Enhanced neuropeptide profiling via capillary electrophoresis off-line coupled with MALDI FTMS

Anal Chem. 2008 Aug 15;80(16):6168-77. doi: 10.1021/ac800382t. Epub 2008 Jul 22.

Abstract

An off-line interface incorporating sheathless flow and counter-flow balance is developed to couple capillary electrophoresis (CE) to matrix-assisted laser desorption ionization Fourier transform mass spectrometry (MALDI FTMS) for neuropeptide analysis of complex tissue samples. The new interface provides excellent performance due to the integration of three aspects: (1) A porous polymer joint constructed near the capillary outlet for the electrical circuit completion has simplified the CE interface by eliminating a coaxial sheath liquid and enables independent optimization of separation and deposition. (2) The electroosmotic flow at reversed polarity (negative) mode CE is balanced and reversed by a pressure-initiated capillary siphoning (PICS) phenomenon, which offers improved CE resolution and simultaneously generates a low flow (<100 nL/min) for fraction collection. (3) The predeposited nanoliter volume 2,5-dihydroxybenzoic acid (DHB) spots on a Parafilm-coated MALDI sample plate offers an improved substrate for effective effluent enrichment. Compared with direct MALDI MS analysis, CE separation followed by MALDI MS detection consumes nearly 10-fold less sample (50 nL) while exhibiting 5-10-fold enhancement in S/N ratio that yields the limit of detection down to 1.5 nM, or 75 attomoles. This improvement in sensitivity allows 230 peaks detected in crude extracts from only a few pooled neuronal tissues and increases the number of identified peptides from 19 to 43 (Cancer borealis pericardial organs (n = 4)) in a single analysis. In addition, via the characteristic migration behaviors in CE, some specific structural and chemical information of the neuropeptides such as post-translational modifications and family variations has been visualized, making the off-line CE-MALDI MS a promising strategy for enhanced neuropeptidomic profiling.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Brachyura / physiology
  • Cellulose / analogs & derivatives
  • Cellulose / chemistry
  • Electrophoresis, Capillary / instrumentation*
  • Fourier Analysis*
  • Insect Proteins / chemistry*
  • Neuropeptides / analysis*
  • Pericardium / cytology
  • Sensitivity and Specificity
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / methods*

Substances

  • Insect Proteins
  • Neuropeptides
  • acetylcellulose
  • Cellulose