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Quantitation of cardioexcitatory Asn‐ D ‐Trp‐Phe‐NH 2 diastereomers in Aplysia 's central nervous system by nanoscale liquid chromatography‐tandem mass spectrometry
Author(s) -
Song Yaru,
Liu YiMing
Publication year - 2008
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/jms.1408
Subject(s) - chemistry , diastereomer , aplysia , chromatography , tandem mass spectrometry , formic acid , liquid chromatography–mass spectrometry , enantiomer , mass spectrometry , stereochemistry , evolutionary biology , biology
Abstract A tripeptide, Asn‐ D ‐Trp‐Phe‐NH 2 (NdWFa) that contains a D ‐amino acid residue (i.e. D ‐tryptophan) was previously identified in Aplysia 's central nervous system (CNS) and found to be cadioexcitatory. However, the occurrence of its diastereomers including NWFa, theoretically the precursor of NdWFa, remains largely unknown. In this work, a nanoscale liquid chromatographic/tandem mass spectrometric (nano‐LC‐MS/MS) method was developed for a sensitive determination of the diastereomers of NWFa. Resolution of the diastereomers including NWFa, NdWFa, NWdFa, and dNWFa was achieved on capillary columns packed with C 18 silica particles with an MS detection‐friendly mobile phase consisting of water, acetonitrile, and formic acid. Columns of different internal diameters (IDs) ranging from 75 to 250 µm were evaluated to achieve the best sensitivity. With the use of a 75 µm ID column integrated with a nanoelectrospray emitter, the method had limits of detection (LOD) of 0.21 n M (or 0.49 pg on column, 5 µl injected) NdWFa in tissue homogenate (S/N = 3). The five major ganglia in Aplysia californica 's CNS (i.e. buccal, cerebral, abdominal, plural, and pedal) were analyzed. NdWFa was detected only in abdominal ganglion at the ng/g tissue level. Further, its diastereomer, NWFa, was also detected for the first time and also only in abdominal ganglion at a significantly lower level. The levels of both NWFa and NdWFa varied from animal to animal in the range from 0 to 81 ng/g tissue. Copyright © 2008 John Wiley & Sons, Ltd.