D—氨基酸在人体的来龙去脉：人体中D—氨基酸,D—氨基酸氧化酶,D…

本文分析近年,特别是近两年有关人体、食物中Ｄ－氨基酸、Ｄ－氨基酸氧化酶、Ｄ－天冬氨酸氧化酶研究进展,强调：１．必须研究食品中Ｄ－氨基酸水平;２．Ｄ－氨基酸氧化酶、Ｄ．天冬氨酸氧化酶作为药物治疗因Ｄ－氨基酸过量所致疾病。     

维生素D——结肠癌治疗的新希望

众所周知,维生素D可以用于结肠癌治疗,然而近日刊登的一项研究首次阐明了维生素D在这个过程中的确切机制。人们已经知道维生素D对结肠癌的疗效主要可分为两个方面：一是诱导E—cadherin在内的一些黏附分子的表达,加强细胞的黏附而阻止迁移;二是可以抑制过度激活的wnt／catenin通路,抑制癌细胞的增生。     

D6——神秘的趋化因子诱饵受体

趋化因子可能受神经、激素、酶及结合蛋白等的调节,D6是继DARC之后发现的另一种特殊的趋化因子诱饵性结合蛋白。D6不仅为炎性CC族趋化因子的转录后调控所必需,在肿瘤等人类疾病中的作用也引人注目。     

β—D—呋喃果糖苷酶酶学特性

对来源于米曲霉（Aspergillus oyzae001)中的β－D－呋喃果糖苷酶的酶学特性进行研究,β－D－呋喃果糖苷酶具有如下特性,在温度≤40℃时,酶稳定,最适反应温度为35－45℃,在pH5-9范围内稳定,最适pH为7－9,在选择的金属离子范围内,Ag^ 对酶有较强的激活作用,K^ ,Zn^2 ,Mg^2 对酶也有激活作用,但程度不如Ag^ ,其他金属离子对酶的活性基本没有影响。     

D—氨基酸生物化学的进展

<正> 人们对氨基酸的认识,最初是从蛋白质水解物中得到,自然界中氨基酸也主要以蛋白质的结合态存在,由于蛋白质中所得到的氨基酸均为L型,所以很自然把天然氨基酸都认为是L型。而D-氨基酸则是实验室人工合成后才认识的。由于它是人工合成的于是认为它属非天然氨基酸而打入“另册”。这种认识延续了近百年成为传统观念。可是近二十年来新发现氨基酸种数剧增(达400多种),其中包括不少D—氦基酸在微生     

D—葡萄糖苷酶抑制剂的研究

用高灵敏度的荧光法研究了１３种糖类化合物对α或β－Ｄ－葡萄糖苷酶的抑制作用,实验结果表明：５－氨基－５－脱氧－Ｄ－吡喃葡萄糖－１－磺酸铵盐（１）、５－氨基－５－脱氧－Ｄ－吡喃葡萄糖－１－磺酸（２）、５－氨基－５－脱氧－Ｄ－葡萄糖－１－亚硫酸加成物（３）等三种氮杂糖对α或β－Ｄ－葡萄糖苷酸均呈现竞争性抑制作用,化合物（１）的Ｋ＝３７２μｍｏｌ／Ｌ;Ｋｉ＾β＝６．３８μｍｏｌ／Ｌ,化合物（２）的Ｋｉ＾     

海枣曲霉β—D—岩藻糖苷酶的研究

Although beta-D-fucosidase (beta-D-fucoside fucohydrolase, EC 3.2.1.38) has been isolated from various sources, the identity of this enzyme is still not settled. We have purified a specific beta-D-fucosidase in electrophoretically homogeneous form crude extracts of Aspergillus phoenicis by polyethyleneglycol 6000-phosphate buffer aqueous two-phase separation, and successive chromatography on DEAE-Sephadex A-50, hydroxyapatite and Sephadex G-100 columns. The molecular weight of the enzyme was estimated to be 57000 by SDS-polyacrylamide gel electrophoresis and 50000 to 60000 by gel filtration on Sephadex G-100. The enzyme showed optimum coside were 2.4mmol/L, and 1.28 mumol min-1 the pH range 5.5-6.5 and below 35 degrees C. The Km and the Vmax values for pNP-beta-D-fucoside were 2.4mmol/L, and 1.28 mumol.min-1.mg-1 respectively. The enzyme was strongly inhibited by sulfhydryl group reagents, PCMB-NEM and iodoacetate. It was also inhibited by EDC, DEP and NBS. Thus, -SH, -COOH groups, histidyl and tryptophyl residues were essential for enzyme activity. The purified beta-D-fucosidase showed high specificity toward p-nitrophenyl beta-D-fucoside. The enzyme was inhibited by D-fucose and D-fucono-gamma-lactone, but not by D-galactose, D-galactono-gamma-lactone, D-glucose or D-glucono-gamma-lactone; the latter compounds are specific inhibitors of beta-D-galactosidase and beta-D-glucosidase respectively. Thus, this enzyme is the most strictly specific beta-D-fucosidase when compared with those previously reported.     

D—苯丙氨酸的不对称合成

本文以D-樟脑与甘氨酸持丁酯缩合的D-樟脑酮亚胺为手性合成子,通过不对称苄基化反应,再经酸水解,对映选择合成了D—苯丙氨酸,其光学纯度和对映体过量百分率达95%,这是一种合成光学纯氨基酸的新方法。     

N—氨甲酰基—D—苯甘氨酸不对称热水解反应的研究

Ｎ氨甲酰基Ｄ苯甘氨酸不对称热水解反应的研究江宁贺鹏卢大军强亚静杨柳孙万儒（中国科学院微生物研究所北京１０００８０）Ｄ苯甘氨酸是半合成β内酰胺类抗生素的重要原料,它的合成主要是从５苯基海因出发,经海因酶开环生成Ｎ氨甲酰基Ｄ苯甘氨酸后,...     

