Effect of denaturation of DNA on the molecular organization of a fluorescent dye in ultra thin films

Acridine Orange (AO) forms H-dimer in solid state and in ultra thin films. However, H dimer of AO reduces its efficiency as a usefull material for fluorescence probe. In the present work detailed investigations has been done on the interaction of AO with different forms of DNA in order to check the effectiveness in controlling the dimeric sites of AO in the Layer by Layer (LbL) self assembled film. It was found that single stranded DNA (ssDNA) is most effective than the dsDNA and coil-shaped DNA in controlling the dimeric sites of AO in LbL film.     

Chromium complexes of an isomeric N-donor ligand, 2-[(N-arylamino)phenylazo]pyridine: amination reactions,X-ray structure,and redox properties

The chromium chemistry of two positional isomers of the ligand 2-[(N-arylamino)phenylazo]pyridine (HL(1)and HL(2)) are described. While the ligand HL(1) coordinates as a bischelating tridentate N,N,N-donor, [L(1)](-), with deprotonation of the amine nitrogen, its isomer HL(2) coordinates as a neutral bidentate N,N-donor. The amine nitrogen in this case remains protonated. Thus the reaction of CrCl(3).nH(2)O with HL(1) produced the brown cationic complex, [Cr(L(1))(2)](+), [1](+). The representative X-ray structure of [1a](ClO(4)) is reported. The two azo nitrogens of the anioinc tridentate ligand approach the metal center closest with Cr(1)-N(azo) av 1.862(6) A. There is a significant degree of ligand backbone conjugation in the coordinated ligands, which resulted in shortening of the C-N distances and also in lengthening of the diazo (N=N) distances. Two synthetic approaches for the synthesis of chromium complexes of HL(2) are investigated. The first approach is based on the substitution reaction, wherein all the coordinated CO ligands of Cr(CO)(6) were completely substituted by the three bidentate HL(2) ligands to produce a violet complex [Cr(HL(2))(3)]. The second approach is based on para-amination reaction of coordinated 2-(phenylazo)pyridine (pap). Thus the reaction of an inert complex, [CrCl(2)(pap)(2)], with ArNH(2) yields a mixed ligand complex, [CrCl(2)(pap)(HL(2))], 3. In this reaction one of the two coordinated pap ligands in [CrCl(2)(pap)(2)] undergoes amination at the para carbon (with respect to the diazo function) to yield HL(2) in situ. This metal-promoted transformation is authenticated by the X-ray structure determination of a representative complex, [CrCl(2)(pap)(HL(2a))], 3a. Notable differences in bond distances along the ligand backbones of the two coordinated ligands in 3a indicate different levels of metal-ligand overlap in this complex. All the chromium complexes of HL(2) are characterized by their intense blue-violet color. The frequencies of the visible range transitions in these complexes linearly correlate with the Hammett's substitution constant. Intraligand charge-transfer transitions in the visible region are believed to be responsible for the intense color. Redox properties of all these complexes are reported.     

Stereoselective synthesis of beta-substituted phenylalanine-beta-phenylisoserine-derived tripeptides using N-cinnamoyl-L-proline as template: synthesis of structural analogues of HIV protease inhibitors

N-Cinnamoyl-L-proline can be used as a template on which beta-substituted phenylalanine and beta-phenylisoserine residues can be synthesized leading to tripeptide derivatives as structural analogues of HIV protease inhibitors.     

The first total synthesis of lipid II: the final monomeric intermediate in bacterial cell wall biosynthesis

Bacterial peptidoglycan is composed of a network of beta-[1,4]-linked glyan strands that are cross-linked through pendant peptide chains. The final product, the murein sacculus, is a single, covalently closed macromolecule that precisely defines the size and shape of the bacterial cell. The recent increase in bacterial resistance to cell wall active agents has led to a resurgence of activity directed toward improving our understanding of the resistance mechanisms at the molecular level. The biosynthetic enzymes and their natural substrates can be invaluable tools in this endeavor. While modern experimental techniques have led to isolation and purification of the biosynthetic enzymes utilized in peptidoglycan biosynthesis, securing useful quantities of their requisite substrates from natural substrates has remained problematic. In an effort to address this issue, we report the first total synthesis of lipid II (4), the final monomeric intermediate utilized by Gram positive bacteria for peptidoglycan biosynthesis.     

