棕尾别麻蝇(Sarcophaga peregrina)幼虫与蛹血淋巴凝集素的纯化与特性

用亲和层析法纯化了棕尾别麻蝇幼虫和蛹血淋巴凝集素。以兔红细胞吸附幼虫血淋巴凝集素为抗原制备的抗体、球球蛋白和甲状腺蛋白等三种亲和层析吸附剂纯化得到的幼虫凝集素是相同的,其分子量73kD左右。用甲状腺球蛋白为亲和配基纯化的蛹血淋巴凝集素由二种亚基组成,其分子量分别为30和32kD。幼虫和蛹血淋巴凝集素活性的抑制糖明显不同：乳糖、岩藻糖和N－乙酰半乳糖胺对幼虫血淋巴凝集素活性有抑制作用;而甘露糖胺、半乳糖胺和葡萄糖胺则对蛹血淋巴集素有一定抑制。而且,用兔红细胞吸附幼虫血淋巴凝集素为抗原制备的抗血清对蛹的凝集素活性无交叉反应,表明这两种凝集素是不相同的。虽然本文所纯化的麻蝇蛹血淋巴凝集素的分子量和Komano等报道的麻蝇蛹以及幼虫体壁 伤害诱导的凝集素SPL相同,但其糖的抑制特性有明显差异。     

雪山豆(Phaseolus sp.)凝集素的亲和层析纯化与其部分性质

 用猪甲状腺球蛋白-对氨基苯砜乙基-交联琼脂作亲和吸附剂,可对雪山豆(Phaseolus sp.)凝集素进行亲和层析纯化。纯化后的凝集素在聚丙烯酰胺凝胶电泳中显示单一蛋白质带。Sephadex G-100凝胶层析法测得分子量为65,000道尔顿,SDS-聚丙烯酰胺凝胶电泳表明该凝集素分子仅有一个分子量为65,000道尔顿的亚基,酚-硫酸法测得总糖含量为4.6％,氨基酸组成分析表明雪山豆凝集素富含门冬氨酸,而甲硫氨酸含量甚少。该凝集素是强促有丝分裂原,对人外周血中淋巴细胞的转化率大于90％,细胞分裂比率达12％。雪山豆凝集素不仅能凝集多种动物红细胞,还能凝集人精细胞。经体外实验表明,雪山豆凝集素对人肝癌细胞有抑制作用。     

免疫亲和层析法纯化苦瓜几丁酶

用扁豆几丁酶免疫家兔,获得抗扁豆几丁酶的抗体,将此抗体与Ｓｅｐｈａｒｏｓｅ ４Ｂ偶联,制备免疫亲和吸附剂,用以纯化苦瓜几丁酶．苦瓜叶片的粗提液经过免疫亲和吸附柱后,可获得电泳纯的几丁酶,其分子量为３５ ｋＤ,与用几丁质凝胶为亲和吸附剂的纯化结果一致．表明利用植物几丁酶在结构上的保守性,用免疫亲和法可纯化不同植物的同类几丁酶．与几丁质凝胶亲和柱相比,免疫亲和法纯化植物几丁酶具有快速、亲和柱可重复使用等的优点．利用免疫亲和层析获得的纯化样品,研究了苦瓜几丁酶对真菌的抑制试验,研究结果表明,苦瓜几丁酶能分解棉花枯萎病菌的菌丝体细胞壁制备物,并对其孢子芽管的伸长有一定抑制作用．     

单克隆抗体亲和层析纯化人白细胞干扰素的研究

本文报道了一种单克隆抗体亲和层析纯化人白细胞干扰素的方法．我们采用自己研制的α－干扰素单克隆抗体亲和层析柱进行了人白细胞干扰素较大规模纯化的研究,结果表明,其活性回收率平均达１０６．９％以上,经ＳＤＳ－ＰＡＧＥ银染法鉴定,白细胞干扰素的大多数活性成分均被吸附和回收,所得的干扰素蛋白成分主要位于分子量１５０００～２１０００Ｄ的干扰素活性区域,产品的纯度大大提高,比活可达８×１０６ＩＵ／ｍｇ;ＥＬＩＳＡ夹心法测定,每毫升洗脱样品中鼠源ＩｇＧ含量小于４ｎｇ,我们所建立起的亲和层析法操作简便,亲和吸附和洗脱条件温和,可适用于大规模的白细胞干扰素的纯化．     

A型血专一性凝集素(Phaseolus lunatus Linn vel aff)的纯化和性质研究

 <正> 对人类A型血具有专一性的凝集素已有几种被纯化出来,纯化方法都是基于生物特异性的吸附作用:(1)以修饰的或天然的多糖为吸附剂;(2)利用偶联的糖肽或糖蛋白作配基进行亲和层析;(3)利用结合单糖或双糖作配基的亲和吸附。本文用猪胃粘蛋白-Sepha-rose 4B作亲和吸附剂对Phaseolus Iunatus Linn vel aff种子中的凝集素进行了研究。     

