02487nas a2200181   4500008004100000022001400041245009500055210006900150260007100219300001600290490000800306520178100314100002402095700002102119700001802140700001902158856012802177       2015                        eng d  a1520-610600aCosolvent effects on solute-solvent hydrogen-bond dynamics: ultrafast 2D IR investigations0 aCosolvent effects on solutesolvent hydrogenbond dynamics ultrafa  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcDEC  a15334-153430 v1193 a<p>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.</p>1 aKashid, Somnath, M.1 aJin, Geun, Young1 aBagchi, Sayan1 aKim, Yung, Sam  uhttps://library.ncl.res.in/content/cosolvent-effects-solute-solvent-hydrogen-bond-dynamics-ultrafast-2d-ir-investigations-001961nas a2200181   4500008004100000245013300041210006900174260000800243300001400251490000600265520127600271100002401547700002101571700002301592700001901615700001801634856012701652       2017                        eng d00aTwo-dimensional infrared spectroscopy reveals cosolvent-composition-dependent crossover in intermolecular hydrogen bond dynamics0 aTwodimensional infrared spectroscopy reveals cosolventcompositio  cAPR  a1604-16090 v83 aCosolvents have versatile composition-dependent applications in chemistry and biology. The simultaneous presence of hydrophobic and hydrophilic groups in dimethyl sulfoxide (DMSO), an industrially important amphiphilic cosolvent, when combined with the unique properties of water, plays key roles in the diverse fields of pharmacology, cryoprotection, and cell biology. Moreover, molecules dissolved in aqueous DMSO exhibit an anomalous concentration-dependent nonmonotonic behavior in stability and activity near a critical DMSO mole fraction of 0.15. An experimental identification of the origin of this anomaly can lead to newer chemical and biological applications. We report a direct spectroscopic observation of the anomalous behavior using ultrafast twodimensional infrared spectroscopy experiments. Our results demonstrate the cosolventconcentration-dependent nonmonotonicity arises from nonidentical mechanisms in ultrafast hydrogen-bond-exchange dynamics of water above and below the critical cosolvent concentration. Comparison of experimental and theoretical results provides a molecular-level mechanistic understanding: a distinct difference in the stabilization of the solute through dynamic solute solvent interactions is the key to the anomalous behavior.1 aKashid, Somnath, M.1 aJin, Geun, Young1 aChakrabarty, Suman1 aKim, Yung, Sam1 aBagchi, Sayan  uhttps://library.ncl.res.in/content/two-dimensional-infrared-spectroscopy-reveals-cosolvent-composition-dependent-crossover01542nas a2200217   4500008004100000245012100041210006900162260000800231300001400239490000600253520079700259100001601056700002101072700002301093700001601116700001701132700001501149700001801164700001901182856012301201       2018                        eng d00aInterconverting hydrogen-bonding and weak n -> pi* interactions in aqueous solution: A direct spectroscopic evidence0 aInterconverting hydrogenbonding and weak n pi interactions in aq  cSEP  a5425-54290 v93 a<p>Molecular structure and function depend on myriad noncovalent interactions. However, the weak and transient nature of noncovalent interactions in solution makes them challenging to study. Information on weak interactions is typically derived from theory and indirect structural data. Solvent fluctuations, not revealed by structure analysis, further complicate the study of these interactions. Using 2D infrared spectroscopy, we show that the strong hydrogen bond and the weak n -&gt; pi* interaction coexist and interconvert in aqueous solution. We found that the kinetics of these interconverting interactions becomes faster with increasing water content. This experimental observation provides a new perspective on the existence of weak noncovalent interactions in aqueous solution.</p>1 aDeb, Pranab1 aJin, Geun, Young1 aSingh, Santosh, K.1 aMoon, Juran1 aKwon, Hyejin1 aDas, Aloke1 aBagchi, Sayan1 aKim, Yung, Sam  uhttps://library.ncl.res.in/content/interconverting-hydrogen-bonding-and-weak-n-pi-interactions-aqueous-solution-direct