Construction of humanized carcinoembryonic antigen specific single chain variable fragment and mitomycin conjugate

AIM： To construct a new target-oriented conjugate of humanized carcinoembryonic antigen （CEA） specific single chain variable fragment （scFv） and mitomycin （MMC） against colorectal cancer, and to investigate its influence on the growth and apoptosis of colorectal cancer cells. METHODS： The primer was designed according to the gene sequence described in reference 16, which respectively contains restriction enzyme cleavage sites BamH I and EcoR I in its upstream and downstream. PCR was performed with the plasmid as template containing genes of humanized anti-CEA scFv. The product was digested by BamH I and EcoR I, and connected to an expression vector which also has the restriction enzyme cleavage sites BamH I and EcoR. Expression of the reaction was induced by isopropy-β -D-thiogalactoside （IPTG）. Then the expression product was covalently coupled with MMC by dextran T-40. The immunoreactivity of the conjugate against colorectal cancer cells as well as CEA was measured by enzyme linked immunosorbent assay （ELISA）. The inhibiting ratio of conjugate on the growth of colorectal cancer cells was also measured by ELISA. The effect of conjugate on the apoptosis of colorectal cancer cells was determined by flow cytometry （FCM）. RESULTS： Restriction endonuclease cleavage and gene sequencing confirmed that the expression vector was successfully constructed. Sodium dodecyl sulfate polyacrylamide gel electropheresis （SDS-PAGE） confirmed that this vector correctly expressed the fusion protein. ELISA confirmed that the conjugate had quite a strong immunoreactivity against colorectal cancer cells and CEA. The conjugate had inhibitory effects on colorectal cancer cells in a concentration-dependent manner and could induce apoptosis of colorectal cancer cells in a concentration-dependent manner.CONCLUSION： The CEA-scFv-MMC conjugate can be successfully constructed and is able to inhibit the growth and induce apoptosis of colorectal cancer cells.

Correctness and accuracy of template-based modeled single chain fragment variable (scFv) protein anti-breast cancer cell line (MCF-7)

Multiple sequence alignments can be used in the template-based modelling of protein structures to build fragment-based assembly models. Therefore, useful functional information on the 3D structure of the anti-MCF-7 scFv protein can be obtained using available bioinformatics tools. This paper utilises several commonly-used bioinformatics tools and databases, including BLAST (Basic Local Alignment Search Tool), GenBank, PDB (Protein Data Bank), KABAT numbering and SWISS-MODEL, to gain specific functional insights into the anti-MCF-7 scFv protein and the assembly of single-chain fragment variable (scFv) antibodies, which consist of a variable heavy chain (VH) and a variable light chain (VL) connected by the linker (Gly4-Ser)3. The linker has been built as a loop structure using the Insight II software. The accuracy of the loop structure has been evaluated using Root Mean Square Deviation (RMSD). The accuracies of the VL and VH template-based structures are enhanced by using the evaluation methods Verify3D, ERRAT and Ramchandran plotting, which measure the error in the residues. In the results, 100% of the light-chain residues scored above 0.2, whereas 88.5% of the heavy-chain residues’ scored above 0.15 in the Verify3D evaluation method. Meanwhile, using ERRAT, the alignments of both chains scored more than 70% in space. Additionally, the Ramchandran plot evaluation method showed large numbers of residues in the favoured areas in both chains;these findings demonstrated that all of the chosen templates were the best candidates.

Screening and evaluation of human single-chain fragment variable antibody against hepatitis B virus surface antigen

