In-plane normal vibrations of 1,2,5-oxa-, thia- and selena-diazoles, 1,3,4-oxa- and thia-diazoles and 1,2,3,4-thiatriazoles

In-plane vibration modes of 1,2,5- and 1,3,4-oxa- and thia-diazoles, and 1,2,5-selenadiazole have been assigned on the basis of detailed normal coordinate analysis employing data on several deuterated species. In-plane vibration frequencies of two 1,2,3,4-thiatriazole derivatives have been calculated and compared with observed values.

Stereospecific photodimerization of coumarins in crystalline inclusion complexes. Molecular and crystal structure of 1:2 complex of (S,S)-(-)-1,6-bis(o-chlorophenyl)-1,6-diphenyl-hexa-2,4-diyne-1,6-diol and coumarin

Proximity of molecules is a crucial factor in many solid- state photochemical processes.'S2 The biomolecular photodimerization reactions in the solid state depend on the relative geometry of reactant molecules in the crystal lattice with center-to-center distance of nearest neighbor double bonds of the order of ca. 4 A. This fact emanates from the incisive studies of Schmidt and Cohen.2 One of the two approaches to achieve this distance requirement is the so-called "Crystal-Engineering" of structures, which essentially involves the introduction of certain functional groups that display in-plane interstacking interactions (Cl...Cl, C-He-0, etc.) in the crystal The chloro group is by far the most successful in promoting the /3- packing m ~ d e ,th~o,u~gh recent studies have shown its limitations? Another approach involves the use of constrained media in which the reactants could hopefully be aligned.

Heterojunctions between amorphous and crystalline niobium oxide with enhanced photoactivity for selective aerobic oxidation of benzylamine to imine under visible light

The formation of heterojunctions between two crystals with different band gap structures, acting as a tunnel for the unidirectional transfer of photo-generated charges, is an efficient strategy to enhance photocatalytic performance in semiconductor photocatalysts. The heterojunctions may also promote the photoactivity in the visible-light-response of any surface complex catalysts by influencing the transfer of photo-generated electrons. Herein, Nb2O5 microfibers, with a high surface area of interfaces between an amorphous phase and crystalline phase, were designed and synthesised by the calcination of hydrogen-form niobate while controlling the crystallization The photoactivity of these microfibers towards selective aerobic oxidation reactions was investigated. As predicted, the Nb2O5 microfibres containing heterojunctions exhibited the highest photoactivity. This could be due to the band gap difference between the amorphous phase and the crystalline phase, which shortened the charge mobile distance and improved the efficiency.

Role of γ1 Laminin and Its KDI Peptide in the Central Nervous System

Since the 1980 s, laminin-1 has been linked to regeneration of the central nervous system (CNS) and promotion of neuronal migration and axon guidance during CNS development. In this thesis, we clarify the role of γ1 laminin and its KDI tripeptide in development of human embryonic spinal cord, in regeneration of adult rat spinal cord injury (SCI), in kainic acid-induced neuronal death, and in the spinal cord tissue of amyotrophic lateral sclerosis (ALS). We demonstrated that γ1 laminin together with α1, β1, and β3 laminins localize at the floor plate region in human embryonic spinal cord. This localization of γ1 laminin is in spatial and temporal correlation with development of the spinal cord and indicates that γ1 laminin may participate in commissural axon guidance during the embryonic development of the human CNS. With in vitro studies using the Matrigel culture system, we demonstrated that the KDI tripeptide of γ1 laminin provides a chemotrophic guidance cue for neurites of the human embryonic dorsal spinal cord, verifying the functional ability of γ1 laminin to guide commissural axons. Results from our experimental SCI model demonstrate that the KDI tripeptide enhanced functional recovery and promoted neurite outgrowth across the mechanically injured area in the adult rat spinal cord. Furthermore, our findings indicate that the KDI tripeptide as a non-competitive inhibitor of the ionotropic glutamate receptors can provide when administered in adequate concentrations an effective method to protect neurons against glutamate-induced excitotoxic cell death. Human postmortem samples were used to study motor neuron disease, ALS (IV), and the study revealed that in human ALS spinal cord, γ1 laminin was selectively over-expressed by reactive astrocytes, and that this over-expression may correlate with disease severity. The multiple ways by which γ1 laminin and its KDI tripeptide provide neurotrophic protection and enhance neuronal viability suggest that the over-expression of γ1 laminin may be a glial attempt to provide protection for neurons against ALS pathology. The KDI tripeptide is effective therapeutically thus far in animal models only. However, because KDI containing γ1 laminin exists naturally in the human CNS, KDI therapies are unlikely to be toxic or allergenic. Results from our animal models are encouraging, with no toxic side-effects detected even at high concentrations, but the ultimate confirmation can be achieved only after clinical trials. More research is still needed until the KDI tripeptide is refined into a clinically applicable method to treat various neurological disorders.

