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Kim, Yung Sam
Ultrafast 2D IR Spectroscopy Lab
Research Interests
  • 2D IR, chemical exchange of H-bond, fast reaction dynamics, protein dynamics

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Cosolvent Effects on Solute-Solvent Hydrogen-Bond Dynamics: Ultrafast 2D IR Investigations

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Title
Cosolvent Effects on Solute-Solvent Hydrogen-Bond Dynamics: Ultrafast 2D IR Investigations
Author
Kashid, Somnath M.Jin, Geun YoungBagchi, SayanKim, Yung Sam
Issue Date
2015-11
Publisher
AMER CHEMICAL SOC
Citation
JOURNAL OF PHYSICAL CHEMISTRY B, v.119, no.49, pp.15334 - 15343
Abstract
Cosolvents strongly influence the solute-solvent interactions of biomolecules in aqueous environments and have profound effects on the stability and activity of several proteins and enzymes. Experimental studies have previously reported on the hydrogen-bond dynamics of water molecules in the presence of a cosolvent, but understanding the effects from a solute's perspective could provide greater insight into protein stability. Because carbonyl groups are abundant in biomolecules, the current study used 2D IR spectroscopy and molecular dynamics simulations to compare the hydrogen-bond dynamics of the solute's carbonyl group in aqueous solution, with and without the presence of DMSO as a cosolvent. 2D IR spectroscopy was used to quantitatively estimate the time scales of the hydrogen-bond dynamics of the carbonyl group in neat water and 1:1 DMSO/water solution. The 2D IR results show spectral signatures of a chemical exchange process: The presence of the cosolvent was found to lower the hydrogen-bond exchange rate by a factor of 5. The measured exchange rates were 7.50 X 10(11) and 1.48 X 10(11) s(-1) in neat water and 1:1 DMSO/water, respectively. Molecular dynamics simulations predict a significantly shorter carbonyl hydrogen-bond lifetime in neat water than in 1:1 DMSO/water and provide molecular insights into the exchange mechanism. The binding of the cosolvent to the solute was found to be accompanied by the release of hydrogen-bonded water molecules to the bulk. The widely different hydrogen-bond lifetimes and exchange rates with and without DMSO indicate a significant change in the ultrafast hydrogen-bond dynamics in the presence of a cosolvent, which, in turn, might play an important role in the stability and activity of biomolecules.
URI
https://scholarworks.unist.ac.kr/handle/201301/17998
URL
http://pubs.acs.org/doi/10.1021/acs.jpcb.5b08643
DOI
10.1021/acs.jpcb.5b08643
ISSN
1520-6106
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CHM_Journal Papers
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