Predominant expression and cellular distribution of fish Agr2 in renal collecting system

Anterior gradient 2 (Agr2) genes encode secretory proteins, and play significant roles in anterior-posterior patterning and tumor metastasis. Agr2 transcripts were shown to display quite diverse tissue distribution in different species, and little was known about the cellular localization of Agr2 proteins. In this study, we identified an Agr2 homologue from gibe[ carp (Carassius auratus gibelio), and revealed the expression patterns and cellular localization during embryogenesis and in adult tissues. The full-length cDNA of CagAgr2 is 803 nucleotides (nt) with an open reading frame of 510 nt encoding 169 amino acids. The Agr2 C-terminus matches to the class I PDZ-interacting motif, suggesting that it might be a PDZ-binding protein. During embryogenesis, CagAgr2 was found to be transcribed in the mucus-secreting hatching gland from tailbud stage and later in the pharynx region, swim bladder and pronephric duct as revealed by RT-PCR and whole mount in situ hybridization. In the adult fish, its transcription was predominantly confined to the kidney, and lower transcription levels were also found in the intestine, ovary and gills. To further localize the Agr2 protein, the anti-CagAgr2 polyclonal antibody was produced and used for immunofluorescence observation. In agreement with mRNA expression data, the Agr2 protein was localized in the pronephric duct of 3dph larvae. In adult fish, Agr2 protein expression is confined to the renal collecting system with asymmetric distribution along the apical-basolateral axis. The data provided suggestive evidence that fish Agr2 might be involved in differentiation and secretory functions of kidney epithelium. (C) 2009 Elsevier Inc. All rights reserved.

Molecular cloning, characterization and expression analysis of the PKZ gene in rare minnow Gobiocypris rarus

Double-stranded RNA-activated protein kinase (PKR) plays an important rote in interferon-induced antiviral responses, and is also involved in intracellular signaling pathways, including the apoptosis, proliferation, and transcription pathways. In the present study, a PKR-like gene was cloned and characterized from rare minnow Gobiocypris rarus. The full length of the rare minnow PKR-like (GrPKZ) cDNA is 1946 bp in Length and encodes a polypeptide of 503 amino acids with an estimated molecular mass of 57,355 Da and a predicted isoelectric point of 5.83. Analysis of the deduced amino acid sequence indicated that the mature peptide contains two Zalpha domains and one S_TKc domain, and is most similar to the crucian carp (Carassius auratus) PKR-like amino acid sequence with an identity of 77%. Quantitative RT-PCR analysis showed that GrPKZ mRNA expression is at low levels in gill, heart, intestine, kidney, liver, muscle and spleen tissues in healthy animals and up-regulated by viruses and bacteria. After being infected by grass carp reovirus, GrPKZ expression was up-regulated from 24 h post-injection and lasted until the fish became moribund (P < 0.05). Following infection with Aeromonas hydrophila, GrPKZ transcripts were induced at 24 h post-injection (P < 0.05) and returned to control levels at 120 h post-injection. These data imply that GrPKZ is involved in antiviral defense and Toll-like receptor 4 signaling pathway in bacterial infection. (C) 2008 Elsevier Ltd. All rights reserved.

Cloning and expression of medaka dazl during ernbryogenesis and gametogenesis

The Deleted in azoospermia family consists of RNA-binding proteins Bottle, Daz, and Daz-like (Dazl) that are expressed in the germline. Here, we report the cloning and expression of the medakafish (Oryzias latipes) dazl gene (odazl). Interestingly, although the predicted medaka Dazl protein (oDazl) contains a RRM motif and a DAZ repeat characteristic of its mammalian homologs, it lacks 80 aa at the C-terminus. By RT-PCR, RNA in situ hybridization, Western blotting and fluorescent immunohistochemistry using a rabbit anti-DazI antibody (alpha Oazl), we analyzed the expression patterns of odazl and its protein. The odazl transcript persists throughout embryogenesis and delineates with primordial germ cells. In adults, the expression of odazl RNA and its protein is restricted to germ cells of both the testis and ovary. We observed differential expression of RNA and protein at critical stages of gametogenesis. In the testis, the odazl RNA is low at premeiotic stages, abundant at meiotic stages, but absent in postmeiotic stages; whereas the oDazl protein is rich in premeiotic stages, reduced at meiotic stages, becomes barely detectable or absent in postmeiotic round spermatids or sperm, respectively. This is in sharp mature spermatozoa. In the ovary, the odazl RNA contrast to the human situation where the Dazl transcript and protein are present in and protein persist throughout oogenesis and also show differential expression at premeiotic, meiotic and postmeiotic stages. Thus, the odazl or its protein is a marker for germ cells during embryogenesis and at critical stages of gametogenesis in both sexes of medaka. (c) 2006 Elsevier B.V. All rights reserved.