Cu(II) complexes of 1-benzyl-2-phenyl-benzimidazole

Copper(II) complexes of 1-benzyl-2-phenylbenzimidazole (BPBI) of the general formula Cu(BPBI)2X2, nH2O [X= Cl-, Br-, NO3 or OAc- (n = O) and X = NO3- or 1 2SO42-(n = 2H2O)] have been prepared. The complexes are found to be nonelectrolytes in nitrobenzene. Conductivity in nonaqueous media, magnetic susceptibilities and i.r. and electronic spectra of the complexes are reported. A tetragonally distorted octahedral structure has been suggested for these complexes.

Oxidation of vitamin A1 and vitamin A2 aldehydes to the corresponding acids by enzymes from pig and rat livers

VITAMIN A is stored in rat liver largely as its ester with small amounts of the alcohol, but is transported in the normal circulating blood in the latter form1. Although it was generally believed that the alcohol form is the more physiological state of the vitamin, since the work of Dowling and Wald2, it is being recognized that vitamin A acid and not the alcohol may be nearer to the 'active vitamin A'. If this were to be so, it would be important to demonstrate that a mechanism exists in the rat for the production of vitamin A acid from vitamin A alcohol through the intermediate, the aldehyde. Regarding the formation of the aldehyde, it has been well established that the alcohol dehydrogenase can bring about the conversion of vitamin A alcohol to retinene3. The presence of an enzyme in rat and pig liver catalysing the oxidation of retinene1 and retinene2 to the corresponding acids has been demonstrated in the present work and the partially purified enzyme preparation shown to be completely devoid of alcohol dehydrogenase activity.

Synthesis of 1,3-dimethyl-1,3-dicarboxycyclohexane-2-acetic acid. An isomer of the degradation product of abietic acid

A synthesis of 1,3-dimethyl-1,3-dicarboxycyclohexane-2-acetic acid has been described, and proved to be an isomer of the C12-acid-an oxidative degradation product of abietic acid.

Chromatographic separation, fractionation and oxidation of selected beta-lactoglobulin peptides

The literature review elucidates the mechanism of oxidation in proteins and amino acids and gives an overview of the detection and analysis of protein oxidation products as well as information about ?-lactoglobulin and studies carried out on modifications of this protein under certain conditions. The experimental research included the fractionation of the tryptic peptides of ?-lactoglobulin using preparative-HPLC-MS and monitoring the oxidation process of these peptides via reverse phase-HPLC-UV. Peptides chosen to be oxidized were selected with respect to their amino acid content which were susceptible to oxidation and fractionated according to their m/z values. These peptides were: IPAVFK (m/z 674), ALPMHIR (m/z 838), LIVTQTMK (m/z 934) and VLVLDTDYK (m/z 1066). Even though it was not possible to solely isolate the target peptides due to co-elution of various fractions, the percentages of target peptides in the samples were satisfactory to carry out the oxidation procedure. IPAVFK and VLVLDTDYK fractions were found to yield the oxidation products reviewed in literature, however, unoxidized peptides were still present in high amounts after 21 days of oxidation. The UV data at 260 and 280 nm enabled to monitor both the main peptides and the oxidation products due to the absorbance of aromatic side-chains these peptides possess. ALPMHIR and LIVTQTMK fractions were oxidatively consumed rapidly and oxidation products of these peptides were observed even on day 0. High rates of depletion of these peptides were acredited to the presence of His (H) and sulfur-containing side-chains of Met (M). In conclusion, selected peptides hold the potential to be utilized as marker peptides in ?-lactoglobulin oxidation.

