黄曲霉毒素B1人工抗原的合成及鉴定

采用衍生化在黄曲霉毒素B1(aflatoxin B1,AFB1）上引入羧基合成AFB1羧甲基活化物,通过N-羟琥珀酰亚胺酯(N-hydroxy-succinimide NHS）法将AFB1O与牛血清白蛋白(BSA)偶联,制备黄曲霉毒素B1完全抗原AFB1-BSA。ECI-MS和紫外光谱法的鉴定结果表明目标半抗原合成成功。结合紫外分光光度法和回归方程,分别测得不同浓度的半抗原和蛋白质线性曲线为：Y=0.1440X+0.0103,R2=0.9986;Y=0.0059X+0.0808,R2=0.9889。偶联物中半抗原和蛋白质的浓度分别为186.32 μg/mL、6127.46 μg/mL,即求得抗原分子结合比为5.13:1,从而为制备抗AFB1抗体奠定基础。     

黄曲霉毒素B1人工抗原及鼠源多克隆抗血清的制备

目的:研究合成并鉴定了黄曲霉毒素B1(aflatoxin B1,AFB1)人工抗原,通过动物免疫生产亲和力高、特异性好的鼠源AFB1多克隆抗血清。方法:采用N-羟琥珀酰亚胺酯(N-hydroxy-succinimide NHS)法将AFB1分别偶联于载体蛋白BSA和OVA上,分别合成免疫抗原AFB1-BSA和包被抗原AFB1-OVA,采用紫外分光光度法和SDS-PAGE进行鉴定,通过动物免疫实验获得鼠源多抗血清,并使用间接ELISA和阻断ELISA的方法对多抗血清进行了鉴定。结果:结果表明半抗原AFB1分别和载体蛋白BSA及OVA偶联成功;免疫的6只小鼠效价均达1×10-4以上,3号小鼠多抗血清敏感性最好,半数抑制浓度IC50(50% inhibitive concentration,IC50)为8.199ng/mL。结论:实验成功合成了AFB1人工抗原,并生产了高效价、高敏感性的鼠源多克隆抗体血清,为AFB1单克隆抗体制备及其快速检测试剂的研制奠定了坚实的基础。     

泰拉霉素完全抗原的合成和鉴定

利用丁二酸酐法对泰拉霉素的羟基衍生化,引入游离羧基,合成泰拉霉素半抗原。采用活泼酯法将泰拉霉素半抗原分别与牛血清白蛋白(BSA)和鸡卵清白蛋白(OVA)偶联,合成人工完全抗原泰拉霉素-BSA和泰拉霉素-OVA。利用LC-MS鉴定衍生化后半抗原的合成,利用荧光光谱、考马斯亮法鉴定完全抗原的合成。用泰拉霉素-BSA免疫小鼠,采用间接ELISA法测定小鼠抗血清效价。泰拉霉素半抗原和BSA的偶联比为17∶1。三免后小鼠抗血清效价可达1∶8 000。     

莱克多巴胺和土霉素人工抗原的合成及鉴定

研究莱克多巴胺和土霉素免疫抗原的制备。实验中用碳二亚胺法将莱克多巴胺(ractopamine,RAC)与载体蛋白牛血清白蛋白(bovine serum albumin,BSA)偶联,制备完全抗原;采用混合酸酐法将土霉素(oxytetracycline,OTC)与载体蛋白BSA偶联,制备完全抗原,并对合成产物进行表征。紫外扫描对合成产物RAC-BSA、OTC-BSA进行鉴定结果显示偶联成功,经重氮化后利用混合酸酐法制备完全抗原的偶联比为5:1;经衍生后利用碳二亚胺法制备RAC完全抗原偶联比为7:1。利用制备的免疫原免疫兔子可以获得相应的抗体。     

