Evidence for the prion hypothesis: induction of the yeast [PSI+] factor by in vitro- converted Sup35 protein

Starting with purified, bacterially produced protein, we have created a [PSI(+)]-inducing agent based on an altered (prion) conformation of the yeast Sup35 protein. After converting Sup35p to its prion conformation in vitro, we introduced it into the cytoplasm of living yeast using a liposome transformation protocol. Introduction of substoichiometric quantities of converted Sup35p greatly increased the rate of appearance of the well-characterized epigenetic factor [PSI+], which results from self-propagating aggregates of cellular Sup35p. Thus, as predicted by the prion hypothesis, proteins can act as infectious agents by causing self-propagating conformational changes.     

Evidence for macromolecular protein rings in the absence of bulk water

We have examined the architecture of a protein complex in the absence of bulk water. By determining collision cross sections of assemblies of the trp RNA binding protein, TRAP, we established that the 11-membered ring topology of the complex can be maintained within a mass spectrometer. We also found that the binding of tryptophan enhances the stability of the ring structure and that addition of a specific RNA molecule increases the size of the complex and prevents structural collapse. These results provide definitive evidence that protein quaternary structure can be maintained in the absence of bulk water and highlight the potential of ion mobility separation for defining shapes of heterogeneous macromolecular assemblies.     

中性蛋白酶水解蛋清蛋白的工艺

通过单因子试验及正交试验,确定中性蛋白酶水解制备蛋清蛋白肽的最佳工艺条件为底物溶液pH值为7.0、加酶量5 000 U.g-1、水解温度为55℃,水解6 h,氮回收率为49.22%。     

甲鱼蛋白抗氧化肽的中性蛋白酶酶解条件优化

采用甲鱼蛋白为原料制备抗氧化活性肽,以DPPH(1,1 二苯基 2 三硝基苯肼)清除率和DH(水解度)为评价指标,在单因素试验的基础上,采用响应面法优化了中性蛋白酶酶解甲鱼蛋白制备抗氧化肽的酶解条件。结果表明: 温度5065℃,酶解pH值748,加酶量29%时, DPPH清除率最高,为(8556±152)%,对应的水解度为(768±052)%。     

合作猪血液蛋白多型性研究

以简单随机抽样法 ,应用淀粉凝胶电泳技术对 55头合作猪 1 3个血液蛋白座位的多型性进行了分析。结果表明 :合作猪在运铁蛋白 ( Tf)、淀粉酶 ( Am)、6-磷酸葡萄糖酸脱氢酶 ( 6PGD)及碳酸酐酶 ( Ca) 4个座位表现多型 ,分别受 4,4,2 ,3个共显性等位基因支配 ,其中 Ca C基因为首次发现。其余 9个座位即 Cp、Hp、CEs、Pa、Es D、PHI、G6PD、PGM、MDH未发现多型。     

Evidence for a malarial parasite interaction site on the major transmembrane protein of the human erythrocyte

Soluble oligosaccharides derived from the surface of human erythrocytes were tested for their ability to competitively inhibit invasion of erythrocytes by Plasmodium falciparum, a malarial parasite. Invasion was most effectively inhibited by erythroglycan, a carbohydrate component of the band 3 transmembrane protein. The lactosamine chains of erythroglycan contributed much of the inhibitory activity. This indication of a primary parasite interaction site on band 3 supports a role for this protein in mediating the radical alterations of the erythrocyte cytoskeleton that accompany invasion.     

Evidence that enzyme polymorphisms are selectively neutral, but blood group polymorphisms are not

Data on enzyme polymorphism and blood group polymorphism were examined with special reference to molecular evolution, by using a statistic that depends on neither population structure nor other ecological factors. The data of the former are consistent with the hypothesis of neutral mutant and random genetic drift, whereas the latter are in accord with the hypothesis of balanced selection.     

济宁青山羊血液酶与非酶蛋白质多型性研究

以系统随机整群抽样法检测济宁青山羊血液酶和非酶蛋白质的 33个基因座位。结果发现 ,济宁青山羊在 Tf,AL P,PA- 3,Es- D,Pe P- B,L AP和 Amy 7个座位上表现多态性 ,分别受 2 ,2 ,2 ,2 ,3,2 ,2个共显性等位基因控制 ,其余 2 6个座位即 Hb-α,HB-β,Alb,Hp,α2 ,Es,CP,PA- 1,PA- 2 ,6 - PGD ,PHI,MDH,Dia,ACP,To,L DH - A ,L DH- B,CES- 1,CES- 2 ,AK,Cat,IDH,Go T,PGM,G- 6 - PD和 Go- 未检测出血液酶与非酶蛋白质座位有多型性。     

Blood serum protein polymorphism in North Siberian pig breed

The gene frequencies of AM allotypes of serum α-macroglobulins, class G immunoglobulins, and allotypes of lipoproteins of blood serum of North Siberian pig breed are determined. Genetic markers for this breed are found     

会计假设的图解研究与探索

会计假设在财务会计理论与实务研究中占有重要地位,它是理解和掌握会计基本理论与核算方法的基础。由于会计假设比较抽象,而且由会计假设引出的基本理论较为复杂,如何直观、清晰地讲解会计假设,以便更好地理解和掌握会计的基本理论?本文根据在教学实践中设计的会计假设图解,介绍了会计理论框架中的会计假设、发出存货计价中的会计假设和固定资产折旧中的会计假设以及图解的应用。     

