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抗人胰岛素原scFv-EGFP融合蛋白的制备及其活性分析

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目录

声明

List of Abbreviations

Chapter One: Introduction

1.1 Introduction to Diabetes and Insulin

1.2 Single-chain Antibody

1.2.1 Introduction to Single-chain Antibodies

1.2.2 Single-chain Antibodies Structure

1.2.3 Applications of Single-chain Antibodies

1.3Fusion Proteins

1.3.1Introduction to Fusion Protein

1.3.2 Progress in Fusion Protein Research

1.4Green Fluorescent Protein

1.4.1Introduction to Green Fluorescent Protein

1.4.2 Green Fluorescent Protein Structure

1.4.3 Applications of Green Fluorescent Protein

1.5Protein Expression System

1.5.1 Introduction to Protein Expression System

1.5.2 Yeastas an Expression System for Foreign Proteins

1.5.3 Promoter of Foreign Protein-glyceraldehyde-3-phosphate dehydrogenase

1.5.4 Exogenous Protein Expression Vector pGAPZαA

1.6Research Purposes, Significance and Prospects of the Thesis

1.7The Previous Related Work of the Construction of Anti-human Proinsulin Single-chain Antibody

1.8Technical routes of the research

Chapter Two: Expression of Human Proinsulin and Preparation

2.1 Materials

2.1.1 Strains and Plasmid Materials

2.1.2 Main Instruments

2.1.3 Main Reagents

2.1.4 Configuration of Medium, Antibiotics and Common Solutions

2.2 Methods

2.2.1 Preparation of E. coli BL21 (DE3) Competent Cells by CaCl2 Method

2.2.2 Transformation

2.2.3Expression of Human Proinsulin Protein

2.2.4 Extraction and Dissolving of Inclusion Bodies with Triton X-100

2.2.5 Dissolving the inclusion bodies

2.2.6 Extracting and Dissolving Inclusion Bodies with Inclusion Body Washing Solution

2.2.7 Coomassie Blue Method for Measuring Protein Content

2.3 Results

2.3.1 Transformant Cells

2.3.2Expression of Human Proinsulin

2.3.3 Extraction and Dissolution of Inclusion Bodies with Uera

2.3.4 Extracting and Dissolving Inclusion Bodieswith Triton X-100 Results

2.5 Discussion

2.4 Summary

Chapter Three:Expression of scFv-EGFP Fusion Protein and Preparation

3.1 Materials

3.1.1 Strainsand Plasmid Materials

3.1.2 Main Instruments

3.1.3 Main Reagents

3.1.4 Preparation of Main Reagents

3.2 Methods

3.2.1Screening the Positive Transformants and PCR Identification

3.2.2 Detection of Positive Transgenic P.pastoris by Super-resolution Fluorescence Microscopy

3.2.3 Expression of Recombinant scFv-EGFP Fusion Protein

3.2.4. Precipitation of the Protein by Ammonium Sulfate

3.2.5Purification of Expression Proteins by His-Taq Purification Method

3.2.6Purification of the Expression Protein by Cellulose DE-52 Ion-exchange Chromatography

3.2.7 Examination of Nucleotides Sequence of the pGAPZαA-scFv-EGFP Plasmid

3.2.8Precipitation of Medium Protein by Acetone

3.2.9Identification of Histidine-Taqs of the Fusion Proteins by Western Blot

3.3 Results

3.3.1 Screening of the Positive Transformants and PCR Results

3.3.2Expression of Recombinant scFv-EGFP Fusion Protein

3.3.3Purification of scFv-EGFP Fusion Proteinby His60-Ni Column Affinity Chromatography

3.3.4Purification of scFv-EGFP Fusion Proteinby Cellulose DE-52 Ion-exchange Chromatography

3.3.5Intracellular Localization of Expressed scFv-EGFPFusion Protein

3.3.6Identification of the scFv-EGFP Fusion Proteins by Western Blot

3.4 Discussion

3.5 Summary

Chapter Four: Sensitivity and Specificity of Human Proinsulin to scFv-EGFP Fusion Protein

4.1 Materials

4.1.3 Preparation of Main Reagents

4.2 Methods

4.2.1Sensitivity and Specificity Detection of scFv-EGFP Fusion Proteins to Human Proinsulin by Dot Blot

