Microscale sample deposition onto hydrophobic target plates for trace level detection of neuropeptides in brain tissue by MALDI-MS

✍ Scribed by Hui Wei; Stacey L. Dean; Mark C. Parkin; Kerstin Nolkrantz; James P. O'Callaghan; Robert T. Kennedy

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 549 KB
• Volume: 40
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/jms.916

✦ Synopsis

Abstract

A sample preparation method that combines a modified target plate with a nanoscale reversed‐phase column (nanocolumn) was developed for detection of neuropeptides by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS). A gold‐coated MALDI plate was modified with an octadecanethiol (ODT) self‐assembled monolayer to create a hydrophobic surface that could concentrate peptide samples into a ∼200–500‐µm diameter spot. The spot sizes generated were comparable to those obtained for a substrate patterned with 200‐µm hydrophilic spots on a hydrophobic substrate. The sample spots on the ODT‐coated plate were 100‐fold smaller than those formed on an unmodified gold plate with a 1‐µl sample and generated 10 to 50 times higher mass sensitivity for peptide standards by MALDI‐TOF MS. When the sample was deposited on an ODT‐modified plate from a nanocolumn, the detection limit for peptides was as low as 20 pM for 5‐µl samples corresponding to 80 amol deposited. This technique was used to analyze extracts of microwave‐fixed tissue from rat brain striatum. Ninety‐eight putative peptides were detected including several that had masses matching neuropeptides expected in this brain region such as substance P, rimorphin, and neurotensin. Twenty‐three peptides had masses that matched peaks detected by capillary liquid chromatography with electrospray ionization MS.1, 2 Copyright © 2005 John Wiley & Sons, Ltd.