERTKS
-DLSHLMGRREEGATIGFSMDIDLRPASAWAIYAALTTFITPAVQHAVTTSYNNYSLMAMA
-TQAGVLFGMGKGMPFYAWDFGVPLLMIGCYSQLTPLTLIVAIILLVAHYMYLIPGLQAAA
-ARAAQKRTAAGIMKNPVVDGIVVTDIDTMTIDPQVEKKMGQVLLIAVAVSSAILSRTAWG
-WGEAGALITAATSTLWEGSPNKYWNSSTATSLCNIFRGSYLAGASLIYTVTRNAGLVKRR
-GGGTGETLGEKWKARLNQMSALEFYSYKKSGITEVCREEARRALKDGVATGGHAVSRGSA
-KLRWLVERGYLQPYGKVIDLGCGRGGWSYYAATIRKVQEVKGYTKGGPGHEEPMLVQSYG
-WNIVRLKSGVDVFHMAAEPCDTLLCDIGESSSSPEVEEARTLRVLSMVGDWLEKRPGAFC
-IKVLCPYTSTMMETLERLQRRYGGGLVRVPLSRNSTHEMYWVSGAKSNTIKSVSTTSQLL
-LGRMDGPRRPVKYEEDVNLGSGTRAVVSCAEAPNMKIIGNRIERIRSEHAETWFFDENHP
-YRTWAYHGSYEAPTQGSASSLINGVVRLLSKPWDVVTGVTGIAMTDTTPYGQQRVFKEKV
-DTRVPDPQEGTRQVMSMVSSWLWKELGKHKRPRVCTKEEFINKVRSNAALGAIFEEEKEW
-KTAVEAVNDPRFWALVDKEREHHLRGECQSCVYNMMGKREKKQGEFGKAKGSRAIWYMWL
-GARFLEFEALGFLNEDHWMGRENSGGGVEGLGLQRLGYVLEEMSRIPGGRMYADDTAGWD
-TRISRFDLENEALITNQMEKGHRALALAIIKYTYQNKVVKVLRPAEKGKTVMDIISRQDQ
-RGSGQVVTYALNTFTNLVVQLIRNMEAEEVLEMQDLWLLRRSEKVTNWLQSNGWDRLKRM
-AVSGDDCVVKPIDDRFAHALRFLNDMGKVRKDTQEWKPSTGWDNWEEVPFCSHHFNKLHL
-KDGRSIVVPCRHQDELIGRARVSPGAGWSIRETACLAKSYAQMWQLLYFHRRDLRLMANA
-ICSSVPVDWVPTGRTTWSIHGKGEWMTTEDMLVVWNRVWIEENDHMEDKTPVTKWTDIPY
-LGKREDLWCGSLIGHRPRTTWAENIKNTVNMVRRIIGDEEKYMDYLSTQVRYLGEEGSTP
-GVL
->sp|A0A087WPF7|AUTS2_MOUSE Autism susceptibility gene 2 protein homolog GN=Auts2 OS=Mus musculus OX=10090 PE=1 SV=2
-MDGPTRGHGLRKKRRSRSQRDRERRSRAGLGTGAAGGIGAGRTRAPSLASSSGSDKEDNG
-KPPSSAPSRPRPPRRKRRESTSAEEDIIDGFAMTSFVTFEALEKDVAVKPQERAEKRQTP
-LTKKKREALTNGLSFHSKKSRLSHSHHYSSDRENDRNLCQHLGKRKKMPKGLRQLKPGQN
-SCRDSDSESASGESKGFQRSSSRERLSDSSAPSSLGTGYFCDSDSDQEEKASDASSEKLF
-NTVLVNKDPELGVGALPEHNQDAGPIVPKISGLERSQEKSQDCCKEPVFEPVVLKDPHPQ
-LPQLPSQAQAEPQLQIPSPGPDLVPRTEAPPQFPPPSTQPAQGPPEAQLQPAPLPQVQQR
-PPRPQSPSHLLQQTLPPVQSHPSSQSLSQPLSAYNSSSLSLNSLSSRSSTPAKTQPAPPH
-ISHHPSASPFPLSLPNHSPLHSFTPTLQPPAHSHHPNMFAPPTALPPPPPLTSGSLQVPG
-HPAGSTYSEQDILRQELNTRFLASQSADRGASLGPPPYLRTEFHQHQHQHQHTHQHTHQH
-TFTPFPHAIPPTAIMPTPAPPMFDKYPTKVDPFYRHSLFHSYPPAVSGIPPMIPPTGPFG
-SLQGAFQPKTSNPIDVAARPGTVPHTLLQKDPRLTDPFRPMLRKPGKWCAMHVHIAWQIY
-HHQQKVKKQMQSDPHKLDFGLKPEFLSRPPGPSLFGAIHHPHDLARPSTLFSAAGAAHPT
-GTPFGPPPHHSNFLNPAAHLEPFNRPSTFTGLAAVGGNAFGGLGNPSVTPNSVFGHKDSP
-SVQNFSNPHEPWNRLHRTPPSFPTPPPWLKPGELERSASAAAHDRDRDVDKRDSSVSKDD
-KERESVEKRHPSHPSPAPPVPVSALGHNRSSTDPTTRGHLNTEAREKDKPKEKERDHSGS
-RKDLTTEEHKAKESHLPERDGHSHEGRAAGEEPKQLSRVPSPYVRTPGVDSTRPNSTSSR
