PII S0196-9781(97)00471-3 REVIEW Mass Spectrometry of Peptides in Neuroscience CAROL L. NILSSON, GO ¨ STA KARLSSON, JONAS BERGQUIST, ANN WESTMAN AND ROLF EKMAN 1 Institute of Clinical Neuroscience, Department of Psychiatry and Neurochemistry, Go ¨teborg University, Sahlgrenska University Hospital/Mo ¨lndal, S-431 80 Mo ¨lndal, Sweden Received 2 September 1997; Accepted 21 November 1997 NILSSON, C. L., G. KARLSSON, J. BERGQUIST, A. WESTMAN AND R. EKMAN. Mass spectrometry of peptides in neuroscience. PEPTIDES, 19(4) 781–789, 1998.—This review focuses on the contributions of modern mass spectrometry to neuropeptide research. An introduction to newer mass spectrometric techniques is provided. Also, the use of mass spectrometry in combination with high-resolution separation techniques for neuropeptide identification in biological samples is illustrated. The amino acid sequence information that is important for the identification and analysis of known, novel, or chemically modified neuropeptides may be obtained using mass spectrometric techniques. Because mass spectrometry techniques can be used to reflect the dynamic properties associated with neuropeptide processing in biological systems, they may be used in the future to monitor peptide profiles within organisms in response to environmental challenges such as disease and stress. © 1998 Elsevier Science Inc. Neuropeptides Electrospray ionization mass spectrometry Matrix-assisted laser desorption/ionization mass spectrometry FOR nearly 40 years, immunoassays have been used for studying biomolecules in human tissues and body fluids. Although bioassay and radioreceptor assay have been used extensively, the method of choice for quantifying peptides during the last three decades has been radioimmunoassay (RIA; Reference 13). Unfortunately, the specificity of RIA measurements is often low due to the presence of cross- reactive substances in biological samples. Hence, the inher- ent heterogeneity of peptides found in biological systems, because of truncation, deamidation, oxidation, and many other modifications, raises problems in the interpretation of the results obtained through RIA. The non-specific binding of molecules that block the antigenic sites of the antibody or destroy the tracer is also a source of experimental error (15,46). The separation of biological extracts by reverse- phase high-performance liquid chromatography (RP-HPLC) improves the specificity of RIA. However, the retention time in RP-HPLC is not unique, and thus a complete picture of the processing and chemical modifications of neuropep- tides may not be obtained (45). Modern mass spectrometry permits the acquisition of information about the intact mo- lecular mass and amino acid sequence of biomolecules. In combination with RP-HPLC and RIA, more complete mo- lecular information is possible to obtain than by using either one of these methods alone (19). In the past, mass spectrometers have been very expen- sive, technically advanced, and therefore often difficult for laboratory personnel other than mass spectrometrists to uti- lize. Also, the sensitivity of older instruments was insuffi- cient for most biological tasks. In the last five years, a rapid increase in the use of mass spectrometry in the biological sciences has taken place (17). This increase is mainly due to the introduction of two new mass spectrometry techniques, which has made it possible to detect biomolecules with molecular weights up to 500,000. These techniques, elec- trospray ionization (ESI-MS) and matrix-assisted laser de- sorption/ionization mass spectrometry (MALDI-MS) can both provide sensitive and rapid analysis techniques of peptides and proteins (24,31,41,48,50). Shortly after the introduction of ESI-MS and MALDI- 1 Requests for reprints should be addressed to Prof. Rolf Ekman. E-mail: rolf.ekman@ms.se Peptides, Vol. 19, No. 4, pp. 781–789, 1998 Copyright © 1998 Elsevier Science Inc. Printed in the USA. All rights reserved 0196-9781/98 $19.00 + .00 781