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Stability of secondary structural elements in a solvent-free environment. II: the beta-pleated sheets.

Authors
  • Li, A1
  • Fenselau, C
  • Kaltashov, I A
  • 1 Department of Chemistry and Biochemistry, University of Maryland Baltimore County, Baltimore, USA.
Type
Published Article
Journal
Proteins: Structure, Function, and Bioinformatics
Publisher
Wiley
Publication Date
Jan 01, 1998
Volume
Suppl 2
Pages
22–27
Identifiers
PMID: 9849907
Source
Medline
License
Unknown

Abstract

The stability of single beta-strands and multistrand beta-pleated sheets as elements of secondary structure is examined in the absence of intermolecular interactions. Such experimental conditions (e.g., complete removal of solvent molecules and counterions) are achieved by placing the peptide ions in the gas phase. The metastable multiply- charged peptide ions produced by electrospray ionization undergo unimolecular dissociation. Intercharge repulsion within the precursor ions gives rise to the elevated kinetic energy of fragment ions, which is measured using Mass-analyzed Ion Kinetic Energy (MIKE) spectrometry. Intercharge distances calculated based on these measurements are compared to the numbers derived from molecular mechanics calculations with charge site assignments based on relative proton affinities. Evidence is presented suggesting that single beta-strands form collapsed structures in the absence of solvents, while multistrand beta-pleated sheets are likely to retain "native-like" secondary structures under the same conditions. These results indicate that intramolecular hydrogen bonds are the major factor determining the three-dimensional arrangements of polypeptides in the gas phase, compensating both long- and short-range electrostatic repulsions. This is in good agreement with our earlier findings (Proteins 27:165170, 1997) concerning stability of helical conformation of melittin in the absence of solvent.

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