瓜类疫霉菌毒素的分离与其某些特性的初步研究

本文从瓜类疫霉菌液体培养液中分离到一种毒素，该毒素对新疆甜反幼苗有明显的致萎作用。用ＤＥＡＥ－５２柱纯化该毒素得到二个组合。本文比较了这二个组分的组成、致萎差异和荧光谱差异，并发现该毒素的作用可能是瓜类疫霉菌害新疆矩反的主要原因。     

Single channel properties of lysenin measured in artificial lipid bilayers and their applications to biomolecule detection

Single channel currents of lysenin were measured using artificial lipid bilayers formed on a glass micropipette tip. The single channel conductance for KCl, NaCl, CaCl(2), and Trimethylammonium-Cl were 474 ± 87, 537 ± 66, 210 ± 14, and 274 ± 10 pS, respectively, while the permeability ratio P(Na)/P(Cl) was 5.8. By adding poly(deoxy adenine) or poly(L-lysine) to one side of the bilayer, channel currents were influenced when membrane voltages were applied to pass the charged molecules through the channel pores. Current inhibition process was concentration-dependent with applied DNA. As the current fluctuations of α-hemolysin channels is often cited as the detector in a molecular sensor, these results suggest that by monitoring channel current changes, the lysenin channel has possibilities to detect interactions between it and certain biomolecules by its current fluctuations.     

Design and synthesis of type-III mimetics of ShK toxin

ShK toxin is a structurally defined, 35-residue polypeptide which blocks the voltage-gated Kv1.3 potassium channel in T-lymphocytes and has been identified as a possible immunosuppressant. Our interest lies in the rational design and synthesis of type-III mimetics of protein and polypeptide structure and function. ShK toxin is a challenging target for mimetic design as its binding epitope consists of relatively weakly binding residues, some of which are discontinuous. We discuss here our investigations into the design and synthesis of 1st generation, small molecule mimetics of ShK toxin and highlight any principles relevant to the generic design of type-III mimetics of continuous and discontinuous binding epitopes. We complement our approach with attempted pharmacophore-based database mining.     

马氏钳蝎蝎毒短肽BmK622的分离纯化和一级结构测定

应用凝胶过滤、离子交换和HPLC反相色谱法从马氏蝎粗毒中分离纯化得到蝎毒 多肽BmK622．联合运用串联质谱法和Edman降解法，鉴定了KmK622N端19个残基的序 列，经过数据库检索，发现数据库中用cDNA克隆方法鉴定了序列的马氏钳蝎蝎毒短 肽BmTX3一级序列N端19个残基与BmK622已测定的N端19个残基序列完全相同， BmK622的分子量测定和氨基酸组成分折的结果表明，BmK22与BmTX3分子量相同、氨 基酸组成一致，从而BmK22的一级结构为：GFLID VKCFA SSECW TACKK VTGSG QGKCQ NNQCR CY．     

具有分布时滞的脉冲种群系统的动力学行为

考虑的是带脉冲毒物输入和时滞的单种群模型的动力学行为,特别地,这里时滞项包含常时滞和分布成熟时滞.通过控制成熟个体的收获率,不仅得到了种群灭绝的充分条件,而且得到了种群灭绝周期解的指数渐近稳定和种群持久性的充分条件.这样的话,通过控制收获率,脉冲周期及脉冲毒物的输入量就能保护物种的数量,从而,结果对生物资源的管理具有一定的意义.     

B SUBUNIT OF CHOLERA TOXIN PRODUCED IN Escherichia coli

An engineered E. coli strain containing high expression level of CT-B subunits has beenobtained by the application of recombinant DNA techniques. The B subunit can be secretedinto the medium and reaches 20- 40 μg/ml when this strain is incubated in a 50 1 fermenta-tion tank. The CT-B subunit purified with affinity chromatography in E. coli has the samecharacters as the natural CT- B subunit in molecular weight, N terminal amino acid analysisand antigenicity. The CT-B subunit has good immunogenicity and can be used as a preparation for protect-ing against diarrhea caused by V. cholera and enterotoxigenic E. coli. It can also be usedas a vector for hepatins.     

