光敏核不育水稻61kD特异性蛋白质的纯化和N—端序列分析

用制备型聚丙烯酰胺凝胶电泳和制备型等电聚焦纯化了曾报道的光敏核不育水稻 (Oryza sativa)农垦 58S叶绿体的特异性蛋白质 P2 ,得到 SDS- PAGE和等电聚焦 (IEF )纯的 P2。经 SDS- PAGE和 IEF测定 ,该纯蛋白质的分子量是 61 k D,等电点是 5.8。现称 P2为 P61。氨基酸序列分析表明 P61的 N-端氨基酸序列与水稻和大麦叶绿体 ATPaseβ亚基的 N-端氨基酸序列同源。     

玉米精细胞质膜68kD特异糖蛋白组分的纯化和N—端序列测定

经ＳＤＳ＿ＰＡＧＥ和ＩＥＦ＿ＳＤＳ双向电泳，从玉米（ＺｅａｍａｙｓＬ．）精细胞质膜分离纯化得到等电点（ｐＩ）为５．５的６８ｋＤ糖蛋白的单一组分。伴刀豆球蛋白＿辣根过氧化物酶（ＣｏｎＡ＿ＨＲＰ）染色结果表明，该组分的糖链中含有甘露糖及葡萄糖残基。氨基酸序列分析表明，该组分的Ｎ＿端１５个氨基酸序列与ＣｏｎＡ的Ｎ＿端相应序列相同。根据分子量及ｐＩ值的差异，认为该组分并非ＣｏｎＡ，而可能与玉米精细胞质膜上的ＣｏｎＡ受体有关。它在玉米的精卵识别、粘附及融合中有何作用，无疑是令人感兴趣的问题。     

用混合氨基酸接肽的方法合成OX型肽亚库

肽库合成是药物研究组合化学策略的重要技术之一。建立合成OX型肽亚库的固相合成方法 ,接肽反应采用等摩尔的Fmoc氨基酸混合物和DIC HOBt缩合方法 ,以高浓度的缩合剂和不断缩减溶剂的策略促进偶联反应进行完全。产物的氨基酸组成分析结果显示 ,所使用的常见氨基酸都能以相近的摩尔比例接肽至X位置。推测经多次接肽后最终形成的肽亚库中 ,含低活力氨基酸较多的肽其浓度虽然会较低一些 ,但影响不会太大 ,且本合成方法成本相对较低 ,故可为抗原表位分析、多肽药物筛选及构效关系分析提供一种有用的工具。     

氨基酸的消旋研究

在纯乙酸溶剂中,以乙酸酐酰化消旋酪氨酸,消旋温度为90℃,L-酪氨酸和乙酸酐的摩尔比为12,每消旋1gL-酪氨酸时,溶剂乙酸的用量为5mL,效果较好。同样的方法应用于L-脯氨酸,L-苏氨酸,L-缬氨酸,L-赖氨酸,L-半胱氨酸等氨基酸,消旋率均可达到100%。     

Prebiotic syntheses of vitamin coenzymes: II. Pantoic acid,pantothenic acid,and the composition of coenzyme A

Summary Pantoic acid can by synthesized in good prebiotic yield from isobutyraldehyde or -ketoisovaleric acid + H₂CO + HCN. Isobutyraldehyde is the Strecker precursor to valine and -ketoisovaleric acid is the valine transamination product. Mg²⁺ and Ca²⁺ as well as several transition metals are catalysts for the -ketoisovaleric acid reaction. Pantothenic acid is produced from pantoyl lactone (easily formed from pantoic acid) and the relatively high concentrations of -alanine that would be formed on drying prebiotic amino acid mixtures. There is no selectivity for this reaction over glycine, alanine, or -amino butyric acid. The components of coenzyme A are discussed in terms of ease of prebiotic formation and stability and are shown to be plausible choices, but many other compounds are possible. The -OH of pantoic acid needs to be capped to prevent decomposition of pantothenic acid. These results suggest that coenzyme A function was important in the earliest metabolic pathways and that the coenzyme A precursor contained most of the components of the present coenzyme. Offprint requests to. S.L. Miller     

The template properties of some oligodeoxynucleotides containing cytidine and guanosine

Summary the co-condensation of guanosine- and cytidine-5-phospho-2-methylimidazolide on various oligodeoxynucleotides containing C and G has been studied. We find that GC₇ is an effective template for the incorporation of C into products of the form G_nC, whereas C₇G does not act as a template for C incorporation. The template C₃GC₃GC₃GC₃ directs the synthesis of complementary products, but the yield of long oligomers is very small. Templates in which G residues are contiguous or separated by a single C residue are ineffective, while templates containing the sequence GCCG are very inefficient. The significance of these findings in the context of prebiotic chemistry is discussed.     