盐酸克伦特罗完全抗原的制备及其鉴定

利用重氮化法将小分子半抗原盐酸克伦特罗(CL)偶联到牛血清白蛋白(BSA)上制得盐酸克伦特罗完全抗原(CL-BSA).采用紫外分光光度法快速确定了BSA∶CL偶联比为1∶17,并通过SDS-PAGE法验证了CL与BSA偶联;间接ELISA法检测免疫Balh/c小鼠血清.结果显示1∶1000稀释后的血清在中和掉BSA的抗体后呈阳性;最后,通过细胞融合获得了一株能稳定分泌CL-McAb的细胞株4H5,经鉴定为IgG1.说明合成偶联比为1∶17的完全抗原能刺激小鼠产生针对盐酸克伦特罗的单克隆抗体.     

氯霉素全抗原的合成与鉴定

目的：为获得较高偶联率氯霉素全抗原,探索和优化碳二亚胺法(EDC)合成氯霉素(CAP)与牛血清白蛋白(BSA)全抗原合成条件。方法：采用单因素设计,优化影响合成的主要因素：蛋白浓度、CAP 与BSA 的摩尔比例、反应体系pH 值,通过紫外法和三硝基苯磺酸(TNBS)法测定合成后的偶联率。 结果：EDC 法合成氯霉素抗原较优条件为BSA 浓度15mg/ml、CAP:BSA=70:1、pH7.4,可得到偶联率为15 左右的氯霉素全抗原。结论：EDC法可用于制备较高偶联率的氯霉素全抗原,以用来进行抗体制备。     

3种真菌毒素(ZEN、DON及T2)完全抗原的合成与鉴定

目的:合成玉米赤霉烯酮(ZEN)、脱氧雪腐镰刀菌烯醇(DON)和T2 3种真菌毒素的完全抗原。方法:将ZEN半抗原、DON及T2与阳离子化的载体蛋白(BSA和OVA)偶联,制备高特异性的完全抗原。用高性能基质辅助激光解吸电离-飞行时间质谱仪(MALDI-TOF)检测偶联物及载体蛋白的分子质量,用商品化的ZEN、DON和T2单克隆抗体对偶联物进行免疫滴定验证。结果:平均每个BSA偶联上的ZEN、DON和T2的分子个数分别为20.81,6.03,4.92个,平均每个OVA偶联上的ZEN、DON和T2分子个数分别为7.17,3.05,2.80个,偶联物与ZEN、DON及T2的抗体呈阳性反应。结论:合成的ZEN、DON及T2完全抗原为3种毒素抗体的制备及免疫学方法的建立奠定了基础。     

大分子葡聚糖-牛血清蛋白抗原偶联物的制备与表征

用还原胺化法制备大分子葡聚糖-牛血清蛋白(BSA)拟糖蛋白抗原,通过SDS-聚丙烯酰胺凝胶电泳结合考马斯亮蓝和过碘酸-品红两种染色方法验证偶联物的生成。考察不同反应条件(葡聚糖T40的氧化度,偶联pH,氧化葡聚糖和蛋白质的比值,偶联时间)对偶联反应的影响。确定拟糖蛋白抗原的最佳偶联条件为:葡聚糖T40/氧化剂NaIO4=1/120(物质的量比),偶联溶液pH8.0,葡聚糖T40/BSA=1/1(物质的量比),偶联时间24h。并将此反应条件用于T10和T100拟糖蛋白抗原的合成。     

双酚A完全抗原的制备

采用重氮化法在双酚A(BPA)上引入羧基,将其与牛血清白蛋白(BSA)偶联,制备双酚A完全抗原BPAH-BSA.紫外扫描光谱和红外光谱实验表明偶联成功,为进一步制备抗BPA抗体提供了良好的免疫原.     

