Random poly(ε‐caprolactone‐L‐alanine) by direct melt copolymerization

A series of random polyesteramides (PEAs) with a range of molar composition from 90/10 to 50/50 were synthesized by direct melt polycondensation of ε‐caprolactone and l ‐alanine. Their structure was fully characterized by Fourier transform IR and NMR spectroscopy. The resulting copolymers are completely amorphous with the exception of PEA‐90/10 which possesses a semicrystalline structure. These PEAs present increasing glass transition temperatures at increasing l ‐alanine contents and exhibit fairly good thermal stability with 10% mass loss temperatures reaching 315 °C. © 2020 Society of Industrial Chemistry     

盖子环替换及定点突变提高菜豆环氧化物水解酶对邻甲基苯基缩水甘油醚的催化性能

菜豆环氧化物水解酶1和2（PvEH1、PvEH2）能够动力学拆分外消旋邻甲基苯基缩水甘油醚（rac-oMGE）,从而保留(R)-oMGE。基于对PvEH1和PvEH2结构的同源模拟和分析,发现二者分子中的盖子环差异较大,故本文选择盖子环作为研究目标。经融合聚合酶链式反应（FPCR）,获得了PvEH2的盖子环区域被PvEH1对应区域替换的杂合酶Pv2Pv1。用全细胞酶E. coli/pv2pv1催化rac-oMGE,当(S)-oMGE刚好水解完全时,产物(S)-3-邻甲苯基-1,2-丙二醇（(S)-oTPD）的ee_p由PvEH2的58.3%提高至75.5%。为进一步提高酶的性质,在Pv2Pv1中选取11个氨基酸位点进行丙氨酸(A)突变,获得最优突变子E. coli/pv2pv1^K176A,活性为E. coli/pv2pv1（4.2U/g）的2.1倍,且当S构型的底物刚好完全水解时,(S)-oTPD的ee_p进一步提高为80.3%。分子对接分析发现,盖子环替换和K176位点突变为A,均使(R)-oMGE环氧环中的C_α更易受到酶中D101位点的攻击。利用E. coli/pv2pv1^K176A催化150mmol/L rac-oMGE水解制备(R)-oMGE（ee_s＞99%）和(S)-oTPD（ee_p=80.4%）,二者的产率Y_S和Y_P分别为32.7%和60.1%,时空产率STY_S和STY_P为1.6g/(L·h)和3.3g/(L·h)。本实验为改善EH的催化性质提供了一种有效策略。     

D-柠檬烯对大鼠酒精性肝损伤脂质代谢紊乱的影响

探讨D-柠檬烯（D-limonene）对大鼠酒精性肝损伤脂质代谢紊乱的保护作用及可能作用机制,利用持续酒精灌胃的方法建立大鼠酒精肝损伤模型,分为A、B、C、D、E、F、G共7 组。A组为空白对照组,每日给予蒸馏水灌胃,前2 周8 mL/（kg·d）,后4 周12 mL/（kg·d）;B组为酒精模型组,每日灌胃体积分数为50%的乙醇,前2 周8 mL/（kg·d）,后4 周12 mL/（kg·d）;C、D、E组分别为D-柠檬烯低、中、高剂量组,每日分别灌胃D-柠檬烯100、200、400 mL/（kg·d）,其中D-柠檬烯与A、B组等量的50%的乙醇混合后灌胃;F组为水和D-柠檬烯空白高剂量组,每日给予D-柠檬烯400 mL/（kg·d）;G组为甘利欣药物对照组,灌胃量200 mL/（kg·d）。HE染色和电镜观察肝组织形态结构和肝组织超微结构的变化,测定血清谷丙转氨酶（alanine transaminase,ALT）、谷草转氨酶（aspartate transaminase,AST）、碱性磷酸酶（phosoporic acid,ALP）、胆碱酯酶（cholinesterase,CHE）、甘油三酯（triglyceride,TG）、胆固醇（cholesterol,CHO）、低密度脂蛋白胆固醇（low densitylipoprotein-cholesterol,LDL-C）水平。结果电镜下观察到A组肝细胞结构正常,核呈圆形或椭圆,线粒体形态正常。B组肝细胞次级溶酶体数量增加,线粒体形状不规则,脂滴多。C组可见少量脂滴,高尔基体正常,线粒体清楚。D组少量脂滴,胆小管有内容物,线粒体正常。E组线粒体高尔基体正常,少量脂滴,核圆。F组细胞器无异常,少量脂滴。G组少量脂滴,偶见溶酶,体线粒体正常。B组大鼠血清ALT、AST、ALP、CHE、TG、CHO、LDL-C均高于空白对照组,差异显著（P＜0.05）;F组大鼠血清所测各指标与空白对照组无明显差异;而D-柠檬烯低、中、高剂量干预组和酒精模型组比较,血清所测各指标水平均有不同程度地降低,其中D-柠檬烯中、高剂量干预组血清所测各指标水平明显低于酒精模型组,差异显著（P＜0.05）。结论：过量酒精摄入引起的肝组织超微结构病理损伤与升高血清ALP、CHE、ALT、AST、TG、CHO、LDL-C水平,在D-柠檬烯干预下有所减轻和降低。因此,D-柠檬烯可调节过量酒精摄入造成的脂质代谢紊乱。     

