ψ-esters of depsidones with a lactole ring

The reaction of stictic, norstictic and salazinic acids with methanol, ethanol and tert-butanol has been investigated. 8′-O-Methylstictic acid is identical with methylstictic acid from Lobaria oregana. Ingolfdottir's vesuvianic acid from Stereocaulon vesuvianum and Handong's cetrariastrumin from Cetrariastrum nepalensis have been shown to be 8′-O-ethylstictic acid and 8′,9′-di-O-ethylsalazinic acid, respectively, by reaction of stictic and salazinic acids with ethanol.     

小麦萌发素G和ψG的纯化及其部分特性

利用亲和层析方法纯化了小麦草酸氧化酶G和ψG,并对其生化特性进行了初步分析.G和ψG的最适pH为3.5,在60℃以下较稳定.当草酸浓度大于0.2mmol/L时,G和ψG的活性受到抑制.G和ψG的Km值分别为0.084和0.053mmol/L.0.1 mmol/L的EDTA、NH4 、Cl-、Mn2 、Mg2 、Na 和K 对G和ψG的活性没有影响,0.1 mmol/L的Zn2 、Cu2 、Fez 、Al3 、CO32-、NO3-和SO42-抑制G和ψG的活性.0.1 mmol/L的H2PO4-和HPO42-仅抑制G的活性.0.1 mmol/L的核黄素、FMN和FAD抑制ψG活性,G的活性则不受FAD和FMN的影响.     

恒态光合磷酸化与△pH和△ψ的关系

在恒态下推动ATP形成的△μH~+中,除ApH外,△ψ的贡献也很明显:进行PSP反应,耗用H~+,降低了⊿pH幅度。NH_4Cl,尼日利亚菌素(Nig)对⊿pH和PSP的抑制作用是同步的。CCCP影响膜对质子的透性,加速内部质子外流,降低内部质子浓度,减少⊿pH幅度,抑制了PSP反应。PSP更依赖于类囊体内部质子浓度。在短杆菌环肽(Gram)(～5×10~(-8)mol/L)和缬氨霉素(Val)(～5×10~(-7)mol/L,+K~+)的作用下,⊿ψ几乎被完全消去,并对⊿pH无明显作用,但PSP分别被抑制了～30％(Gram)和～50％(Val),表明在恒态PSP反应中有30％～50％的能量来源可由⊿ψ提供。     

一种用SigmaPlot求PV曲线水分参数ψtlp的方法

以扶桑(Hibiscus Rose-sinensis)为例,用SigmaPlot for Windows软件分别绘制PV曲线双曲线和直线部分的散点图,同时拟合双曲线和直线方程.然后通过联立方程组求出质壁分离点的坐标值,计算出质壁分离时的渗透势(ψtlp)、相对水含量(RWCtlp)和相对渗透水含量(ROWCtlp).并与常用的直线回归法的结果进行了比较.该方法具有简单、准确、快速等特点,是获得PV曲线主要参数的一种新方法.     

ψ-Constrained Simulations of Protein Folding Transition States: Implications for Calculating ?

ψ-analysis has been used to identify interresidue contacts in the transition state ensemble (TSE) of ubiquitin and other proteins. The magnitude of ψ depends on the degree to which an inserted bihistidine (biHis) metal ion binding site is formed in the TSE. A ψ equal to zero or one indicates that the biHis site is absent or fully native-like, respectively, while a fractional ψ implies that in the TSE, the biHis site recovers only part of the binding-induced stabilization of the native state. All-atom Langevin dynamics simulations of the TSE are performed with restrictions imposed only on the distances between the pairs of residues with experimentally determined ψ of unity. When a site with a fractional ψ lies adjacent to a site with ψ = 1, the fractional ψ generally signifies that the “fractional site” has a distorted geometry in the TSE. When a fractional site is distal to the sites with ψ = 1, however, the histidines sample configurations in which the site is absent. The simulations indicate that the ψ = 1 sites by themselves can be used to generate a well-defined TSE having near-native topology. ? values calculated from the TS simulations exhibit mixed agreement with the experimental values. The origin and implication of the disparities are discussed.     

高效位点特异性链霉菌ψC31噬菌体整合酶的研究进展

链霉菌ψC31噬菌体整合酶(ψC31-int)属于位点特异性重组酶的解离酶/转化酶系,该家族催化机制由丝氨酸介导,能识别噬菌体附着位点(attP)和宿主基因组上的细菌附着位点(attB),介导同源序列之间的位点特异性重组.实验证实,ψC31-int是一种高效位点特异性整合工具酶,与其他整合策略相比,具有集高效和安全于一体的优点,通过介导位点特异性整合,将外源基因特异地整合到宿主基因组,使目的基因得以持续、高效的表达,并且具有DNA容量方面的优势.随着研究的深入,人们对ψC31-int介导整合作用机制和影响因素有了进一步的认识.通过一系列成功应用ψC31-int进行的基因治疗的动物学实验,为今后如何利用非病毒载体系统进行基因治疗及转基因动物模型的建立提供了一种新的选择.     