BACKGROUND: Phage display technology has become a vital tool in studies aimed at identifying molecules binding to a specific target. It enables the rapid generation and selection of high affinity, fully human antibody product candidates to essentially any disease target appropriate for antibody therapy. In this study, we prepared the recombinant single-chain fragment variable ( ScFv) antibody to hepatitis B virus surface antigen (HBsAg) by the phage display technology for obtaining a virus-targeting mediator. METHODS: mRNA was isolated from B-lymphocytes from a healthy volunteer and converted into cDNA. The fragment variables of heavy and light chain were amplified separately and assembled into ScFv DNA with a specially constructed DNA linker by polymerase chain reaction. The ScFv DNA was ligated into the phagmid vector pCANT-AB5E and the ligated sample was transformed into competent E. coli TG1. The transformed cells were infected with M13K07 helper phage to form a human recombinant phage antibody library. The volume and recombinant rate of the library were evaluated by bacterial colony count and restriction analysis. After two rounds of panning with HBsAg. the phage clones displaying ScFv of the antibody were selected by enzyme-linked immunosorbant assay ( ELISA) from the enriched phage clones. The antigen binding affinity of the positive clone was detected by competition ELISA. HB2151 E. coli was transfected with the positive phage clone demonstrated by competition ELISA for production of a soluble form of the anti-HBsAg ScFv. ELISA assay was used to detect the antigen binding affinity of the soluble anti-HBsAg ScFv. Finally, the relative molecular mass of soluble anti-HBsAg ScFv was measured by SDS-PAGE. RESULTS: The variable heavy ( VH ) and variable light (VL) and ScFv DNAs were about 340bp, 320bp and 750bp, respectively. The volume of the library was up to 2 × 106 and 8 of 10 random clones were recombinants. Two phage clones could strongly compete with the original HBsAb for binding to HBsAg. Within 2 strong positive phage clones, the soluble anti-HBsAg ScFv from one clone was found to have the binding activity with HBsAg. SDS-PAGE showed that the relative molecular weight of soluble anti-HBsAg ScFv was 32 kDa. CONCLUSION: The anti-HBsAg ScFv successfully produced by phage antibody technology may be useful for broadening the scope of application of the antibody.

Novel Selenium-containing Human Single-chain Variable Fragment with Glutathione Peroxidase Activity from Computer-aided Molecular Design

In order to enhance the glutathione peroxidase（GPX） catalytic activity of the selenium-containing single-chain variable fragments（Se-scFv）, a novel human scFv was designed on the basis of the structure of human antibody and optimized via bioinformatics methods such as homologous sequence analysis, three-dimensional（3D） model building, binding-site analysis and docking. The DNA sequence of the new human scFv was synthesized and cloned into the expression vector pET22b（＋）, then the scFv protein was expressed in soluble form in Escherichia coli BL21（DE3） and purified by Ni2＋-immobilized metal affinity chromatography（IMAC）. The serine residue of scFv in the active site was converted into selenocysteine（Sec） with the chemical modification method, thus, the human Se-scFv with GPX activity was obtained. The GPX activity of the Se-scFv protein was characterized. Compared with other Se-scFv, the new human Se-scFv showed similar efficiency for catalyzing the reduction of hydrogen peroxide by glutathione. It exhibited pH and temperature dependent catalytic activity and a typical ping-pong kinetic mechanism.

Characterization of Oxygen Plasma Modified Polyimide Fibers Interfacial Adhesion Performance by Single Fiber Fragmentation Test

The application of polyimide( PI) fibers in the field of composite materials has been limited because of their smooth surface and chemical inertness. In order to overcome these problems,oxygen plasma was used to modify the surface of fibers. The single fiber fragmentation test( SFFT) was used to characterize the interfacial adhesion performance of PI fiber as a simple and accurate analysis method. It was found that the interfacial shear strength between the fiber and resin after oxygen plasma modification was increased by 54% compared to the untreated fiber. Meanwhile, the surface micromorphology,chemical composition, wettability of fibers and the interface morphology at the fiber fracture were analyzed by field emission scanning electron microscope( FESEM), X-ray photoelectron spectroscopy( XPS),contact angle measurement and polarizing microscope,respectively. All of these results demonstrated that the single fiber fragmentation test for analyzing the interfacial adhesion of PI fibers was effective.

Single Chain Fragment Variables Antibody binding to EGF Receptor in the Surface of MCF7 Breast Cancer Cell Line: Application and Production Review

In this review, single-chain fragment variable construction using phage-display technology as a promising anticancer immunotherapy technology is described. Cloning and the specific bio-panning selection with phage display technology, as well as the use of the epidermal growth factor receptor (EGFR) at the surface of MCF-7 cells as the antigen for the straightforward specific selection of single chain Fvs, are discussed. Moreover, phage display technologies and their application are important for vaccine production and immunotherapy against viruses and cancers. Furthermore, expression of the gene will cause the production and expression of the protein in prokaryotic and eukaryotic cells, which can be used to detect anti-cancer single chain fragment variables (scFvs). Finally, homology modelling is described to show the three-dimensional scFv structure that verifies the Complementary-Determining-Regions (CDRs) on the surface of the model.