转铁蛋白糖链结构对受体亲和性的影响

用伴刀豆凝集素（ＣｏｎＡ）,小扁豆凝集素（ＬＣＡ）,和欧曼陀罗凝集素（ＤＳＡ）亲和层析法,分别从正常人血清转铁蛋白（Ｔｆ）和孕妇血清Ｔｆ中获得二天线糖链的Ｔｆ和多天线糖链的Ｔｆ．用于研究其对从胎盘中纯化得到的转铁蛋白受体（ＴｆＲ）的亲和性。经Ｓｃａｔｃｈａｒｄ作图结果发现,解离常数分别为：４．９７×１０－８ｍｏｌ／Ｌ和９．８０×１０－８ｍｏｌ／Ｌ．最大结合分别是１８０ｆｍｏｌ／Ｌ和１８２ｆｍｏｌ／Ｌ,表明含多天线糖链的Ｔｆ对受体的亲和性比二天线糖链的Ｔｆ降低１倍,而ＴｆＲ的结合位点数不变。     

黄精凝集素Ⅱ的纯化及部分性质研究

囊丝黄精（ＰｏｌｙｇｏｎａｔｕｍｃｙｒｔｏｎｅｍａＨｕａ．）的根状茎,经浸取、用硫酸铵分级沉淀、猪甲状腺球蛋白－Ｓｅｐｈａｒｏｓｅ４Ｂ柱亲和层析、ＣＭ－Ｓｅｐｈａｒｏｓｅ柱离子交换层析和ＳｅｐｈａｄｅｘＧ－１００凝胶过滤,可以分离纯化出黄精凝集素Ⅱ（ＰＣＬⅡ）．纯化的ＰＣＬⅡ在聚丙烯酰胺凝胶电泳中显示单一蛋白染色带;在快速高效液相色谱中亦为单一蛋白峰,经分子筛层析测得分子量为１５．９ｋＤ,最大紫外吸收值在２７８ｎｍ,ＰＣＬⅡ只凝集兔红细胞,当浓度为０．２５μｇ／ｍｌ时,即可发生凝集反应,此凝集兔红细胞的能力可被Ｄ－甘露糖和猪甲状腺球蛋白所抑制．氨基酸组成分析表明ＰＣＬⅡ分子中富含酸性氨基酸,Ｎ末端为丙氨酸．经测定ＰＣＬⅡ分子中含有３个色氨酸和２．４％的中性糖．原子发射光谱分析表明,该凝集素分子中含有Ｍｇ和Ｃａ两种金属元素．     

转铁蛋白糖链结构对其受体亲和性的影响

用伴刀豆凝集素,小扁豆凝集素和欧曼陀罗凝集素亲和层析法,分别从正常人血清转铁蛋白和孕妇血清Ｔｆ中获得二天线糖链Ｔｆ和多天线糖链的Ｔｆ,用于研究其对胎盘中纯化得到的转铁蛋白受体和亲和性。经Ｓｃａｔｃｈａｒｄ作图结果发现,表明含多天线糖链的Ｔｆ对受体的亲和性比二天线糖链的Ｔｆ降低１倍,而ＴｆＲ的结合位点数不变。     

油麻藤种子中凝集素的纯化及性质的研究

中药常春油麻藤种子中含有Ａ型血专一性的凝集素（ＭＳＬ）。该凝集素可经盐析、离子交换及凝胶过滤进行纯化,当其浓度为０．４９μｇ／ｍｌ时就能凝集人Ａ型血细胞,对人类Ｂ、Ｏ型及兔红细胞无作用。Ｇａｌ,ＧａｌＮＡｃ和胃粘蛋白对ＭＳＬ的凝血活性有强抑制作用。ＭＳＬ含中性糖５．７％,凝胶过滤测得分子量为１３１８００,ＳＤＳ－ＰＡＧＥ测得分子量为６６０００和３３０００,表明ＭＳＬ可能由两个不同亚基组成。ＭＳＬ还     