Regulation by hetC of genes required for heterocyst differentiation and cell division in Anabaena sp strain PCC 7120

Unlike those of the wild-type strain, proheterocysts of the Anabaena sp. strain PCC 7120 hetC strain keep dividing. ftsZ, the most critical cell division gene, is up-regulated in hetC proheterocysts. Heterocyst differentiation genes hglD, hglE, patB, nijB, and xisA are no longer expressed in the hetC mutant. hetC also regulates the expression of patA, a pattern formation gene.

Identification of immune genes in grass carp Ctenopharyngodon idella in response to infection of the parasitic copepod Sinergasilus major

The parasitic copepod Sinergasilus major is an important pathogen of grass carp Ctenopharyngodon idella. To understand the immune response of grass carp to the copepod infection, suppression subtractive hybridization method was employed to characterize genes up-regulation during the copepod infection in liver and gills of the fish. One hundred and twenty-two dot blot positive clones from infected subtracted library were sequenced. Searching available databases by using these nucleotide sequences revealed that 23 genes are immune-related, including known acute-phase reactants, and four novel genes encoding proteins such as source of immunodominant MHC-associated peptides (SIMP), TNF receptor-associated factor 2 binding protein (T2BP), poliovirus receptor-related protein 1 precursor, glycoprotein A repetitions predominant (GARP). The differential expression of seven immune genes, i.e. GARP, alpha-2-macroglobulin, MHC class I, C3, SIMP, T2BP, transferrin, as a result of infection was further confirmed by RT-PCR, with the up-regulation of alpha-2-macroglobulin, MHC class I, C3, SIMP and T2BP in the liver of infected fish, and down-regulation of SIMP in the gills of infected fish. The present study provides foundation for understanding grass carp immune response and candidate genes for further analysis.

Enhanced resistance to Aeromonas hydrophila infection and enhanced phagocytic activities in human lactoferrin-transgenic grass carp (Ctenopharyngodon idellus)

Human lactoferrin (hLF) is an iron-binding protein with antimicrobial and immunomodulatory activities. hLF cDNA was transferred into grass carp via electroporated sperm. The production of transgenic fish was as high as 55% tinder the best parameters. 2(11) pulses and 20-min incubation. The expression of the transgene was demonstrated by the detection of hLF mRNA by RT-PCR. We also investigated the response of G(0) transgenic grass carp to Aeromonas hydrophila infection. Serum lysozyme activities (P>0.05) and phagocytic activities of kidney cells (P<0.05) were measured in transgenic individuals. The transgenic fish not only cleared A. hydrophila significantly faster than the control carp (P<0.05), but also showed enhanced phagocytic activities. The result shows that hLF has immunomodulatory activities in hLF-transgenic grass carp. The transgenic grass carp exhibited enhanced immunity to A. hydrophila infection. These results reveal that the mechanisms of disease resistance are different between hLF-transgenic plants and hLF-transgenic grass carp. (C) 2004 Elsevier B.V. All rights reserved.

alr0117, a two-component histidine kinase gene, is involved in heterocyst development in Anabaena sp PCC 7120

Anabaena sp. PCC; 7120 was mutagenized by transposon Tn5-1087b, generating a mutant whose heterocysts lack the envelope polysaccharide layer. The transposon was located between nucleotides 342 and 343 of alr0117, a 918 bp gene encoding a histidine kinase for a two-component regulatory system. Complementation of the mutant with a DNA fragment containing alr0117 and targeted inactivation of the gene confirmed that alr0117 is involved in heterocyst development. RT-PCR showed that alr0117 was constitutively expressed in the presence or absence of a combined-nitrogen source. hepA and patB, the two genes turned on during wild-type heterocyst development, were no longer activated in an alr0117-null mutant. The two-component signal transduction system involving alr0117 may control the formation of the envelope polysaccharide layer and certain late events essential to the function of heterocysts.

