Volume 37, Issue 2 p. 191-196
Research Article

Uncoupled analysis of secondary and tertiary protein structure by circular dichroism and electrospray ionization mass spectrometry

Rita Grandori

Corresponding Author

Rita Grandori

Institute of Chemistry, Johannes Kepler University, Altenbergerstrasse 69, A-4040 Linz, Austria

Institute of Chemistry, Johannes Kepler University, Altenbergerstrasse 69, A-4040 Linz, Austria===Search for more papers by this author
Irena Matecko

Irena Matecko

Institute of Chemistry, Johannes Kepler University, Altenbergerstrasse 69, A-4040 Linz, Austria

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Norbert Müller

Norbert Müller

Institute of Chemistry, Johannes Kepler University, Altenbergerstrasse 69, A-4040 Linz, Austria

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First published: 21 December 2001
Citations: 38

Abstract

An Erratum has been published for this article in Journal of Mass Spectrometry 38 (3) 2003, 345.

Electrospray ionization mass spectrometry (ESI-MS) applied to protein conformational studies is a powerful new method that seems to provide specific information about protein tertiary structure. In this study, we analyzed the effect of trifluoroethanol (TFE) on a myoglobin peptide and cytochrome c (cyt c) at low pH by circular dichroism (CD) and ESI-MS. These experiments show that coil-to-helix transition per se does not affect ESI mass spectra, confirming that this technique is insensitive to the local conformation of the polypeptidic chain and, rather, reports on the tertiary contacts characterizing different protein conformations. This property makes ESI-MS an excellent method, complementary to CD, for the characterization of protein conformational changes. Fluorinated alcohols have been suggested to induce molten globule formation in acid-unfolded cyt c. The experiments described here show that TFE does not induce major changes in the ESI mass spectrum of cyt c at pH 2.2, indicating that no stabilization of compact, globular structures is detectable under the conditions employed. On the other hand, even low concentrations of TFE (2–5%) are shown to destabilize the folded state of the protein around the mid-point of its acid-induced unfolding transition. Copyright © 2001 John Wiley & Sons, Ltd.