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Navnit K. Misra Mahendra Singh Poonam Tandon V. D. Gupta 《Journal of Macromolecular Science: Physics》2013,52(3):454-469
The normal modes and their dispersions for poly(l-asparagine) (PLN) in the α-helical form have been obtained in a reduced zone scheme with Wilson's GF matrix method as modified by Higgs. The results indicate that the modes below 1350 cm?1 show appreciable dispersion. Optically active frequencies corresponding to the zone center and zone boundary are identified and discussed. Some of the characteristic features of the dispersion curves are repulsion accompanied by an exchange of character and von Hove singularities. Amide modes, side chain modes, and mixed modes are reported. The heat capacity calculated from the dispersion curves via density-of-states using Debye's relation is compared with the experimental data in the temperature range of 220–390 K. 相似文献
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Yang Gao Xiaohong Shen Haoping Zheng 《International journal of quantum chemistry》2010,110(4):925-938
The equivalent potential of water for the electronic structure of asparagine(Asn) is constructed by using the first‐principles, all‐electron, ab initio calculation. The process is composed of three steps. The first step is to determine the geometric structure of Asn+nH2O system with a minimum energy. The second step is to calculate the electronic structure of Asn with the potential of water molecules by using the self‐consistent cluster‐embedding (SCCE) method, based on the result obtained in the first step. The last step is to calculate the electronic structure of Asn with the potential of dipole after replacing water molecules with dipoles. The results show that the major effect of water molecules on Asn' electronic structure be raising the occupied electronic states by 0.034 Ry on average and narrowing energy gap by 0.91%. The effect of water on the electronic structure of Asn can be well simulated by using dipole potential. The obtained equivalent potential can be applied directly to the electronic structure calculation of protein in solution by using the SCCE method. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 相似文献
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Nath CE Dallapozza L Eslick AE Misra A Carr D Earl JW 《Biomedical chromatography : BMC》2009,23(2):152-159
A novel assay for the determination of l-asparaginase activity in human plasma is described that is based on the HPLC quantitation of l-aspartic acid produced during enzyme incubation. Methods for monitoring l-asparagine depletion are also described. Chromatography of l-aspartic acid, l-asparagine and l-homoserine (the internal standard) involved derivatization with o-pthaldialdehyde, then separation from other amino acids on a Phenomenex Luna C(18) column using a 1 mL/min flow rate and a mobile phase consisting of di-potassium hydrogen orthophosphate propionate buffer, pH 6, with 10% methanol and 10% acetonitrile. Fluoresence detection was at excitation/emission wavelengths of 357/455 nm. Under these conditions l-aspartic acid, l-asparagine and l-homoserine had retention times of 3.5, 9.8 and 17.7 min, respectively. The l-asparaginase assay was linear from 0.1 to 10 U/mL activity and interday precision and accuracy were less than 13%. The limit of quantitation was approximately 0.03 U/mL. The assay utility was established in 12 children who received E. coli l-asparaginase as treatment for acute lymphoblastic leukaemia. 相似文献
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Ernest G Nolen Adam J KurishKelli A Wong Michael D Orlando 《Tetrahedron letters》2003,44(12):2449-2453
The Grubbs second generation ruthenium catalyst was employed for the cross metathesis between α- and β-C-allyl glycosides and suitably protected l-vinyl glycines to furnish olefinic products in 57-94% yields. Hydrogenation afforded the C-glycosyl asparagines in high yield. 相似文献
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天冬酰胺合成酶B抑制剂高效液相色谱筛选方法的建立与应用 总被引:1,自引:0,他引:1
建立了一种快速、高效测定天冬酰胺合成酶B(AS-B)酶活性的反相高效液相色谱法(RP-HPLC)。酶反应体系中的氨基酸经2,4-二硝基氟苯(DNFB)柱前衍生,通过RP-HPLC测定酶反应体系前后底物及产物的变化来分析酶的活性。采用的色谱柱为Agilent C18柱(250 mm×4.6 mm,5 μm),以50 mmol/L醋酸钠缓冲液(pH 6.2)-乙腈(体积比为15:85)为流动相,流速为1.0 mL/min,柱温为30 ℃,检测波长365 nm,于6 min内实现了各组分的基线分离。通过该方法测定反应动力学参数进行AS-B的抑制定量分析。将已知AS-B抑制剂L-谷氨酸-γ-甲酯作用于酶反应体系,测得的抑制剂的抑制常数与文献值相接近,证明该方法可用于AS-B抑制剂的筛选。 相似文献
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