非洲爪蛙分泌型叶酸结合蛋白及NKX6.3在早期胚胎神经发育中的功能研究

叶酸是B族维生素的一员，参与体内一系列重要的生命过程包括DNA，氨基酸的合成，调控细胞周期，参与一碳单位供体循环，调节DNA,蛋白质甲基化等。叶酸的许多功能都和叶酸结合蛋白有关，体内有多种跨膜形式的叶酸结合蛋白，比如Folbp1，RFC，HCP等。以前的研究表明这些不同的叶酸结合蛋白具有不同的功能。分泌型叶酸结合蛋白是另外一类叶酸结合蛋白，在人类，小鼠，猪中都有序列报道，但是其功能却知之甚少。 我们在非洲爪蛙中鉴定出一个全新的分泌型叶酸结合蛋白并命名为Secreted Folate Binding Protein(sFBP)。在胚胎和转染细胞系中我们都证明该蛋白是分泌性的，表面等离子共振实验发现sFBP能够结合叶酸。在胚胎早期这个基因表达于粘液腺和神经板区域，神经管闭合后在神经管、粘液腺、眼睛，头部以及鳃弓都有表达。特异morpholino 阻断sFBP翻译后发现粘液腺发育异常，神经管闭合缺陷，前后体轴聚集延伸运动受到抑制，尾芽期胚胎表现出体轴缩短，无眼，小头或无头的表型。进一步研究发现显微注射sFBP morpholino 的胚胎神经板区域细胞发生凋亡，中胚层和神经外胚层的一系列粘附分子表达异常，神经细胞的正常分化也受到抑制。通过显微移植实验我们还发现抑制sFBP的翻译后，神经嵴细胞的正常分化和迁移都受到抑制。但是，显微注射叶酸及其类似物或者显微注射甲基供体S-腺苷甲硫氨酸或者亮氨酸甲基转移酶都不能挽救阻断sFBP造成的表形，由此提示sFBP可能不是通过叶酸传统的参与营养合成或者甲基化的途径发挥作用。我们发现注射sFBP morpholino可以抑制Islet-1mRNA和蛋白质的表达，Islet-1的表达区域与sFBP类似。共同注射Islet-1 mRNA和sFBP morpholino可以极大的挽救sFBP morpholino的表型。最后通过morpholino特异阻断Islet-1的表达后，我们发现其表现出与sFBP morpholino类似的粘液腺发育缺陷，神经板细胞凋亡，小头无眼的表形。由此叶酸是B族维生素的一员，参与体内一系列重要的生命过程包括DNA，氨基酸的合成，调控细胞周期，参与一碳单位供体循环，调节DNA,蛋白质甲基化等。叶酸的许多功能都和叶酸结合蛋白有关，体内有多种跨膜形式的叶酸结合蛋白，比如Folbp1，RFC，HCP等。以前的研究表明这些不同的叶酸结合蛋白具有不同的功能。分泌型叶酸结合蛋白是另外一类叶酸结合蛋白，在人类，小鼠，猪中都有序列报道，但是其功能却知之甚少。 我们在非洲爪蛙中鉴定出一个全新的分泌型叶酸结合蛋白并命名为Secreted Folate Binding Protein(sFBP)。在胚胎和转染细胞系中我们都证明该蛋白是分泌性的，表面等离子共振实验发现sFBP能够结合叶酸。在胚胎早期这个基因表达于粘液腺和神经板区域，神经管闭合后在神经管、粘液腺、眼睛，头部以及鳃弓都有表达。特异morpholino 阻断sFBP翻译后发现粘液腺发育异常，神经管闭合缺陷，前后体轴聚集延伸运动受到抑制，尾芽期胚胎表现出体轴缩短，无眼，小头或无头的表型。进一步研究发现显微注射sFBP morpholino 的胚胎神经板区域细胞发生凋亡，中胚层和神经外胚层的一系列粘附分子表达异常，神经细胞的正常分化也受到抑制。通过显微移植实验我们还发现抑制sFBP的翻译后，神经嵴细胞的正常分化和迁移都受到抑制。但是，显微注射叶酸及其类似物或者显微注射甲基供体S-腺苷甲硫氨酸或者亮氨酸甲基转移酶都不能挽救阻断sFBP造成的表形，由此提示sFBP可能不是通过叶酸传统的参与营养合成或者甲基化的途径发挥作用。