荧光假单胞菌抗噬菌体菌株的选育

本实验从荧光假单胞菌（Ｐｓｅｕｄｏｍｏｎａｓｆｌｕｏｒｅｓｃｅｎｓ）ＡＳ—３菌株的不正常发酵液中分离到一种噬菌体,将其命名为ＰＦＡＳ。ＡＳ—３菌株能利用葡萄糖发酵产生Ｄ－异维生素Ｃ的前体物质２－酮基－Ｄ－葡萄糖酸。电镜观察表明ＰＦＡＳ噬菌体呈蝌蚪形,具有直径为６６ｎｍ的六角形头部及长１１７ｎｍ的尾部。通过紫外线诱变及自然选育两种途径,配合简便有效的初筛方法,经多次分离、纯化、复筛最终在摇并发酵试验中获得６株产量稳定地高于对照敏感菌的抗噬菌体菌株,可望用于生产。     

Affinity chromatography—dependent selection （ACDS） of genomic DNA fragments bound specifically to bacterial synthesized Myc／Myn proteins

This paper describes an approach to seek for mouse c-Myc/Myn proteins-bound specific sequences among genomic DNA.cDNA fragment of myn gene was obtained through RT-PCR technique from RNA of NIH3T3 cells.DNA fragments encoding BR/HLH/LZ structure of Myc and Myn proteins were cloned in frame into pGEX-2T vector respectively.Fusion GST-Myc and GST-Myn synthesized in E.coli hosts showed affinity to CACGTG E-box DNA and subsequently interacted with genomic fragments prepared through whole-genome-PCR.A PCR-assisted procedure which combines protein-DNA interaction and affinity chromatography was designed to enrich Myc/Myn bound DNA.At least two genomic DNA fragments obtained exhibit specifical binding capacity to Myc/Myn complex but not to GST alone.Significance of the work and of the technique itself as well asidentification of the DNAs are discussed.     

野生紫斑牡丹和四川牡丹种子萌发特性及与其致濒的关系

野生牡丹种子一般较小,而且不同产地之间形状、大小差异较大。其萌发特性与栽培牡丹相比也有较大差异：萌发期长达半年以上,且萌发温度在１０～１５℃为宜,超过２０℃则明显不利于生根及上胚轴生长。四个不同分布地的四川牡丹种子萌发率较一致,均在６０～７７％之间。三个不同产地的紫斑牡丹种子萌发率则相差甚远,分布于甘肃文县的萌发率达７６％,而分布于陕西略阳和湖北神农架的萌发率则分别只有１２％和４．４％,出苗率则更低。本文认为紫斑牡丹的种子特性是其在自然界处于濒危状态的重要原因之一。     

噬菌蛭弧菌噬菌斑的鉴别与纯化的研究

本文报告了使用１／５００营养肉汤双层琼脂培养基,在含有宿主菌及寄生菌混合物的软琼脂层中,蛭弧菌、变形虫及鞭毛虫等均可形成噬菌斑,但其大小、形态、扩展速度不同。鉴别方法除依据噬菌斑形态特征外,主要靠相差显微镜下的形态学观察。蛭弧菌的纯化用单斑传代,一个直径为１ｍｍ的噬菌斑含有约１０^５－６ｐｆｕ／ｍｌ（每毫升噬菌斑形成单位）。     

Nanometric design of extraordinary hydrophobic-induced pKa shifts for aspartic acid: Relevance to protein mechanisms

Commonly a key element enabling proteins to function is an amino acid residue or residues with functional side chains having shifted pKa values. This article reports the results on a set of protein-based polymers (model proteins) that exhibit hydrophobic folding and assembly transitions, and that have been designed for the purpose of achieving large hydrophobic-induced pKa shifts by selectively replacing Val residues by Phe residues. The high molecular weight polypentapeptides, actually poly (tricosapeptides) with six varied pentamers in fixed sequence, were designed and synthesized to have the same amino acid compositions but different proximities between a single aspartic acid residue and 5 Phe residues per 30 residues. With the 5 Phe residues distal from the Asp residue, the observed pKa shift was 2.9 when compared to the Val-containing reference. With the 5 Phe residues within 1 nm of the Asp residue, the pKa shift was 6.2. This represents a free energy of interaction of 8 kcal/moles. To our knowledge, this is the largest pKa shift documented for an Asp residue in a polypeptide– or protein–water system. Data are reviewed that do not support the usual electrostatic arguments for pKa shifts of charge–charge repulsion and/or unfavorable ion self-energies arising from displacement of water by hydrophobic moieties, but rather the data are interpreted to indicate the presence of an apolar–polar repulsive free energy of hydration, which results from a potentially highly cooperative competition between apolar and polar species for hydration. © 1994 John Wiley & Sons, Inc.     