枯草杆菌JSIM—1018糖代谢突变株积累D—核糖研究

从收集的Bacillus,Brevibacterum,Corynebacterium,Pseudomonas,Arthrobacter等属菌种中进行D-核糖产生菌的筛选,对其中BacillusSM-18菌株用紫外线和甲基磺酸乙酯诱变,选育到莽草酸营养缺陷型突变株JSIM-1018．发酵产物经物理、化学鉴定为D-核糖．某些有机氮源如酵母粉、玉米浆、牛肉膏、蛋白陈以及某些芳香族氨基酸对突变株积累D-核糖有促进作用。在以葡萄糖为碳源的培养液中,摇瓶发酵D-核糖最高可达929／L,3000L发酵罐中试D-核糖最高可达81．759／L,平均在64g／L以上,葡萄糖基本耗尽。     

大肠杆菌α—D—半乳糖苷酶的提纯及特性

大肠杆菌中与抗原K(?)s ab基因相连锁的棉子糖操纵子(raf)编码的α-D-半乳糖苷酶经硫酸铵沉淀,Sepharose 4B和DEAE纤维素等提纯步骤获纯化品,其在PAGE上呈单一电泳区带,分子量80000。粗酶品经Sepharose 4B后呈现为两个酶活性峰。该酶特性与染色体编码的同功酶有明显差异。最适温度为35—37℃,最适pH 7.5。以PNPG、蜜二糖、棉子糖为底物,其米氏常数分别为0.11,2.1和136mmol/L。Mn~2 离子影响酶稳定性,然而可以被巯基试剂消除。双扩散免疫实验初步表明,产H_2S基因连锁的raf操纵子编码的α-D-半乳糖苷酶与该酶可能具有相同抗原性。     

乳酸菌D—80葡萄糖异构酶的研究

采用乳酸菌D-80为试验用菌种,经试验找出了适合产葡萄糖异构酶的培养条件。培养基含有：玉米芯水解液还原物1．2—1．4％,米糠饼2一4％,麸皮0.2～0.4％(二者经1398蛋白酶水解)及MnSO．0.05％。微量通风,开罐发酵,35—37℃培养。培养前期6—7小时,用NaoH调节发酵液pH为4．9—5．1。总的发酵时间为10一14小时。成熟醪中的菌体,经分离后,加入30—40％的葡萄糖浆,pH 6．4—6．7,MnSO4的含量10-4M,60—65℃的条件下转化,果糖的转化率为40％左右。经扩大试验后,进行技术鉴定,认为工艺路线基本上是合理的,经济上也是合算的,可进一步扩大试生产。     

哺乳动物游离D—氨基酸的生理起源

哺乳动物游离Ｄ—氨基酸的生理起源ＨａｌｖｏｒＮ．Ｃｈｒｉｓｔｅｎｓｅｎ著／洪卫国译／徐淇寿校除了甘氨酸，所有氨基酸都以光学活性异构体形式存在，光学活性异构体能够使偏振光平面向左或向右偏转。一般用于蛋白质合成的氨基酸都具有相似的构型，即Ｌ—氨基酸；而Ｄ...     

Crop 3D—a LiDAR based platform for 3D high-throughput crop phenotyping

With the growing population and the reducing arable land, breeding has been considered as an effective way to solve the food crisis.As an important part in breeding, high-throughput phenotyping can accelerate the breeding process effectively. Light detection and ranging(LiDAR) is an active remote sensing technology that is capable of acquiring three-dimensional(3 D) data accurately,and has a great potential in crop phenotyping. Given that crop phenotyping based on LiDAR technology is not common in China,we developed a high-throughput crop phenotyping platform, named Crop 3 D, which integrated LiDAR sensor, high-resolution camera, thermal camera and hyperspectral imager. Compared with traditional crop phenotyping techniques, Crop 3 D can acquire multi-source phenotypic data in the whole crop growing period and extract plant height, plant width, leaf length, leaf width, leaf area, leaf inclination angle and other parameters for plant biology and genomics analysis. In this paper, we described the designs,functions and testing results of the Crop 3 D platform, and briefly discussed the potential applications and future development of the platform in phenotyping. We concluded that platforms integrating LiDAR and traditional remote sensing techniques might be the future trend of crop high-throughput phenotyping.     

D1／D2／Cyt—559复合物的共振拉曼光谱

光系统Ⅱ（ＰＳⅡ）反应中心Ｄ１／Ｄ２／Ｃｙｔｂ－５５９复合物在４８８ｎｍ处激发的共振拉曼谱显示４个主要谱带,其峰位分别在１５３２（ｖｌ）１１６５（ｖ２）１０１０（ｖ３）和９７０（ｖ４）ｃｍ＾－１处,表明ＰＳⅡ反应中心结合的β－胡萝卜素分子是全反式构型。Ｄ１／Ｄ２／Ｃｙｔｂ－５５９复合物在色素抽提液的拉曼光谱也显示４个主要的拉曼峰,其中ｖ４谱带的强度急剧下降,说明ＰＳⅡ反应中心内部结合的β－胡萝卜素