-EAEPRKGEPAYENPKKNAEVKVKEERKEDHDLPTEAPQAHRTSEAPPPSSSASASVHPGP
-LASMPMTVGVTGIHAMNSIGSLDRTRMVTPFMGLSPIPGGERFPYPSFHWDPMRDPLRDP
-YRDLDMHRRDPLGRDFLLRNDPLHRLSTPRLYEADRSFRDREPHDYSHHHHHHHHPLAVD
-PRREHERGGHLDERERLHVLREDYEHPRLHPVHPASLDGHLPHPSLLTPGLPSMHYPRIS
-PTAGHQNGLLNKTPPTAALSAPPPLISTLGGRPGSPRRTTPLSAEIRERPPSHTLKDIEA
-R
->sp|A0A088MLT8|IQIP1_MOUSE IQCJ-SCHIP1 readthrough transcript protein GN=Iqcj-Schip1 OS=Mus musculus OX=10090 PE=1 SV=2
-MRLEELKRLQNPLEQVDDGKYLLENHQLAMDVENNIENYPLSLQPLESKVKIIQRAWREY
-LQRQDPLEKRSPSPPSVSSDKLSSSVSMNTFSDSSTPDYREDGMDLGSDAGSSSSSRASS
-QSNSTKVTPCSECKSSSSPGGSLDLVSALEDYEEPFPVYQKKVIDEWAPEEDGEEEEEED
-DRGYRDDGCPAREPGDVSARIGSSGSGSRSAATTMPSPMPNGNLHPHDPQDLRHNGNVVV
-AGRPNASRVPRRPIQKTQPPGSRRGGRNRASGGLCLQPPDGGTRVPEEPPAPPMDWEALE
-KHLAGLQFREQEVRNQGQARTNSTSAQKNERESIRQKLALGSFFDDGPGIYTSCSKSGKP
-SLSARLQSGMNLQICFVNDSGSDKDSDADDSKTETSLDTPLSPMSKQSSSYSDRDTTEEE
-SESLDDMDFLTRQKKLQAEAKMALAMAKPMAKMQVEVEKQNRKKSPVADLLPHMPHISEC
-LMKRSLKPTDLRDMTIGQLQVIVNDLHSQIESLNEELVQLLLIRDELHTEQDAMLVDIED
-LTRHAESQQKHMAEKMPAK
->sp|A0A0A7EPL0|PIAL1_ARATH E4 SUMO-protein ligase PIAL1 GN=PIAL1 OS=Arabidopsis thaliana OX=3702 PE=2 SV=1
-MVIPATSRFGFRAEFNTKEFQASCISLANEIDAAIGRNEVPGNIQELALILNNVCRRKCD
-DYQTRAVVMALMISVKSACQLGWFPERETQELLAIIDLMWNGFSCPENVTSCVNSPVTLI
-SQVIERFYPCVKLGHILVSFEAKPESKMMMKDFHISKKMPHSPKQKVGLFVVRTEDISRS
-NCIVHPQGVSFLLNGKGIDKRVNISMESGPQLPTNVTALLNLGANLLQAIGCFGGSYLIA
-IAFMDVIPLPNKPLLKDYVHPEVVGSNSDCDIIEGPSRISLSCPISRTRIKLPVKGHVCK
-HLQCFDFWNYVNMNTRRPSWRCPHCNQSVCYTDIRVDQKLRKILEEVGRNAADVVISADG
-TWMVETENDEDVELVPETTHDHGDPNSFINLGPTVKNPARDENEMETSTQVEEHNPCLSE
-IQGPSNDTHRPASDYTMLNQSHTSTNTLPQLPRTLNAFDGQQFVNLPQVINTRDSPASQA
-LPMTFSPTPSPQDILATNAANFGTSMPAAQSSQFQGSHVTSLGNCEGRTSDLMARWNHIY
-GRVQTQFPPAPLSHHHYSMQNQSPSPAQQRPVPSYIAHPQTFHVNYGENADQRWMPSSIA
-HPQTLPVNYGGNTNQRPIPSSIAHPQTLPVNYRGNTDHRSTPYSITHLQTLLNYGGNADQ
-RPMPSSITNLQTLPATYGGYAHQRPMSSSITHPRTSPVNYGGTPDQRPMPSSITHPQTLP
-VSYGGTTDQILNPGGAMGQFSSREFMNLTPANTENWRPQSRMRGSVAPGTGYDHMIIHPT
-RPVHPQAQTPPAPLSTSYDGADEIQAFIGHPSYPVSNNETQAGTSSLPVAEGLGYSGSFW
-SMPPETW
->sp|A0A0B4J1F4|ARRD4_MOUSE Arrestin domain-containing protein 4 GN=Arrdc4 OS=Mus musculus OX=10090 PE=1 SV=1
-MGGEAGADGPRGRVKSLGLVFEDESKGCYSSGETVAGHVLLEAAEPVALRGLRLEAQGRA
-TSAWGPSAGARVCIGGGSPAASSEVEYLNLRLSLLEAPAGEGVTLLQPGKHEFPFRFQLP
-SEPLATSFTGKYGSIQYCVRAVLERPQVPDQSVRRELQVVSHVDVNTPPLLTPMLKTQEK