我们发现注射sFBP morpholino可以抑制Islet-1mRNA和蛋白质的表达，Islet-1的表达区域与sFBP类似。共同注射Islet-1 mRNA和sFBP morpholino可以极大的挽救sFBP morpholino的表型。最后通过morpholino特异阻断Islet-1的表达后，我们发现其表现出与sFBP morpholino类似的粘液腺发育缺陷，神经板细胞凋亡，小头无眼的表形。由此我们认为sFBP结合叶酸后可能通过细胞膜上的受体传递信号，并且Islet-1可能在sFBP的下游发挥作用。 神经嵴是脊椎动物特有的一群多潜能干细胞，产生于表皮和神经板的边界，在原肠运动之后这群细胞通过表皮间充值转换从神经管背侧迁移到不同的区域，分化成不同的细胞类型，包括外周神经系统，色素细胞，软骨等。神经嵴的发生是一个多步骤多基因参与的精细调控过程。目前理论认为最初由一些分泌性信号分子又叫形态生成素比如BMP,Wnt，FGF，Notch等通过不同浓度梯度的相互作用调节一组在表皮和神经板边界的转录因子（Msx、Pax3/7、Zic1、Dlx3/5等）的表达，即边界决定。这些边界决定因子进一步在预定形成神经嵴的区域激活神经嵴特化基因比如Slug/Snail、FoxD3、Twist、Sox9/10的表达完成神经嵴的特化（Specification）。 Nkx6.3是Nkx6家族的一个转录因子，RT-PCR显示其呈现母源性表达。特异抗体显示Nkx6.3蛋白第9期在整个胚胎都表达，大部分蛋白集中在细胞核，有少部分蛋白定位于细胞膜上；神经板时期主要定位于神经嵴区域的细胞膜上。过表达Nkx6.3会影响细胞粘连分子的表达，由此干扰正常的胚胎原肠运动和Activin诱导的动物帽聚集延伸运动。显微注射Nkx6.3特异morpholino阻断其蛋白表达会抑制神经嵴的marker基因Wnt8，Fgf8，Pax3，Msx1，Zic1，FoxD3，Slug的转录，阻碍神经嵴的发育。在动物帽中单独注射Nkx6.3可以在mRNA水平上诱导Wnt8、Fgf8另一方面抑制BMP4的表达进而诱导神经嵴基因Pax3，Zic1，Slug的表达。报告基因实验也显示Nkx6.3能够激活Wnt信号而在动物帽中抑制BMP信号。Nkx6.3蛋白功能域分析发现其EH1结构域（domain）参与对Wnt8信号的激活，而EH1结构域和HD结构域之间的连接区域（linker domain）参与对FGF的激活和对BMP的抑制。进一步在动物帽和胚胎中分析发现Nkx6.3对Wnt8的激活依赖于FGF家族受体信号但是不依赖于Fgf8。有趣的是4细胞时期过表达Nkx6.3促进Fgf8和Wnt8 mRNA表达，但是抑制边界决定基因Msx1、Pax3和神经嵴特化基因Slug的转录。在32细胞时期显微注射Nkx6.3可以在内源神经嵴发生区域抑制Slug的表达，而异位却诱导Slug的mRNA。我们发现与动物帽中对BMP的调节不同，在胚胎中，过表达Nkx6.3会强烈的激活Smad1蛋白在细胞核中的表达即BMP信号被激活，高的BMP信号会抑制神经嵴的发生。另外我们发现过表达Nkx6.3在胚胎中抑制Dlx5而在动物帽中却不影响Dlx5的表达水平，Morpholino阻断Dlx5会抑制Msx1、Pax3和Slug的表达。BMP信号和Dlx5在动物帽和在整体胚胎中对Nkx6.3的不同响应可以一定程度上解释过表达Nkx6.3在2个系统中对神经嵴基因Slug相反的影响结果。

