Azido-derivatized compounds as IR probes of local electrostatic environment: Theoretical studies

Jun H. Choi, Kwang I. Oh, Minhaeng Cho

Research output: Contribution to journalArticle

61 Citations (Scopus)

Abstract

A variety of spectroscopic probe molecules have been used to study the local electrostatic environment in proteins. Particularly, a few IR probes such as nitrile- and thiocyanate-derivatized amino acids were found to be quite useful not just because they are small but also because their IR absorption frequencies strongly depend on the strengths of hydrogen bonds with the surrounding protic solvent molecules. Recently, we experimentally demonstrated that azido-derivatized alanine is an excellent IR probe for studying structural change in protein in solution. The asymmetric stretching mode frequency of CN3 -group becomes blueshifted when it is dissolved in water. Such a blueshifting behavior upon hydrogen-bonding interaction with protic solvent molecules was commonly found in other IR probes containing a triple bond such as CN and SCN groups. In this paper, theoretical descriptions on the solvatochromic frequency shift and fluctuation of the azido stretch frequency are presented by carrying out ab initio calculations and both classical and quantum mechanical/molecular mechanical dynamics simulation studies for azidomethane and azidoalanine dipeptide dissolved in water. Two different methods developed here are based on the distributed multipole interaction models, and they are shown to be useful to describe site-specific hydrogen-bonding interaction-induced red- or blueshift of the azido stretch frequency. To test the validity of thus obtained interpolation formula, numerically simulated IR spectra of azidomethane and azidoalanine dipeptide in water are directly compared with experimental results. We anticipate that the present theoretical approaches will be of use in connecting experimentally measured azido stretch frequency to conformational change in protein containing this azido-derivatized alanine residue.

Original languageEnglish
Article number174512
JournalJournal of Chemical Physics
Volume129
Issue number17
DOIs
Publication statusPublished - 2008 Nov 17

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Static Electricity
Electrostatics
Theoretical Models
Dipeptides
Hydrogen Bonding
electrostatics
Alanine
Hydrogen bonds
Water
probes
Molecules
alanine
Nitriles
Proteins
proteins
Molecular Dynamics Simulation
Hydrogen
water
molecules
Stretching

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Medicine(all)
  • Physics and Astronomy(all)

Cite this

Azido-derivatized compounds as IR probes of local electrostatic environment : Theoretical studies. / Choi, Jun H.; Oh, Kwang I.; Cho, Minhaeng.

In: Journal of Chemical Physics, Vol. 129, No. 17, 174512, 17.11.2008.

Research output: Contribution to journalArticle

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