-MVGCWLFTSGPVSLSVKIERKGYCNGEAIPIYAEIENCSSRLVVPKAAIFQTQTYLASGK
-TKTVRHMVANVRGNHIGSGSTDTWNGKMLKIPPVTPSILDCCIIRVDYSLAVYIHIPGAK
-RLMLELPLVIGTIPYSGFGRRNSSVASQFSMDMCWLALALPEQPEAPPNYADVVSEEEFS
-RHVPPYPQPSDCDGEACYSMFACIQEFRFQPPPLYSEVDPHPGDAQETQPVSFIL
->sp|A0A0B4J1G0|FCG3A_MOUSE Low affinity immunoglobulin gamma Fc region receptor III-A GN=Fcgr4  OS=Mus musculus OX=10090 PE=1 SV=1
-MWQLLLPTALVLTAFSGIQAGLQKAVVNLDPKWVRVLEEDSVTLRCQGTFSPEDNSIKWF
-HNESLIPHQDANYVIQSARVKDSGMYRCQTALSTISDPVQLEVHMGWLLLQTTKWLFQEG
-DPIHLRCHSWQNRPVRKVTYLQNGKGKKYFHENSELLIPKATHNDSGSYFCRGLIGHNNK
-SSASFRISLGDPGSPSMFPPWHQITFCLLIGLLFAIDTVLYFSVRRGLQSPVADYEEPKI
-QWSKEPQDK
->sp|A0A0B4J1N3|GP15L_MOUSE Protein GPR15LG GN=Gpr15lg OS=Mus musculus OX=10090 PE=2 SV=1
-MRLLALSGLLCMLLLCFCIFSSEGRRHPAKSLKLRRCCHLSPRSKLTTWKGNHTRPCRLC
-RNKLPVKSWVVPGALPQI
->sp|A0A0B5A8P4|INS3A_CONGE Con-Ins G3 OS=Conus geographus OX=6491 PE=1 SV=1
-MTTSFYFLLVALGLLLYVCQSSFGNQHTRNSDTPKHRCGSELADQYVQLCHGKRNDAGKK
-RGRASPLWQRQGFLSMLKAKRNEAFFLQRDGRGIVEVCCDNPCTVATLRTFCH
->sp|A0A0B5AC95|INS1A_CONGE Con-Ins G1a OS=Conus geographus OX=6491 PE=1 SV=1
-MTTSSYFLLMALGLLLYVCQSSFGNQHTRTFDTPKHRCGSEITNSYMDLCYRKRNDAGEK
-RGRASPLWQRRGSLSKLKARAKRNGAFHLPRDGRGVVEHCCHRPCSNAEFKKYCG
->sp|A0A0C5B5G6|MOTSC_HUMAN Mitochondrial-derived peptide MOTS-c GN=MT-RNR1 OS=Homo sapiens OX=9606 PE=1 SV=1
-MRWQEMGYIFYPRKLR
diff --git a/test_files/mgf/Velos005137.mgf b/test_files/mgf/Velos005137.mgf
index f5b32d0..5406688 100644
--- a/test_files/mgf/Velos005137.mgf
+++ b/test_files/mgf/Velos005137.mgf
@@ -2,7 +2,7 @@ BEGIN IONS
 TITLE=824.836730957031_212.9232
 PEPMASS=824.836730957031
 RTINSECONDS=212.9232
-CHARGE=2
+CHARGE=2+
 118.936477661133 429.616
 122.26781463623 354.588
 138.923324584961 369.316
@@ -24,7 +24,7 @@ BEGIN IONS
 TITLE=567.810852050781_249.8916
 PEPMASS=567.810852050781
 RTINSECONDS=249.8916
-CHARGE=2
+CHARGE=2+
 115.411254882813 417.992
 130.114776611328 334.547
 137.004974365234 429.248
@@ -64,7 +64,7 @@ BEGIN IONS
 TITLE=521.822143554688_251.90179999998
 PEPMASS=521.822143554688
 RTINSECONDS=251.90179999998
-CHARGE=2
+CHARGE=2+
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diff --git a/test_files/mgf/example.mgf b/test_files/mgf/example.mgf
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\ No newline at end of file