Work with lipid names in Python

LipidHandler is a Python package build to work with common abbreviations for lipids such as CE(20:2) or PG(18:2/20:2). Those lipid names are used in publications, data reports and data analysis tools.

The main goal of LipidHandler is to parse those lipid names, provide facilities to translate them into other represantations and map them to official identifiers.

LipidHandler does not replace toolkits to work with molecules and chemical structures.

:warning: LipidHandler was built for a specific research project and is not able to solve every use case about lipid names. It overlaps with other projects such as liputils.

:warning: The developer is not an expert on lipidomics, some of the naming might not make sense from a chemistry perspective.

:mailbox: Feedback through GitHub issues is appreciated.

Getting started

Work with lipid names

The Lipid class

Parse a lipid name:

from lipidhandler import Lipid

mylipid = Lipid.parse('CE 20:2')

The Lipid has a LipidClass

print(mylipid.lipidclass)

>>> CE

The Lipid contains a ResidueList which holds the Residues.

# iterate the ResidueList
for residue in mylipid.residueslist:
    print(residue.carbon_atoms)
    print(residue.double_bonds)

>>> 20
>>> 0

Multiple residues and different formats are possible:

mylipid = Lipid.parse("CE(20:2/18:2)")
mylipid = Lipid.parse("CE 20:2/18:2")
mylipid = Lipid.parse("CE(20:2_18:0)")

The Reside class

Next to the core attributes (C and double bonds) the Residue has an oxidation state, a generic chemical modification descriptor and details on the isomer.

Oxidation state

mylipid = Lipid.parse("CE(16:1;0)")
print(mylipid.residues[0].oxidation)

>>> 0

chemical modification

mylipid = Lipid.parse("PE(O-16:1)")
print(mylipid.residues[0].modification)

>>> O-

isomer

mylipid = Lipid.parse("CE(16:1(6Z))")
print(mylipid.residues[0].zstatelist[0]

>>> 6Z

The ResidueList has functions to aggregate over the residues:

mylipid = Lipid.parse("CE(20:2/18:2)")
print(mylipid.residuelist.sum().carbon_atoms) # the .sum() functions returns a Residue instancte

Connect to external databases

LipidHandler can query external sources to search for terms or get identifiers from external databases. Right now LipidHandler only works with SwissLipids but the underliying interface is generic and can be extended.

from lipidhandler.externalapis import SwissLipids

lipids = SwissLipids.search("CE 20:2")
for l in lipids:
    print(l)

>>> CE(20:2)

The output of the .search() function is a LipidList which contains Lipid instances. If you search for more generic terms you get a list with multiple results.

from lipidhandler.externalapis import SwissLipids

lipids = SwissLipids.search("CE 20")
for l in lipids:
    print(l)


>>> CE(20:1)
>>> CE(20:2)
>>> CE(20:5)
>>> CE(20:0)
>>> CE(20:4)
>>> CE(20:3)
>>> CE(20:4)
>>> CE(20:3)

You can also ask for the SwissLipds ID for a specific Lipid instance:

from lipidhandler.externalapis import SwissLipids

mylipid = Lipid.parse("CE(20:2)")
db_xrefs = SwissLipids.get_xrefs(mylipid)
for xref in db_xrefs:
    print(xref.target_db, xref.target_id)

>>> SwissLipids SLM:00050028

install

pip install lipidhandler

develop

run tests

Install project and test dependencies

pip install -r requirements.txt
pip install -r test_requirements.txt

Run test suite on sources

python -m pytest