02097nas a2200229 4500008004100000022001400041245015800055210006900213260000800282300001400290490000800304520125600312100002301568700001901591700001801610700001601628700002301644700002701667700002401694700001801718856013101736 2019 eng d a1520-610600aHydrocarbon chain-length dependence of solvation dynamics in alcohol-based deep eutectic solvents: a two-dimensional infrared spectroscopic investigation0 aHydrocarbon chainlength dependence of solvation dynamics in alco cNOV a9355-93630 v1233 a

Deep eutectic solvents (DESs) have gained popularity in recent years as an environmentally benign, inexpensive alternative to organic solvents for diverse applications in chemistry and biology. Among them, alcohol-based DESs serve as useful media in various applications due to their significantly low viscosity as compared to other DESs. Despite their importance as media, little is known how their solvation dynamics change as a function of the hydrocarbon chain length of the alcohol constituent. In order to obtain insights into the chain-length dependence of the solvation dynamics, we have performed two-dimensional infrared spectroscopy on three alcohol-based DESs by systematically varying the hydrocarbon chain length. The results reveal that the solvent dynamics slows down monotonically with an increase in the chain length. This increase in the dynamic timescales also shows a strong correlation with the concomitant increase in the viscosity of DESs. In addition, we have performed molecular dynamics simulations to compare with the experimental results, thereby testing the capacity of simulations to determine the amplitudes and timescales of the structural fluctuations on fast timescales under thermal equilibrium conditions.

1 aChatterjee, Srijan1 aGhosh, Deborin1 aHaldar, Tapas1 aDeb, Pranab1 aSakpal, Sushil, S.1 aDeshmukh, Samadhan, H.1 aKashid, Somnath, M.1 aBagchi, Sayan uhttps://library.ncl.res.in/content/hydrocarbon-chain-length-dependence-solvation-dynamics-alcohol-based-deep-eutectic-solvents02238nas a2200181 4500008004100000022001400041245012800055210006900183260000900252300001400261490000800275520156400283100002301847700001801870700001901888700001801907856013101925 2020 eng d a1520-610600aElectrostatic manifestation of micro-heterogeneous solvation structures in deep-eutectic solvents: a spectroscopic approach0 aElectrostatic manifestation of microheterogeneous solvation stru cMAY  a3709-37150 v1243 a

Deep eutectic solvents have emerged as inexpensive green alternatives to conventional solvents for diverse applications in chemistry and biology. Despite their importance as useful media in various applications, little is known about the microscopic solvation structures of deep eutectic solvents around solutes. Herein, we show that the electrostatic field, which can be estimated both from infrared experiments and theory, can act as a unified concept to report on the microscopic heterogeneous solvation of deep eutectic solvents. Using a fluorophore containing the carbonyl moiety as the solute and the electrostatic field as a descriptor of the solvation structure of the deep eutectic solvents, we report the residue-specific distribution, orientation, and hydrogen bonding in deep eutectic solvents constituting of choline chloride and alcohols of varying chain-lengths. We observe that an increase in alcohol chain-length not only affects the alcohol's propensity to form hydrogen bond to the solute but also alters the spatial arrangement of choline cations around the solute, thereby leading to a microheterogeneity in the solvation structure. Moreover, to extend our electrostatic field based strategy to other deep eutectic solvents, we report an emission spectroscopy based method. We show that this method can be applied, in general, to all deep eutectic solvents, irrespective of their constituents. Overall, this work integrates experiments with molecular dynamics simulations to provide insights into the heterogeneous DES solvation.

1 aChatterjee, Srijan1 aHaldar, Tapas1 aGhosh, Deborin1 aBagchi, Sayan uhttps://library.ncl.res.in/content/electrostatic-manifestation-micro-heterogeneous-solvation-structures-deep-eutectic-solvents01987nas a2200193 4500008004100000022001400041245008500055210006900140260000800209300001400217490000800231520133800239100002301577700001901600700002201619700001901641700001801660856011501678 2021 eng d a1520-610600aCurious case of aqueous warfarin: structural isomers or distinct excited states?0 aCurious case of aqueous warfarin structural isomers or distinct  cMAR a2871-28780 v1253 a

