手性流动相HPLC法拆分对羟基苯甘氨酸对映体的研究

将β-环糊精、羟丙基-β-环糊精作为手性流动相添加剂,系统地研究了D,L对羟基苯甘氨酸在RP-HPLC系统中的拆分。分别考察了手性流动相的种类,手性试剂β-环糊精的浓度,流动相的pH,修饰剂的种类及浓度,色谱柱温度等对拆分效果的影响,以-βCD为手性流动相添加剂,建立了-βCD手性流动相分离对羟基苯甘氨酸对映体的方法。结果表明:用ODS柱(250 mm×4.6 mmi.d.),以V(甲醇-β环糊精)∶V(pH 4.5磷酸盐缓冲液)=30∶70为流动相,流速0.2 mL/min,柱温25℃,检测波长为230 nm时对羟基苯甘氨酸对映体得到了良好的基线分离,分离度可达1.71。     

木质素先进材料的研究进展

综述了木质素改善合成高分子材料的性能和制备光电材料、阻燃材料、电磁屏蔽材料等方面的研究进展。加强木质素结构和性能的基础研究,解决木质素反应活性偏低以及与基体相容性差的问题,将木质素的耐辐射、可生物降解、阻燃、电磁屏蔽等特异性能引入到传统合成高分子材料中,制备性能优异、功能多样的先进高分子材料,是木质素高值化利用的一个重要方向。     

Entrapment of photosystem I within self-assembled films

We have developed a process to incorporate an integral membrane protein, Photosystem I (PSI), into an organic thin film at an electrode surface and thereby insulate the protein complex on the surface while mimicking its natural environment. The PSI complex, which is primarily more hydrophobic on the exterior than interior, is hydrophobically confined in vivo within the thylakoid membrane. To mimic the thylakoid membrane and entrap PSI on an electrode, we have designed a series of steps using a thin self-assembled monolayer (SAM) to adsorb and orient PSI followed by exposures to longer-chained methyl-terminated alkanethiols that place exchange with components of the original SAM in the interprotein domains. In this process, PSI is first adsorbed onto a HOC(6)S/Au substrate through a short exposure to a dilute solution of the protein to achieve a protein coverage of approximately 25%. The PSI/HOC(6)S/Au substrate is then placed into a solution containing one of various longer-chained alkanethiols including C(22)SH or C(18)OC(19)SH. Changes in thickness, interfacial capacitance, infrared spectra, and surface wettability were used to assess the extent of backfilling by the long-chained thiols. The coverage of the protein layer and the solvent used for backfilling affected the rate and quality of the SAM formed in the interprotein regions. After exposure of the PSI layer to solvents containing alkanethiols, there was only minor loss of protein on the surface and no real change in protein secondary structure as evidenced by reflectance absorption infrared spectroscopy.     

聚苯基硅氧烷与聚甲基苯基硅氧烷改性环氧树脂的合成与性能比较

热熔法制备了一系列聚苯基甲氧基硅氧烷(PPMS)、聚甲基苯基甲氧基硅氧烷(PMPS)改性环氧树脂,通过环氧值、红外光谱(IR)分析表明聚硅氧烷接枝了E-20环氧树脂且环氧基保持不变.探讨了有机硅含量对改性树脂固化体系耐热性能及韧性的影响.实验表明,当E-20环氧树脂与PPMS、PMPS的质量比为7∶3时,改性树脂固化体系的耐热性能明显提高,玻璃化转变温度(Tg)为95.8、88.3℃,分别比改性前提高了9.0℃和1.5℃;质量损失50%时的热分解温度(Td)为476.5、487.8℃,分别比改性前提高了58.3℃和69.5℃.与ED-30固化体系相比,EPMS-30固化物的耐热性能,韧性等力学性能提高的更加明显,并且还具有优良的涂膜性能.     

