Theoretical study of the gas-phase structures of sodiated and cesiated leucine and isoleucine: zwitterionic structure disfavored in kinetic method experiments

Rožman, Marko (2005) Theoretical study of the gas-phase structures of sodiated and cesiated leucine and isoleucine: zwitterionic structure disfavored in kinetic method experiments. Journal of Mass Spectrometry, 40 (10). pp. 1357-1361. ISSN 1076-5174

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Abstract

Themost stable charge-solvated (CS) and zwitterionic (ZW) structures of sodiated and cesiated leucine and isoleucine were studied by density functional theorymethods. According to the Boltzmann distribution in gas phase, both forms of LeuNa+ and IleNa+ exist, but in LeuCs+ and IleCs+, the ZW forms are dominant. Results for the sodiated compounds are consistentwith the relationship found between decrease in relative stability of CS versus ZW form and aliphatic amino acid side chain length. The observed degeneracy in energy for IleNa+ conformers is at odds with kinetic method results. Additional calculations showed that kinetic method structural determinations for IleNa+ do not reflect relative order of populations in the lowest energy conformers. Since complexation of cationized amino acids into ion-bound dimers disfavors ZW structure by ∼ 8 kJmol− 1, it is suggested that for energy close conformers of sodium-cationized amino acids, the kinetic method may not be reliable for structural determinations.

Item Type:	Article
Additional Information:	"This is the peer reviewed version of the following article: Rožman, Marko (2005) Theoretical study of the gas-phase structures of sodiated and cesiated leucine and isoleucine: zwitterionic structure disfavored in kinetic method experiments. Journal of Mass Spectrometry, 40 (10). pp. 1357-1361, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/jms.926/full . This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."
Uncontrolled Keywords:	leucine; isoleucine; alkali metals; gas-phase structure; density functional theory; kinetic method
Subjects:	NATURAL SCIENCES > Chemistry
Divisions:	Division of Physical Chemistry
Depositing User:	Kristina Ciglar
Date Deposited:	20 Jan 2017 13:39
URI:	http://fulir.irb.hr/id/eprint/3335
DOI:	10.1002/jms.926

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