Background:
The sperm plasma membrane meets the requirements of sperm transit
through the female genital tract and subsequent fertilization. Commonly, the (phospho)lipid composition
of sperm is characterized by tremendous amounts of highly unsaturated fatty acyl residues such
as docosahexaenoic and docosapentaenoic acid. While human sperm contain almost exclusively diacyl
lipids, many animal sperm additionally contain significant amounts of ether lipids such as alkylacyl-
and alkenyl-acyl lipids (plasmalogens).
Hypothesis/Objective:
It is suggested that deviations from the typical lipid composition are indicative
of pathological changes. Therefore, simple methods to elucidate the sperm lipid composition are essential.
Method:
Matrix-assisted laser desorption and ionization (MALDI) mass spectrometry (MS) is a fast
and simple method. Since the selection of the most suitable matrix is a crucial step in MALDI MS,
this topic will be highlighted. It will also be shown that MALDI MS can be easily combined with
thin-layer chromatography to overcome ion suppression effects.
Results:
The lipid composition of sperm from different species can be elucidated by MALDI MS.
However, different matrix compounds have to be used to record positive and negative ion mass spectra.
Since some sperm (glyco)lipids are characterized by the presence of sulfate residues which suppress
the detection of less acidic lipids in the negative ion mode, previous separation is often necessary.
It will be also emphasized that plasmalogens can be easily identified by either enzymatic digestion
or treatment with acids.
Conclusion:
MALDI MS is a reliable method to obtain sperm lipid fingerprints in a simple and convenient
way.
A binary matrix for the rapid detection and characterization of small-molecule cardiovascular drugs by MALDI-MS and MS/MS