Catalysis in abiotic structured media: an approach to selective synthesis of biopolymers

Micro- and nanoenvironments formed by amphiphile self-assembled structures, water-ice lattices and minerals have well-defined, repeating, chemical and physical properties that can be used for selective synthesis of biopolymers, such as RNAs and proteins. The advances made in the development of polymerization supported by these micro- and nanosystems are reviewed here. In particular, it is shown that these systems promote non-enzymatic biopolymerization, yielding long polymers whose sequence composition is determined by the interactions between monomers and the supporting environment. When used to compartmentalize enzymatic biopolymerization, micro- and nanostructures allow the implementation of molecular selection and evolution schemes, which are difficult in homogeneous medium, yielding very active molecules. Thus, micro- and nanoenvironment approaches to the synthesis and selection of biopolymers could be developed into a new biotechnological tool for the production of biopolymers with novel functions.Received 3 August 2004; received after revision 6 October 2004; accepted 21 October 2004     

The structure and functions of the presenilins

The presenilins (PSs) were new proteins discovered in 1995 to be involved, among other functions, in the molecular mechanisms leading to Alzheimers disease. These proteins have been the subject of many investigations since then to elucidate their molecular structures and functions. Until now, the conclusions about PS structure have been discordant, but the 8-TM structure has been accepted by the Alzheimers community, with the evidence for the 7-TM structure largely ignored. Here the evidence is reviewed for the 6-TM, 7-TM, 8-TM and other proposed models of PS topography and possibilities offered for the differences in interpretation of the various sets of data. The conclusion is that at this stage, the 7-TM model for cell surface PS is most likely the correct one.Received 22 December 2004; accepted 26 January 2005     

Role of Sam68 as an adaptor protein in signal transduction

Sam68, the substrate of Src in mitosis, belongs to the family of RNA binding proteins. Sam68 contains consensus sequences to interact with other proteins via specific domains. Thus, Sam68 has various proline-rich sequences to interact with SH3 domain-containing proteins. Moreover, Sam68 also has a C-terminal domain rich in tyrosine residues that is a substrate for tyrosine kinases. Tyrosine phosphorylation of Sam68 promotes its interaction with SH2 containing proteins. The association of Sam68 with SH3 domain-containing proteins, and its tyrosine phosphorylation may negatively regulate its RNA binding activity. The presence of these consensus sequences to interact with different domains allows this protein to participate in signal transduction pathways triggered by tyrosine kinases. Thus, Sam68 participates in the signaling of T cell receptors, leptin and insulin receptors. In these systems Sam68 is tyrosine phosphorylated and recruited to specific signaling complexes. The participation of Sam68 in signaling suggests that it may function as an adaptor molecule, working as a dock to recruit other signaling molecules. Finally, the connection between this role of Sam68 in protein-protein interaction with RNA binding activity may connect signal transduction of tyrosine kinases with the regulation of RNA metabolism.Received 16 July 2004; received after revision 12 August 2004; accepted 18 August 2004     

花生蛋白脂肪乳状液中蛋白质的聚沉作用

花生蛋白脂肪乳状液中花生蛋白质的聚沉作用,是发生在一个ｐＨ值区间。当提取剂ｐＨ值在６４时,聚沉ｐＨ值为３１７～６０９;ｐＨ值＝８～１０时为４１～６３７,静置时间愈长聚沉愈完全,但聚沉ｐＨ值不变。在花生蛋白脂肪乳状液中通入ＣＯ２时,可使花生蛋白质聚沉。     

Calcium carbonate nanoparticles promote osteogenesis compared to adipogenesis in human bone-marrow mesenchymal stem cells

Rhombohedron-like and fusiform calcium carbonate nanoparticles were fabricated using a new method. Their geometry was controlled by varying the mixing speed and ratio of ethanol versus water in reaction system. The calcium carbonate nanoparticles(CCNPs) have slight effect on viability of human bone-marrow mesenchymal stem cells(hBMSCs) with dose-dependent and shape-dependent, but they can significantly promote osteogenic differentiation of hBMSCs in vitro by 10–37% increase of alkaline phosphatase(ALP) activity, 9–36% growth of collagen secretion and 1.13–1.83 folds upregulation of osteogenesis-related genes, even at lower dose ranges(5–20 μg/ml). The efficacity of promoting osteogenesis depends on the shape and dose of CCNPs. Furthermore,adipogenesis was inhibited by less accumulation of lipid droplets, lower triglyceride(TG) secretion and downregulation of adipogenesis-related genes. These findings improve the understanding of effects CCNPs on hBMSCs fate towards osteoblasts or adipocytes and have meaningful impact for combining use of CCNPs and hBMSCs in tissue engineering and regenerative medicine fields.     