Expression of secreted human single-chain fragment variable antibody against human amyloid beta peptide in Pichia pastoris

BACKGROUND：Studies have shown that monoclonal or polyclonal antibody injections of amyloid β peptide are effective in removing amyloid β peptide overload in the brain. OBJECTIVE： Based on successful screening of a human single-chain fragment variable antibody specific to amyloidβpeptide, this paper aimed to express recombinant human single-chain variable antibody against amyloid β peptide. DESIGN, TIME AND SETTING： A single sample experiment was performed at the Department of Nuclear Medicine, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Hospital （Beijing, China） from January to July 2006. MATERIALS： Human single-chain fragment variable antibody gene against amyloid β peptide was screened from a human phage-display antibody library. METHODS： Human single-chain fragment variable antibody gene was mutated to eliminate a BamHI restriction site and cloned into a T easy plasmid for pT-scFvAβ construction, which was identified by PCR amplification and endonuclease digestion. Plasmid pT-scFvAβ was cut by EcoRI and NotI endonucleases, and the antibody gene was cloned into pPIC9K plasmid to construct pPIC9K-scFvAβ expression vector, which was confirmed by gene sequencing. Linearized pPIC9K-scFvAβ was used to transform a Pichia pastoris GS115 cell line, and the recombinant was induced by 0.5% methanol to express human single-chain fragment variable antibody specific to amyloid β peptide. MAIN OUTCOME MEASURES： Protein electrophoresis was used to identify PCR products, gene sequencing was used to verify the pPIC9K-scFvA sequence, and SDS-PAGE was used to detect recombinant expression of human single-chain fragment variable antibody specific to amyloid β peptide in Pichia pastoris. RESULTS： Gene sequencing confirmed pPIC9K-scFvAβ orientation. Recombinants were obtained by linearized pPIC9K-scFvAβ transformation. After induction with 0.5% methanol, the recombinant yeast cells secreted proteins of 33-ku size. CONCLUSION： The expression vector pPIC9K-scFvAβ was successfully constructed. Human single-chain fragment variable antibody specific to amyloid β peptide was recombinantly expressed in Pichia pastoris.

Fusion protein of single-chain variable domain fragments for treatment of myasthenia gravis

Single-chain variable domain fragment （scFv） 637 is an antigen-specific scFv of myasthenia gravis. In this study, scFv and human serum albumin genes were conjugated and the fusion pro-tein was expressed in Pichia pastoris. The afifnity of scFv-human serum albumin fusion protein to bind to acetylcholine receptor at the neuromuscular junction of human intercostal muscles was detected by immunolfuorescence staining. The ability of the fusion protein to block myas-thenia gravis patient sera binding to acetylcholine receptors and its stability in healthy serum were measured by competitive ELISA. The results showed that the inhibition rate was 2.0-77.4%, and the stability of fusion protein in static healthy sera was about 3 days. This approach suggests the scFv-human serum albumin is a potential candidate for speciifc immunosuppressive therapy of myasthenia gravis.

Monte-Carlo Simulation on the Failure of Fiber in a Single Filament Composite

A Monte-Carlo method is used to simulate gradual fracture of fiber in a single filament composite with the increase of virtual stress. A simple computational algorithm is developed to judge where breaking point will happen in the composite and a probability model based on Weibull- distribution is designed to calculate the average fragment length by producing stable and uniform random number in (0, 1). Compared to the published experiment results, the simulating average fragment length is quite perfect.