A Facile Synthesis of the Phosphoramidites of 2-N-Methyl-2′-deoxy (or 2′-O-allyl)-ψ-isocytidine, 1, 3-Dimethyl-2′-deoxy-ψ-uridine and N1-Methyl-2′-O-allyl-ψ-uridine as Synthons Suitable for Oligonucleotide Synthesis

Abstract

An efficient and facile syntheses of 5′-O-(4, 4′-dimethoxytrityl)-3′-[2-cyanoethyl bis(1-methylethyl)]phosphoramidites of 2-N-methyl-2′-deoxy-ψ-isocytidine (6), 2-N-methyl-2′-deoxy-α-ψ-isocytidine (13), 2-N-methyl-2′-O-allyl-ψ-isocytidine (11), 1, 3-dimethyl-2′-deoxy-ψ-uridine (4) and N1-methyl-2′-O-allyl-ψ-uridine (19) have been accomplished in good overall yields. The pyrimidine-pyrimidine transformation reaction was found to be useful for the preparation of 2-N-methyl-2′-O-allyl-ψ-isocytidine (10). The utility of these novel phosphoramidites is demonstrated by their incorporation into oligonucleotides via solid-support, oligonucleotide methodology.     

利用Gibson Assembly法构建狂犬病SRV9ψ区缺失株感染性cDNA

本研究为高效构建狂犬病SRV9ψ区缺失株感染性cDNA克隆,在细胞内进行重组狂犬病病毒的拯救提供帮助。按照Isothermal in vitro recombination system or"Gibson Assembly"连接方法设计引物,分别扩增得到去除狂犬病SRV9标准疫苗株的伪基因区(ψ区)的首尾均存在互补序列的5个结构蛋白基因的目的片段。利用T5核酸外切酶、DNA聚合酶及T4连接酶的协同作用,两步即可获得狂犬病SRV9ψ区缺失株的感染性cDNA。本研究利用Gibson Assembly连接法成功高效构建了狂犬病SRV9ψ区缺失株的感染性cDNA。此方法避免了传统的酶切连接方法中繁琐的实验步骤,实现了多个基因片段间的无缝连接,大大提高了载体构建的效率,为进一步研究狂犬病病毒的基因功能提供高效的方法。同时也为Gibson Assembly法应用于其它载体的构建提供借鉴。     

ψ—混合误差下非参数回归权函数估计的渐近正态性

本文在一定条件下讨论了ψ混合误差下非参数回归权函数估计     

基于LMI方法的多时滞中立型随机神经网络的ψ~γ稳定性

研究了一类具有多个时滞的中立型随机神经网络的均方φ~γ稳定性问题,应用Lyapunov-Krasovskii泛函稳定性理论和线性矩阵不等式(LMI)方法,建立了系统解的均方φ~γ稳定性判别准则.     

地中海拟无枝菌酸菌专一的噬菌体ψMMR1的研究

从生产力复霉素ＳＶ的地中海拟无枝菌酸菌Ｕ１１９的工业发酵罐裂解液中,分离到一株新的噬菌体ψＭＭＲ。该噬菌体经多次单斑分离、纯化,得到的噬斑多数为清亮的（约占９０％）,其它噬斑为浑浊斑,但未能从中分离到溶源菌。在被测试的可能的宿主菌中,ψＭＭＲ１不能感染除地中海拟无枝菌酸菌以外的菌株,说明寄生范围很窄。对ψＭＭＲ１的增殖和储存条件,诸如ｐＨ值、温度、二价金属离子、有机溶剂等对ψＭＭＲ１的影响进行了较     

Stereochemical Assessment of (φ,ψ) Outliers in Protein Structures Using Bond Geometry-Specific Ramachandran Steric-Maps

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产Shiga毒素噬菌体ψ297在大肠杆菌K12染色体上整合位点的定位研究

鉴定大肠杆菌O157产生Shiga毒素(Stx)的噬菌体ψ297在大肠杆菌K12染色体上的插入位点.采用加接头PCR方法从与噬菌体933W的整合酶基因int同源的核苷酸开始向未知区域进行步移测序,寻找目的基因.将获得的DNA序列与核苷酸数据库进行比较,确定了细菌性噬菌体ψ297的attL、attR和中心序列位于大肠杆菌K12的yecE基因内.噬菌体ψ297在宿主细胞E.coliK12染色体上的整合位点是yecE基因.     

Measurement of membrane potentials (ψ) of erythrocytes and white adipocytes by the accumulation of triphenylmethylphosphonium cation

Summary The accumulation of the lipophilic cation, triphenylmethylphosphonium, has been employed to determine the resting membrane potential in human erythrocytes, turkey erythrocytes, and rat white adipocytes. The triphenylmethylphosphonium cation equilibrates rapidly in human erythrocytes in the presence of low concentrations of the hydrophobic anion, tetraphenylborate. Tetraphenylborate does not accelerate the uptake of triphenylmethylphosphonium ion by adipocytes. The cell associatedvs. extracellular distribution of the triphenylmethylphosphonium ion is proportional to changes in membrane potential. The distribution of this ion reflects the membrane potential determining concentration of the ion with dominant permeability in a Nernst fashion. The resting membrane potentials for the human erythrocyte, turkey erythrocyte, and rat white adipocyte were found to be –8.4±1.3, –16.8±1.1, and –58.3±5.0 mV, respectively, values which compare favorably with values obtained by other methods. In addition, changes in membrane potential can be assessed by following triphenylmethylphosphonium uptake without determining the intracellular water space. The method has been successfully applied to a study of hormonally induced changes in membrane potential of rat white adipocytes.     