Antimicrobial activity in the skin of the channel catfish Ictalurus punctatus: characterization of broad-spectrum histone-like antimicrobial proteins

Three antibacterial proteins were isolated from acid extracts of channel catfish (Ictalurus punctatus) skin by cation exchange chromatography and reverse-phase high-pressure liquid chromatography. The molecular masses of the proteins were 15.5, 15.5 and 30 kD as determined by SDS-polyacrylamide gel electrophoresis. Mass spectrometry, amino acid composition and amino acid sequence data suggest that the most abundant protein is closely related to histone H2B. The H2B-like protein was inhibitory to Aeromonas hydrophila and Saprolegnia spp., which are important bacterial and fungal pathogens of fish. These findings suggest that histones may be important defensive molecules in fish. Received 22 December 1997; received after revision 5 March 1998; accepted 5 March 1998     

大鼠染色体的非组蛋白、核糖核蛋白(RNP)与银染蛋白三者关系的研究

本文应用ＴＥＭ技术、电镜细胞化学、胶体金标记和银染技术结合研究了大鼠骨髓细胞染色体现有架。超薄切片结合ＲＮＰ优先染色法在染色体原位显示ＲＮＰ，同时又结合银染电镜扭亏为盈主ＲＮａｓｅ－胶体金定位显示ＲＮＡ，结果显示金颗粒与银颗粒在染色体中分布的位置与ＲＮＰ所在部位恰好一致。说明ＲＮＰ中的蛋白质含有角染的酸性蛋白，即所观察到的染色体骨架非组蛋白、ＲＮＰ中的蛋白部分，银染蛋白三者是一致的。     

花生(Arachis hypogea L.)体细胞胚胚性特异蛋白的研究

花生萌发３ｄ的胚叶在诱导培养基上出现高频率的体细胞胚发生．ＳＤＳ－ＰＡＧＥ分析结果表明：在体细胞胚发生过程中，诱导第三天开始出现３条新的蛋白谱带，７ｄ后出现２条新带，１５ｄ后又出现３条；而在非胚性组织中检测到抑制性的特异蛋白条带．     

Effects of point mutation C→T at - 64 of human δ globin gene promoter on DNA binding proteins

By electrophoretic mobility shift assay (EMSA), the effect of point mutation C→T at - 64 of human δ-globin gene on its binding proteins has been studied. Two segments of 36 bp from - 83- - 48 bp of the 6 globin gene promoter, named WOG and MOG, were synthesized. WOG includes wild type CAAT-like box (CCAAC), while MOG includes the mutant CAAT-like box (CCAAT, -64 C→T). Results indicate that: ( i ) in erythroid cell lines MEL, K562 and Hemin induced K562, the affinity of MOG with CCAAT binding protein (CBF) and GATA-1 was greatly increased; ( ii ) in Hemin induced K562 cell line, there were another two novel specific DNA binding proteins, named C and D temporarily, besides the above two factors. The former was combined with WOG and MOG, likely indicating its relation with the increased gene expression after induction. The latter was only combined with MOG, which had possible relationship with the point mutation of - 64 C→T; ( iii ) EMSA also indicates that the suppression mechanisms of the expression of 6 globin gene is different in various periods of human developments. The result evidently supports the hypothesis that the defect CAAT-like box in human 6 globin gene contributes the main reason of its low level expression. The defect c/s-acting element CAAT-like box affects gene expression by its combination with the frans-acting element CBF and GATA-1.     

纤毛虫皮层细胞骨架的研究进展

纤毛虫皮层的研究对探讨细胞的发育、分化、结构模式及其遗传控制有着极其重大的生物学意义,纤毛虫细胞皮层中含有非常丰富的细胞骨架成分,它们在结构上表现出来的特殊性有利于更深地探索皮层分化和皮层模式的控制机理,本综述了有关纤毛虫皮层细胞骨架的结构和形态发生方面的研究及皮层细胞骨架蛋白质构成的生化和分子生物学研究进展。