Exploring the potential of 3'-O-carboxy esters of thymidine as inhibitors of ribonuclease A and angiogenin.

In this study, compounds with a carboxy ester in lieu of the phosphate ester at the 3'-position have been employed to inhibit the ribonucleolytic activity of ribonuclease A (RNase A). Phosphates at the 3'-position of pyrimidine bases are well-known inhibitors of the protein. We have investigated the inhibition of RNase A by 3'-O-carboxy esters of thymidine. The compounds behave as competitive inhibitors with inhibition constants ranging from 42 to 95 microM. The mode of inhibition has also been confirmed by (1)H NMR studies of the active site histidines of RNase A. Docking studies have further substantiated the experimental results. The compounds are also found to inhibit the ribonucleolytic activity of angiogenin, a homologous protein and potent inducer of blood vessel formation.

Studies on the interaction of isoxazolcurcumin with calf thymus DNA.

The interaction of isoxazolcurcumin (IOC), a synthetic derivative of curcumin, with calf thymus-DNA (ct-DNA) has been investigated by UV-Vis, fluorescence, circular dichroism spectroscopies, viscosity measurements and docking studies. From these analyses, the binding constant, number of binding sites and mode of binding of IOC to ct-DNA has been determined. The binding constant of IOC to DNA calculated from both UV-Vis and CD spectra was found to be in the 10(4)M(-1) range. Analyses of fluorescence spectra, viscosity measurements and molecular modeling of IOC-DNA interactions indicate that IOC is a minor groove binder of ct-DNA and preferentially binds to AT rich regions. Ethidium bromide displacement studies revealed that IOC did not have any effect on ethidium bromide bound DNA which is indicative of groove binding. To elucidate the preferred region of binding of IOC to DNA, docking studies have been performed and changes in accessible surface area (DeltaASA) of nucleobases determined due to IOC-DNA complexation.

Electric quadrupole moments of the D states of alkaline-earth-metal ions.

The electric quadrupole moment for the 4d(2)D(5/2) state of (88)Sr(+); one of the most important candidates for an optical clock, has been calculated using the relativistic coupled-cluster theory. This is the first application of this theory to determine atomic electric quadrupole moments. The result of the calculation is presented and the important many-body contributions are highlighted. The calculated electric quadrupole moment is (2.94 +/- 0.07)ea(2)(0), where a(o) is the Bohr radius and the electronic charge while the measured value is (2.6 +/- 0.3) ea(2)(0). This is so far the most accurate determination of the electric quadrupole moment for the above mentioned state. We have also calculated the electric quadrupole moments for the metastable 4d(2)D(3/2) state of 88(Sr(+) and for the 3d(2)D(3/2.5/2) and 5d(2)D(3/2.5/2) states of (43)Ca(+) and (138)Ba(+), respectively.

Relativistic coupled-cluster theory of atomic parity nonconservation: application to 137Ba+.

We report the result of our ab initio calculation of the 6s2S1/2-->5d2D3/2 parity nonconserving electric dipole transition amplitude in 137Ba+ based on relativistic coupled-cluster theory. Considering single, double, and partial triple excitations, we have achieved an accuracy of less than 1%. If the accuracy of our calculation can be matched by the proposed parity nonconservation experiment in Ba+ for the above transition, then the combination of the two results would provide an independent nonaccelerator test of the standard model of particle physics.