变铅青链霉菌对噬菌体ψHAU3抗性与异常修饰之间的相互关系

变铅青链霉菌异常修饰突发菌株ＺＸ１同时丧失了对噬菌体ψＨＡＵ３的抗性。遗传学杂交结果揭示,ＤＮＡ降解和对ψＨＡＵ３抗性这两种表型从不发生分离。以ＺＸ１为宿主和链霉菌低拷贝质粒ＳＣＰ２衍生的载体ｐＩＪ９２２为载体,构建了变铅青链霉菌ＪＴ４６的基因组文库。在８０００多个转化子中获得了一个能使ＺＸ１对ψＨＡＵ３显示抗性的杂合质粒,命名为ｐＩＪ８３１０。它除了含有完整的ｐＩＪ９２２外,还携带了大约１１ｋｂ     

(φ,ψ)₂ motifs: a purely conformation-based fine-grained enumeration of protein parts at the two-residue level

A deep understanding of protein structure benefits from the use of a variety of classification strategies that enhance our ability to effectively describe local patterns of conformation. Here, we use a clustering algorithm to analyze 76,533 all-trans segments from protein structures solved at 1.2 Å resolution or better to create a purely φ,ψ-based comprehensive empirical categorization of common conformations adopted by two adjacent φ,ψ pairs (i.e., (φ,ψ)₂ motifs). The clustering algorithm works in an origin-shifted four-dimensional space based on the two φ,ψ pairs to yield a parameter-dependent list of (φ,ψ)₂ motifs, in order of their prominence. The results are remarkably distinct from and complementary to the standard hydrogen-bond-centered view of secondary structure. New insights include an unprecedented level of precision in describing the φ,ψ angles of both previously known and novel motifs, ordering of these motifs by their population density, a data-driven recommendation that the standard C^α_i…C^α_i + 3 < 7 Å criteria for defining turns be changed to 6.5 Å, identification of β-strand and turn capping motifs, and identification of conformational capping by residues in polypeptide II conformation. We further document that the conformational preferences of a residue are substantially influenced by the conformation of its neighbors, and we suggest that accounting for these dependencies will improve protein modeling accuracy. Although the CUEVAS-4D(r₁₀?₁₄) ‘parts list’ presented here is only an initial exploration of the complex (φ,ψ)₂ landscape of proteins, it shows that there is value to be had from this approach, and it opens the door to more in-depth characterizations at the (φ,ψ)₂ level and at higher dimensions.     

噬菌体ψHAU3的cos位点及其与寄主相互作用的功能位点attP和attB的…

ψＨＡＵ３是寄主范围很广的放线菌噬菌体。Ｓｏｕｔｈｅｒｎ杂交实验表明,ψＨＡＵ３可以整合到吸水链霉菌应城变种１０－２２和变铅青链霉菌６６的突变体ＺＸ１的染色体中,形成溶原,其溶原菌自发释放ψＨＡＵ３,不受热激和紫外线照射的诱导。通过比较ψＨＡＵ３衍生噬粒ＰＩＪ８３００的ＤＮＡ酶切片段的中热前、后电泳带谱的区别,将ψＨＡＵ３的ｃｏｓ位点在ＰＩＪ８３００的图谱上得到了定位。还利用Ｓｏｕｔｈｅｒｎ杂交的     

产生志贺样毒素的噬菌体ψ297整合酶基因(int) 的克隆和序列分析

目的克隆并分析细菌性噬菌体ψ297的整合酶基因(int).方法采用加接头的基因DNA片断为模板进行步移PCR,根据溶源性噬菌体ψ297的染色体DNA上类似于噬菌体933W的整合酶基因的一个40个核苷酸设计引物,进行扩增、克隆、亚克隆、测序和序列分析.结果得到了噬菌体ψ297编码的整合酶基因(int)的完整序列,它的长度是1287bp,编码了428个氨基酸的Int蛋白质.将它们的序列与λ噬菌体的整合酶家族其它成员进行了比较,发现噬菌体ψ297的整合酶基因(int)与噬菌体VT1-Sakai的整合酶基因有79%的同源性,噬菌体ψ297的Int蛋白与噬菌体VT1-Sakai的Int蛋白在氨基酸序列上有82%的同源性.N-末端的氨基酸区域是完全保守的,而中心区和C-末端则显示出较大差异.结论噬菌体ψ297与λ噬菌体的int基因来源于同一基因库,噬菌体ψ297可能属于λ噬菌体家族.