米诺环素完全抗原的制备与表征

研究制备能有效用于米诺环素(MNC)残留检测的完全抗原。采用戊二醛合成法和重氮化合成法,将米诺环素与牛血清白蛋白(BSA)偶联,分别制备MNC 完全抗原MNC-BSA。经红外和紫外光谱扫描结果表明：两种物质已经偶联,两种完全抗原的平均偶联比分别为9.9 和5.9。采用戊二醛法合成的完全抗原免疫兔,检测抗血清效价为1:16000,表明合成的完全抗原可以作为免疫原用于制备抗体及检测时的包被原进行ELISA 检测。     

Binding of aflatoxin B1 to cell wall components of Lactobacillus rhamnosus strain GG.

The surface of Lactobacillus rhamnosus strain GG (LGG) has previously been shown to bind aflatoxin B(1) (AFB(1)) effectively, it being a food-borne carcinogen produced by certain species of Aspergillus fungi. To establish which components of the cell envelope are involved in the AFB(1) binding process, exopolysaccharides and a cell wall isolate containing peptidoglycan were extracted from LGG and its AFB(1) binding properties were tested. LGG was also subjected to various enzymatic and chemical treatments and their effects on the binding of AFB(1) by LGG were examined. No evidence was found for exopolysaccharides, cell wall proteins, Ca(2+) or Mg(2+) being involved in AFB(1) binding. The AFB(1) binding activity of the cell wall isolate indicates that AFB(1) binds to the cell wall peptidoglycan of LGG or compounds tightly associated with the peptidoglycan.     

抗AFB_1单域重链抗体文库淘选方法的研究

比较两种从噬菌体展示文库中淘选抗黄曲霉毒素B1单域重链抗体的方法,并为淘选针对小分子物质的单域重链抗体提供参考.采用固相淘选技术,以黄曲霉毒素B1人工抗原为靶分子,淘选天然单域重链抗体库,分别采用Gly-HCl法和AFB1竞争法洗脱结合噬菌体,对洗脱物进行滴度测定,以回收率和富集度为指标,对两种洗脱方法进行比较.采用phage-ELISA法鉴定噬菌体克隆,并对阳性克隆进行交叉反应分析以及序列测定.滴度测定结果显示,Gly-HCl法回收率比竞争法高5～10倍.分别随机挑取20个单克隆进行phage-ELISA鉴定,其中,Gly-HCl洗脱法未获得阳性克隆,AFB1竞争洗脱法得到8个阳性克隆.序列测定结果显示,这8个克隆均编码单域重链抗体.     

Binding of aflatoxin B1 to bifidobacteria in vitro

Aflatoxins are mycotoxins that cause health and economic problems when they contaminate food and feed. One potential method for reducing human health effects due to aflatoxin ingestion is to block uptake via binding by bacteria that either make up the normal gut flora or are present in fermented foods in our diet. These bacteria would bind aflatoxin and make it unavailable for absorption in the intestinal tract. Bifidobacteria comprise a large fraction of the normal gut flora, are thought to provide many probiotic effects and are increasingly used in fermented dairy products. These qualities targeted bifidobacteria for studies to determine if various strains of heat-killed bifidobacteria can bind aflatoxin B1 (AFB1) in vitro. The AFB1 binding affinities of various strains of bifidobacteria, Staphylococcus aureus, and Escherichia coli were quantitated utilizing enzyme-linked immunosorbent and [3H]AFB1 binding assays. The bacteria analyzed were found to bind significant quantities of AFB1 ranging from 25% to nearly 60% of the added toxin. The data also suggest that there are reproducible strain differences in AFB1 binding capacity.     