The origin of polynucleotide-directed protein synthesis

Summary If protein synthesis evolved in an RNA world it was probably preceded by simpler processes by means of which interaction with amino acids conferred selective advantage on replicating RNA molecules. It is suggested that, at first, the simple attachment of amino acids to the 2′(3′)-termini of RNA templates favored initiation of replication at the end of the template rather than at internal positions. The second stage in the evolution of protein synthesis would probably have been the association of pairs of charged RNA adaptors in such a way as to favor noncoded formation of peptides. Only after this process had become efficient could coded synthesis have begun.     

Synthesis of Nucleoside <Emphasis Type="Italic">N</Emphasis>-Phosphoamino Acids and Peptide Formation

Nucleoside N-phosphoamino acids were synthesized through Atherton-Todd reaction of nucleoside H-phosphonate with amino acids, and their structures were confirmed by NMR and ESI-MS. After nucleoside N-phosphoamino acid was incubated in anhydrous methanol at 40 °C for 72 h, di- to tetra-peptide derivatives were detected by ESI-MS, and their structures were further identified by multistage mass spectrometry. These and previously published studies in aqueous solution suggest that nucleoside N-phosphoamino acids could have been prebiotic precursors of oligopeptides.     

外消旋薄荷醇对映选择性酶促酯化中酸酐与羧酸的比较研究

利用脂肪酶在有机溶剂中催化对映选择性酯化反应对外消旋薄荷醇进行了有效的光学拆分。对分别使用酸酐和相应的游离羧酸作酰基给体时的反应性能进行了比较。发现酸酐的反应性远高于对应的游离羧酸,但在酶的催化作用下酸酐易水解成为游离羧酸;在微水系统中使用过高浓度的酸酐会导致酶缺水而失活,同时会促进手性醇的非选择性酯化,从而降低产物的光学纯度。然而,在连续流加丙酸酐的半批式反应系统中,所有这些缺点均可有效地克服。与使用游离丙酸的批式反应系统相比,ｄｌ-薄荷醇的反应时间缩短了一半,酶的稳定性大幅度提高,而产物ｌ薄荷醇酯的光学纯度不相上下（＞９８％ｅ）。     

液蜡发酵制取混合二元酸的研究

A mutant of Candida tropicalis FYD-2 was obtained from its parental strain SFP-1186 by ultraviolet treatments.On shaking flask,the yield of mixed dicarboxylic acid(DCA) by the mutant was 21.4% higher than that by its ancestor.The amount of mixed DCA reached 156g/L for 120h incubation in a 10 L autoconrolled fermentor where the culture medium contained 25% n-paraffin.The process of induced and screening mutant was introduced and the time course of fermentation in 10 L fermentor was discussed.     

Pyrophosphate and Adenosine 5′-Diphosphate Synthesis from Phospho(enol)pyruvate: Catalysis by Phosphate Minerals and Modulation by Dimethyl Sulfoxide

Phospho(enol)pyruvate (PEP) undergoes transphosphorylation to form pyrophosphate (PPi) and adenosine 5′-diphosphate (5′-ADP) with high yields in the presence of an adsorbent surface of calcium phosphate (Pi.Ca), which is considered to be an ancient mineral with catalytic properties. PPi formation is a result of the phosphorolytic cleavage of the enol phosphate group of PEP by precipitated Pi. The synthesis of PPi is dependent on the amount of the solid matrix; it increases with the amount of adsorbed PEP and upon addition of dimethyl sulfoxide (Me₂SO), a molecule with high dipolar moment. Although it is saturated with PEP at neutral pH, the phosphorylating Pi.Ca surface becomes effective only in alkaline conditions. In a parallel reaction, PEP phosphorylates 5′-AMP to 5′-ADP with a yield that is sevenfold higher in the presence of the Pi.Ca surface than in its absence, indicating that the solid matrix promotes interaction between adsorbed molecules with a high potential for phosphoryl transfer. In contrast to phosphorolysis, this latter reaction is stimulated by Me₂SO only in homogeneous solution. It is concluded that phosphate minerals may have coadjuvated in reactions involving different phosphorylated compounds and that molecules with high dipolar moment may have acted in mildly alkaline, primitive aqueous environments to modulate phosphoryl transfer reactions catalyzed by phosphate minerals. Received: 31 January 1996 / Revised: 31 May 1996     

Question 1: Peptide Nucleic Acids and the Origin and Homochirality of Life

The possibilities of pseudo peptide DNA mimics like PNA (peptide nucleic acid) having a role for the prebiotic origin of life prior to an RNA world is discussed. In particular a scenario is proposed in which protocells with an achiral genetic material through several generations stepwise is converted into a chiral genetic material, e.g., by incorporation of RNA units. Provided that a sufficiently large sequence space is occupied, a selection process based on catalytic function in which a single cell (first common ancestor) has a definite evolutionary advantage, selection of this cell would by contingency also lock it into homochirality. Presented at: International School of Complexity – 4th Course: Basic Questions on the Origins of Life; “Ettore Majorana” Foundation and Centre for Scientific Culture, Erice, Italy, 1–6 October 2006.