浮游板优化精液与密度梯度离心结合上游法的比较

目的应用浮游板和密度梯度离心结合上游法优化人类精液,明确优化效果并比较两种方法优化后精子参数的差异。方法收集正常精液样本85例和轻中度少弱精子症精液样本59例,每例样本分为原液组、密梯组和浮游组各1 ml进行后续处理。原液组在精液液化后未做任何处理;密梯组精液液化后用密度梯度离心法结合上游法进行处理,浮游组则在精液液化后应用精子浮游板进行处理。比较原液组、密梯组、浮游组3个亚组间的精子浓度、前向运动精子百分率、正常形态精子百分率;应用流式细胞仪检测精子线粒体膜电位和精子DNA碎片指数,使用单精子活性氧分析仪检测单精子活性氧水平,使用电子显微镜观察精子超微结构并进行组间比较。结果无论是正常精液还是轻中度少弱精子症精液,与原液组比较,密梯组与浮游组的前向运动精子百分率、正常形态精子百分率及精子线粒体膜电位均显著升高(P<0.05),精子DNA碎片指数显著降低(P<0.05);密梯组和浮游组各指标无显著性差异(P>0.05)。正常精液中,浮游组的精子浓度显著高于密梯组(P=0.029),单精子活性氧水平显著低于原液组(P=0.038)。轻中度少弱精子症精液中3亚组间的单精子活性氧水平均无显著性差异(P>0.05)。电子显微镜观察发现正常精液中3个亚组的精子均未见明显异常;轻中度少弱精子症精液中密梯组部分精子可观察到精子细胞膜断裂和线粒体肿胀等异常,而浮游组精子超微结构未见明显异常。结论密度梯度离心结合上游法和浮游板法用于精液的处理和优化,均可有效回收活力、形态和功能更好的精子。精子浮游板法的体外干预小,操作简便,可以获得活性氧更少、损伤更小的精子。

应用噬菌体展示随机12肽库筛选诺如病毒抗原模拟表位

目的:利用Ph.D.-12噬菌体展示肽库筛选诺如病毒(NoV)的抗原模拟表位。方法:包被与GⅡ.4、GⅡ.6、GⅡ.17型NoV具有高特异性及中和能力较强的单链可变片段抗体(scFv),用Ph.D.-12噬菌体展示肽库进行3轮生物淘选。ELISA鉴定淘选所得噬菌体与scFv的结合活性及其与NoV P蛋白的竞争作用;阳性克隆测序后进行生物信息学分析,合成多肽鉴定其抗原性。结果:发现1段与GⅡ.6 VP1区同源性较高的氨基酸序列“MG-D-W”,综合分析提示其可能为GⅡ.6 NoV的抗原模拟表位,且合成的包含“MG-D-W”的多肽可竞争抑制P蛋白与人类组织血型抗原(HBGAs)受体的结合。结论:“MG-DW”是与NoV单链抗体高亲和力的肽段,可能模拟了GⅡ.6 NoV与scFv结合的抗原表位。

优化精液处理中的密度梯度离心法以提高受精结局的探讨

【目的】本研究旨在改进生殖男科领域现有的精液处理方法,特别是针对双层密度梯度法中的300×g 20 min处理条件,以提高受精结局。【方法】收集2020年7月和9月以及2022年3月和5月在中山大学附属第六医院生殖医学中心进行辅助生殖助孕的1623例患者的精液标本进行实验。预实验中,比较四种不同的双层密度梯度方法(200×g 10 min、200×g 20 min、300×g 10 min和300×g 20 min)处理后标本的精子DNA碎片率和回收率。然后,筛选出一种最优的方法作为新方法,并与目前在用的旧方法(300×g 20 min双层梯度法)进行对比,检验受精率是否有统计学差异。在新方法的基础上,进一步优化为单层密度梯度法,并与双层密度梯度法进行对比,检验是否存在统计学差异。实验过程中严格控制温度、离心速度和离心时间,同时记录每组样本的数量和处理条件。【结果】在保证足够的精子回收率的基础上,发现四种双层密度梯度法中300×g 10 min的精子DNA碎片率低于300×g 20 min。因此,选择300×g 10 min作为新方法进行试验。结果表明,新方法300×g 10 min的总受精率、二核体(2pn)受精率均高于300×g 20 min,且差异有统计学意义(P<0.05);300×g 10 min的卵裂率也略高于300×g 20 min,但差异没有统计学意义(P>0.05)。单层密度梯度法的总受精率、2pn受精率均高于双层密度梯度法,但差异没有统计学意义(P>0.05);单层密度梯度法的卵裂率高于双层密度梯度法,囊胚形成率低于双层密度梯度法,且差异均有统计学意义(P<0.05)。【结论】相对于现有的300×g 20 min双层梯度法,300×g 10 min双层梯度法成功提高了总受精率、2pn受精率、卵裂率,缩短了精液优化处理的时间;而单层密度梯度法虽提高了卵裂率、节约了试剂成本和操作时间,但其囊胚形成率却出现了下降的情况。这些发现为生殖男科领域的精液处理方法提供了有益的指导和启示。

