A statistical method for correlating tRNA sequence with amino acid specificity.

A statistical method for finding the nucleotide positions in tRNA sequences that correlate with amino acid specificity has been developed. The procedure involves finding the subset of nucleotide positions and groups of positions where the marginal density of one amino acid tRNA class does not overlap that of any other amino acid class. The procedure is an application of a statistical method known as the Expectation Maximization algorithm.     

FOLATE LEVELS IN DEVELOPING MOUSE BRAIN1

Abstract— The folate coenzymes of mouse brain underwent quantitative and qualitative changes during the first few weeks after birth. The total folate coenzymes per unit wet weight declined by approximately 60 per cent. In the newborn brains a relatively small proportion of the total folates were poly-γ-glutamyl derivatives, but the percentage of the total folates in these forms increased as the brain matured.     

A mechanism for inhibition of luminol-dependent neutrophil chemiluminescence by polyanions

Heparin has been reported to have antiinflammatory properties in both experimental animal and human disease states. Previous investigators assumed that the antiinflammatory properties of heparin were related to its anticoagulant effect. In this study we confirm the ability of heparin to inhibit luminol-dependent chemiluminescence by neutrophils stimulated with serum-activated zymosan. This inhibition is due to a combination of the diminished release of myeloperoxidase and the scavenging of the luminol oxidant generated by the myeloperoxidase-H2O2-chloride system. Although the polyanions heparin and dextran sulfate were effective in inhibiting luminol-dependent myeloperoxidase-H2O2-chloride chemiluminescence, the uncharged polysaccharide dextran T500 was without effect. None of the polysaccharides inhibited oxygen consumption by stimulated neutrophils. Additionally, heparin was able to reduce the myeloperoxidase release from zymosan-stimulated neutrophils by nearly 50%. Recent studies have shown that some antiinflammatory drugs scavenge peroxidase-generated oxidants of luminol. Such a property may explain the previously observed antiinflammatory effects of heparin and other polyanions.     

Shape effects in elastic scattering by orientationally random ensembles of simple model viruses

Recent theoretical work has shown that the complete set of polarized elastic light scattering studies should yield information about particle structure that has so far hardly been utilized. We present calculations of such light-scattering properties for a number of model structures, exploring particularly the size limit at which the new effects should become visible. The particles are assumed to be randomly oriented in aqueous suspension, and all identical to each other. We compare several particle models of differing geometrical shape, but with identical forward scattering power and identical radii of gyration. We find that one of the ten observables shows particularly desirable properties as a general large-particle characterization parameter: it is nonzero for all structures, it approaches zero as particle size decreases, and it shows an angular dependence that distinguishes among models of different shape. Assuming incident light at 350 nm, it differentiates between different shaped particles with radii of gyration as small as 50 nm. Such particles are well below the optical resolution limit and about the size of many types of viruses.     

嗜盐耐盐微生物抗盐胁迫相关离子转运蛋白研究进展

离子转运蛋白在维持细胞内pH稳态、离子动态平衡等方面发挥着重要作用。钠离子转运体和钾离子转运体在嗜盐耐盐微生物中广泛存在,其"保钾排钠"机制是微生物抗盐胁迫的两大策略之一。近年来,嗜盐耐盐微生物中许多新型钠、钾离子转运体被陆续发现,如RDD蛋白、UPF0118蛋白、DUF蛋白和KimA蛋白等;Fe³⁺、Mg²⁺等其他金属离子的转运蛋白也被证实可通过影响微生物胞内相容性溶质的合成起到渗透调节的作用。本文综述了嗜盐耐盐微生物中抗盐胁迫相关的各类离子转运蛋白,分析其分子结构和工作机理,并对这些蛋白在农业方面的应用进行了展望。继续发现新的离子转运蛋白,探究抗盐胁迫相关离子转运蛋白的结构和机理,解析各转运系统的协同作用及分子调控机制,将进一步加深对嗜盐耐盐微生物抗盐胁迫调控的认识,并为盐碱地农作物的改良等提供新的思路。     

苹果柠檬酸合酶3基因家族成员鉴定及表达分析

柠檬酸合酶(citrate synthase 3, CS3)是细胞代谢途径中的关键酶之一,其活性调节着生物体的物质和能量代谢过程。本研究旨在从苹果全基因组中鉴定CS3基因家族成员,并进行生物信息学和表达模式分析,为研究苹果CS3基因的潜在功能提供理论基础。利用BLASTp基于GDR数据库鉴定苹果CS3家族成员,通过Pfam、SMART、MEGA5.0、clustalx.exe、ExPASy Proteomics Server、MEGAX、SOPMA、MEME和WoLF PSORT等软件分析CS3蛋白序列基本信息、亚细胞定位情况、结构域组成、系统进化关系以及染色体定位情况。利用酸含量的测定和实时荧光定量PCR (real-time fluorescence quantitative polymerase chain reaction, qRT-PCR)技术检测苹果6个CS3的组织表达和诱导表达特性。苹果CS3基因家族包含6个成员,这些CS3蛋白包括473−608个不等的氨基酸残基,等电点分布在7.21−8.82。亚细胞定位结果显示CS3蛋白分别定位在线粒体和叶绿体。系统进化分析可将其分为3类,各亚家族基因数量分别为2个。染色体定位结果显示,CS3基因分布在苹果不同的染色体上。蛋白二级结构以a-螺旋为主,其次是无规则卷曲,b-转角所占比例最小。筛选的6个家族成员在不同苹果组织中均有表达,整体表达趋势从高到低依次为MdCS3.4相对表达含量最高,MdCS3.6次之,其他家族成员相对表达量依次为MdCS3.3>MdCS3.2>MdCS3.1>MdCS3.5。qRT-PCR结果显示,MdCS3.1和MdCS3.3基因在酸含量较低的‘成纪1号’果肉中相对表达量最高,酸含量较高的‘艾斯达’果肉中MdCS3.2和MdCS3.3基因相对表达量最高。因此,本研究对不同苹果品种中CS3基因相对表达量进行了检测,并分析了其在苹果果实酸合成过程中的作用。结果表明,CS3基因在不同苹果品种中的相对表达量存在差异,为后续研究苹果品质形成机制提供了参考。     

粳稻SRAP分子标记遗传群的构建与分析

用超级稻品种‘沈农606’和普通粳稻‘丽江新团黑谷’为亲本杂交获得的102份F_2代单株,通过SRAP分子标记遗传分析,构建了包含14个连锁群,由129个多态性位点组成的水稻连锁图谱,此图谱覆盖基因组长度1671.5 cM,平均图距13.0 cM。连锁群上有17.2%的多态性位点表现偏分离,偏分离标记在连锁群上存在热点区域。     

长白落叶松（Larix olgensis）工业人工林的模拟间伐

应用马尔柯夫过程理论,在获得林分直径转移概率的基础上,采用间伐最小径阶林木,最大径阶林木,中间径阶林木三种间伐方式,在保留不同密度情况下对长白落叶松工业人工林进行模拟间伐,提出了适宜的保留密度和相应的抚育间伐对象。结果表明：马尔柯夫过程确能反映长白落叶松工业人工林的直径转移过程,利用马尔可夫过程理论对长白落叶松工业人工林进行模拟间伐实现了依据培育时间来确定间伐方法和措施,提高了长白落叶松工业人工林经营管理的精准性;长白落叶松工业人工林成林后的间伐无论从培育森林方面,还是从取得木材、加大林分收益方面考虑,都应该以间伐小径阶的林木为主,注重培育I、II级木,间伐III, IV级木;20～25 a长白落叶松工业人工林间伐后的保留经营密度以0.7为宜。