http://192.168.1.40:8080/xmlui/handle/123456789/1062 2026-05-31T10:20:38Z 2026-05-31T10:20:38Z De, Mithu Das, Kali Pada Chakrabartty, Pran Krishna http://192.168.1.40:8080/xmlui/handle/123456789/2428 2018-11-27T11:54:26Z 2005-10-01T00:00:00Z

Purification and characterization of α-amylase from Bacillus amyloliquefaciens NCIM 2829 De, Mithu; Das, Kali Pada; Chakrabartty, Pran Krishna α-Amylase (EC 3.2.1.1) was purified to homogeneity (specific activity 58,000 μmole min -1 mg protein -1) from the culture filtrate of Bacillus amyloliquefaciens NCIM 2829. Its molecular mass was found to be 67.5 kDa. The activity of the enzyme increased by almost 50% in the presence of Co +2 ion. Hg 2+ and Cu 2+ acted as strong inhibitors of the enzyme. The tryptophan moities of the enzyme were fairly protected from the aqueous environment. However, the globular interior of the protein was somewhat loosely packed. The protein had nearly an equal amount of α-helical and β-sheet structure in dilute solution. In concentrated solution, its secondary structure had a higher proportion of β-sheet at the expense of some random coil structure. The protein showed a molten globule state at a low concentration of chaotropic agent. The denaturation profile of the protein showed no cooperativity. Co 2+ enhanced the structural stability of the enzyme.

2005-10-01T00:00:00Z Bhattacharjee, Chaitali Ghosh, L. Das, Kali Pada http://192.168.1.40:8080/xmlui/handle/123456789/2426 2018-11-27T11:54:25Z 2004-01-01T00:00:00Z

Accessibility of the various regions of β-lactoglobulin during thermal unfolding and refolding Bhattacharjee, Chaitali; Ghosh, L.; Das, Kali Pada Structure of the refolded β-lactoglobulin has been compared with that of native β-lactoglobulin by measuring the accessibility of the various regions of the protein molecule. Site selective fluorescence labelling was employed to introduce fluorophores into various regions of β-lactoglobulin and collisional quenching of intrinsic and labelled fluorophores was used to measure the Stern-Volmer quenching constant used here as a measure of the exposure or accessibility of the region. Our data indicate that tryptophan residues of the refolded β-lactoglobulin relocate from the central region towards the protein surface and this relocation helps to open up the access path to the central cavity. Measurement of kinetics of reaction of the free thiol group with DTNB reveals that in the refolded β-lactoglobulin most of the free thiols are involved in the interchange reaction with disulphides. Blocking of the thiol group with IAEDANS inhibits this interchange reaction. There is difference in quaternary structure between the native and the thermally refolded β-lactoglobulin. On heating and subsequent cooling of β-lactoglobulin solution, much of the native dimeric form dissociates into monomer and some minor fractions of the high molecular species of β-lactoglobulin were also observed.

2004-01-01T00:00:00Z Dastidar, K. G. Maitra, S. Goswami, L. Roy, D. Das, Kali Pada Majumder, A. L. http://192.168.1.40:8080/xmlui/handle/123456789/2238 2013-03-15T06:04:29Z 2006-04-01T00:00:00Z

An insight into the molecular basis of salt tolerance of L-myo-inositol 1-P synthase (PcINO1) from Porteresia coarctata (Roxb.) Tateoka, a halophytic wild rice Dastidar, K. G.; Maitra, S.; Goswami, L.; Roy, D.; Das, Kali Pada; Majumder, A. L. The molecular basis of salt tolerance of L myo-inositol 1-P synthase (MIPS; EC 5.5.1.4) from Porteresia coarctata (Roxb.) Tateoka (PcINO1, AF412340) earlier reported from this laboratory, has been analyzed by in vitro mutant and hybrid generation and subsequent biochemical and biophysical studies of the recombinant proteins. A 37-amino acid stretch between Trp-174 and Ser-210 has been confirmed as the salt-tolerance determinant domain in PcINO1 both by loss or gain of salt tolerance by either deletion or by addition to salt-sensitive MIPS(s) of Oryza (OsINO1) and Brassica juncea (BjINO1). This was further verified by growth analysis under salt environment of Schizosaccharomyces pombe transformed with the various gene constructs and studies on the differential behavior of mutant and wild proteins by Trp fluorescence, aggregation, and circular dichroism spectra in the presence of salt. 4,4'-Dianilino-1,1'-binaphthyl-5,5-disulfonic acid binding experiments revealed a lower hydrophobic surface on PcINO1 than OsINO1, contributed by this 37-amino acid stretch explaining the differential behavior of OsINO1 and PcINO1 both with respect to their enzymatic functions and thermodynamic stability in high salt environment. Detailed amino acid sequence comparison and modeling studies revealed the interposition of polar and charged residues and a well-connected hydrogen-bonding network formed by Ser and Thr in this stretch of PcINO1. On the contrary, hydrophobic residues clustered in two continuous stretches in the corresponding region of OsINO1 form a strong hydrophobic patch on the surface. It is conceivable that salt-tolerant MIPS proteins may be designed out of the salt-sensitive plant MIPS proteins by replacement of the corresponding amino acid stretch by the designated 37-amino acid stretch of PcINO1. DOI: 10.1104/pp.105.075150

2006-04-01T00:00:00Z Chattoraj, D. K. Halder, E. Das, Kali Pada Mitra, A. http://192.168.1.40:8080/xmlui/handle/123456789/2237 2013-03-14T12:35:36Z 2006-11-16T00:00:00Z

Surface activity coefficients of spread monolayers of behenic acid salts at air-water interface Chattoraj, D. K.; Halder, E.; Das, Kali Pada; Mitra, A. The pressure-area isotherms of ionized monolayers of behenic acid at air-water interface at pH 12.0 have been obtained from the Langmuir film balance experiments under various physico-chemical conditions. The value of the measured surface pressure at a given area per molecule is equal to the sum of the ideal pressure, cohesive pressure and electrical pressure. The electrical pressure term is regarded as the sum of the pressure originating from the Gouy-Chapman double layer including discrete ion effect, ion binding and monolayer hydration effect. At a given area, the deviation of the measured surface pressure from its ideal value has been calculated in terms of the apparent surface compressibility coefficients, surface fugacity coefficients for gaseous monolayer and surface activity coefficients of solute forming two-dimensional solutions in the monolayer phase respectively. Values of all these coefficients have been calculated for different compositions of the monolayer using non-ideal gas model and Raoult's and Henry's laws modified for two-dimensional non-ideal solutions respectively. Values of these coefficients may be higher or lower than unity depending upon ionic strengths and nature of inorganic salts present in the sub-phase. Using these values of surface activity coefficients, the standard free energies of formation, of spread monolayers of salts of behenic acid have been calculated at different standard states of reference. DOI: 10.1016/j.cis.2006.05.002

2006-11-16T00:00:00Z