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Selected AbstractsImportance of tyrosine residues of Bacillus stearothermophilus serine hydroxymethyltransferase in cofactor binding and l - allo -Thr cleavageFEBS JOURNAL, Issue 18 2008Crystal structure, biochemical studies Serine hydroxymethyltransferase (SHMT) from Bacillus stearothermophilus (bsSHMT) is a pyridoxal 5,-phosphate-dependent enzyme that catalyses the conversion of l -serine and tetrahydrofolate to glycine and 5,10-methylene tetrahydrofolate. In addition, the enzyme catalyses the tetrahydrofolate-independent cleavage of 3-hydroxy amino acids and transamination. In this article, we have examined the mechanism of the tetrahydrofolate-independent cleavage of 3-hydroxy amino acids by SHMT. The three-dimensional structure and biochemical properties of Y51F and Y61A bsSHMTs and their complexes with substrates, especially l - allo -Thr, show that the cleavage of 3-hydroxy amino acids could proceed via C, proton abstraction rather than hydroxyl proton removal. Both mutations result in a complete loss of tetrahydrofolate-dependent and tetrahydrofolate-independent activities. The mutation of Y51 to F strongly affects the binding of pyridoxal 5,-phosphate, possibly as a consequence of a change in the orientation of the phenyl ring in Y51F bsSHMT. The mutant enzyme could be completely reconstituted with pyridoxal 5,-phosphate. However, there was an alteration in the ,max value of the internal aldimine (396 nm), a decrease in the rate of reduction with NaCNBH3 and a loss of the intermediate in the interaction with methoxyamine (MA). The mutation of Y61 to A results in the loss of interaction with C, and C, of the substrates. X-Ray structure and visible CD studies show that the mutant is capable of forming an external aldimine. However, the formation of the quinonoid intermediate is hindered. It is suggested that Y61 is involved in the abstraction of the C, proton from 3-hydroxy amino acids. A new mechanism for the cleavage of 3-hydroxy amino acids via C, proton abstraction by SHMT is proposed. [source] Systematic Studies on Photoluminescence of Oligo(arylene-ethynylene)s: Tunability of Excited States and Derivatization as Luminescent Labeling Probes for ProteinsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 14 2006Yong-Gang Zhi Abstract Functionalized oligo(phenylene-ethynylene)s (OPEs) with different conjugation lengths, p -X(C6H4C,C)nSiMe3 (n = 1,4; X = NH2, NMe2, H) were synthesized by Sonogashira coupling of (phenylene-ethynylene)s and 1-iodo-4-(trimethylsilylethynyl)benzene, followed by desilylation of the p -substituted (trimethylsilylethynyl)benzenes with potassium hydroxide. The photoluminescent properties for the OPE series with different chain lengths and their solvatochromic responses were examined. The absorption maxima were red-shifted with increasing numbers of ,(C6H4C,C), units (n), and a linear plot of the absorption energy maxima vs. 1/n was obtained for each series. The emission spectra in dichloromethane showed a broad and structureless band, the energies of which (in wavenumbers) also fit linearly with 1/n. Both the absorption and emission wavelength maxima of the NH2 - and NMe2 -substituted OPEs exhibited significant solvent dependence, whereas the parent OPEs (X = H) showed only minor shifts of the ,max values in different solvents. Substituent effects upon the photoluminescent characteristics of the OPEs and the tunability of the excited states were examined with the p -X(C6H4C,C)nSiMe3 (n = 2, 3; X = NH2, NMe2, H, SMe, OMe, OH, and F) series. The H- and F-substituted counterparts exhibited high-energy vibronically structured emissions attributed to the 3(,,*) excited states of the (arylene-ethynylene) backbone. For compounds bearing NH2 and NMe2 groups, a broad red-shifted emission with a remarkable Stokes shift from the respective absorption maximum was observed, which can be assigned to an n , ,* transition. The n , ,* assignment was supported by MO calculations on the model compounds p -X(C6H4C,C)2SiH3 (X = NH2, H). Functionalization of the oligo(arylene-ethynylene)s with the N -hydroxysuccinimidyl (NHS) moiety enabled covalent attachment of the fluorophore to HSA protein molecules. A series of fluorescent labels, namely p -X(C6H4C,C)nC6H4NHS, (n = 1, X = NH2, NMe2, SMe, OMe, OH, F; n = 2, X = NH2, NMe2) and p -Me2NC6H4C,C(C4H2S)C,CC6H4NHS were synthesized, and their conjugates with HSA (human serum albumin) were characterized