Kinetics and mechanism of acid catalysed dissociation of some octahedral complexes of cobalt(III) and chromium(III)

Summary The kinetics of dissociation of glycinepentaamminecobalt(III) and tetraaquomonoacetylacetonatochrormium(III) ions in moderately strong perchloric acid media have been investigated spectrophotometrically. From the dependence of the rate on various acidity functions and the observed isokinetic and free energy relationships, both the complexes appear to react by an associative process involving interaction of the conjugate acid form of the substrate complex and H₃O⁺.     

2-Bromohydroquinone: structures, vibrational assignments and RHF, B- and B3-based density functional calculations

Vibrational spectral measurements, namely, infrared (4000-400 cm(-1)) and Raman (3500-50 cm(-1)) spectra have been made for 2-Bromohydroquinone. Optimized geometrical structures, harmonic vibrational frequencies and intensities have been computed by the ab initio (RHF), B-based (BLYP, BP86) and B3-based (B3P86, B3LYP, B3PW91) density functional methods using 6-31G(d) basis set. A complete assignment of the observed spectra has been proposed. Coupling of vibrations has been determined by calculating potential energy distributions (PEDs) at BP86/6-31G(d) level of theory. In the computed equilibrium geometries by all the levels, the bond lengths and bond angles show changes in the neighborhood of Bromine. Similarly, the vibrational spectra exhibit some marked spectral features unlike in hydroquinone and phenol. On the other hand, the infrared spectrum shows a clear evidence of O-H...O bonding near 3200 cm(-1) as in hydroquinone. Evaluation of the theoretical methods demonstrates that all the levels but the RHF have reproduced frequencies fairly accurately in the 2000-500 cm(-1); below 500 cm(-1) the RHF has performed reasonably well.     

Number of points on certain hyperelliptic curves defined over finite fields

For odd primes p and l such that the order of p modulo l is even, we determine explicitly the Jacobsthal sums _l(v), ψ_l(v), and ψ_2l(v), and the Jacobsthal–Whiteman sums and , over finite fields F_q such that . These results are obtained only in terms of q and l. We apply these results pertaining to the Jacobsthal sums, to determine, for each integer n1, the exact number of F_qⁿ-rational points on the projective hyperelliptic curves aY²Z^e−2=bX^e+cZ^e (abc≠0) (for e=l,2l), and aY²Z^l−1=X(bX^l+cZ^l) (abc≠0), defined over such finite fields F_q. As a consequence, we obtain the exact form of the ζ-functions for these three classes of curves defined over F_q, as rational functions in the variable t, for all distinct cases that arise for the coefficients a,b,c. Further, we determine the exact cases for the coefficients a,b,c, for each class of curves, for which the corresponding non-singular models are maximal (or minimal) over F_q.     

Chemoprofiling and Solamargine Estimation from a Few Solanum Species Used as ‘Brihati’ and Its Market Samples Using a Validated High-Performance Thin-Layer Chromatography Method

JPC – Journal of Planar Chromatography – Modern TLC - An ingredient of ‘Dasamoola’ and ‘Laghupanchamoola’ group of drugs, the source of ‘Brihati’ has...     

Proximal pointwise contraction

In this paper, we introduce the notion of proximal pointwise contraction and obtain the existence of a best proximity point on a pair of weakly compact convex subset of a Banach space and generalize a result of [W.A. Kirk, Mappings of generalized contractive type, J. Math. Anal. Appl. 32 (1970) 567-570; W.A. Kirk, H.K. Xu, Asymptotic pointwise contractions, Nonlinear Anal. 69 (2008) 4706-4712].     

Osmolyte changes the binding affinity and mode of interaction of minor groove binder hoechst 33258 with calf thymus DNA

The aim of this work was to investigate the effect of altered water activity on Hoechst 33258-calf thymus DNA (CtDNA) interaction by using osmotic stress approach. Water activity was changed by using osmolytes viz., sucrose and triethylene glycol (TEG). We have reported the results of thermal denaturation, absorption and fluorescence spectroscopy and binding affinity measurements as a function of osmolytes concentration. TEG dramatically lowered the thermal stability of CtDNA, ΔT(m)=-16 °C whereas sucrose induced very little decrease. Hoechst 33258 increases the stability of CtDNA, but in the presence of TEG, the ΔT(m) was -37 °C and a marginal decrease was observed with sucrose. Binding affinity of Hoechst 33258 with CtDNA was found to be reduced from 4.75×10? to 0.16×10? M?1 in TEG and this was accompanied with the increased uptake of 74±2 water molecules. In the presence of sucrose this uptake of water molecules was found to be 30±1. Method of continuous variation suggests that the osmolytes lowered the stoichiometry of Hoechst 33258-CtDNA complex. On the contrary, van't Hoff plot revealed the hydrophobic interaction (ΔS=130.66 J mol?1 K?1) between the Hoechst 33258 and CtDNA. The detailed absorption and fluorescence spectral measurements including the fluorescence lifetime and anisotropy indicated bound state of Hoechst 33258 in osmotic stress condition. Fluorescence lifetime measurement revealed that the contribution from the planar conformer of Hoechst 33258 dominated the binding interaction with CtDNA in presence of TEG. These results can be useful for understanding of interaction of Hoechst 33258 with genomic DNA in a complex environment having altered water activity.