中国沙棘(Hippophae rhamnoides subsp. sinensis)不同种群对干旱胁迫的响应差异与干旱诱导蛋白的分析

沙棘广泛分布于亚欧大陆的温带地区和亚洲亚热带的高海拔地区。沙棘能适应多种生态环境，能耐受多种逆境(如干旱、低温、高温和盐害等)。在中国，沙棘常常被用作植被恢复中的先锋树种而大量栽培。本文以中国沙棘为试验材料，探索沙棘适应干旱机制，以及沙棘对干旱胁迫的适应机制是否存在种群间的差异，同时试图通过分析干旱胁迫下沙棘叶片蛋白质表达变化探索沙棘适应干旱胁迫的分子机理。 对三个分别来自低海拔湿润地区、低海拔干旱地区和高海拔湿润地区的中国沙棘种群进行干旱胁迫处理。干旱胁迫能提高根冠比，比叶面积，降低平均叶面积和总生物量，提高沙棘的抗氧化性酶活性、脯氨酸含量、脱落酸(ABA)含量、降低光合作用，提高长期用水效率。实验中的这两个低海拔种群比高海拔种群抵抗干旱的能力更强,不同的种群采用了不同的策略来耐受干旱胁迫和过氧化胁迫。 在2004 年度的实验中，干旱胁迫处理下，高海拔湿润种群(道孚种群)严重失水，生长也受到更大的抑制，非气孔因素在抑制光合作用方面占支配地位，抗坏血酸含量下降，ABA和脯氨酸含量增加幅度比九寨沟种群的要高，这可能是因为道孚种群严重失水而引起的；而低海拔湿润种群(九寨沟种群)的体内水分状况几乎不受干旱的影响，生长情况也较道孚种群要好。 在2005 年度的试验中，和高海拔湿润地区种群(道孚)相比较，低海拔干旱地区种群(定西)在叶片相对水含量、根冠比、抗氧化酶活性(过氧化氢酶、抗坏血酸过氧化物酶和谷胱甘肽过氧化物酶)、保护性物质(脯氨酸，脱落酸)含量等方面都要高，光能热耗散能力也更强，而且气体交换参数(气孔扩散阻力和胞间CO2浓度等)对干旱也更不敏感。 分析了干旱胁迫下沙棘叶片蛋白质表达的变化。共发现319 个蛋白质，有4 个蛋白在干旱胁迫下消失(Putative ABCtransporter ATP-binding protein 、Hypothetical proteinXP-515578，热激蛋白Hslu219 和一个没得到鉴定的蛋白)，4 个只在干旱胁迫下出现(没命名的蛋白质产物，对甲基苯-丙酮酸双加氧酶，NTrX 和一个没得到鉴定的蛋白)，46 个蛋白质的表达丰度变化显著，包括32 个干旱负调蛋白，14 个干旱正调蛋白(3 个Rubisco 的大亚基、J-type–co-chaperone Hsc20、putative protein DSM3645-2335、putative acyl-COA 脱氢酶、nesprin-2 和两个没有得到鉴定的蛋白质)。这些蛋白质参与了氮代谢调控、抗氧化行物质的合成、脂肪酸β－氧化、核骨架构造、[Fe-S]基团组装、物质跨膜运输、细胞分裂或作为分子伴侣和蛋白质酶起作用。putative ABC transporter ATP-binging protein、NtrX、nesprin-2 和Hslu 是本试验新发现的高等植物蛋白，我们主要从它们的保守结构域或在其他生物中的同源物来猜测它们的功能。实验结果为我们研究植物抗干旱机制提供了新线索和新视野。 Seabuckthorn (Hippophae rhamnoides L.) is widly distributed throughtout the temperatureresiogn of Europe and Asia and sub-tropical plateau zone of Asia. H. rhamnoides can adapatseveral different environments, and can tolerant several envioronmental stresses (e.g, lowtemperature, high temperature, drought and salty). It has been widely used in forest restoration asthe pioneer species in China. In present study, we applied H.rhamnoides subsp. Sinensis asexperimental materials to study its drought-tolerant mechanism, and expected to findpopulational difference in drought-tolerant mechanism that may exist among populations, and tryto get some insight in drought-tolerant mechanism of it at morecular level through analyzing thechange of leaf protein expression. Three populations from high altitude wet zone, low altitude wet zone and low altitude arid znoe,respectively, were applied in our experiment, and were subjected to drought. Drought increasedthe root/shoot ratio(RS), special leaf area, long-term water use efficinency, activity of antioxidantenzymes, proline content and abscisic acid (ABA) content, declined the net photosynthesis rate(A), average leaf area (ALA), total biomass (TB). Both two low altitude populations were moredrought-tolerant than the high altitude population, and different population applied differentstratedgies to tolerant oxidant stress and drought stress. The results of the exprement in 2004 showed that Daofu population was more drought-sensitivethan Jiuzhai population. Under drought conditions, leaf relative water content (RWC) greatlydecreased in Daofu population, but not in Jiuzhai population. The large loss of water in Daofupopulation resulted in a limitation on A mainly caused by non-stomatal factors, severer suppression in growth rate and a significant reduction in ascorbic acid (AsA) content, comparedwith Jiuzhai population. The greater increase in content of ABA and proline in Daofu populationmay be also induced by large loss in water, so that enable plants to cope with sever drought. In the exprement of 2005, drought significantly increased RS, activities of catalase (CAT),peroxidase (POD), glutathione peroxidase (GPX) and ascorbate peroxidase (APX), and alsosignificantly increased ABA and proline contents. On the other hand, compared with Daofupopulation, drought induced larger RS and activities of CAT, GPX and APX, and higher ABAcontent in Dingxi population, whereas gas exchange traits, e.g., stomatal limitation value (LS) andintercellular CO2 concentration (Ci), were less responsive to drought in Dingxi population thanthose in Daofu population. All these factors enable Dingxi population to tolerant drought betterthan Daofu population. The leaf protein profile of seabuchthorn subjected to drought was analyzed. Altogether 319proteins were detected in well-watered sample, four proteins disappeard by drought (putativeABCtransporter ATP-binding protein, hypothetical protein XP-515578, Hslu219and aunidentified protein), four only appeared under drought (a probable nitrogen regulation protein(NtrX), a 4-hydroxyphenylpyruvate dioxygenase , an unnamed protein product and an identified protein), 32 drought down-regulated proteins, and 14 drought up-regulated proteins (nine wereidentified: three large subunits of Rubisco, a hypothetical protein DSM3645-23351, a putativeacyl-COA dehydrogenase, a nesprin-2, a J-type-co-chaperone HSC20 and two unmatchedproteins). These proteins may involve in β-oxidation, cross-membrane transport, cell division,cytoskeleton stabilization, iron-sulfur cluster assembly, nitrogen metabolism regulation andantioxidant substance biosynthesis or function as molecular chaperone or protease. Four proteins(a putative ABC transporter ATP-binging protein, NtrX, nesprin-2, Hslu) were new found in highplants, and their functions were estimated from their conserved domain or their homologues inother organism. Our results provided new clue and new insight for us to study thedrought-tolerant mechanism in plants.

