Preparation, Characterization And Properties Of C-60 And C-70 - Spectroscopy, Structure, Anions, Interaction With Electron-Donors And Superconductivity

Preparation and characterization of the fullerenes, C60 and C70, are described in detail, including the design of the generators fabricated locally. The characterization techniques employed are UV-visible, IR, Raman and C-13 NMR spectroscopies, scanning as well as transmission electron microscopy and mass spectrometry. The electron energy level diagram of C60 as well as the one-electron reductions of C60 and C70 leading to various anions are discussed. Electronic absorption spectra of C60- and C60(2-) are reported. Phase transitions from the plastic to the crystalline states of C60 and C70 are examined. Based on a C-13 NMR study in a mixture of nematic liquid crystals, it has been demonstrated that C60 retains its extraordinary symmetry in solution phase as well. Interaction of C60 and C70 with strong electron-donor molecules has been investigated employing cyclic voltammetry. Superconductivity of K(x)C60 has been studied by non-resonant microwave absorption; Na(x)C60 as well as K(c)C70 are shown to be non-superconducting. Doping C60 with iodine does not make it superconducting. Interaction of C60 with SbCl5 and liquid Br2 gives rise to halogenated products.

Microscopic origin of the chirality driven morphologies of the amphiphilic monolayers and bilayers

It is widely known that the compressed monolayers and bilayers of chiral lipids or fatty acids form helical morphologies, while the corresponding racemic modification gives only flat platelets without twist. No molecular explanation of this phenomenon is yet available, although subtle interactions at the chiral centers have often been proposed as the driving force behind the morphology of the aggregate to form a particular shape. In the present study, the morphologies of the chiral amphiphilic assemblies have been predicted on the basis of an effective pair potential between the molecules, which depends on the relative sizes of the groups attached to the chiral centers, the orientation of the amphiphilic molecules and also on the distance between them. It is shown that fur a pair of same kind of enantiomers, the minimum energy conformation favours a twist angle between them. This twist between the neighbouring molecules gives rise to the helicity of the aggregate. The present theory also shows from the molecular considerations that for a pair of mirror-image isomers (i.e. the racemic modification) the minimum energy conformation corresponds to the zero angle between the molecules, thus giving rise to flat platelets as observed in experiments. Another fascinating aspect of such chirality driven helical structures is that the sense (or the handedness) of the helix is highly specific about the chirality of the monomer concerned. The molecular theory shows, for the first time, that the sense of the helical structures in many cases is determined by the sizes of the groups attached to the chiral centers and the effective potential between them. The predicted senses of the helical structures are in complete agreement with the experimental results.

Comparative-Study of Photonic Switching architectures

The basic photonic switching elements of practical importance are outlined. A detailed comparative study of photonic switching architectures is presented both for guided wave fabrics and free-space fabrics. The required equations for comparative study are obtained, after considering the parameters like bend losses, effects of waveguide crossings, etc. The potential areas of application of photonic switching are pointed out.

Potassamide induced in situ alkylation of 5,6-dihydroisoquinoline with allyl bromide and Michael acceptors

Potassamide induced in situ alkylation of 4-cyano-3-methoxy-1-methyl-5, 6-dihydroisoquinoline (1a) with allyl bromide gives the 5-allyl- and 5,9-diallyl-5,6-dihydroisoquinolines (1c and 1d), isoquinoline derivative 2 and 4-allyl-1, 2, 3, 4-tetrahydroisoquinolin-3(2H)-one (3a). However, potassamide induced in situ alkylation of In with buten-2-one, mesityl oxide and acrylonitrile results in the formation of only 5-alkylated 5,6-dihydroisoquinoline derivatives 1e-g along with fully aromatised compound 2.

Solubilization of n-decane into n-decyl-polyoxyethylene surfactants: A cavity forming free energy based model

The present paper reports the results of a theoretical study of the forces and factors driving the solubilization of n-alkane solubilizates into the micellar core of some non-ionic surfactants, based on a micellar model which includes the cavity forming free energy as a component of micellization. The solubilizate is n-decane and the non-ionic surfactants considered are n-decyl-polyoxyethylene surfactants. The extent of solubilization, i.e. the mole fraction of the solubilizate within the core has been calculated. The results indicate that the incorporated solubilizate has more translational and rotational degrees of freedom as compared to those of the tail parts of the surfactants present in the core. This drives the total free energy of aggregation after solubilization into a more favourable direction. The results are in fair agreement with the experimental results.