考虑岩石破碎程度的数字化钻进单齿推力模型

数字化超前钻探依赖于建立随钻参数与围岩特征之间的定量关系,如何定量分析围岩破碎程度对于推力的影响是个重要难题,对于预测不良地质地层具有重要意义。提出一个基于小孔扩张理论的单齿推力理论模型,模型采用HoekBrown破坏准则和非关联流动法则,描述岩石破碎程度对于岩石强度的影响。基于弹塑性力学,推导小孔扩张模型的应力场和位移场,并将模型应用到岩石贯入试验中,建立单齿贯入岩石过程中贯入深度与无量纲塑性区半径的定量关系。该理论模型考虑了刀头形状参数、岩石破坏程度和围压等重要参数对于推力的影响,并可以得到单齿贯入岩石过程中贯入深度与贯入力的定量关系。为验证模型的准确性,开展2种不同地质强度指标的楔形探头贯入岩石试验,试验结果与模型曲线趋势及数量级一致。将模型预测结果与文献中试验数据相对比,进一步验证了模型的可靠性,且表明本文模型在实际工程利用贯入力预测掌子面围岩破碎程度时更趋于安全。参数分析研究表明,岩石破坏程度、围压和岩石强度参数对于推力影响较大,推力与地质强度指标呈负相关关系,与围压和楔形刀头倾角呈正相关关系。结合钻头中单齿分布情况,该理论模型可以用来探讨实际工程推力参数与围岩参数的关系,推进实现数字化超前钻探。

PEAR1基因多态性与缺血性脑卒中复发易感性的关系研究

目的分析血小板内皮聚集受体1(PEAR1)基因多态性与缺血性脑卒中复发的相关性,为防治缺血性脑卒中复发提供依据。方法选取该院神经内科门急诊和住院确诊为急性缺血性脑卒中的150例患者作为研究对象,根据是否为脑卒中复发分为初发脑卒中组(127例)和复发脑卒中组(23例)。应用聚合酶链反应-限制性片断长度多态性(PCR-RFLP)方法分析PEAR1基因rs12041331位点单核苷酸多态性,并测序验证基因型。结果初发脑卒中组和复发脑卒中组PEAR1基因rs12041331G>A位点GG、GA、AA基因型和G、A等位基因频率比较,差异有统计学意义(P<0.05);复发脑卒中组的年龄较初发脑卒中组高,差异有统计学意义(P<0.05)。Logistic回归分析显示,年龄、PEAR1基因rs12041331位点AA基因型与缺血性脑卒中复发有关,是缺血性脑卒中复发的危险因素(P<0.05)。结论PEAR1基因rs12041331G>A位点多态性与缺血性脑卒中复发相关。PEAR1基因纯合突变可能是缺血性脑卒中复发的危险因素,PEAR1基因可能是缺血性脑卒中复发风险预测的候选基因。

Research on the Correlation Between rs2110385 Polymorphisms of the Visfatin Gene and Nonproliferative Diabetic Retinopathy

Objective:To investigate the association between rs2110385 polymorphisms of the visfatin gene and the risk of type 2 diabetic retinopathy(DR).Methods:172 Han subjects were selected from Xi’an Shaanxi Province;140 patients with type 2 diabetes mellitus(T2DM)and 32 normal controls(NC)were selected from our hospital.Patients with diabetes were divided into a non-DR group(T2DM)(n=69)and a nonproliferative diabetic retinopathy Group(DR)(n=71)after dilated fundus photography and fundus fluorescein angiography.rs2110385/AluⅠgenotypes were detected by standardized polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP),and the differences in the detection rates of different genotypes in the above populations were compared.Results:1)The visfatin level in the DR Group was significantly higher than that in the NC and T2DM groups(P<0.05).2)The frequency of GG genotype and G allele of rs2110385 in the DR Group were higher than those in the T2DM and NC groups(80.3,69.6,50.0,86.6,79,65.6,P<0.05).3)There were significant differences in allele frequency and genotype frequency distribution of rs2110385 between the DR Group and the NC group(P<0.01).Conclusion:Visfatin increased in the nonproliferative diabetic retinopathy group and could be a potential indicator for the clinical prediction of DR.The G allele of the rs2110385 polymorphic site may be related to the risk of DR.