Physical adsorption of aflatoxin B1 by lactic acid bacteria and Saccharomyces cerevisiae: a theoretical model

The ability of lactic acid bacteria (LAB) and Saccharomyces cerevisiae to remove aflatoxin B1 (AFB1) from liquid medium was tested. The experimental results indicated that (i) AFB1 binding to microorganisms was a rapid process (no more than 1 min); (ii) this binding involved the formation of a reversible complex between the toxin and microorganism surface, without chemical modification of the toxin; (iii) the amount of AFB1 removed was both toxin- and bacteria concentration-dependent; and (iv) quantitatively similar results were obtained with viable and nonviable (heat-treated) bacteria. According to these details, a physical adsorption model is proposed for the binding of AFB1 to LAB and S. cerevisiae, considering that the binding (adsorption) and release (desorption) of AFB1 to and from the site on the surface of the microorganism took place (AFB1 + S <--> S - AFB1). The model permits the estimation of two parameters: the number of binding sites per microorganism (M) and the reaction equilibrium constant (K(eq)) involved, both of which are useful for estimating the adsorption efficiency (M x K(eq)) of a particular microorganism. Application of the model to experimental data suggests that different microorganisms have similar K(eq) values and that the differences in toxin removal efficiency are mainly due to differences in M values. The most important application of the proposed model is the capacity to select the most efficient microorganism to remove AFB1. Furthermore, it allows us to know if a modification of the adsorption efficiency obtained by physical, chemical, or genetic treatments on the microorganism is a consequence of changes in M, K(eq), or both.     

Aflatoxin B1 binding by dairy strains of lactic acid bacteria and bifidobacteria.

Various food commodities including dairy products may be contaminated with aflatoxins, which, even in small quantities, have detrimental effects on human and animal health. Several microorganisms have been reported to bind or degrade aflatoxins in foods and feeds. This study assessed the binding of aflatoxin B1 (AFB1) from contaminated solution by 20 strains of lactic acid bacteria and bifidobacteria. The selected strains are used in the food industry and comprised 12 Lactobacillus, five Bifidobacterium, and three Lactococcus strains. Bacteria and AFB1 were incubated (24 h, +37 degrees C) and the amount of unbound AFB1 was quantitated by HPLC. Between 5.6 and 59.7% AFB1 was bound from solution by these strains. Two Lactobacillus amylovorus strains and one Lactobacillus rhamnosus strain removed more than 50% AFB1 and were selected for further study. Bacterial binding of AFB1 by these strains was rapid, and more than 50% AFB1 was bound throughout a 72-h incubation period. Binding was reversible, and AFB1 was released by repeated aqueous washes. These findings further support the ability of specific strains of lactic acid bacteria to bind selected dietary contaminants.     

Aflatoxin B1 binding by a mixture of Lactobacillus and Propionibacterium: in vitro versus ex vivo

Aflatoxin B1 (AFB) is a well-known carcinogen and reducing its bioavailability is of great interest for human and animal health. Several probiotic bacteria are able to bind AFB1 in vitro, including Lactobacillus rhamnosus LC-705 and Propionibacterium freudenreichii subsp. shermanii JS. A mixture of these two probiotics is used by the food and feed industry as biopreservative (Bioprofit), making it a promising candidate for future applications. Consequently, this study aims to investigate the in vitro and ex vivo ability of this probiotic mixture to bind AFB1. For in vitro experiments, probiotic mixture was suspended in an AFB1 solution (5 microM), incubated for 1 to 30 min, centrifuged, and AFB1 residues were quantitated in supernatant and pellet. For ex vivo experiments, duodenal loops of chicks were ligated and injected with either AFB1 solution alone or probiotic mixture suspension and AFB1 solution. Lumen content was centrifuged and AFB1 was quantitated in supernatant and pellet. Additionally, AFB1 was extracted from duodenal tissue to calculate tissue uptake. In vitro, 57 to 66% of AFB1 was removed from the solution by the probiotic mixture, but only 38 to 47% could be extracted from the bacterial surface. In ex vivo experiments, only up to 25% of AFB1 was bound by bacteria, and tissue uptake of AFB1 was significantly reduced when probiotic bacteria were present in the duodenal loop. Furthermore, the effect of intestinal mucus on the bacterial binding ability was investigated in vitro and was found to significantly reduce AFB1 binding by the probiotic mixture. However, probiotic mixture could only retard but not prevent AFB1 absorption in duodenal loops. Further work needs to assess the potential of probiotics in different experimental setups.     