by MALDI-TOF mass spectrometry, UV/Vis absorption spectroscopy, and gel electrophoresis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Spectrophotometric determination of the transition system for interactions involving model hydrogen bonds in acetonitrileJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 4 2002Józef Mago Abstract The bonds formed by interactions of picric acid (HA) with each of 12 (un)substituted pyridines (B) in acetonitrile (AN) were studied by UV,vis spectrophotometry to determine the corresponding to the transition system. The choice of both model system and experimental technique enabled the effect of heteroconjugation to be observed and the effects of formation of two theoretically possible homoconjugates (AHA, and BHB+) to be eliminated. The relationship between the wavelength at the absorbance maximum (,max) for 10,4,M solutions of complexes of picric acid with (un)substituted pyridines in acetonitrile and was found to have a sigmoidal shape with an inflection point at of ca ,0.3. On the basis of this relationship and UV,vis spectra, the picric acid,3-acetylpyridine system was recognized as that being the nearest to the transition system. The fact that the transition was lower than zero has been explained by the remarkable effect of species having the average structures A,···+HB on the established ,max values. The general results of this work and our previous results based on IR and 1H NMR studies, and also the lack of any experimental counterexamples, indicate that the zero value of constitutes a fundamental basis for predicting which one, among the given family of protonic hetero systems, is the most likely to show transitional properties in acetonitrile. Finally, it is postulated that the protonic hetero systems which are the most likely to show transitional properties in a given solvent S are those for which is close to zero, the eventual shift arising from peculiarity of the technique applied. Copyright © 2002 John Wiley & Sons, Ltd. [source] To see in different seas: spatial variation in the rhodopsin gene of the sand goby (Pomatoschistus minutus)MOLECULAR ECOLOGY, Issue 20 2009MAARTEN H. D. LARMUSEAU Abstract Aquatic organisms living in a range of photic environments require specific mechanisms to tune their visual pigments. Maximum absorbance (,max) of retinal rods in populations of the marine demersal sand goby, (Pomatoschistus minutus; Gobiidae, Teleostei) correlates with the local optic environment. It has been shown that this is not regulated through a physiological response by exchanging the rhodopsin chromophore. To test for evolutionary adaptation, the sequence of the rhodopsin (RH1) gene was analysed in 165 Pomatoschistus minutus individuals from seven populations across its distribution range. Analysis showed a high level of intraspecific polymorphism at the RH1 gene, including nonsynonymous mutations on amino acids, known as spectral tuning sites. Population differentiation at these sites was in agreement with the observed differentiation in ,max values. Analyses of dN/dS substitution rate ratios and likelihood ratio tests under site-specific models detected a significant signal of positive Darwinian selection on the RH1 gene. A strong discrepancy in differentiation was noticed between RH1 gene variation and the presumably neutral microsatellites and mitochondrial data. Samples did not cluster according to geographical or historical proximity with regards to RH1, but according to the general photic conditions of the habitat environment of the sand goby. This study highlights the usefulness of sensory genes, like rhodopsin, for studying the characteristics of local adaptation in marine nonmodel organisms. [source] Synthesis and properties of new aromatic poly(ester-imide)s derived from 4- p -biphenyl-2,6-bis(4-trimellitimidophenyl) pyridine and various dihydroxy compoundsPOLYMER INTERNATIONAL, Issue 1 2007Hossein Behniafar Abstract A novel class of wholly aromatic poly(ester-imide)s, having a biphenylene pendant group, with inherent viscosities of 0.32,0.49 dL g,1 was prepared by the diphenylchlorophosphate-activated direct polyesterification of the preformed imide-ring-containing diacid, 4- p -biphenyl-2,6-bis(4-trimellitimidophenyl)pyridine (1) with various aromatic dihydroxy compounds in the presence of pyridine and lithium chloride. A reference diacid, 2,6-bis(trimellitimido)pyridine (2) without a biphenylene pendant group and two phenylene rings in the