基于神经网络算法的LCDs模组强度提升研究

针对超轻薄窄边框笔电显示模组强度不足导致的破片问题,提出一种基于神经网络的模组强度预测模型,旨在设计阶段评估LCDs模组强度表现,并指导系统设计。首先,基于系统组装受力分析,建立模组强度单体评价标准和实验平台;其次,基于有限元力学仿真,研究不同设计对模组强度的影响规律,确认模组强度关键影响因子;然后,基于单因子交叉实验研究,并通过神经网络算法对数据进行训练学习,建立模组强度预测模型。实验值与预测值对比表明,该模型可准确预测不同设计条件下的模组强度,为前期的强度优化和系统设计提供有效技术指导。

碳纤维表面状态对其复合材料界面性能的影响

为了研究上浆剂和湿热处理对复合材料微观界面性能的影响,通过单丝断裂实验测试去浆处理及湿热处理前后T300、T700SC、T800S碳纤维单丝/环氧树脂体系的界面剪切强度(IFSS),结合扫描电镜测试手段分析了纤维表面物理特性对IFSS的影响.结果表明:去浆及湿热处理均会引起三种单丝复合材料体系IFSS降低,断点形貌由X状向鞘状发生变化,但不同的单丝复合体系IFSS降幅以及断点形貌变化程度不同;去浆后,T700SC/环氧树脂体系IFSS降幅达70.67%,T300/环氧树脂体系仅下降6.05%;湿热处理72 h后,T300/环氧树脂体系IFSS下降幅度最小;湿热作用下,去浆后的单丝/环氧树脂体系IFSS的下降更为显著.

纤维增强树脂基复合材料界面粘结强度测试方法探讨

基体和增强材料界面的粘结性能直接影响到复合材料的力学性能 ,如何测量复合材料界面的粘结强度是界面研究的关键问题之一。本文侧重回顾了目前使用的复合材料界面粘结强度测试方法 ,如微脱粘、单纤维复合材料断裂、单纤维拔出和压出法 。

抗黄曲霉毒素B_1单链抗体的表达载体的比较

目的:比较4种不同的pET载体在表达抗黄曲霉毒素B1(AFB1)的单链抗体(scFv)克隆的特点,确定用以表达scFv-H4的合适载体。方法:将目的基因H4分别克隆到载体pET20b、pET22b、pET28a和pET32a上,分别转入大肠杆菌BL21(DE3)或Origami(DE3)中,比较诱导过程中细胞的生长状况和诱导结束后细胞破碎液中scFv-H4的生物活性以及细胞各部分包涵体。结果:pET20b和pET22b能表达具有生物活性的scFv-H4,这些具有生物活性的蛋白主要存在于周质中;pET28a和pET32a不能表达有生物活性的scFv-H4,而pET32a仅能在细胞质中产生大量的包涵体。结论:pET22b可能是表达AFB1的单链抗体较优的表达载体。

伏马菌素B_1特异单链抗体的同源建模及分子对接模拟研究

目的分析伏马菌素B1(Fumonisin B1,FB1)与其特异单链抗体的分子互作模式。方法通过同源建模构建和优化抗FB1单链抗体的三维结构,结合Procheck和Verify 3D等方法评价得到稳定的抗体模型,利用分子对接研究单链抗体与其抗原FB1的结合特性、疏水性和表面静电力作用。结果单链抗体的互补决定区参与同其抗原FB1的结合,抗体与抗原之间不仅形成稳定的氢键,疏水性和静电力的匹配也很好。结论氢键结合力、分子间疏水相互作用和静电力的共同作用,使得单链抗体形成一个能够与FB1高度互补的相互作用区域,并在抗体与抗原的特异性识别及结合稳定性等方面起着关键作用。