稀土离子(Nd3+)对金黄色葡萄球菌细胞壁结构的影响

本文的研究目的是探索稀土离子Nd^3＋对金黄色葡萄球菌细胞壁结构的影响作用。采用透射电镜、氨基酸自动分析仪和红外光普法等检测手段,提出了Nd^3＋可使金黄色葡萄球菌细胞壁的形态和结构发生改变;低于抑菌浓度的NdCl3对金黄色葡萄球菌细胞壁的古成具有促进作用：高浓度（指杀菌浓度和抑菌浓度）Nd^3＋可断裂细胞壁中肽聚糖的大部分肽键和氢键,致使细胞壁中肽聚糖的交联网状结构被破坏。     

真菌菌丝细胞壁提取物对马铃薯块茎组织抗干腐病的诱导效应

以马铃薯(品种'大西洋')块茎切片为材料,研究了马铃薯非亲和菌株粉红单端孢(Trichothecium roseum)菌丝细胞壁提取物处理对马铃薯块茎组织干腐病抗性的诱导效果及其机理.结果表明,150 μg/mL(以中性糖含量为标准)菌丝细胞壁提取物预处理马铃薯切片72 h后进行损伤接种能显著降低干腐病菌(Fusarium sulphureum)的侵染能力,预处理块茎的病斑直径仅为对照的43.6%;菌丝细胞壁提取物处理能显著增强与马铃薯块茎组织抗病相关的过氧化物酶(POD)、多酚氧化酶(PPO)和苯丙氨酸解氨酶(PAL)活性.可见,粉红单端孢菌丝细胞壁提取物预处理能显著增强马铃薯块茎组织对干腐病的抗性,而且主要是通过提高马铃薯块茎组织中与抗病性相关酶的活性来实现的.     

河北汉族拇指超伸展人群的指纹分析

采用面对面调查方式获取被检者拇指关节活动度资料。用无油墨法采集研究对象的指纹．放大镜下鉴定。通过对120名河北汉族拇指超伸展者的指纹组合及频率进行了分析,并与120名拇指直型者的指纹进行了对比研究,探讨人类指纹纹型及组合与拇指关节活动度之间是否具有关联性。发现超伸展组中小指出现的Lr频率显著高于对照组小指出现的Lr频率（p〈0．05）,而超伸展组ALO纹型组合中的230组合频率显著低于对照组（p〈0．05）。结论是河北汉族指纹的分布与拇指关节活动度具有一定相关性,但还有待进一步研究。     

ABA诱导玉米叶质外体H2O2积累的机制

通过组织化学染色和电镜观察并结合酶活性分析表明,ABA可通过诱导玉米（Zea mays L、）叶片质膜NADPH氧化酶、细胞壁POD及质外体PAO活性的升高,使其质外体产生H2O2;其中质膜NADPH氧化酶起主要作用。     

草莓果实发育成熟过程中糖苷酶和纤维素酶活性及细胞壁组成变化

以丰香和红丰草莓为试材,对果实发育成熟过程中细胞壁水解酶活性和细胞壁成份变化进行了研究．结果表明：半乳糖苷酶和α-甘露糖苷酶活性随草莓果实成熟而提高,葡萄糖苷酶活性不随草莓果实成熟而提高．随着果实发育成熟,纤维素酶活性、果胶酶活性不断提高．果实中未检测到内切多聚半乳糖醛酸酶活性,外切多聚半乳糖醛酸酶活性变化不随果实成熟软化而提高．随果实发育成熟,细胞壁中可溶性果胶和半纤维素增加,而离子结合果胶和共价结合果胶及纤维素减少．     

H4K5去乙酰化对镍胁迫下酿酒酵母细胞壁完整性途径的调控作用

【目的】金属镍(nickel, Ni)是人类广泛接触的重金属污染物之一,镍暴露会激活细胞内的细胞壁完整性(cell wall integrity, CWI)信号通路,也会导致细胞内组蛋白乙酰化水平降低,但CWI途径在镍胁迫时是否受组蛋白乙酰化调控尚不完全清楚。【方法】利用组蛋白定点突变型菌株H4K5R (模拟去乙酰化状态),分析镍胁迫下H4K5去乙酰化对酿酒酵母CWI途径的调控作用【结果】与野生型菌株相比,定点突变型菌株H4K5R具有较强的镍抗性:在5.0 mmol/L NiCl₂胁迫下,定点突变型菌株仍能生长良好;Western blotting与qRT-PCR结果表明,野生型菌株BY4741在5.0 mmol/L NiCl₂胁迫下细胞壁完整性途径被激活,甘露聚糖与葡聚糖调控基因Mnn9表达量显著上调3.13倍、Fks1表达量显著上调1.49倍,甘露聚糖、β-葡聚糖的含量也增加,说明此时野生型菌株激活了CWI途径,细胞壁成分含量增加;定点突变型菌株H4K5R在5.0 mmol/L NiCl₂胁迫下CWI途径激活程度较轻,虽然Mnn9、Fks1表达量上调,但甘露聚糖含量变化并不显著,而相较于野生型菌株β-葡聚糖含量增加幅度较小。【结论】在5.0 mmol/L NiCl₂胁迫下,定点突变型菌株H4K5位点的去乙酰化调控CWI途径,进而影响细胞壁组分的变化。     