Food microbiology update emerging foodborne pathogens

A review of three “emerging” foodborne pathogen groups is presented, includingCampylobacter jejuni/coli, Yersinia enterocolitica, and foodborneVibrio sp.     

Efficient Cholera Toxin B Subunit‐Based Nanoparticles with MRI Capability for Drug Delivery to the Brain Following Intranasal Administration

Alzheimer's disease (AD) is an incurable neurodegenerative brain disorder that exhibits clear pathologic changes in the hippocampus. Traditional drug delivery systems are ineffective due to the existence of the blood–brain barrier (BBB). In this study, an efficient, stable, and easily constructed nanosystem (CB‐Gd‐Cy5.5) based on the cholera toxin B subunit (CB) is designed to improve the efficiency of drug delivery to the brain, especially the hippocampus. Through intranasal administration, CB‐Gd‐Cy5.5 is easily delivered to the brain without intervention by the BBB. The CB in CB‐Gd‐Cy5.5 is used for specifically combining with the monosialoganglioside GM1, which is widely found in the hippocampus. This nanosystem exhibits impressive performance in accumulating in the hippocampus. In addition, the good magnetic resonance imaging (MRI) capability of CB‐Gd‐Cy5.5 can satisfy the monitoring of AD in the different stages.     

Detection of cholera toxin in seafood using a ganglioside-liposome immunoassay

Microbiological contamination of foods continues to be a major concern in public health. Biological toxins are one class of important contaminants that can cause various human diseases. Outbreaks related to contamination by biological toxins or toxin-producing microorganisms have made it extremely important to develop rapid (approximately 20 min), sensitive and cost-effective analytical methods. This paper describes the development of a sensitive bioassay for the detection of cholera toxin (CT) in selected seafood samples, using ganglioside-incorporated liposomes. In this study, the assays were run with food samples spiked with various concentrations of CT. The limit of detection (LOD) increased by a factor of about 10–20 in most food samples, compared with the LOD in the buffer system previously reported. However, the LOD of toxins in food samples (8 × 10–3 × 10³ fg/mL for CT) was still comparable to, or lower than, that previously reported for other assays. The results from this study demonstrate that the bioassays using ganglioside-liposomes can detect the toxin directly in the field screening of food samples rapidly, simply and reliably, without the need for complex instrumentation.     

蝎子毒素多肽WaTx的高效化学合成及氧化折叠研究

相比于1-羟基-7-氮杂苯并三氮唑(HOAt)、1-羟基苯并三唑(HOBt)等传统偶联试剂, 新型多肽偶联试剂2-肟氰乙酸乙酯(Oxyma)具有安全、偶联效率高、消旋率低等优势, 在多肽合成特别是微波固相合成中得到广泛应用. 但是, 不同反应温度(例如28、50和75 ℃)对N,N'-二异丙基碳二亚胺(DIC)/Oxyma的偶联效率以及对甲硫氨酸(Met)等易氧化氨基酸的影响尚有待研究. 瞬时受体电位锚蛋白1(TRPA1)通道在感受温度、听觉和炎症痛中发挥重要作用. 蝎子毒素多肽芥末受体毒素(WaTx)是一种新型、非共价结合的TRPA1特异性激动剂. 本研究利用6-氯苯并三氮唑-1,1,3,3-四甲基脲六氟磷酸酯(HCTU)/N,N'-二异丙基乙胺(DIEA)和DIC/Oxyma缩合体系, 首次探索了不同温度下线性WaTx的合成效率以及Met残基的氧化情况. 通过一次氧化折叠和两次氧化折叠策略, 实现了WaTx的体外快速复性折叠, 利用圆二色谱和钙荧光检测等技术评价WaTx的结构和活性. 本研究建立了WaTx的温和、高效合成以及复性折叠方法, 为固相多肽合成特别是手动固相合成WaTx等含有易氧化基团的二硫键构象锁定多肽提供了重要参考.