人胰岛素生长因子1的原核表达及其单克隆抗体的制备

目的原核表达、纯化人胰岛素样生长因子1（hIGF-I）,并制备其单克隆抗体（mAb）。方法通过RT-PCR方法从人体肝脏组织中扩增得到hIGF-I基因片段,构建重组原核表达质粒pET-28a（＋）/hIGF-I,在大肠杆菌BL21（DE3）中进行表达。将表达蛋白纯化后免疫BALB/c小鼠,取其脾脏和小鼠杂交瘤细胞融合制备针对hIGF-I的特异性单克隆抗体。结果成功表达出了hIGF-I蛋白。SDS-PAGE电泳显示所表达蛋白质的相对分子量（Mr）大小约为18 KD。获得了1株能够稳定表达抗hIGF-I抗体的杂交瘤细胞株（8F2）,其分泌的mAb的IgG亚类（型）为IgG2b,ELISA检测,对应腹水mAb的效价分别为1∶7.5×10^5。Western-blot结果显示抗hIGF-I mAb具有良好的特异性。结论成功制备了抗hIGF-I mAb,为进一步研究IGF-I在肿瘤治疗中的作用提供了有力的工具。     

Oxidation of Human Insulin-like Growth Factor I in Formulation Studies: Kinetics of Methionine Oxidation in Aqueous Solution and in Solid State

Purpose. The aim of this work was to study the kinetics of oxidation of methionine in human Insulin-like Growth Factor I (hIGF-I)¹ in aqueous solution and in the solid state by the aid of quantification of oxygen. Methods. The oxidized form of hIGF-I was characterized by tryptic peptide analysis, RP-HPLC and FAB-MS and quantified by RP-HPLC. The oxygen content was quantified polarographically by a Clark-type electrode. Results. Second-order kinetics with respect to amount of protein and dissolved oxygen was found to be appropriate for the oxidation of methionine in hIGF-I. The rate constants ranged from 1 to 280 M^–1 month^–l and had an activation energy of 95 (+/–4) kJ/mole. Light exposure, storage temperature and oxygen content were found to have a considerable impact on the oxidation rates. No significant difference in reaction rates was found for the oxidation of hIGF-I in aqueous solution or in the solid state. A method for decreasing the oxygen content in aqueous solution without purging is described. Conclusions. Polarographic quantification of dissolved oxygen makes it possible to establish the kinetics for oxidation of proteins. The oxidation of methionine in hIGF-I appears to follow second-order kinetics.     

Solvent Effects on the Solubility and Physical Stability of Human Insulin-Like Growth Factor I

Purpose. The solubility and physical stability of human Insulin-like Growth Factor I (hIGF-I) were studied in aqueous solutions with different excipients. Methods. The solubility of hIGF-I was determined by UV-absorption and quantification of light blocking particles. The physical stability of hIGF-I was studied with differential scanning calorimetry (DSC) and circular dichroism (CD) spectroscopy. Results. Human IGF-I precipitated at low temperature in the presence of 140 mM benzyl alcohol and 145 mM sodium chloride. CD data showed that the tertiary structure of hIGF-I during these conditions was perturbed compared to that in 5 mM phosphate buffer. In the presence of benzyl alcohol 290 mM mannitol stabilized hIGF-I. Sodium chloride or mannitol by themselves had no effect on either the solubility or the tertiary structure. Benzyl alcohol was attracted to hIGF-I, whereas sodium chloride was preferentially excluded. The attraction of benzyl alcohol was reinforced by sodium chloride leading to salting-out of hIGF-I. The CD-data indicated interactions of benzyl alcohol with phenylalanine in hIGF-I. Thermal denaturation of hIGF-I occurred in all solutions with sodium chloride, whereas mannitol or benzyl alcohol had no effect on the thermal stability. The thermal stability of hlGF-I was thus decreased in 145 mM sodium chloride although it was excluded from hIGF-I. Conclusions. The self-association and thermal aggregation of hIGF-I is driven by hydrophobic interactions. Benzyl alcohol is attracted to hIGF-I and induces changes in the tertiary structure causing hydrophobic attraction of the protein at low temperatures.     

逆转录病毒载体介导人胰岛素样生长因子-Ⅰ在软骨细胞中的表达

目的 探讨逆转录病毒载体介导人胰岛索样生长因子-Ⅰ(human insulin-like growth factor-I,hIGF-I)体外转染兔软骨细胞后软骨细胞hIGF-I的表达情况及其生物学行为变化.方法 将构建的含有目的 基因的逆转录病毒载体pLNc-IGF-GFP体外转染兔关节软骨细胞,经G418筛选阳性克隆,采用RT-PCR及免疫化学染色检测转染软骨细胞中hIGF-I的表达情况,并在荧光显微镜下观察标记基因GFP的表达情况.采用MTT法、流式细胞仪、免疫细胞化学染色、二甲基驱甲蓝法及ELISA法对转染hIGF-I后的软骨细胞的增殖能力及表型进行检测.结果 G418筛选后获得的软骨细胞阳性克隆,经RT-PCR和免疫细胞化学检测表明hIGF-1基因在mRNA和蛋白质水平得到稳定表达,荧光显微镜下观察转染的软骨细胞可激发出绿色荧光,证明转染成功.转染软骨细胞株的增殖能力、Ⅱ型胶原和蛋白多糖的分泌水平,在转染后6 w内均高于同时间点未转染的软骨细胞,差异具有显著性(P<0.05).结论 逆转录病毒载体能有效地将hIGF-I基因转染至兔软骨细胞并获得稳定表达,同时转染后的软骨细胞增生活跃,能够在较长时间维持软骨细胞表型,为进一步研究软骨缺损的组织工程修复和基因治疗打下基础.