NEW ALANINE/EPR DOSIMETER USING EVA COPOLYMER/PARAFFIN AS A BINDER FOR HIGH-DOSE RADIATION DOSIMETRY: PERFORMANCE CHARACTERIZATION

Alanine/EPR rods (3 × 10 mm) for routine use in high-dose radiation applications have been prepared by a simple technique in the laboratory where alanine powder was mixed with molten mixture of paraffin wax and ethylene vinyl acetate copolymer (EVA). The binding mixture EVA/Paraffin does not present interference or noise in the EPR signal before or after the irradiation. The rods show good mechanical properties for safe and multi-use handling. The rods can be used with good precision in the dose range from 1 to 125 kGy. The overall uncertainty for calibration of the EVAPA rod dosimeters at 2σ was found to be 4.56%. The dose response, influence of humidity and temperature during irradiation, energy dependence as well as post–irradiation storage at different conditions are discussed.     

Alanine : glyoxylate aminotransferase of Saccharomyces cerevisiae-encoding gene AGX1 and metabolic significance

Alanine : glyoxylate aminotransferase is one of three different enzymes used for glycine synthesis in Saccharomyces cerevisiae. The open reading frame YFL030w (named AGX1 in the following), encoding this enzyme, was identified by comparing enzyme specific activities in knockout strains. While 100% activity was detectable in the parental strain, 2% was found in a YFL030w::kanMX4 strain. The ORF found at that locus was suspected to encode alanine : glyoxylate aminotransferase because its predicted amino acid sequence showed 23% identity to the human homologue. Since the YFL030w::kanMX4 strain showed no glycine auxtrophic phenotype, AGX1 was replaced by KanMX4 in a Delta GLY1 Delta SHM1 Delta SHM2 background. These background mutations, which cause inactivation of threonine aldolase, mitochondrial and cytosolic serine hydroxymethyltransferase, respectively, lead to a conditional glycine auxotrophy. This means that growth is not possible on glucose but on ethanol as the sole carbon source. Additional disruption of AGX1 revealed a complete glycine auxotrophy. Complementation was observed by transformation with a plasmid-encoded AGX1.     

Digestion and protein metabolism of Trogoderma granarium (Coleoptera: Dermestidae) fed on different barley varieties

The Khapra beetle, Trogoderma granarium Everts, is one of the most important pests of grains which rapidly infests durable stored products in hot and dry conditions. In the current study, effects of omit ten varieties of barley (Abidar, Bahman, Line20, Line22, Line30, Lisivi, Lokht11, Makuyi, Sahand and Sahraa) were determined on digestive enzymes and protein metabolsim of T. granarium larvae under laboratory conditions as 33 ± 1 °C, 65 ± 5% RH and photoperiod of 14:10 (L: D) h. The highest and the lowest activities of α-amylase were observed in T. granarium larvae fed on Line30 and Lisivi varieties, respectively but the glucosidases showed the highest activities followed by feeding on Lokht 11. Also, the latter variety caused the highest lipase activity in the larvae while Abidar, Line20, Lisuei and Sahand imposed the lowest lipase activity. The highest activities of serine proteases including trypsin, chymotrypsin and elastase were detected in the larvae fed on Line 30 but the two exopeptidases, amino- and carboxypeptidases, showed the highest activities when the larvae fed on Lisuei. All the three aminotransferses had the highest activities in the larvae fed on Lokht 11 as the related individuals contained the maximum amount of protein compared to other ones. Results of the current study highlighted Line30 as the most suitable variety to be digested by serine proteases and α-amylase but Lokht11 is appropriately digested by glucosidases and lipase which emboss their susceptibilities to T. granarium. Our findings on digestion and protein metabolism imply on susceptibility of varieties Line30 and Lokht11 to T. granarium larvae.     