铝球弹丸高速斜撞击铝Whipple防护结构时后板的损伤特性

 为了研究空间碎片对航天器防护结构的高速斜撞击损伤特性,采用二级轻气炮发射铝球弹丸,对铝Whipple防护结构进行高速斜撞击实验。弹丸直径为3.97 mm,撞击速度为1.14～5.35 km/s,撞击角度为0°～70°。实验得到了铝Whipple防护结构在不同撞击速度区间的后板损伤模式,分析了后板撞击损伤及弹坑分布特性,建立了预测铝球弹丸高速斜撞击铝Whipple防护结构时后板弹坑分布的经验公式。结果表明：在大角度斜撞击条件下,对于一定的撞击速度,铝Whipple防护结构的后板弹坑分布会出现两个区域;弹丸的撞击破碎临界速度将影响后板损伤随撞击角的变化关系;对于铝Whipple防护结构,存在使后板撞击损伤最严重的临界撞击角。     

k-型卡拉胶/聚乙烯吡咯烷酮共混水凝胶的辐射制备及性质研究

采用辐射技术制备了κ-型卡拉胶(KC)/聚乙烯基吡咯烷酮(PVP)共混水凝胶,研究了共混凝胶内KC含量、PVP的分子量和辐照剂量等对KC/PVP共混水凝胶性质的影响.实验发现,KC与高分子量的PVP(k-90)共混后在一定剂量范围内辐照可得到高强度、高溶胀行为的KC/PVP共混水凝胶,随着共混凝胶内KC含量的增加,凝胶强度及溶胀性能均显著提高.分析表明,KC与高分子量的PVP共混后,在较低剂量下KC的降解被抑制,从而获得一种由物理交联的KC和化学交联的PVP形成的互穿网络(IPN)凝胶.     

石墨炉原子吸收光谱法测定大鼠血清中硒

通过考察不同基体改进剂效果,提出了以硝酸锶和硝酸钯做为混合基体改进剂。建立了用石墨炉原子吸收法测定牛血清和大鼠血清中痕量硒的分析方法。线性范围为0-120ng/mL,硒的检出限为0．095ng／mL,方法用于标准牛血清测定。结果与标准值基本吻合,大鼠血清测定标准加入回收率为102％。     

Application of DEPBT on the Synthesis of the Protected Dipeptides Containing Histidine with Unprotected Imidazole Group by Solution Method

3- (Diethoxyphosphoryloxy)- 1,2,3-benzotriazln-4 (3H)-one (DE-PBT) was an organophosphorus coupling reagent developed by our group. It was an effective coupling reagent for the synthesis of protected peptides containing Tyr, Ser and Thr with unprotected hydroxy group on their side chain. The further study of the synthesis of a series of protected dipeptides containing hisfidine with unprotected imidazole group using DEPBT is reported. During the synthetic procedure, the imidazole group of histidine did not need to be protected. When the carboxyl components were N-protected aromatic amino acids or basic amino acids, the yields were relatively high (63%--81%). However,when the carboxyl components were N-protected acidic amino acids, the yields were relatively low (47%--48%). The results expanded the application of DEPBT on the synthesis of bioactive peptides containing histidine.     

Resonance Raman determination of vinyl group disposition in different derivatives of native myoglobin and its heme‐disoriented form

In heme‐reconstituted heme proteins, the heme inserts such that some of the heme is rotated 180° about the α–γ meso axis, eventually equilibrating to native conformations. Also, proteins from different species may naturally possess both conformers. Resonance Raman (RR) spectroscopy is effective in signaling this conformational heterogeneity, detecting altered interactions with active site residues. While shifts of the vibrational modes of the two vinyl groups could be readily detected, they could not be assigned to a particular vinyl group. This deficiency is alleviated by employing a specifically labeled protoheme isotopomer, wherein only the 4‐vinyl group is labeled (i.e. –CH=C²H₂), providing a spectral editing mechanism for selectively tracking the individual vinyl groups. The RR spectral data acquired here for the met‐, deoxy‐, and ferrous CO adduct of myoglobin, along with their ‘flipped heme’ isomers, provide convincing evidence for the anticipated effects of ‘swapping’ the environments of the two vinyl groups; i.e., in the native form, the 2‐vinyl group assumes a more out‐of‐plane orientation with respect to the pyrrole plane than does the (nearly in‐plane) 4‐vinyl group, whereas in the ‘reversed’ orientation, the 4‐vinyl group now assumes a position that is more out‐of‐plane than the newly positioned 2‐vinyl group. The ability of RR spectroscopy to document such differences in the orientation of the vinyl substituents is made important by the fact that changes in the disposition of these groups has long been known to carry functional consequences. Copyright © 2014 John Wiley & Sons, Ltd.     

ChemInform Abstract: Azidopentazole is Probably the Lowest-Energy N8 Species - A Theoretical Study.

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