@article { ISI:000283110500021, title = {Temperature effect on the molecular interactions between ammonium ionic liquids and N,N-dimethylformamide}, journal = {Journal of Physical Chemistry B}, volume = {114}, number = {42}, year = {2010}, month = {OCT}, pages = {13415-13425}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

In view of the wide scope of molecular interactions between the highly polar compound of N,N-dimethylformamide (DMF) and ammonium ionic liquids (ILs), we have measured thermophysical properties such as densities (rho) and ultrasonic sound velocities (u) over the whole composition range at temperatures ranging from 25 to 50 degrees C under atmospheric pressure. To gain some insight into the several aggregations of molecular interactions present in these mixed solvents, we predicted the excess molar volume (V(E)) and the deviations in isentropic compressibilities (Delta K(s)) as a function of the concentration of IL. These results are fitted to the Redlich-Kister polynomials. The materials investigated in the present study included the hydroxide series of ammonium ILs of tetramethylammonium hydroxide [(CH(3))(4)N][OH] (TMAH), tetraethylammonium hydroxide [(C(2)H(5))(4)N][OH] (TEAH), and tetrapropylammonium hydroxide [(C(2)H(7))(4)N][OH] (TPAH). The intermolecular interactions and structural effects were analyzed on the basis of the measured and the derived properties. A qualitative analysis of the results is discussed in terms of the ion-dipole and ion-pair interactions, and hydrogen bonding between ILs and DMF molecules and their structural factors.

}, issn = {1520-6106}, doi = {10.1021/jp108003x}, author = {Attri, Pankaj and Venkatesu, Pannuru and Kumar, Anil} } @article { ISI:000286890500041, title = {Activity and stability of alpha-chymotrypsin in biocompatible ionic liquids: enzyme refolding by triethyl ammonium acetate}, journal = {Physical Chemistry Chemical Physics}, volume = {13}, number = {7}, year = {2011}, month = {FEB}, pages = {2788-2796}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

In view the of wide scope of structural information of biomolecules in biocompatible ionic liquids (ILs) in various applications including chemical and biochemical, it is essential to study the productive preferential interactions between biological macromolecules and biocompatible ILs. We have therefore explored the stability and activity of alpha-chymotrypsin (CT) in the presence of five ILs from different families, such as triethyl ammonium acetate (TEAA), triethyl ammonium phosphate (TEAP) from ammonium salts, 1-benzyl-3-methylimidazolium chloride ([Bzmim][Cl]), 1-benzyl-3-methylimidazolium tetrafluoroborate ([Bzmim][BF(4)]) from imidazolium salts and tetra-butyl phosphonium bromide (TBPBr) from phosphonium families. Circular dichroism (CD) and UV-vis spectrophotometer experiments were used to study CT stabilization by ILs, related to the associated structural changes and enzyme activity studies, respectively. We observed that all ILs have a dominant contribution to the stabilization of CT. The stability and activity of CT depends on the structural arrangement of the ions of ILs. Our experimental results explicitly elucidate that more hydrophobic imidazolium and phosphonium cations carrying longer alkyl chains of ILs ([Bzmim][Cl], [Bzmim][BF(4)] and TBPBr) were weak stabilizers for CT, while small alkyl chain molecules of triethyl ammonium salts (TEAA and TEAP) are strong stabilizers and therefore more biocompatible for CT stability. Our CD and NMR measurements reveal that TEAA is a refolding additive for CT from a quenched thermal unfolded enzyme structure.

}, issn = {1463-9076}, doi = {10.1039/c0cp01291b}, author = {Attri, Pankaj and Venkatesu, Pannuru and Kumar, Anil} } @article { ISI:000295128000013, title = {Protic ionic liquid attenuates the deleterious actions of urea on alpha-chymotrypsin}, journal = {Physical Chemistry Chemical Physics}, volume = {13}, number = {38}, year = {2011}, month = {SEP}, pages = {17023-17026}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

We present a biocompatible ionic liquid, triethyl ammonium acetate (TEAA), that attenuates the denaturation action of a non-ionic chaotrope, urea, on the industrially relevant proteolytic enzyme alpha-chymotrypsin.

}, issn = {1463-9076}, doi = {10.1039/c1cp22195g}, author = {Attri, Pankaj and Venkatesu, Pannuru and Kumar, Anil and Byrne, Nolene} } @article { ISI:000339628400010, title = {Quantitative evaluation of the ability of ionic liquids to offset the cold-induced unfolding of proteins}, journal = {Physical Chemistry Chemical Physics}, volume = {16}, number = {30}, year = {2014}, month = {JUN}, pages = {15806-15810}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Significant non-reversible two-state denaturation was observed for proteins such as myoglobin (Mb) and alpha-chymotrypsin (CT) with decreasing temperature in the presence of 1-butyl-3-methylimidazolium-based ([C(4)mim]X-+(-)) ionic liquids (ILs) with various anions (X-). Interestingly, for the first time, ILs having acetate and bromide anions were proven to counteract the cold-induced unfolding of proteins.

}, issn = {1463-9076}, doi = {10.1039/c4cp01001a}, author = {Kumar, Awanish and Rani, Anjeeta and Venkatesu, Pannuru and Kumar, Anil} }