Gas phase hydrogen deuterium exchange reactions of a model peptide: FT-ICR and computational analyses of metal induced conformational mutations

Abstract

We utilized gas phase hydrogen/deuterium (H/D) exchange reactions and ab initio calculations to investigate the complexation between a model peptide (Arg-Gly-Asp[triple bond]RGD) with various alkali metal ions. The peptide conformation is drastically altered upon alkali metal ion complexation. The associated conformational changes depend on both the number and type of complexing alkali metal ions. Sodium has a smaller ionic diameter and prefers a multidentate interaction that involves all three amino acids of the peptide. Conversely, potassium and cesium form different types of complexes with the RGD. The [RGD + 2Cs - H]+ species exhibit the slowest H/D exchange reactivity (reaction rate constant of approximately 6 x 10(-13) cm3molecule(-1)s(-1) for the fastest exchanging labile hydrogen with ND3). The reaction rate constant of the protonated RGD is two orders of magnitude faster than that of the [RGD + 2Cs - H]+. Addition of the first cesium to the RGD reduces the H/D exchange reaction rate constant (i.e., D0) by a factor of seven whereas sodium reduces this value by a factor of thirty. Conversely, addition of the second alkali metal ions has the opposite effect; the rate of D0 disappearance for all [RGD + 2Met - H]+ species (Met[triple bond]Na, K, and Cs) decreases with the alkali metal ion size.

Bimolecular and unimolecular contributions to the disparate self-chemical ionizations of α-Pinene and camphene isomers

“…All experiments were performed on a 7-T FT-ICR mass spectrometer (IonSpec Corporation, Forest Lake, CA) in the internal ion generation mode [19]. The previous GC/FT-ICR MS studies were performed at 24 eV electron energy to eliminate ionization of the helium carrier gas [1].…”

A preconcentrator coupled to a GC/FTMS: Advantages of self-chemical ionization, mass measurement accuracy, and high mass resolving power for GC applications

“…To investigate self-chemical ionization characteristics of terpene isomers, controlled ion-molecule reactions were performed on a different FT-ICR MS system. This system shared a common 7 T magnet with the GC/FT-ICR and was equipped with internal electron impact ionization source as well as a pulsed-leak valve sample introduction system [48].…”

“…Controlled ion-molecule experiments, using a pulsed-leak valve sample introduction system [48], were performed to determine the factors giving rise to the different SCI patterns of camphene and ␣-pinene. Preliminary results were presented [55] and full details and results will be published in the near future.…”

Further studies on the origins of asymmetric charge partitioning in protein homodimers

“…In contrast, mass spectrometry requires little sample, and with electrospray ionization (ESI) or soft laser desorption/ionization (John Fenn and Kiochi Tanaka 2002 in chemistry), a wide variety of biomolecules and specific complexes can be introduced into a mass spectrometer. A number of methods have been developed to probe the general three-dimensional shapes of biomolecule ions and noncovalent complexes using the techniques of ion mobility [1][2][3][4][5][6][7][8], H/D exchange both in solution [9,10] and the gas phase [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], and proton-transfer reactivity [29,30].…”

“…Although gas-phase H/D exchange has been used extensively to characterize peptides and small molecules [11][12][13][14][15][16][17][18][19][20][21], and the structure of some gas-phase proteins [22][23][24], very little work has been done with noncovalent complexes involving biological ions, and this noncovalent work has focused on peptide dimers [25,26] and peptide complexes with metal ions [16,18,21,27] and small molecules [15,28].…”