Alanine Scan of the Peptide Antibiotic Feglymycin: Assessment of Amino Acid Side Chains Contributing to Antimicrobial Activity

The antibiotic feglymycin is a linear 13‐mer peptide synthesized by the bacterium Streptomyces sp. DSM 11171. It mainly consists of the nonproteinogenic amino acids 4‐hydroxyphenylglycine and 3,5‐dihydroxyphenylglycine. An alanine scan of feglymycin was performed by solution‐phase peptide synthesis in order to assess the significance of individual amino acid side chains for biological activity. Hence, 13 peptides were synthesized from di‐ and tripeptide building blocks, and subsequently tested for antibacterial activity against Staphylococcus aureus strains. Furthermore we tested the inhibition of peptidoglycan biosynthesis enzymes MurA and MurC, which are inhibited by feglymycin. Whereas the antibacterial activity is significantly based on the three amino acids D ‐Hpg1, L ‐Hpg5, and L ‐Phe12, the inhibitory activity against MurA and MurC depends mainly on L ‐Asp13. The difference in the position dependence for antibacterial activity and enzyme inhibition suggests multiple molecular targets in the modes of action of feglymycin.     

Taurine ameliorates alcoholic steatohepatitis via enhancing self-antioxidant capacity and alcohol metabolism

Chronic alcohol consumption or alcohol abuse is the main cause of alcoholic steatohepatitis or further cirrhosis. This study was to exam if the antioxidant capacity and alcohol metabolism in livers of chronic alcohol-fed rats were improved by supplementing taurine (Tau). Rats were randomly divided into four groups with five times per week of treatment: 1) isocaloric solution; 2) 3 g alcohol/kg BW/day; 3) 3 g alcohol/kg BW/day + 1 g taurine (Tau)/kg BW/day; and 4) 3 g alcohol/kg BW/day + 2 g Tau/kg BW/day. A 6-week alcohol consumption resulted in lower (p < 0.05) body weight gain and self-antioxidant capacities, as well as increased (p < 0.05) liver size, serum/hepatic lipids, and AST and ALT values. However, alcohol-fed rats co-treated with Tau have decreased (p < 0.05) liver lipid levels via increasing fecal lipid output and cholesterol metabolism. Besides, co-treatment of Tau also enhanced (p < 0.05) self-antioxidant capacities and alcohol metabolism in livers via enhancing GSH contents, CAT, GSH-Px, ADH, and ALDH activities, but decreasing MDA contents. In a histological examination of rat liver, microvesicular steatosis and necrotic cells were observed in alcohol-fed rats without Tau while largely suppressed microvesicular steatosis and no necrotic cells were observed in alcohol-fed rat supplemented with Tau. Therefore, Tau could be an effective hepatoprotective agent against alcohol-induced damage via enhancing self-antioxidant capacity and alcohol metabolism.     

N—马来酰基——氨基丙酸丁酯的微乳液聚合研究

以马来酸酐（MA）、氨基丙酸（ALn）、丁醇为原料合成了N-马来酰基-D，L-氨基丙酸丁酯（BAM），配制了以十二烷基硫酸钠和正戊醇为复合乳化剂，含有BAM的微乳液。用过硫酸钾引发该体系进行微乳液聚合，考察了聚合温度对聚合的影响，并用PERKIN-ELMERFTIR-1710红外光谱仪、DSC、TG、元素分析仪对产品进行了检测。     

太明清对扑热息痛致小鼠肝损伤的保护作用

本研究对韩国传统饮品太明清(TMC)对扑热息痛所致小鼠肝损伤的保护作用进行了研究,ICR小鼠连续14 d灌胃给予低(100 mg/kg)、中(250 mg/kg)、高(500 mg/kg)三个剂量的太明清及阳性药物水飞蓟素(100 mg/kg)后,腹腔注射扑热息痛(800mg/kg)建立动物急性肝损伤模型,动物处死后取血液和脏器测定各项指标。相对于模型对照组,太明清实验组的肝指数明显降低。三个剂量的太明清均明显降低血清谷丙转氨酶(ALT),谷草转氨酶(AST),碱性磷酸酶(ALP),甘油三酯(TG),尿素氮(BUN)水平,提高血清总胆固醇(TC),白蛋白(ALB)水平(p0.05)。且三个剂量呈现了一定的量效关系。其中太明清高剂量组对小鼠肝损伤的保护效果最佳,仅次于阳性药物水飞蓟素组(p0.05)。另外,从小鼠肝脏病理图来看,相对于模型对照组,太明清实验组对炎症及肝细胞坏死有明显改善。可见太明清对扑热息痛所致小鼠肝损伤具有较好的保护作用。