厚果鸡血藤凝集素的纯化及性质

从厚果鸡血藤（ＭｉｌｅｔｉａｐａｃｈｙｃａｒｐａＢｅｎｔｈ．）的种子中分离纯化出一种具强凝集活性和强促有丝分裂原的凝集素。种子经磨粉、浸取、硫酸铵分级、ＤＥＡＥＳｅｐｈａｒｏｓｅ离子交换和ＳｅｐｈａｄｅｘＧ１００分子筛层析,即可获得在ＰＡＧＥ和ＳＤＳＰＡＧＥ上均呈现单一蛋白染色带的凝集素纯品,分子筛层析测得分子量为４０７００,ＳＤＳＰＡＧＥ测得亚基分子量为１９８００;含有１７８％的中性糖。氨基酸组成分析表明,该凝集素富含Ａｓｐ、Ｇｌｕ、Ｔｈｒ、Ｓｅｒ和Ｌｅｕ,同时含有４个Ｔｒｐ,当凝集素浓度为０．４８μｇ／ｍＬ时,即可凝集兔红细胞;对人Ａ、Ｂ和Ｏ型血细胞都能发生凝集,故无血型专一性;其凝集兔红细胞的凝集活性,不能被常见糖类抑制,但可被甲状腺球蛋白、胃粘蛋白和卵粘蛋白所抑制;其凝集活性强烈地依赖于Ｃａ２＋的存在,但Ｍｇ２＋、Ｍｎ２＋、Ｚｎ２＋对其凝集活性全无促进作用;该凝集素是一种强促有丝分裂原,对人外围血中淋巴细胞的转化率高达８４３％,细胞分裂比率可达７８％。     

A novel method for the purification of recombinant subunit I of theDolichos biflorus seed lectin

Lectins are carbohydrate-binding proteins that are ubiquitous in nature. Their ability to specifically bind carbohydrates has been used as a means of purification mainly through affinity chromatography techniques. Plant lectins are one of the most thoroughly studied class of lectins, however, details of theirin situ function remains elusive. Recent advances in recombinant DNA techniques have been used in several laboratories to study the function of these lectins by heterologous over-expression. The larger subunit of theDolichos biflorus seed lectin was described by Chao et al. in 1994 and purification through affinity chromatography techniques was described. Here we report on a new method for the purification of this recombinant protein with techniques that are not dependent on the ability of the lectin to bind sugars. This method may have uses in the purification of mutant proteins that may not bind carbohydrates. Characterization of the purified protein by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption ionization (MALDI) mass spectroscopy shows that the lectin is over 99% pure with a molecular weight of 27,090±16.17 Da, and hemagglutination assays confirm that the lectin retains its biological activity.     

Distribution of cell surface saccharides on pancreatic cells

We describe here a simple, general procedure for the purification of a variety of lectins, and for the preparation of lectin-ferritin conjugates of defined molar composition and binding properties to be used as probes for cell surface saccharides. The technique uses a “universal” affinity column for lectins and their conjugates, which consists of hog sulfated gastric mucin glycopeptides covalently coupled to agarose. The procedure involes: (a) purification of lectins by chromatography of aqueous extracts of seeds or other lectin-containing fluids over the affinity column, followed by desorption of the desired lectin with its hapten suge; (b) iodination of the lectin to serve as a marker during subsequent steps; (c) conjugation of lectin to ferritin with glutaraldehyde; (d) collection of active lectin-ferritin conjugates by affinity chromatography; and (e) separation of monomeric lectin-ferritin conjugates from larger aggregates and unconjugated lectin by gel chromatography. Based on radioactivity and absorbancy at 310 nm for lectin and ferritin, respectively, the conjugates consist of one to two molecules of lectin per ferrritin molecule. Binding studies of native lectins and their ferritin conjugates to dispersed pancreatic acinar cells showed that the conjugation procedure does not significantly alter either the affinity constant of the lectin for its receptor on the cell surface or the number of sites detected.     

Mechanisms of the insecticidal action of TEL (Talisia esculenta lectin) against Callosobruchus maculatus (Coleoptera: Bruchidae)

Plant lectins have insecticidal activity that is probably mediated through their ability to bind carbohydrates. To examine the influence of sugars on the insecticidal activity of a lectin from Talisia esculenta seeds (TEL), the lectin was mixed with mannose, glucose, or mannose plus glucose. Mannose abolished the insecticidal activity. Affinity chromatography showed that TEL bound to midgut proteins of the insect Callosobruchus maculatus. Immunoblotting showed that TEL recognized some proteins, probably glycoproteins, present in the midgut membrane of this insect. The principal proteases responsible for digestive proteolysis in fourth instar larvae of C. maculatus were purified by chromatography on activated thiol-Sepharose. These purified proteases were unable to digest TEL after a 15-h incubation. These results suggest that the insecticidal activity of TEL involves a specific carbohydrate-lectin interaction with glycoconjugates on the surface of digestive tract epithelial cells, as well as binding to assimilatory glycoproteins present in midgut extracts and resistance to enzymatic digestion by cysteine proteinases.     

Anti-tumor factor in insects' hemolymph

We have purified a lectin from the hemolymph of Sarcophaga peregrina larvae, obtained after injury of their body wall. This lectin recognizes galactose residues and suggested to be involved in the defense mechanism of this insect. We also demonstrated that this lectin induced cytotoxic effects on tumor cells in the presence of murine macrophages. It was found that the murine macrophages had Sarcophaga lectin binding proteins. Using pupal hemocytes and fatbody of this insect, we established an in vitro system that mimics dissociation of the fatbody in vivo. New membrane protein, induced on the surface of the hemocytes at pupation, suggested to participate in the recognition of the fatbody.     