Photocytotoxicity and DNA photocleavage activity of La(III) and Gd(III) complexes of phenanthroline bases

Lanthanide(II) complexes La(B)(acac)(3)] (1-3) and Gd(B)(acac)(3)] (4-6), where B is a N,N-donor phenanthroline base, viz., 1,10-phenanthroline (phen in 1, 4), dipyrido3,2-d:2',3'-f]quinoxaline (dpq in 2, 5) and dipyrido3,2-a:2',3'-c]phenazine (dppz in 3, 6), have been prepared and characterized. The Gd(111) complexes 4 6 are structurally characterized by single crystal X-ray crystallography. The complexes display GdO6N2 coordination with the ligands showing bidentate chelating mode of bonding. The complexes are non-electrolytic in aqueous DMF and exhibit ligand-centered absorption bands in the UV region. The dppz complexes show a band at 380 nm in DMF. The La(111) complexes are diamagnetic. The Gd(III) complexes are paramagnetic with magnetic moment that corresponds to seven unpaired electrons. The Complexes are avid binders to calf thymus DNA giving K-b values in the range of 4.7 x 10(4) 6.1 x 10(5) M-1 with a relative binding order: 3, 6 (dppz) > 2, 5 (dpq) > 1, 4 (phen). The binding data suggest DNA surface and/or groove binding nature of the complexes. The dpq and dppz complexes efficiently cleave SC DNA to its nicked circular form in UV-A light of 365 nm via formation of both singlet oxygen (O-1(2)) and hydroxyl radical (HO center dot) species. The dppz complexes 3 and 6 exhibit significant PDT effect in He La cervical cancer cells giving respective IC50 value of 460(+/- 50) and 530(+/- 30) nM in UV-A light of 365 rim, and are essentially non-toxic in dark with an IC50 value of >100 mu M. The dppz ligand alone is cytotoxic in dark and UV-A light. A significant decrease in the dark toxicity of the dppz base is observed on binding to the Ln(III) ion while retaining its photocytotoxicity.

Reactivity Of Pph3 Toward Ru2cl(O2cme)4 - Synthesis And X-Ray Crystal-Structure Of [Ru(O2cme)(Mecn)2(Pph3)2](Clo4)

A new ruthenium(II) complex of the type [Ru(O2CMe)(MeCN)2(PPh3)2](CiO4) (1) has been isolated from a reaction between Ru2Cl(O2CMe), and PPh3 in MeCN followed by the addition of NaClO4. The structure of 1 is determined by single crystal X-ray studies. The crystal belongs to the monoclinic space group C2/m with the following unit cell dimensions for the C42H39N2O6P2ClRu(M = 866.15): a = 23.295(1)angstrom, b = 23.080(1)angstrom, c = 9.159(1)angstrom, beta = 107.32(1)-degrees, V = 4701(1)angstrom3, Z = 4, D(c) = 1.224 gcm-3, lambda(Mo - K-alpha) = 0.7107 angstrom, mu(Mo - K-alpha) = 4.09 cm-1, T = 293K, R = 0.081 (R(w) = 0.094) for 2860 reflections with I greater-than-or-equal-to 3-sigma(I) and g = 0.015853. In the complex cation, the symmetry about the metal centre is essentially octahedral showing the presence of a chelating acetato, two cis-oriented MeCN and two trans-disposed PPh3 ligands. The mechanistic aspects of the core cleavage reaction are discussed.

Rice-Husk-Ash Cement - A Review

The use of silica from rice-husk for the production of various materials, including rice-husk ash-lime binder, has gained significance. In this context, the decomposition of husk, the properties of the silica ash, including its crystallization and the ash-lime reaction, are reviewed. The mechanism of ash-lime reaction is controlled mostly by the development of osmotic pressure. For lime-deficient ash-lime mixtures the reaction is complete in the initial few days and therefore no strength development is observed for such mortars in the later ages. The use of optimum ash/lime ratio is recommended for obtaining consistently good performance for the mortar. A method for the determination of this ratio is also discussed.

Simple Structural And Bonding Representations Of Fullerenes

Bonding in buckminsterfullerene, C60, can be described in terms of a unique canonical representation in which all six membered rings have a benzenoid Kekule structure while the pentagons are all made of exclusively single bonds. The corresponding valence bond structure reflects the full symmetry of the molecule and is consistent with the observed bond length variations. Computational support for the bonding description is provided using localized MO's obtained at the MNDO level. The requirement of benzenoid structures for all the hexagons can be used as a criterion of stability of fullerenes which complements the pentagon isolation rule. A convenient two-dimensional representation of the fullerene structures incorporating the above bonding description is suggested, especially for use in mechanistic discussions.

