Release of Warfarin from Human Serum Albumin by Water-soluble CdSe Nanotetrapods

Water soluble CdSe nanotetrapods are prepared by ligand exchange from organic-soluble ones. In order to achieve this, oleic acid, which is the capping agent for as prepared water-insoluble nanotetrapods, is exchanged with mercaptopropanoic acid (MPA). Shape and size of nanotetrapods are conserved upon ligand exchange. Ground state bleach recovery dynamics remain the same as well. However, they are completely non-emissive. These water-soluble nanotetrapods disrupt the secondary structure of Human Serum Albumin (HSA) and consequently, release warfarin bound to the protein.     

SOLVENT EFFECT ON PHOTOSENSITIZED OXIDATION OF IODIDE ION BY ANTHRACENE SULPHONATES

Abstract— Iodide ion oxidation by singlet oxygen is found to be influenced by two properties of the solvent. One is the polarity of the solvent and the other is the availability of protons in the solvent. By suitable choice of solvents and solvent mixtures both kinds of effects have been studied. In water-methanol mixtures the reaction is found to be facilitated in more polar medium. In isodielectric media as obtained by mixtures of acetonitrile and methanol the reaction is repressed with increase in the aprotic component (CH₃CN) in the solvent. The same effect is observed in the DMSO-H, O mixtures. In heavy water the reaction rate is doubled and the effect fits well into the proposed kinetic scheme involving singlet oxygen for photosensitized oxidation of I^- by anthracene sulphonates.     

Fluorescence Investigation of the Binding of Model PDT Drugs to Nonionic and Zwitterionic Surfactants

The binding of two model photodynamic therapy drugs, chlorin p ₆ and purpurin 18, with surfactants has been studied using steady-state and time-resolved fluorescence techniques. The surfactants used are amphiphilic nonionic surfactant (Tween 80 and Tween 40) and zwitterionic surfactant (HAPS). These have applications in drug delivery. The studies have been performed at pH 7 and 5 for chlorin p ₆ and at pH 7 for purpurin 18. The binding constants have been estimated from the change in fluorescence parameters and have been compared with those for Cremophor EL and human serum albumin. Chlorin p ₆ is found to bind to the surfactants to a greater extent at pH 5 than at pH 7. The same ionic species of chlorin p ₆ is found to exist at the maximum concentrations of the surfactants.     

The role of the ring nitrogen and the amino group in the solvent dependence of the excited-state dynamics of 3-aminoquinoline

The nonradiative rate in 3-aminoquinoline is found to exhibit anomalous solvent dependence, being rather fast in nonpolar solvents and remarkably slower in more polar and especially, more protic ones. The cause of such behavior is investigated by studying the dependence of fluorescence spectral and temporal parameters on the solvent properties such as polarity and hydrogen bonding ability. Complementary quantum mechanical calculations have been performed and the picture that emerges from these studies is that of an excited state with a short radiative lifetime due to the flipping of the amino group. This state is selectively populated in nonpolar, nonhydrogen bonding solvents, but is destabilized with respect to the more polar intramolecular charge transfer (ICT) state in polar solvents and even more so in protic solvents and dimethylsulfoxide. The slower nonradiative rates in the ICT state is attributed to the more restricted motion of the amino group in this state. The role of hydrogen bonding of the amino group and the ring nitrogen in stabilization/destabilization of the ICT state and therefore on the nonradiative rate is also explored.     

Correlated algebraic-geometric codes: Improved list decoding over bounded alphabets

We define a new family of error-correcting codes based on algebraic curves over finite fields, and develop efficient list decoding algorithms for them. Our codes extend the class of algebraic-geometric (AG) codes via a (nonobvious) generalization of the approach in the recent breakthrough work of Parvaresh and Vardy (2005).

Our work shows that the PV framework applies to fairly general settings by elucidating the key algebraic concepts underlying it. Also, more importantly, AG codes of arbitrary block length exist over fixed alphabets , thus enabling us to establish new trade-offs between the list decoding radius and rate over a bounded alphabet size.