4.3 Results

4.3.1 Sensitivity and Specificity of scFv-EGFP Fusion Protein to Human Proinsulin

4.4 Discussion

4.5 Summary

参考文献

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摘要

特异性靶向临床生物标志物的重组单克隆抗体越来越多地被用作诊断许多疾病的有力工具。绿色荧光蛋白(GFP)作为荧光体及其红移突变体,增强型绿色荧光蛋白(EGFP),其荧光强度比野生型GFP强35倍,已被用作荧光标记物,用于观察体内和体外蛋白质的定位。GFP/EGFP与抗体的遗传融合导致荧光抗体的扩增,荧光抗体已被用作体外研究和肿瘤成像的可靠检测工具。胰岛素原被用作靶抗原并且广泛用于治疗糖尿病。最近,几种针对胰岛素原的scFv被用于构建免疫测定,其特异性地靶向血清和血液中的胰岛素物质。本论文制备了重组胰岛素原和scFv-EGFP融合蛋白,并测试了它们的活性。 主要研究成果如下: (1)将大肠杆菌BL21pET-Ins菌株在30℃,220rpm下培养至OD600≥0.6,然后用1mmol/L IPTG在26℃,220rpm下诱导4小时。通过SDS-PAGE分析显示,破碎后离心上清液中没有重组人胰岛素原的显著积累。在破碎后的离心沉淀中,重组人胰岛素原蛋白占总沉淀蛋白的49.9%。这表明人胰岛素原主要以包涵体的形式存在。 (2)提取人胰岛素原包涵体,分别用尿素和包涵体洗涤液溶解。SDS-PAGE分析显示,包涵体中人胰岛素原的纯度为84.4%。来自洗涤和重新溶解的包涵体的人胰岛素原的纯度为99.8%。融合蛋白的产量约为197.12mg/L。 (3)提取1~6株转基因巴斯德毕赤酵母GS115scFv-EGFP的核DNA,用一对引物SEP1和SEP2扩增,scFv-EGFP编码片段的1208~1724bp(总长516bp)。结果显示,巴斯德毕赤酵母GS115scFv-EGFP1-6菌株呈现出清晰的特异性条带,大小为500bp。 (4)通过荧光显微镜分析转基因巴斯德毕赤酵母scFv-EGFP-6和巴斯德毕赤酵母GS115菌株的细胞。重组蛋白的荧光在整个细胞质中可见。 (5)将巴斯德毕赤酵母GS115scFv-EGFP1,2,3,4,5,6,7,8,9,10,11和12号菌株在30℃和220rpm下培养96小时。通过SDS-PAGE电泳分析来自沉淀的发酵液和来自破碎的细胞沉淀的蛋白质。电泳结果显示菌株1~12的特异性条带接近54.6kDa(scFv-EGFP的理论分子量)。带蛋白分别占30.3%,11.1%,19.1%,60.6%,63.2%,68.1%,35.4%在通过超声破碎(按1至12号菌株的顺序)破碎后,细胞沉淀中总蛋白质的含量为3.8%,4.1%,10.8%,7.1%和15.9%。来自发酵液的蛋白质首先通过丙酮沉淀,然后通过SDS-PAGE分析。蛋白质条带接近54.6kDa,占发酵液中总蛋白质的30.0%,14.8%,23.3%,31.7%,30.4%,27.3%,35.3%,18.4%,14.1%,0.0%,5.9%和0.0%(按1至12号菌株的顺序)。 (6)通过蛋白质印迹检测含有scFv-EGFP融合蛋白的样品,发现scFv-EGFP样品可以与抗GFP的抗体结合。 (7)用30%,40%和50%硫酸铵沉淀巴斯德毕赤酵母GS115scFv-EGFP-6细胞的上清液。离心后,在Ni-NTA亲和柱上进一步纯化分级沉淀后制备的溶液。结果显示,接近54.6kDa的蛋白质条带未出现在洗脱缓冲液中。这些结果表明重组融合蛋白scFv-EGFP可能不与Ni-NTA结合。 (8)根据(7)结果,重新检查了pGAPαA-scFv-EGFP载体序列,发现scFv-EGFP编码片段末端出现了移码突变,在Myc和His的标签前面出现终止密码子TAG。重组融合蛋白scFv-EGFP不含有6×His标签。其他菌株的纯化结果与6号菌株的纯化结果相似,表明终止密码子在构建转基因酵母之前出现。 (9)根据(7)和(8)的结果,使用离子交换树脂DEAE(DE-52)来纯化重组融合蛋白scFv-EGFP。将破碎的巴斯德毕赤酵母GS115scFv-EGFP6菌株上清液上柱,用40mM Tris-HCl(pH6.5)平衡。通过超过蛋白质等电点(pI)的1-2M NaCl缓冲液(pH5.31)作为洗脱蛋白质,并测量280nm处的吸光度。最大吸收峰出现在管1中。根据管2-9的级分样品的SDS-PAGE分析显示,特异性条带接近54.6kDa(scFv-EGFP的理论分子量)带蛋白分别占62.3%,50.1%,28.8%,28.8%,17.7%,15.4%,7.4%,17.9%。此外,除了54.6kDa的蛋白质条带外,还存在其他蛋白质条带。 (10)为了检测scFv-EGFP融合蛋白对胰岛素原的敏感性,使用scFv-EGFP检测不同浓度的人胰岛素原(4.1ng/ml,4.5ng/ml,5.9ng/ml和8.6ng/ml)(7.9ng/ml)并显示出良好的点荧光。阴性对照(大肠杆菌BL21(DE3))未显示暴露信号或荧光,这表明重组融合蛋白scFv-EGFP与人胰岛素原具有特异性结合。

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