小尾寒羊血液蛋白多态性与多羔性研究

通过非连续性垂直板聚丙烯酰胺凝胶电泳(PAGE)对小尾寒羊的8种血液蛋白(酶)进行多态性检测,同时以甘肃藏羊作为对照,探索绵羊多羔性与血液生化遗传的相关性。结果表明:Hb位点的HbB基因、Tf位点的TfC基因、Es的Es-基因与绵羊多羔性可能存在相关性,Ep是否可以作为小尾寒羊多羔性的遗传标记,还需进一步探讨,其它4个蛋白(酶)AIb、Pr、AMY、LDH与绵羊多羔性不相关;同时得出与多羔性相关的蛋白位点基因与目前所研究的多胎基因FecB等主效基因均不连锁,但存在相关性。     

Evidence from cassette mutagenesis for a structure-function motif in a protein of unknown structure

The three-dimensional structure of most enzymes is unknown; however, many enzymes may have structural motifs similar to those in the known structures of functionally related enzymes. Evidence is presented that an enzyme of unknown structure [Ile-transfer RNA (tRNA) synthetase] may share a functionally important structural motif with an enzyme of related function (Tyr-tRNA synthetase). This approach involves (i) identifying segments of Ile-tRNA synthetase that have been unusually conserved during evolution, (ii) predicting the function of one such segment by assuming a structural relation between Ile-tRNA synthetase and Tyr-tRNA synthetase, and (iii) testing the predicted function by mutagenesis and subsequent biochemical analysis. Random mutations were introduced by cassette mutagenesis into a ten-amino-acid segment of Ile-tRNA synthetase that was predicted to be involved in the formation of the binding site for isoleucine. Few amino acid substitutions appear to be tolerated in this region. However, one substitution (independently isolated twice) increased the Michaelis constant Km for isoleucine in the adenylate synthesis reaction by greater than 6000-fold, but had little effect on the Km for adenosine triphosphate, the apparent Km for tRNA, or the rate constant kcat.     

非线性中立型差分方程振动的充分条件

给出了在比较弱的条件下非线性中立型差分方程振动的几个充分条件．即若记（H1）：｜f（x）｜≥c｜x^a｜,（c〉0）;（H2）：∑n=r^∞qn=＋∞,下面4个条件之一成立：①Pn=1,且（H1）和（H2）成立;②pn=1,（H1）成立,且对（H1）中的a,∑n=rn^aqn（∑n=rqi）^a=∞成立;③0〈pn≤1,（H1）、（H2）成立,f（x）非减且（H1）中的a〈1;④1≤pn≤p,（H1）、（H2）成立,k≥m＋1,f（x）非减且（H1）中的a〉1,则非线性中立型差分方程△（xn-pnxn-k）＋qnf（xn-m）=0（n≥r）振动,其中m、n,k∈N,r=max{k,m},△xn=xn＋1-xn,f（x）连续,f（0）=0,且当x≠0时,xf（x）〉0,     

汉族人群聚腺苷二磷酸核糖聚合酶-1遗传多态性的检测

目的:通过检测人聚腺苷二磷酸核糖聚合酶-1(hPARP-1)7个外显子核苷酸多态性,了解在广东的汉族人群中hPARP-1基因多态性分布,为建立民族特色的DNA修复基因多态性数据提供基础资料。方法:选取在广东地区的汉族健康人群320名的基础资料及血液样本,抽提血液DNA,用PCR法扩增hPARP-1基因7个外显子,采用聚合酶链式反应(PCR)-单链构象多态性(SSCP)和银染技术检测hPARP-1基因多态性,并进行DNA序列测定。结果:在广东的汉族正常人320名血标本的7个外显子扩增产物SSCP电泳条带中,4个样本hPARP-1基因外显子17的SSCP电泳条带检出1条多态性条带,3个样本第12内含子检出1条多态性条带,其余6个外显子扩增产物SSCP电泳未见多态性条带。正常带型DNA测序结果与genebank中已知序列完全一致,第17外显子上有1种基因突变类型(T→C)。结论:在广东地区的汉族人群的hPARP-1基因第17外显子和第12内含子上可能存在多态性。     

白香猪血液蛋白多态性与若干性状表现的相关性

采用垂直板聚丙烯酰胺凝胶电泳技术，检测了白香猪群体的血液中血红蛋白（Hb)，转铁蛋白（Tf)，后白蛋白（Po)，后转铁蛋白（Ptf)4个蛋白座位的多态性。其中Tf、Po、Ptf发现了多态性而Hb没发现多态性。用方差分析的方法检测了各种基因型猪生产性能方面的差异，结果显示Po、Tf各种基因型之间的体长、体高无差异（P＞0．05）。Ptf的AA型的体长长于AB（P＜0．05），而2基因型之间的体高差异不显著（P＞0．05）。因此Ptf的多态性与香猪某些体尺性状之间存在一定的相关性。     

Mechanism of transmitter release: voltage hypothesis and calcium hypothesis

The calcium hypothesis of synaptic transmission has been challenged by experimental results using the crayfish neuromuscular junction that suggest that presynaptic depolarization can trigger transmitter release directly without calcium influx. Results from electrophysiological experiments using the same preparation do not support this voltage hypothesis, but are consistent with the calcium hypothesis. Voltage may modulate, but not elicit, transmitter release.