The work of Parvaresh and Vardy (2005) was extended in Guruswami and Rudra (2006) to give explicit codes that achieve the list decoding capacity (optimal trade-off between rate and fraction of errors corrected) over large alphabets. A similar extension of this work along the lines of Guruswami and Rudra could have substantial impact. Indeed, it could give better trade-offs than currently known over a fixed alphabet (say, ), which in turn, upon concatenation with a fixed, well-understood binary code, could take us closer to the list decoding capacity for binary codes. This may also be a promising way to address the significant complexity drawback of the result of Guruswami and Rudra, and to enable approaching capacity with bounded list size independent of the block length (the list size and decoding complexity in their work are both where is the distance to capacity).

Similar to algorithms for AG codes from Guruswami and Sudan (1999) and (2001), our encoding/decoding algorithms run in polynomial time assuming a natural polynomial-size representation of the code. For codes based on a specific ``optimal' algebraic curve, we also present an expected polynomial time algorithm to construct the requisite representation. This in turn fills an important void in the literature by presenting an efficient construction of the representation often assumed in the list decoding algorithms for AG codes.

     

An enantioselective enzymatic desymmetrization route to hexahydro-4H-furopyranol,a high-affinity ligand for HIV-1 protease inhibitors

An enantioselective synthesis of (3aS,4S,7aR)-hexahydro-4H-furo[2,3-b]pyran-4-ol, a high-affinity nonpeptide ligand for a variety of potent HIV-1 protease inhibitors is described. The key steps involved a highly enantioselective enzymatic desymmetrization of meso-diacetate, an efficient transacetalization, and a highly diastereoselective reduction of a ketone. This route is amenable to large-scale synthesis using readily available starting materials.     

Steady state and time-resolved fluorescence investigation of the specific binding of two chlorin derivatives with human serum albumin

The specific binding of two model drugs for photodynamic therapy, namely chlorin p6 and purpurin 18 in the vicinity of Sudlow's Site I of HSA has been investigated by monitoring the intrinsic fluorescence of single tryptophanyl residue and by competitive binding with warfarin. The distance from the tryptophanyl residue has been ascertained by FRET from Trp to the chlorins and has been found to indicate a binding to Sudlow's Site I. The principal driving force for the interaction is found to be the hydrophobic effect. The main mechanism of protein fluorescence quenching was static. Time-resolved fluorescence results of competitive binding with warfarin are found to confirm that they bind to the warfarin binding site.     

Bäcklund transformation for the first flows of the relativistic Toda hierarchy and associated properties

In this communication we study a class of one parameter dependent auto-Bäcklund transformations for the first flow of the relativistic Toda lattice and also a variant of the usual Toda lattice equation. It is shown that starting from the Hamiltonian formalism such transformations are canonical in nature with a well defined generating function. The notion of spectrality is also analyzed and the separation variables are explicitly constructed.     

A novel di-triazole based peptide as a highly sensitive and selective fluorescent chemosensor for Zn2+ ions

A di-triazole based peptide has been synthesised by copper catalyzed Huisgen cycloaddition. Fluorescence intensity is enhanced selectively in the presence of Zn(2+), which is ascribed to reversal of photoelectron transfer. Compound 7 was found to self-assemble in the presence of Zn(ClO(4))(2) in an exclusive 2:1 ratio, which is supported by (1)H NMR titration and mass spectral data. The fluorescence intensity of 7 shows a subsequent ON-OFF phenomenon upon repetitive and alternate addition of Zn(ClO(4))(2) and HClO(4).     

Half-heusler semiconductors as piezoelectrics

We use a first-principles rational-design approach to demonstrate the potential of semiconducting half-Heusler compounds as a previously unrecognized class of piezoelectric materials. We perform a high-throughput scan of a large number of compounds, testing for insulating character and calculating structural, dielectric, and piezoelectric properties. Our results provide guidance for the experimental realization and characterization of high-performance materials in this class that may be suitable for practical applications.