蜘蛛丝的好记性

每个人都知道，蜘蛛丝非常结实，但是谁又能想到，这些细丝还有着非凡的“记性”。     

悦目金蛛拖牵丝力学性能的变异

蜘蛛丝作为一种具有优良机械性能的天然动物蛋白纤维,其特有的结构和机械性能与其生物学功能密切相关。由大壶状腺纺出的拖牵丝在蜘蛛的行走、建网、捕食、逃生、繁殖等多种生命活动中均发挥了重要的功能,其机械性能会受到多种内外因素相互作用的影响。本文对在不同体重、不同猎物饲养和不同营养状态3种条件下人工抽出的悦目金蛛(Argiope amoena)拖牵丝与其不同单丝间的力学性能进行了比较研究。结果表明,悦目金蛛拖牵丝的力学性能在组间、组内不同个体,以及同一个体不同丝纤维间变异都较大。随着蜘蛛个体的增大,蛛丝横截面直径逐渐增大,这会使得蛛丝的力学性能更好,便于作为救命索的拖牵丝在遇到危险时承受蜘蛛体重;蜘蛛在经过1个月的饥饿后,蛛丝在屈服点附近的力学性能并未发生显著变化,而断裂点应变和断裂能均显著减小,同时也表明无论对于作为救命索还是网丝,拖牵丝的弹性形变性能在与蛛丝相关的微观进化中要优先于塑性形变。这是蜘蛛在能量摄入受到限制时对拖牵丝的投入权衡的结果。     

蜘蛛丝蛋白的结构及其应用

蜘蛛的拖丝是一种既具有抗张强度又具有高度弹性的奇特蛋白质纤维。近看来,生物学者用现代生物工程技术和其它技术对蛛丝蛋白分子的结构和物理特性,主要是机械特性,进行了广泛深入的研究,取得了很大进展,指出了蛛丝蛋白的工业应用价值。1蛛丝蛋白结构研究进展概述编码一种拖丝蛋白（Spidroiril）的部分cDNA克隆以前已获分离产物,但是所预期的氨基酸顺序并不能解释拖丝蛋白的氨基酸组成。此后又分离出一种编码另一拖丝蛋白（SPidloin2）的部分dD：NA克隆,说明蜘蛛的拖丝是由复合蛋白组成的。Spidroin2的氨基酸顺序是一种与Spidro…     

蜘蛛丝的组成结构与生物学功能

蜘蛛是纺丝种类最多的一种节肢动物,目前共发现有8种丝腺,各纺出具有不同生物学功能的丝纤维,可分别用于织网、捕食、逃避、扩散、织制卵袋等行为活动。蜘蛛丝是一种天然的动物蛋白纤维,是随蜘蛛4亿年进化的结果,也是为蜘蛛的生存与繁殖所设计的,蜘蛛丝的适应与进化使蜘蛛丝具有多样化的生物学功能。但蜘蛛不是唯一能纺丝的节肢动物,除蛛形纲以外,还有其它很多节肢动物,如昆虫纲和多足纲的动物都有具有丝腺,能纺出一种或多种丝蛋白纤维。本文将以昆虫作为比较来概述蜘蛛丝腺的起源与种类,蜘蛛丝的化学组成、结构、种类与其生物学功能。     

蜘蛛丝蛋白研究进展

由于蜘蛛丝蛋白分子高度重复的一级结构、特殊的溶解特性和分子折叠行为以及具有形成非凡力学特性丝纤维的能力而引人注目。本文从蛛丝蛋白基因、天然蛛丝形成过程、蛛丝蛋白的基因工程生产及蛛丝蛋白的应用前景等几个方面着重介绍了近20年来对蛛丝蛋白的研究进展。围绕蛛丝蛋白展开的研究将有助于揭示蛋白质一级结构、蛋白质分子折叠与蛋白质大分子特性之间的内在联系。     