The binding of fucose-containing glycoproteins by hepatic lectins. Purification of a fucose-binding lectin from rat liver

A lectin with a high affinity for binding ligands through fucose residues has been purified to homogeneity from rat liver. Affinity chromatography of the lectin on fucosyl-bovine serum albumin-agarose is the key step in the purification. Contaminating amounts of a previously described lectin that binds mannose and N-acetylglucosamine are removed from the fucose-binding lectin by either immunoadsorption on anti-mannose/N-acetylglucosamine lectin IgG-agarose or by specific elution of the fucose-binding lectin from fucosyl-bovine serum albumin-agarose. The pure fucose-binding lectin contains two polypeptide subunits with molecular weights of 88,000 and 77,000, respectively, as judged by gel electrophoresis. Peptide maps of the subunits, however, show that they are very similar structurally. In addition, peptide maps show that the fucose lectin is structurally distinct from other rat hepatic lectins. This is supported by the lack of cross-reaction among the different rat liver lectins and their specific antibodies and the inability of specific antibodies to the mannose/N-acetylglucosamine lectin to inhibit the binding of fucosyl-bovine serum albumin by the fucose lectin.     

Purification of Sarcophaga (fleshfly) lectin and detection of sarcotoxins in the culture medium of NIH-Sape-4, an embryonic cell line of Sarcophaga peregrina.

An established cell line originating from a Sarcophaga peregrina (fleshfly) embryo, NIH-Sape-4, was found to synthesize mRNAs for Sarcophaga lectin and sarcotoxin IA, but not those for storage protein or 25 kDa protein. These four proteins are known to be synthesized in the fat-body of third-instar larvae, and the two former in particular are known to participate in the defence mechanism of this insect and to be induced in response to injury of the body wall. Thus the embryonic cell line NIH-Sape-4 synthesizes certain defence proteins constitutively. This cell line will be useful for large-scale purification of Sarcophaga lectin, since 50 micrograms of purified Sarcophaga lectin could be obtained from about 400 ml of culture medium.     

Purification of human interleukin-2 fusion protein produced in insect larvae is facilitated by fusion with green fluorescent protein and metal affinity ligand

The fusion protein of green fluorescent protein (GFP) and human interleukin-2 (hIL-2) was produced in insect Trichoplusia ni larvae infected with recombinant baculovirus derived from the Autographa californica nuclear polyhedrosis virus (AcNPV). This fusion protein was composed of a metal ion binding site (His)6 for rapid one-step purification using immobilized metal affinity chromatography (IMAC), UV-optimized GFP (GFPuv), enterokinase cleavage site for recovering hIL-2 from purified fusion protein, and hIL-2 protein. The additional histidine residues on fusion protein enabled the efficient purification of fusion protein based on immobilized metal affinity chromatography. In addition to advantages of GFP as a fusion marker, GFP was able to be used as a selectable purification marker; we easily determined the correct purified fusion protein sample fraction by simply detecting GFP fluorescence.     

Purification of a lectin from the marine red alga Gracilaria ornata and its effect on the development of the cowpea weevil Callosobruchus maculatus (Coleoptera: Bruchidae)

A lectin from the marine red alga Gracilaria ornata (Gracilariaceae, Rodophyta) was purified and characterized. The purification procedure consisted of extracting soluble proteins in 0.025 M Tris-HCl buffer, pH 7.5, followed by ammonium sulfate precipitation (70% saturation), ion exchange chromatography on DEAE-cellulose and affinity chromatography on mucin-Sepharose 4B. The purified G. ornata lectin (GOL) showed a single protein band with an apparent molecular mass of 17 kDa when submitted to SDS-polyacrylamide gel electrophoresis under reducing conditions. The native molecular mass of GOL determined by gel filtration on a Sephadex G-100 column was 17.4 kDa and its carbohydrate content was estimated to be 2.9%. Therefore, GOL is a monomeric glycoprotein. The purified lectin agglutinated trypsin-treated erythrocytes from rabbit and chicken but not from human. Its activity was not inhibited by any of the mono- and disaccharides tested but by the complex glycoproteins porcine stomach mucin, lactotransferrin, asialofetuin and bovine and porcine thyroglobulins. Isoelectric focusing showed that GOL is an acidic protein with a pI of 5.4 with analysis of its amino acid composition revealing high contents of Asx, Glx, Ser, Glu, Ala and Cys. When incorporated in artificial seeds, GOL significantly affected the development of Callosobruchus maculatus larvae, indicating the possibility of using this lectin in a biotechnological strategy for insect management of stored cowpea seeds.