缢蛏碱性磷酸酶胍溶液中分子折叠与活力变化研究

报道了缢蛏碱性磷酸酶（简称ＡＬＰ）经不同浓度盐酸胍处理时酶的分子构象发生的变化以及酶变化和失活的动力学过程。在胍中酶荧光发谢峰强度下降,紫外差光谱在２４６ｎｍ和２８５ｎｍ处出现２个负峰,ＣＤ谱中酶的α螺旋度下降,且随浓度增大,变化程度也加大。动力学研究表明,酶在０．５ｍｏｌ／Ｌ、１．０ｍｏｌ／Ｌ、２．０ｍｏｌ／Ｌ、３．０ｍｏｌ／Ｌ、４．０ｍｏｌ／Ｌ盐酸胍中的变性速度常数分别为３．２１×１０＾－４ｓ     

应用自然界的规律与化学家的工具是创造新蛋白质的一条途径

最近蛋白质研究的一个新领域引起了人们的关注,它被雄心勃勃地称为‘从头设计蛋白质’。M.Mutter认为,设计予定立体构象的多肽顺序的工作由于对蛋白质折迭与拓扑结构的规律认识有限而受到阻碍。将化学合成的非天然的链用于构建蛋白质可以克服从头合成(de novo design)蛋白质时遇到的这种困难。     

The Phosphate Transporter PHT4;6 Is a Determinant of Salt Tolerance that Is Localized to the Golgi Apparatus of Arabidopsis

Insertion mutations that disrupt the function of PHT4;6 （At5g44370） cause NaCI hypersensitivity of Arabidopsis seedlings that is characterized by reduced growth of the primary root, enhanced lateral branching, and swelling of root tips. Mutant phenotypes were exacerbated by sucrose, but not by equiosmolar concentrations of mannitol, and attenuated by low inorganic phosphate in the medium. Protein PHT4;6 belongs to the Major Facilitator Superfamily of permeases that shares significant sequence similarity to mammalian type-I Pi transporters and vesicular glutamate transporters, and is a member of the PHT4 family of putative intracellular phosphate transporters of plants. PHT4;6 localizes to the Golgi membrane and transport studies indicate that PHT4;6 facilitates the selective transport of Pi but not of chloride or inorganic anions. Phenotypic similarities with other mutants displaying root swelling suggest that PHT4;6 likely functions in protein N-glycosylation and cell wall biosynthesis, which are essential for salt tolerance. Together, our results indicate that PHT4;6 transports Pi out of the Golgi lumenal space for the re-cycling of the Pi released from glycosylation processes.     

ABA-Mediated Inhibition of Germination Is Related to the Inhibition of Genes Encoding Cell-Wall Biosynthetic and Architecture： Modifying Enzymes and Structural Proteins in Medicago truncatula Embryo Axis

Radicle emergence and reserves mobilization are two distinct programmes that are thought to control germination. Both programs are influenced by abscissic acid （ABA） but how this hormone controls seed germination is still poorly known. Phenotypic and microscopic observations of the embryo axis of Medicago truncatula during germination in mitotic inhibition condition triggered by 10 μM oryzalin showed that cell division was not required to allow radicle emergence. A suppressive subtractive hybridization showed that more than 10% of up-regulated genes in the embryo axis encoded proteins related to cell-wall biosynthesis. The expression of α-expansins, pectin-esterase, xylogucan-endotransglycosidase, cellulose synthase, and extensins was monitored in the embryo axis of seeds germinated on water, constant and transitory ABA. These genes were overexpressed before completion of germination in the control and strongly inhibited by ABA. The expression was re-established in the ABA transitory-treatment after the seeds were transferred back on water and proceeded to germination. This proves these genes as contributors to the completion of germination and strengthen the idea that cell-wall loosening and remodeling in relation to cell expansion in the embryo axis is a determinant feature in germination. Our results also showed that ABA controls germination through the control of radicle emergence, namely by inhibiting cell-wall loosening and expansion.