Synthesis of DEF ring skeleton of naulafine alkaloid

6, 8-Dichloro-4, 5-dihydro-2-methyl-[2, 7]acenaphthyridin-1-one (5), obtained from the. reaction of 5-cyano-2, 6-dihydroxy-3, 4-cyclopentenopyridine with Vilsmeier reagent, has been transformed to the key synthon 4a in two steps.

Transmembrane domains participate in functions of integral membrane proteins

Integral membrane proteins have one or more transmembrane a-helical domains and carry out a variety of functions such as enzyme catalysis, transport across membranes, transducing signals as receptors of hormones and growth factors, and energy transfer in ATP synthesis. These transmembrane domains are not mere structural units anchoring the protein to the lipid bilayer but seem to-contribute in the overall activity. Recent findings in support of this are described using some typical examples-LDL receptor, growth factor receptor tyrosine kinase, HMG-CoA reductase, F-0-ATPase and adrenergic receptors. The trends in research indicate that these transmembrane domains participate in a variety of ways such as a linker, a transducer or an exchanger in the overall functions of these proteins in transfer of materials, energy and signals.

Effect of beta-lactamase-catalyzed hydrolysis of cephalosporins on peroxynitrite-mediated nitration of serum albumin and cytochrome c

The hydrolysis of beta-lactam antibiotics by beta-lactamases is one of the major bacterial defense systems. These enzymes generally hydrolyze a variety of antibiotics including the latest generation of cephalosporins, cephamycins and imipenem. In this paper, the effect of cephalosporins-based antibiotics on the peroxynitrite-mediated nitration of protein tyrosine is described. Although some of the antibiotics have weak inhibitory effect on the nitration reactions in the absence of beta-lactamase, they exhibit very strong inhibition in the presence of beta-lactamase. This is due to the elimination of heterocyclic thiol/thione moieties from cephalosporins by beta-lactamase-mediated hydrolysis. After the elimination, the thiols/thiones effectively scavenge peroxynitrite, leading to the inhibition of the nitration reactions.

Copper(I) complexes of modified nucleobases and vitamin B3 as potential chemotherapeutic agents: In vitro and in vivo studies

Three new complexes of Cu(I) have been synthesized using ancillary ligands like thiopyrimidine (tp) a modified nucleobase, and nicotinamide (nie) or vitamin B3, and characterized by spectroscopy and X-ray crystallography. In vitro cytotoxicity studies of the complexes on various human cancer cell lines such as Colo295, H226, HOP62, K562, MCF7 and T24 show that Cu(PPh3)(2)(tp)Cl] and Cu(PPh3)(2)(tp)ClO4 (2) have in vitro cytotoxicity comparable to cisplatin. Complex Cu(nic)(3)PPh3]ClO4 (3) is non-toxic and increases the life span by about 55 % in spontaneous breast tumor model. DNA binding and cleavage studies show that complex (3) binds to calf thymus DNA with an apparent binding constant of 5.9 x 10(5)M and completely cleaves super-coiled DNA at a concentration of 400 mu M, whereas complexes (1) and (2) do not bind DNA and do not show any cleavage even at 1200 mu M. Thus, complex (3) may exhibit cytotoxicity Via DNA cleavage whereas the mechanism of cytotoxicity of (1) and (2) probably involves a different pathway.

ChemInform Abstract: Enantioselective Formal Total Synthesis of (-)-Homogynolide-A

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Expression of the Japanese encephalitis virus NS3 and NS2b proteins as glutathione S-transferase fusions

Flaviviruses generate their structural and nonstructural proteins by proteolytic processing of a single large polyprotein precursor. These proteolytic events are brought about both by host cell signalase and a virally encoded protease. The virally encoded proteolytic activity has been shown to reside within the nonstructural protein 3 (NS3) and requires the product of the nonstructural 2b (NS2b) gene. In order to obtain sufficient quantities of pure NS2b and NS3 proteins for kinetic analysis, we have expressed both these proteins in recombinant systems as fusions to glutathione S-transferase (GST). The fusion constructs were driven by the strong bacteriophage T7 promoter. Transfection of these constructs into the African green monkey kidney cell line CV-1 previously infected with a recombinant vaccinia virus expressing the T7 RNA polymerase resulted in synthesis of the fusion proteins. Both the fusion proteins could be purified to homogeneity in a single step using a glutathione agarose affinity matrix.