01365nas a2200205   4500008004100000022001400041245006300055210006300118260000800181300001400189490000800203520073300211100002400944700002100968700001700989700001901006700002101025700001801046856009501064       2019                        eng d  a1520-610600aArresting an unusual amide tautomer using divalent cations0 aArresting an unusual amide tautomer using divalent cations  cOCT  a8419-84240 v1233 a<p>Ion-specific effects on peptides and proteins are key to biomolecular structure and stability. The subtle roles of the cations are far less understood, compared to the pronounced effects of the anions on proteins. Most importantly, divalent cations such as Ca2+ and Mg2+ are crucial to several biological functions. Herein, we demonstrate that an amide-iminolate equilibrium is triggered by the binding of the divalent cations to the amide oxygen in aqueous solution. The excellent agreement between the experimental and theoretical results confirms the arrest of an unusual amide tautomer by the divalent cations, which is a rarely known phenomenon that might open up an array of applications in chemistry and biology.</p>
1 aKashid, Somnath, M.1 aSingh, Reman, K.1 aKwon, Hyejin1 aKim, Yung, Sam1 aMukherjee, Arnab1 aBagchi, Sayan  uhttps://library.ncl.res.in/content/arresting-unusual-amide-tautomer-using-divalent-cations02349nas a2200217   4500008004100000022001400041245008500055210006900140260000800209300001200217490000800229520163400237100001901871700002301890700002301913700002701936700001701963700001901980700001801999856011402017       2022                        eng d  a1520-610600aAssociation-dissociation dynamics of ionic electrolytes in low dielectric medium0 aAssociationdissociation dynamics of ionic electrolytes in low di  cJAN  a239-2480 v1263 a<p>
	Ionic electrolytes are known to form various complexes which exist in dynamic equilibrium in a low dielectric medium. However, structural characterization of these complexes has always posed a great challenge to the scientific community. An additional challenge is the estimation of the dynamic association-dissociation time scales (lifetime of the complexes), which are key to the fundamental understanding of ion transport. In this work, we have used a combination of infrared absorption spectroscopy, two-dimensional infrared spectroscopy, molecular dynamics simulations, and density functional theory calculations to characterize the various ion complexes formed by the thiocyanate-based ionic electrolytes as a function of different cations in a low dielectric medium. Our results demonstrate that thiocyanate is an excellent vibrational reporter of the heterogeneous ion complexes undergoing association-dissociation dynamics. We find that the ionic electrolytes exist as contact ion pairs, dimers, and clusters in a low dielectric medium. The relative ratios of the various ion complexes are sensitive to the cations. In addition to the interactions between the thiocyanate anion and the countercation, the solute-solvent interactions drive the dynamic equilibrium. We have estimated the association-dissociation dynamics time scales from two-dimensional infrared spectroscopy. The exchange time scale involving the cluster is faster than that between a dimer and an ion pair. Moreover, we find that the dynamic equilibrium between the cluster and another ion complex is correlated to the solvent fluctuations.</p>
1 aGhosh, Deborin1 aSakpal, Sushil, S.1 aChatterjee, Srijan1 aDeshmukh, Samadhan, H.1 aKwon, Hyejin1 aKim, Yung, Sam1 aBagchi, Sayan  uhttps://library.ncl.res.in/content/association-dissociation-dynamics-ionic-electrolytes-low-dielectric-medium