Metformin and glitazones: does similarity in biomolecular mechanism originate from tautomerism in these drugs?

This theoretical study attempts to find out similarity between metformin and glitazone class of antidiabetic drugs. It was found that some tautomeric forms of both metformin and thiazolidinedione ring of glitazones have similar molecular electrostatic potential (MESP) surface and may bind to a common complementary surface. Complexation and docking studies were also carried out in order to support this hypothesis. Copyright © 2007 John Wiley & Sons, Ltd.     

Singlet-Higgs-Boson signals at hadron colliders

Many extensions of the Standard Model includeSU(2) _L ×U(1) _Y singlet higgs bosons,h ⁰, and also vector-like fermions which couple to it. The production and detection possibilities of such singlet neutral scalars at hadron colliders are considered for different scenarios of vectorlike fermions. We find that for some values of masses and couplings, detection at the CERN large hadron collider (LHC) appears to be a distinct possibility, while at the Fermilab Tevatron upgrade theh ⁰ might be observed only in very favourable circumstances.     

Kinetic studies on the reduction of a nickel (III) oxime-imine complex by sulphur(IV) and selenium(IV)

The kinetics of the reduction of [Ni^III(L¹)]²⁺ (where HL¹ = 15-amino-3-methyl-4,7,10,13-tetraazapentadec-3-en-2-one oxime) by sulphur(IV) and selenium (IV) over the regions pH 2.50–8.02 and 2.01–4.00 respectively have been investigated at 30°C. Attempts were made to evaluate the reactivity of all the reacting species, of sulphur(IV) and selenium(IV) by considering suitable pH ranges. The oxidation of SC₂·H₂O and HSO ₃ ⁻ is proposed to proceed through the formation of a hydrogen-bonded adduct. The reaction with SO ₃ ²⁻ seems to follow a direct outer-sphere route which is well supported by Marcus crossrelation calculation. The oxidation of HSeO _l3 ⁻ is ≈ 10³ times slower than that of H₂SeO₃. The kinetic data indicate that the oxidation of sulphur(IV) by [Ni^IIIL¹)]²⁺ is much more favourable as compared to the corresponding oxidation of selenium(IV).     

Three symbol partially balanced arrays

Summary Two methods of construction of partially balanced arrays of strength two and three are presented.     

Viscous fluid motion around the Kerr-Newman black hole

In some recent papers, it has been shown that electrovac spacetimes may sometimes be interpreted as space-time filled with a viscous fluid—one such spacetime being the Kerr-Newman metric. Here the possible fluid motion in that case is studied in some detail and some interesting features of the motion in the black hole region are pointed out.     

Crystal and molecular structure of hexahydropyridine (piperidine) hydrochloride

The structure of hexahydro pyridine (piperidine), a compound of psychobiological importance, has been determined in the form of its hydrochloride by the heavy-atom technique, using three-dimensional X-ray data. Hexahydro pyridine hydrochloride, (C₅H₅N)H₆.HC1, crystallizes in the orthorhombic space groupPbcm with four molecules per unit cell of dimensionsa = 9.68(2),b = 7.30(3),c = 9.67(2) Å. The positions of the hydrogen atoms were located from a difference-Fourier synthesis. The structure was refined by the full-matrix least-squares method, using anisotropic temperature factors, leading to the finalR-value of 0.094. The hexahydro pyridine ring has a chair conformation. The crystallographic mirror plane atz = 1/4 coincides with the molecular mirror plane passing through the C1, N and C(3) atoms of the molecule in such a way that C(1)′ and C(2)′ are the mirror images of C(1) and C(2). The dihedral angles which plane I, containing C(1), C(2), C(2)′ and C(1)′, makes with plane II, containing C(2), C(3) and C(2)′, and planeIII, containing C(1), N and C(1)′, are 120.47 and 116∶42 °, respectively. The molecules are held together by a network of hydrogen bonds of type N⁺ —H ... C1^? in thexy-plane, and by van der Waals forces in thez-direction. Both the hydrogen atoms in the NH ₂ ⁺ group of the molecule take part in the formation of hydrogen bonds.