Spectrin: an alternate target for cytoskeletal drugs.

Cytoskeletal drugs having enormous therapeutic potential act on the cytoskeletal components like actin, tubulin either by promoting polymerization or destabilizing the same. Here we present the interaction of the popular cytoskeletal drugs such as taxol, latrunculin and cytochalasin with spectrin, a huge protein with multi domains that forms the cytoskeletal network. Particularly, the actin binding domain of spectrin regulates the dynamics of the actin cytoskeleton.

Spin-Controlled Photoluminescence in Hybrid Nanoparticles Purple Membrane System.

Spin-dependent photoluminescence (PL) quenching of CdSe nanoparticles (NPs) has been explored in the hybrid system of CdSe NP purple membrane, wild-type bacteriorhodopsin (bR) thin film on a ferromagnetic (Ni-alloy) substrate. A significant change in the PL intensity from the CdSe NPs has been observed when spin-specific charge transfer occurs between the retinal and the magnetic substrate. This feature completely disappears in a bR apo membrane (wild-type bacteriorhodopsin in which the retinal protein covalent bond was cleaved), a bacteriorhodopsin mutant (D96N), and a bacteriorhodopsin bearing a locked retinal chromophore (isomerization of the crucial C13═C14 retinal double bond was prevented by inserting a ring spanning this bond).

The role of retinal light induced dipole in halorhodopsin structural alteration.

The present work studies the mechanism of light induced protein conformational changes in the over-expressed mutant of halorhodopsin (phR) from Natronomonas pharaonis. The catalytic effect of light is reflected in accelerating hydroxyl amine reaction rate of light adapted phR. Light catalysis was detected in native phR but also in artificial pigments derived from tailored retinal analogs locked at the crucial C13=C14 double bond.

Conjugated Cofactor Enables Efficient Temperature-Independent Electronic Transport Across ∼6 nm Long Halorhodopsin.

We observe temperature-independent electron transport, characteristic of tunneling across a ∼6 nm thick Halorhodopsin (phR) monolayer. phR contains both retinal and a carotenoid, bacterioruberin, as cofactors, in a trimeric protein-chromophore complex. This finding is unusual because for conjugated oligo-imine molecular wires a transition from temperature-independent to -dependent electron transport, ETp, was reported at ∼4 nm wire length.

Cation binding to halorhodopsin.

A member of the retinal protein family, halorhodopsin, acts as an inward light-driven Cl(-) pump. It was recently demonstrated that the Natronomonas pharaonis halorhodopsin-overproducing mutant strain KM-1 contains, in addition to the retinal chromophore, a lipid soluble chromophore, bacterioruberin, which binds to crevices between adjacent protein subunits. It is established that halorhodopsin has several chloride binding sites, with binding site I, located in the retinal protonated Schiff base vicinity, affecting retinal absorption.

Engineered-membranes and engineered-micelles as efficient tools for purification of halorhodopsin and bacteriorhodopsin.

We describe two alternative and complementary purification methods for halorhodopsin and bacteriorhodopsin. The first relies on a unique form of detergent micelles which we have called engineered-micelles. These are specifically conjugated in the presence of [hydrophobic chelator:Fe(2+)] complexes and form detergent aggregates into which membrane proteins partition, but hydrophilic water-soluble proteins do not.

Azido carbonyl compounds as DNA cleaving agents.

Irradiation of azido carbonyl compounds using UV light (≥310 nm) produced triplet alkyl nitrenes and aroyl radicals, which resulted in efficient cleavage of single strand DNA at pH 7.0. DNA cleaving ability of azido carbonyl compounds was found to be dependent on its concentration and substituents on its aromatic ring.

Synthesis, photophysical, photochemical, DNA cleavage/binding and cytotoxic properties of pyrene oxime ester conjugates.

A new series of (E)-pyrene oxime ester conjugates of carboxylic acids including amino acids were synthesized by coupling with an environment sensitive fluorophore 1-acetylpyrene. (E)-Pyrene oxime esters exhibited strong fluorescence properties and interestingly their fluorescence properties were found to be highly sensitive to the surrounding environment. Direct irradiation of the (E)-pyrene oxime esters by UV light (≥350 nm) resulted in both the photo-Beckmann rearrangement product and products resulting from N-O bond homolysis.

Cytotoxic and necrotic responses in human amniotic epithelial (WISH) cells exposed to organophosphate insecticide phorate.

The in vitro interaction of the organophosphorous insecticide (OPs) phorate with calf thymus DNA (ctDNA), and its potential to cause changes in cell cycle, membrane damage, and cytotoxicity leading to cell death (necrosis) was investigated in human amnion epithelial (WISH) cells. Fluorescence quenching revealed high binding affinity (K(a)=5.62×10(4)M(-1)) of phorate to ctDNA.

N,O-diacyl-4-benzoyl-N-phenylhydroxylamines as photoinduced DNA cleaving agents.

Photoinduced homolytic fission of nitrogen-oxygen bond in N,O-diacyl-4-benzoyl-N-phenylhydroxylamines using 310 nm UV light for 10 min produced acylaminyl and acyloxy radicals, which resulted in single strand cleavage of DNA at pH 7.0. Further the DNA cleaving ability of N,O-diacyl-4-benzoyl-N-phenylhydroxylamines found to depend both on its concentration and acyl substituents.

Synthesis and ribonuclease A inhibition activity of resorcinol and phloroglucinol derivatives of catechin and epicatechin: Importance of hydroxyl groups.

The reported ribonuclease A inhibitory activity of the green tea extracts prompted us to synthesize novel catechin/epicatechin based conjugates with resorcinol and phloroglucinol with the aim to increase the number of phenolic OH groups. These are found to be more effective inhibitors of ribonuclease A as compared to catechin and epicatechin thus indicating the importance of number of phenolic OH groups for the inhibition of ribonucleolytic activity. Fluorescence studies have been carried out to evaluate the binding parameters.

Methyl thiophanate as a DNA minor groove binder produces MT-Cu(II)-DNA ternary complex preferably with AT rich region for initiation of DNA damage.

Interaction of a genotoxic fungicide methyl thiophanate (MT) has been studied in vitro with calf thymus DNA. Fluorescence quenching data revealed the binding constant (K(a)=3.23 x 10(4)M(-1)) and binding capacity (n=1.

Design and synthesis of enediyne-peptide conjugates and their inhibiting activity against chymotrypsin.

Novel enediyne-amino acid conjugates 1-4 have been synthesized. All of these effectively target the enzyme chymotrypsin inhibiting its proteolytic activity. The conjugate with a directly linked phenyl alanine is the most effective inhibitor with a K(i) of 3 microM.

Design, synthesis and RNase A inhibition activity of catechin and epicatechin and nucleobase chimeric molecules.

Several novel catechin/epicatechin and nucleobase chimeric molecules 1-6 have been synthesized via azide-alkyne click chemistry. The structures of these hybrids have been confirmed by NMR and mass spectroscopic data. The synthesized molecules were tested for their RNase A inhibition activities.