Differential expression inArabidopsis ofLhca2, a PSI cab gene

A cDNA clone of the geneLhca2 encoding a photosystem I (PSI) type II chlorophylla/b-binding protein was isolated fromArabidopsis thaliana. The isolation of this, the fourth PSI cab gene fromArabidopsis, confirms a previous report [1] that indicatedArabidopsis may contain all four PSI cab genes identified in other plant species.Lhca2 is a single-copy gene as are the other knownArabidopsis PSI cab genes. The patterns of developmental expression and tissue-specific regulation ofLhca2 are similar to those of other PSI and PSII cab genes, but the light induction pattern and the steady-state mRNA level ofLhca2 are distinct. This suggests that a different mechanism may be employed to regulate the expression ofLhca2.     

Ca^2＋敏感性微电极在心肌胞浆Ca^2＋活度检测中的应用

改进的中性载体Ｃａ２＋敏感性微电极（Ｃａ－ＩＳＥ）在尖端直径为０．４—０．８μｍ时仍具有良好特性,可用于心肌胞浆Ｃａ２＋活度（αＣａｉ）的检测。测得豚鼠右心乳头肌、狗心室肌和浦肯野纤维静息时分别为０．１９±０．０１（ｎ＝２２）,０．２０±０．０２（ｎ＝１１）和０．４６±０．０７（ｎ＝１３）μｍｏｌ·Ｌ－１。毒毛旋花苷Ｇ３μｍｏｌ·Ｌ－１使静态及动态心肌分别增高０．１８±０．０２和６．６９±２．０９μｍｏｌ·Ｌ－１（ｎ＝２２）,并出现触发活动（ＴＡ）。１００μｍｏｌ·Ｌ－１蝙蝠葛碱可抑制毒毛旋花苷Ｇ引起的增高,同时使其ＴＡ消失。表明Ｃａ－ＩＳＥ技术可用于心肌组织ＴＡ与的同步检测。     

牛生长激素释放因子的融合表达及其产物的化学加工

通过寡核苷酸引导的定位突变,在人工全合成的第２７位为Ｉｌｅ的牛生长激素释放因子［Ｉｌｅ２７］ｂＧＲＦ（１－４４）ＯＨ基因的５＇端ＡＴＧ后插入Ｔｒｐ密码子序列,并分别了构建了Ｐｌ ｐｒｏｍｏｔｅｒ控制下、以β－半乳糖苷酶和ｐｒｏｔｅｉｎ Ａ结合ＩｇＧ ｄｏｍａｉｎＢ、Ｃ为载体蛋白的融合型基因表达质粒ｐＢＬＥ３１０和ｐＢＬＰＡＥ２Ｄ,在大肠杆菌中得到高效表达。经ＳＤＳ－ＰＡＧＥ分析,表达产物β－Ｇａｌ     

高脂血症兔球结膜微循环的改变

本实验用胆固醇粉喂家兔,造成实验性高脂血症,活体观察球结膜微循环的形态、流态及血管周围状态等１５项指标,并用球结膜微循环综合定量评价方法计算了综合积分值。处死后取球结膜进行组织学检查。结果表明：高脂血症家兔球结膜微循环有明显改变,主要为微血管形态异常、血流减慢、红细胞聚集、白微栓、静脉壁上有白色斑块等改变。球结膜微循环综合积分值明显增加,高于实验前。球结膜组织学检查发现上皮层下有泡沫细胞、血管壁增厚、有空泡、静脉内有血栓。虹膜睫状体内除有多数泡沫细胞外,还有胆固醇的菱形结晶。上述改变表明,高脂血症兔球结膜微循环有明显改变。血液有高凝、高聚倾向。黑茶中的茶色素有抗凝、抑制血小板聚集、促进纤溶等作用,口服黑茶可改善高脂血症兔球结膜微循环障碍。