Coordination of Trivalent Metal Cations to Peptides: Results from IRMPD Spectroscopy and Theory

TitleCoordination of Trivalent Metal Cations to Peptides: Results from IRMPD Spectroscopy and Theory
Publication TypeJournal Article
Year of Publication2010
AuthorsJ.S Prell, T.G Flick, J. Oomens, G. Berden, E.R Williams
JournalJournal of Physical Chemistry A
Volume114
Number2
Pagination854-860
Date PublishedJan
Type of ArticleArticle
ISBN Number1089-5639
Accession NumberISI:000273400600021
Keywordsaction spectroscopy, AMINO-ACIDS, GAS-PHASE CONFORMATION, infrared, LANTHANIDE ION-BINDING, LUMINESCENCE SPECTROSCOPY, PHOTON DISSOCIATION SPECTROSCOPY, PROTONATED PEPTIDES, SALT BRIDGE STRUCTURES, vibrational spectroscopy, ZWITTERION STABILIZATION
Abstract

Structures of trivalent lanthanide metal cations La3+, Ho3+, and Eu3+ with deprotonated Ala(n) (n = 2-5) or Leu-enk (Tyr-Gly-Gly-Phe-Leu) are investigated with infrared multiple photon dissociation (IRMPD) spectroscopy between 900 and 1850 cm(-1) and theory. In all of these complexes, a salt bridge is formed in which the metal cation coordinates to the carboxylate group of the peptide, resulting in a limited conformational space and many sharp IRMPD spectral bands. The IRMPD spectra clearly indicate that all carbonyl groups solvate the metal cation in each of the Ala(n) complexes. Due to strong vibrational coupling between the carbonyl groups, a sharp, high-energy amide I band due to in-phase stretching of all of the amide carbonyl groups bound to the metal cation is observed that is separated by similar to 50 cm(-1) from a strong, lower-energy amide I band. This extent of carbonyl coupling, which is sometimes observed in condensed-phase peptide and protein IR spectroscopy, has not been reported in IRMPD spectroscopy studies of other cationized peptide complexes. Intense bands due to carbonyl groups not associated with the metal cation are observed for Leu-enk complexes, indicating that a side chain group, such as the Tyr or Phe aromatic ring, prevents complete carbonyl coordination of the metal cation. Substitution of smaller lanthanide cations for La3+ in these peptide complexes results only in minor structural changes consistent with the change in metal cation size. These are the first IRMPD spectra reported for lanthanide metal cationized peptides, and comparison to previously reported protonated and alkali metal or alkaline earth metal cationized peptide complexes reveals many trends consistent with the higher charge state of the lanthanide cations.

URL<Go to ISI>://000273400600021
Division

GUTHz

Department

Molecular Dynamics

PID

7f1d70764d7a03b668192fb16a39cc84

Alternate TitleJ. Phys. Chem. A

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