Ability of Lactobacillus and Propionibacterium strains to remove aflatoxin B, from the chicken duodenum

The ability of Lactobacillus rhamnosus strains GG and LC-705 to remove AFB1 from the intestinal luminal liquid medium has been tested in vivo using a chicken intestinal loop technique. In this study, the GG strain of L. rhamnosus decreased AFB1 concentration by 54% in the soluble fraction of the luminal fluid within 1 min. This strain was more efficient in binding AFB1 compared with L. rhamnosus strain LC-705 (P < 0.05) that removed 44% of AFBl under similar conditions. Accumulation of AFB1 into the intestinal tissue was also determined. There was a 74% reduction in the uptake of AFB1 by the intestinal tissue, in the presence of L. rhamnosus strain GG compared with 63% and 37% in the case of Propionibacterium freudenreichii ssp. shermanii JS and L. rhamnosus strain LC-705, respectively. The complexes formed in vitro between either L. rhamnosus strain GG or L. rhamnosus strain LC-705 and AFB1 were stable under the luminal conditions for a period of 1 h.     

降解花生粕中黄曲霉毒素菌株的筛选及其在发酵酶解偶联工艺中的应用

本研究从污染AFB1严重的花生粕中筛选出一株能够高效降解AFB1的菌株,根据形态特征、16S rDNA序列比对鉴定目的菌株,确定其为枯草芽孢杆菌,命名为Bacillus subtilis Y-6.通过添加筛选出的枯草芽孢杆菌,利用微生物发酵结合复合酶制剂的生物偶联工艺处理花生粕,比较处理前后花生粕中AFB1含量的变化....     

Kinetics of adsorption and desorption of aflatoxin B1 by viable and nonviable bacteria

The reactions involved in the binding (adsorption) and release (desorption) of aflatoxin B1 (AFB1) to and from the surface of bacteria were investigated. Viable and heat-killed Lactobacillus rhamnosus GG, L. rhamnosus LC-705, and Propionibacterium freudenreichii subsp. shermanii JS were incubated in phosphate-buffered saline containing variable concentrations (0.0017 to 13.3 microg/ml) of AFB1. The relationship between the bacterial surface hydrophobicity and the AFB1 adsorption affinity was also investigated. A linear relationship was observed between the specific rate of AFB1 adsorption and the AFB1 concentration for all bacteria. The nature of desorption of adsorbed AFB1 was investigated by repetitive aqueous washes. A linear relationship was observed between the natural log value of the concentration of AFB1 adsorbed and the number of washes for all bacteria studied. The desorption constants were strain-dependent and were lower for heat-killed bacteria than for viable bacteria. Heat treatment appears to alter the surface properties of the bacteria rather than expose new adsorption sites. No correlation was found between the hydrophobicity and the AFB1 adsorption affinity.     

重组漆酶降解黄曲霉毒素B1分子对接分析及产物结构解析

以重组漆酶lac3基因同源性最高的3KW7作为模板进行同源模建,采用分子对接预测漆酶与黄曲霉毒素B1（aflatoxin B1,AFB1）的结合模式,结果显示漆酶与AFB1可以相互作用,氢键是其关键作用力,漆酶可用于黄曲霉毒素的降解。随后,通过实际的降解实验进行验证,响应面优化获得AFB1降解率最优的条件为底物AFB1 1 μg、孵育时间15 h、孵育温度34 ℃、酶活力2 U,降解率可达91.08%。在此条件下利用超高效液相色谱-飞行时间串联质谱分析AFB1降解产物结构,发现4 个主要降解产物,根据其二级质谱信息和精确分子质量,推测出降解产物的分子式分别为C16H22O4、C14H16N2O2、C7H12N6O和C24H30O6。