Nickel(II) complexes of 1-benzyl-2-phenylbenzimidazole

Nickel(II) complexes of 1-benzyl-2-phenylbenzimidazole (BPBI) of the general formula [Ni(BPBI)2X2](X=Cl-, Br-, NCS- or NO3-) have been prepared and their magnetic moments, i.r. and electronic spectra studied. [Ni(BPBI)2Cl2] has a pseudotetrahedral structure while [Ni(BPBI)2 Br2] exists as square planar and speudotetrahedral isomers. [Ni(BPBI)2I2] and [NI(BPBI)2(NCS)2] have square planar stereochemistry. The nitrato complex [Ni(BPBI)2(NO)3)2] exists in two different octahedral modifications in the solid state.

Heterocyclic Steroids .7. Rearrangement Of 1-Diethylamino-5-(Met-Methoxyphenoxy)-Pent-2-Yne

Thermal rearrangement of diethylamino5-(m methoxyphenoxy)-pent-2-yne (3) gives 1-(m-methexyphenoxy)-pent-3,4-diene (14) in about 8% yield. Hydration of the latter yields 1-(m-methoxyphenoxy)-pentan-4-one (6), which has been synthesised by an unambiguous route. A mechanism of formation of the allene (14) from the amine (3) has been suggested.

Synthesis and Antileukemic Activity of 1-((S)-2-Amino-4,5,6,7-tetrahydrobenzo[d]thiazol-6-yl)-3-(substituted phenyl)urea Derivatives

Heterocyclic urea derivatives play an important role as anticancer agents because of their good inhibitory activity against receptor tyrosine kinases (RTKs), raf kinases, protein tyrosine kinases (PTKs), and NADH oxidase, which play critical roles in many aspects of tumorigenesis. Benzothiazole moiety constitutes an important scaffold of drugs, possessing several pharmacological functions, mainly the anticancer activity. Based on these interesting properties of benzothiazoles and urea moiety to obtain new biologically active agents, we synthesized a series of novel 1-((S)-2-amino-4,5,6.7-tetrahydrobenzo[d]thiazol-6-yl)-3-(substituted phenyl)urea derivatives and evaluated for their efficacy as antileukemic agents against two human leukemic cell lines (K562 and Reh). These compounds showed good and moderate cytotoxic effect to cancer cell lines tested. Compounds with electron-withdrawing chloro and fluoro substituents on phenyl ring showed good activity and compounds with electron-donating methoxy group showed moderate activity. Compound with electron-withdrawing dichloro substitution on phenyl ring of aryl urea showed good activity. Further, lactate dehydrogenase (LDH) assay, flow cytometric analysis of annexin V-FITC/propidium iodide (PI) double staining and DNA fragmentation studies showed that compound with dichloro substitution on phenyl ring of aryl urea can induce apoptosis.

Chiral synthons from carvone, Part 40. A simple, enantiospecific approach to both enantiomers of 1 alpha,25-dihydroxyvitamin D-3 A-ring precursors from R-carvone

A simple and direct approach to both enantiomeric series of A-ring derivatives of 1 alpha,25-dihydroxyvitamin D-3 and the corresponding 1 alpha,3 alpha-derivatives, starting from the abundantly available R-carvone, is described. (C) 2000 Elsevier Science Ltd. All rights reserved.