蜘蛛丝蛋白的结构

很多蛋白在高浓度时都形成纤维状结构，可溶性变差。但蜘蛛网蛋白（有高度重复片段，侧面为非重复性末端区域）却有不同行为。     

不同 pH 值条件下蜘蛛丝收缩与延展性能的变化

研究不同p H值条件下,蜘蛛丝拉伸性能的变化。在酸性条件下,设置p H值梯度,比较经丝、纬丝的拉伸性能;使用同样方法,在碱性条件下,比较经丝、纬丝的拉伸性能。将实验数据应用统计学中的单因素方差分析方法分析。结果表明不同p H值对这两类蛛丝的拉伸性能的变化均有显著影响:在酸性条件下,随着p H值的升高,经丝和纬丝收缩度逐渐升高;在碱性条件下,随着p H值的升高,其收缩度逐渐降低。当p H值为7时,经丝和纬丝的收缩度最高,分别为经丝(27.00±0.60)%,纬丝(28.30±0.31)%。     

蜘蛛丝蛋白的模块结构性能和重组表达

蜘蛛丝是一类天然蛋白质纤维,具有独特的机械性能（高强度、高弹性和高断裂功等）和卓著的生物学特性（生物可降解性和与生物组织的相容性等）,在生物医学、材料、纺织和军事等领域都有着很高的潜在应用价值。综述了不同蜘蛛丝蛋白的模块结构特征及与其功能的关系,扼要介绍了目前利用各种基因工程方法表达重组蜘蛛丝蛋白的研究进展。     

2厘米粗蜘蛛丝可提起2吨重物

据美国《科学》杂志在线新闻报道,这是研究人员将蜘蛛丝交替暴露在干燥和湿润的空气中,从而导致其以循环的方式放松和收缩后得出的结论。为了搞清蜘蛛丝究竟可以举起多大的重量,研究人员用吸管分别在每根蛛丝上加上了2mg到100mg的重量,并测量了它们随着蛛丝收缩而上下运动的总量。     

大腹园蛛大壶状腺丝蛋白-1基因部分cDNA的克隆和序列分析

大腹园蛛大壶状腺表达拖丝蛋白新基因的克隆, 为进一步研究蛛丝蛋白基因以及人工表达蛛丝蛋白提供参考依据。文章利用“通用方法”即反转录—置换法构建大腹园蛛(Araneus ventricosus)大壶状腺(Major ampullate gland) cDNA文库, 并筛选出具有典型重复结构的大腹园蛛大壶状腺丝蛋白-1部分cDNA序列AvMaSp1 (GenBank登录号: AY177203)。该部分序列大小为1 408 bp, 编码区为1 288 bp, 编码氨基酸429个, 预测分子量为34.07 kDa, 典型的重复结构为 (GA)nAm(GA)N, 与十字园蛛(Araneus diadematus)丝蛋白基因ADF-1 (GenBank登录号: ADU47853)同源关系最近, 一致性为75.0%。     

悦目金蛛和棒络新妇卵袋丝物理化学结构表征及其力学性能研究

蜘蛛丝是一种具有优良机械性能的天然动物蛋白纤维,它特有的结构和性能与其生物学功能密切相关。作者采用氨基酸自动分析仪、傅立叶转换红外光谱仪、扫描电镜和电子单纤强力仪对悦目金蛛（Argiope amoena）和棒络新妇（Nephila clavata）的卵袋丝进行了物理化学结构表征与力学性能的研究,结果表明两种蜘蛛卵袋均由微米级柱状腺丝、大壶状腺丝、亚微米级或纳米级葡萄状腺丝构成。卵袋丝的表面形貌特征、极性氨基酸含量、大侧链与小侧链氨基酸的比值、无定型区、β-折叠结构与结晶结构的含量等氨基酸组成种类与蛋白质二级结构特征,均满足各自生物学功能对断裂强度、延展性、初始模量等力学性能的要求。     

Silk Production after Mechanical Pulling Stimulation in the Ampullate Silk Glands of the Barn Spider, Araneus cavaticus