backbone, was also synthesized for comparison purposes. At first, with due attention to structural similarity and to compare the characterization data, a model compound (3) was synthesized by the reaction of compound 1 with two mole equivalents of phenol. Moreover, the optimum condition of polymerization reactions was obtained via a study of the model compound synthesis. All of the resulting polymers were characterized by Fourier transform infrared and 1H NMR spectroscopy and elemental analysis. The ultraviolet ,max values of the poly(ester-imide)s were also determined. All of the resulting polymers exhibited excellent solubility in common organic solvents, such as pyridine, chloroform, tetrahydrofuran, and m -cresol, as well as in polar organic solvents, such as N -methyl-2-pyrrolidone, N,N -dimethylacetamide, N,N -dimethylformamide, and dimethyl sulfoxide. The crystalline nature of the polymers obtained was evaluated by means of wide-angle X-ray diffraction. The resulting poly(ester-imide)s showed nearly an amorphous nature, except poly(ester-imide) derived from 4,4,-dihydroxy biphenyl. The glass transition temperatures (Tg) of the polymers determined by differential scanning calorimetry thermograms were in the range 298,342 °C. The 10% weight loss temperatures (T10%) from thermogravimetric analysis curves were found to be in the range 433,471 °C in nitrogen. Films of the polymers were also prepared by casting the solutions. Copyright © 2006 Society of Chemical Industry [source] Synthesis and characterization of novel aromatic poly(amide-imide)s derived from 2,2,-bis(4-trimellitimidophenoxy)biphenyl or 2,2,-bis(4-trimellitimidophenoxy)-1,1,-binaphthyl and various aromatic diaminesPOLYMER INTERNATIONAL, Issue 7 2003Ahmad Banihashemi Abstract New aromatic diimide-dicarboxylic acids having kinked and cranked structures, 2,2,-bis(4-trimellitimidophenoxy)biphenyl (2a) and 2,2,-bis(4-trimellitimidophenoxy)-1,1,-binaphthyl (2b), were synthesized by the reaction of trimellitic anhydride with 2,2,-bis(4-aminophenoxy)biphenyl (1a) and 2,2,-bis(4-aminophenoxy)-1,1,-binaphthyl (1b), respectively. Compounds 2a and 2b were characterized by FT-IR and NMR spectroscopy and elemental analyses. Then, a series of novel aromatic poly(amide-imide)s were prepared by the phosphorylation polycondensation of the synthesized monomers with various aromatic diamines. Owing to structural similarity, and a comparison of the characterization data, a model compound was synthesized by the reaction of 2b with aniline. The resulting polymers with inherent viscosities of 0.58,0.97 dl g,1 were obtained in high yield. The polymers were fully characterized by FT-IR and NMR spectroscopy. The ultraviolet ,max values of the poly(amide-imide)s were also determined. The polymers were readily soluble in polar aprotic solvents. They exhibited excellent thermal stabilities and had 10% weight loss at temperatures above 500 °C under a nitrogen atmosphere. Copyright © 2003 Society of Chemical Industry [source] Study of the Reliability and Validity of the Community Health Intensity Rating Scale (CHIRS) in the Turkish CommunityPUBLIC HEALTH NURSING, Issue 3 2007Aysun Çelebio ABSTRACT The purpose of this study was to examine the reliability and validity of the Community Health Intensity Rating Scale (CHIRS) that was translated into the Turkish language and applied in the Turkish community. The CHIRS is a tool that assesses the intensity of need for care of persons/families in the community. The original version of the tool was translated into Turkish, examined for face validity and language appropriateness by the Turkish experts, and then applied to 372 families living in Odemis, Turkey. Significant correlations were found between total scale score (TSS) and total number of household members, and between the TSS and the total number of visits to any health institution within the previous month. In addition, the self-health care needs evaluation scores supported predictive validity. For reliability, min,max values, standard errors and deviations, skewness, and kurtosis coefficients of parameter scores, domain scores, and TSS were examined. The mean TSS was 26.7 (± 5.32) and the mean age of the participants was 35.0 years. For internal consistency, Cronbach's , (.525) and Guttman split-half coefficient (.629) values were established for the TSS. In conclusion, the reliability and validity of the Turkish version of CHIRS have been established. [source] | ||||||||||