Warfarin is a potent anti-coagulant drug and is on the World Health Organization's List of Essential Medicines. Additionally, it displays fluorescence enhancement upon binding to human serum albumin, making warfarin a prototype fluorescent probe in biology. Despite its biological significance, the current structural assignment of warfarin in aqueous solution is based on indirect evidence in organic solvents. Warfarin is known to exist in different isomeric forms-open-chain, hemiketal, and anionic forms-based on the solvent and pH. Moreover, warfarin displays a dual absorption feature in several solvents, which has been employed to study the ring-chain isomerism between its open-chain and hemiketal isomers. In this study, our pH-dependent experiments on warfarin and structurally constrained warfarin derivatives in aqueous solution demonstrate that the structural assignment of warfarin solely on the basis of its absorption spectrum is erroneous. Using a combination of steady-state and time-resolved spectroscopic experiments, along with quantum chemical calculations, we assign the observed dual absorption to two distinct pi ->pi* transitions in the 4-hydroxycoumarin moiety of warfarin. Furthermore, we unambiguously identify the isomeric form of warfarin that binds to human serum albumin in aqueous buffer.

1 aSakpal, Sushil, S.1 aGhosh, Deborin1 aManae, Meghna, A.1 aHazra, Anirban1 aBagchi, Sayan uhttps://library.ncl.res.in/content/curious-case-aqueous-warfarin-structural-isomers-or-distinct-excited-states01633nas a2200193 4500008004100000022001400041245011200055210006900167260000800236300001400244490000700258520093500265100002301200700002701223700002301250700001901273700001801292856012901310 2021 eng d a1948-718500aTransition of a deep eutectic solution to aqueous solution: a dynamical perspective of the dissolved solute0 aTransition of a deep eutectic solution to aqueous solution a dyn cSEP a8784-87890 v123 aDisruption of the deep eutectic solvent (DES) nanostructure around the dissolved solute upon addition of water is investigated by polarization-selective two-dimensional infrared spectroscopy and molecular dynamics simulations. The heterogeneous DES nanostructure around the solute is partially retained up to 41 wt % of added water, although water molecules are gradually incorporated in the solute's solvation shell even at lower hydration levels. Beyond 41 wt %, the solute is observed to be preferentially solvated by water. This composition denotes the upper hydration limit of the deep eutectic solvent above which the solute senses an aqueous solvation environment. Interestingly, our results indicate that the transition from a deep eutectic solvation environment to an aqueous one around the dissolved solute can happen at a hydration level lower than that reported for the ``water in DES'' to ``DES in water'' transition.1 aSakpal, Sushil, S.1 aDeshmukh, Samadhan, H.1 aChatterjee, Srijan1 aGhosh, Deborin1 aBagchi, Sayan uhttps://library.ncl.res.in/content/transition-deep-eutectic-solution-aqueous-solution-dynamical-perspective-dissolved-solute02349nas 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

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.

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-medium01877nas a2200181 4500008004100000022001400041245012300055210006900178260000900247300001400256490000700270520120100277100002701478700002301505700001901528700001801547856013001565 2022 eng d a1948-718500aLigand dynamics time scales identify the surface-ligandinteractions in thiocyanate-capped cadmium sulfide nanocrystals0 aLigand dynamics time scales identify the surfaceligandinteractio cAPR  a3059-30650 v133 a

The nanocrystal surface, which acts as an interface between thesemiconductor lattice and the capping ligands, plays a significant role in theattractive photophysical properties of semiconductor nanocrystals for use in awide range of applications. Replacing the long-chain organic ligands with shortinorganic variants improves the conductivity and carrier mobility of nanocrystal-based devices. However, our current understanding of the interactions betweenthe inorganic ligands and the nanocrystals is obscure due to the lack ofexperiments to directly probe the inorganic ligands. Herein, using two-dimensional infrared spectroscopy, we show that the variations in the inorganicligand dynamics within the heterogeneous nanocrystal ensemble can identifythe diversities in the inorganic ligand-nanocrystal interactions. The liganddynamics time scale in SCN-capped CdS nanocrystals identifies three distinctligand populations and provides molecular insight into the nanocrystal surface.Our results demonstrate that the SCN-ligands engage in a dynamic equilibriumand stabilize the nanocrystals by neutralizing the surface charges through both direct binding and electrostatic interaction.