Synthesis of protein by the major ampullate silk glands in the barn spider, Araneus cavaticus was stimulated by depleting the storage of silk protein in the ampulla by mechanically pulling fiber from the spigot. After this treatment, fine structural changes of the glandular epithelium during silk production were examined using light and transmission electron microscopes. In the process of rapid production, major secretory silk was synthesized at the tail region via rER of glandular epithelial cells, and was transported into the ampulla region. The mature secretory product in glandular epithelium appears almost spherical vacuoles which were grown up by fusion with the surrounding small vesicles including the secretory silk. Unlike to a typical process of the secretion, the ampullate silk of tail region seems to bypass either concentrating or packaging steps by the Golgi apparatus. However there's no doubt that the Golgi apparatus also play an important role in the secretory process of the ampulla region. After mechanical pulling stimulation, both epithelia of ampulla and tail regions appeared as a thinner layer of columnar cells with less definitive cell membrane. There are few secretory droplets within these cells, thus causing this region to stain much lighter. It is obvious that the cell loses part of its cytoplasm in this process, and disorganization of the secretory product occurs when it is extruded from the cells by a apocrine release.     

Novel In Silico Analyses of Repetitive Spider Silk Sequences to Understand the Evolution and Mechanical Properties of Fibrous Protein Materials

The mechanical properties of spider silks have diverged as spiders have diversely speciated. Because the main components of silks are proteins, it is valuable to investigate their sequences. However, silk sequences have been regarded as difficult information to analyze due to their imbalance and imperfect tandem repeats (ITR). Here, an in silico approach is applied to systemically analyze a group of silk sequences. It is found that every time new spider groups emerge, unique trimer motifs appear. These trimer motifs are used to find additional clues of evolution and to determine relationships with mechanical properties. For the first time, crucial evidence is provided that shows silk sequences coevolved with spider species and the mechanical properties of their fibers to adapt to new living environments. This novel approach can be used as a platform for analyzing other groups of ITR‐harboring proteins and to obtain information for the design of tailor‐made fibrous protein materials.     

外源丙氨酸提高蜘蛛牵引丝蛋白天然基因在原核系统中的表达

蜘蛛丝蛋白天然基因的体外表达受诸多因素的限制。本研究在获得生长于中国的Nephila clavipes蜘蛛牵引丝蛋白Spidroin2 cDNA（Genbank Accession No. AF441245）的基础上,利用限制性内切酶双酶切反应构建含有Spidroin2 cDNA的重组表达质粒pET-28b(+)-Sp。将该质粒转化至大肠杆菌BL21（DE3）宿主细胞感受态菌中,以不同浓度的IPTG进行诱导,并通过诱导时间、培养温度、加入外源丙氨酸等途径提高Spidroin2 cDNA的表达量,同时利用多克隆抗体对表达产物进行Western blot检测。重组质粒pET-28b(+)-Sp的测序结果表明Spidroin2 cDNA基因以正确的阅读框插入到原核表达载体中;SDS-PAGE结果表明菌体表达蛋白中存在着大小约为31 kDa的目的蛋白带（加入外源丙氨酸条件下）,Western blot检测结果进一步证实,目的基因在大肠杆菌中得到正确表达。本研究证实,蜘蛛牵引丝蛋白Spidroin2 cDNA可在原核细胞内正确表达,外源丙氨酸的加入对于提高天然蜘蛛丝蛋白基因在原核系统的表达作用明显。     

三种类型蜘蛛丝的结构及生物学功能

利用付里叶变换红外光谱仪(FFIR)对棒络新妇(Nephila clavata)、悦目金蛛(Argiope amoena)的大壶状腺丝(拖丝)、悦目金蛛的捕丝(粘性螺旋丝)和卵袋丝这3种不同类型蜘蛛丝的二级结构进行了测试研究。结果表明：蜘蛛丝同时包含无规则卷曲、α-螺旋和β-折叠构象;对这3种蛛丝的红外光谱进行比较表明同一蜘蛛的不同类型蛛丝所含的这3种二级结构的比例不同,这种不同组成的二级结构就赋予了蜘蛛丝不同的特性,这种特性又与其不同的功能相适应。此外,还用扫描电镜(SEM)和光学显微镜对悦目金蛛和小悦目金蛛(A．minuta)的拖丝和捕丝做了形态结构观察。蜘蛛丝这种天然动物蛋白纤维所具有的特殊的形态结构、蛋白质二级结构与其特殊的性能和生物学功能是高度一致的。     