the estimation of thyroxine in human plasma by an electrophoretic technique

A new method for the determination of thyroxine in blood is described. It relies upon the quantitative dependence of the distribution of thyroxine between albumin and thyroxine-binding protein when exogenous 131I-labelled thyroxine is added to serum in vitro. Preliminary results suggest an accuracy in the estimate of the hormone of about 5–10%. Results in a group of patients whose plasma P.B.I, levels were also determined are given and shown to be similar.

Studies on interaction of bovine serum albumin with indo-1 by fluorescence spectroscopic method

The binding-site number was calculated by using fluorescence spectroscopic method with bovine serum albumin(BSA) and Indo-1 as protein and ligand models, respectively. The method for calculating binding-site number in BSA for Indo-1 was developed based on the relationships between the changes of Indo-1 fluorescence intensity and the analytical concentration of BSA. And the interaction of BSA with Indo-1 was investigated comprehensively by using fluorescence techniques as well as fluorescence resonance energy transfer, and the thermodynamic parameters were calculated according to the changes of enthalpy on temperature.,

Atomic force microscopic study of low temperature induced disassembly of RecA-dsDNA filaments

The assembly and disassembly of RecA-DNA nucleoprotein filaments on double-stranded DNA (dsDNA) or single-stranded DNA (ssDNA) are important steps for homologous recombination and DNA repair. The assembly and disassembly of the nucleoprotein filaments are sensitive to the reaction conditions. In this work, we investigated different morphologies of the formed nucleoprotein filaments at low temperature under different solution conditions by atomic force microscopy (AFM). We found that low temperature and long keeping time could induce the incomplete disassembly of the formed nucleoprotein filaments.

金属离子与钙调蛋白相互作用的基质辅助激光解析电离飞行时间质谱研究

Calmodulin is a ubiquitous calcium-binding protein in eukaryote cells and engages in various important biological pathways. In the present study, binding interactions between several metal ions and calmodulin were nvestigated by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).The results revealed that the specific binding of metal ions with the protein could be detected using MALDI-TOF MS.

Influence of Polyelectrolyte on DNA-RecA Nucleoprotein Filaments: Poly-L-Lysine Used as a Model

RecA of Escherichia coli and its active nucleoprotein filaments with DNA are important for the genomic integrity and the genetic diversity. The formation of the DNA-RecA nucleoprotein filaments is a complex multiple-step process and can be affected by many factors. In this work, the effects of poly-L-lysine (PLL) on the DNA-RecA nucleoprotein filaments are investigated in vitro by agarose gel electrophoresis and atomic force microscopy (AFM). The observed morphologies vary with the concentration, the length, and the addition order of PLL. These distinctions provide information for the conformation change of DNA and the binding sites of RecA protein in the formation process of nucleoprotein filaments.