1 aDeshmukh, Samadhan, H.1 aChatterjee, Srijan1 aGhosh, Deborin1 aBagchi, Sayan uhttps://library.ncl.res.in/content/ligand-dynamics-time-scales-identify-surface-ligandinteractions-thiocyanate-capped-cadmium02446nas a2200277 4500008004100000022001400041245017700055210006900232260000800301300001100309490000900320520145300329653001601782653002201798653002201820653002101842653002101863100002801884700001901912700001801931700001801949700002501967700001901992700002702011856013002038 2023 eng d a0022-286000aInteractive study of Au-20 nanocluster and methyl substituted amide linked tyrosine/tryptophan to develop representative model for studying protein-nanoparticle interaction0 aInteractive study of Au20 nanocluster and methyl substituted ami cJAN a1341770 v12723 a

Investigations on UV-vis, steady-state fluorescence and synchronous fluorescence properties of human hemoglobin (HHb) reveals greater spectral shifts in peaks arising due to alterations in microenvironment of Tyr-compared to Trp-during interactions with gold nanoparticle (GNP). Besides, interactions of Au-20 nanocluster with modified Tyr/Trp (possessing methyl substituted amide bonds) by quantum chemical calculations demonstrate significant role of amide bonds and the spectral shift, binding energy and alteration in bond distances appear to be higher for modified Tyr-compared to modified Trp. Moreover, close resemblance of frequency shift of modified Tyr/Trp-in presence of Au 20 is observed with respect to the experimental FT-IR study of HHb upon interaction with GNP, suggesting participation of amide bonds in both cases. Furthermore, CD DFT calculations using optimized helical stretch of HHbin presence of Au-20 and experimental CD results of HHb in presence of GNP further indicate participation amide bonds and biocompatibility of GNP. Apparently, the theoretical and experimental interactions are going in good agreement with each other. Overall, the study of interactions of modified Tyr/Trp-as representative models of protein microenvironment and Au-20 nanocluster as prototype of GNP to develop models for exploring protein nanoparticle interactions has been highlighted. (C) 2022 Elsevier B.V. All rights reserved.

10aamide bonds10aAu-20 nanocluster10aGold nanoparticle10aHuman hemoglobin10aModified Tyr/Trp1 aBanerjee, Nineesha, Sen1 aGhosh, Deborin1 aMitra, Ishani1 aPaul, Somnath1 aShow, Bibhutibhushan1 aGanguly, Tapan1 aChakraborty, Madhurima uhttps://library.ncl.res.in/content/interactive-study-au-20-nanocluster-and-methyl-substituted-amide-linked-tyrosinetryptophan01962nas a2200265 4500008004100000022001400041245016500055210006900220260000800289300001100297490000900308520103100317653000901348653002101357653002501378653002801403653001001431653001001441100002701451700002801478700001901506700002801525700001901553856012401572 2025 eng d a2210-271X00aRevealing the functional importance of tyrosine and tryptophan of human hemoglobin for development of structural templates representing protein microenvironment0 aRevealing the functional importance of tyrosine and tryptophan o cDEC a1154830 v12543 a

Microenvironment surrounding Tyrosine (Tyr) / Tryptophan (Trp) and heme appear to characterize the UV-vis absorption spectra of human hemoglobin (HHb). Structural elucidation of HHb using multiple tools, that may contribute to its spectral properties, then indicate greater structural stability of subunit A and the significance of its heme, Tyr42 and Trp14. Mutagenesis of Tyr42 and Trp14 of subunit A to Glycine (Gly) further validate their contribution in determining the structural stability, physicochemical properties, functional properties, and secondary structure of HHb. Accordingly, the use of structural coordinates of Tyr42 and heme as the first cluster and Trp14, Tyr42 and heme as the second cluster to represent the microenvironment of HHb is assessed for the first time. The calculated (DFT) absorption and FTIR properties of both the clusters are in well agreement with experimental absorption and FTIR characteristics of whole HHb suggesting prospective biomedical applications of these clusters.

10aHeme10aHuman hemoglobin10aNano-peptide cluster10aRepresentative template10aTrp1410aTyr421 aChakraborty, Madhurima1 aBanerjee, Nineesha, Sen1 aGhosh, Deborin1 aBhattacharya, Prabuddha1 aGanguly, Tapan uhttps://library.ncl.res.in/content/revealing-functional-importance-tyrosine-and-tryptophan-human-hemoglobin-development