菜田蜘蛛群落组成及生态位分析

根据2006年5月至8月对蕃茄、茄子、豆角、青椒、尖椒及油菜共6种蔬菜田蜘蛛种类及数量的系统调查,经初步整理鉴定,隶属于9科19属27种。通过时空二维生态位分析,星豹蛛的二维宽度最大,草间钻头蛛和齿螯额角蛛的二维重叠值最大。应用模糊聚类法对群落的相似性进行分析,以λ=0.68为聚类阈值,可将9种菜田优势种蜘蛛划分为1个明显竞争群及3个分离种。以λ=0.9736为聚类阈值,可将菜田蜘蛛时间序列分为5月份,6、7月份和8月份3个状态集,即蜘蛛群落建立、发展和瓦解3个阶段。     

Microdissection of Black Widow Spider Silk-producing Glands

Modern spiders spin high-performance silk fibers with a broad range of biological functions, including locomotion, prey capture and protection of developing offspring ^1,2. Spiders accomplish these tasks by spinning several distinct fiber types that have diverse mechanical properties. Such specialization of fiber types has occurred through the evolution of different silk-producing glands, which function as small biofactories. These biofactories manufacture and store large quantities of silk proteins for fiber production. Through a complex series of biochemical events, these silk proteins are converted from a liquid into a solid material upon extrusion.Mechanical studies have demonstrated that spider silks are stronger than high-tensile steel ³. Analyses to understand the relationship between the structure and function of spider silk threads have revealed that spider silk consists largely of proteins, or fibroins, that have block repeats within their protein sequences ⁴. Common molecular signatures that contribute to the incredible tensile strength and extensibility of spider silks are being unraveled through the analyses of translated silk cDNAs. Given the extraordinary material properties of spider silks, research labs across the globe are racing to understand and mimic the spinning process to produce synthetic silk fibers for commercial, military and industrial applications. One of the main challenges to spinning artificial spider silk in the research lab involves a complete understanding of the biochemical processes that occur during extrusion of the fibers from the silk-producing glands.Here we present a method for the isolation of the seven different silk-producing glands from the cobweaving black widow spider, which includes the major and minor ampullate glands [manufactures dragline and scaffolding silk] ^5,6, tubuliform [synthesizes egg case silk] ^7,8, flagelliform [unknown function in cob-weavers], aggregate [makes glue silk], aciniform [synthesizes prey wrapping and egg case threads] ⁹ and pyriform [produces attachment disc silk] ¹⁰. This approach is based upon anesthetizing the spider with carbon dioxide gas, subsequent separation of the cephalothorax from the abdomen, and microdissection of the abdomen to obtain the silk-producing glands. Following the separation of the different silk-producing glands, these tissues can be used to retrieve different macromolecules for distinct biochemical analyses, including quantitative real-time PCR, northern- and western blotting, mass spectrometry (MS or MS/MS) analyses to identify new silk protein sequences, search for proteins that participate in the silk assembly pathway, or use the intact tissue for cell culture or histological experiments.     

Molecular studies of a novel dragline silk from a nursery web spider, Euprosthenops sp. (Pisauridae)

Various spider species produce dragline silks with different mechanical properties. The primary structure of silk proteins is thought to contribute to the elasticity and strength of the fibres. Previously published work has demonstrated that the dragline silk of Euprosthenops sp. is stiffer then comparable silk of Nephila edulis, Araneus diadematus and Latrodectus mactans. Our studies of Euprosthenops dragline silk at the molecular level have revealed that nursery web spider fibroin has the highest polyalanine content among previously characterised silks and this is likely to contribute to the superior qualities of pisaurid dragline.