重组人睫状神经营养因子的聚乙二醇化修饰

目的:研究重组人睫状神经营养因子(rhCNTF)突变体的聚乙二醇(PEG)化修饰,对rhCNTF的PEG化产物进行初步分离纯化及相关生物活性检测。方法:采用分子生物学技术经点突变得到rhCNTF的突变体CN10,通过实验设计研究CN10的最佳PEG化条件;采用分子筛层析方式对偶联产物进行初步纯化,最后用ELISA和小鼠体重增长抑制法检测PEG化后的CN10蛋白的生物活性。结果:能运用mPEG-MAL对CN10进行定点修饰,PEG化后用Superdex200能够分离CN10;PEG化后的CN10每2 d腹腔注射1次,对小鼠体重的增长抑制率可达50%,与rhCNTF每天注射2次的体重增长抑制作用相当。结论:CN10蛋白在PEG化修饰后,其减重效应持续时间明显延长。     

RP-HPLC法检测CN_(10)蛋白的PEG化修饰率及含量

目的建立一种简单有效的测定CN10蛋白PEG化修饰率的方法 ,用于PEG化修饰工艺中的质量控制。方法采用反相高效液相色谱(RP-HPLC)法,以TSKgel Octadecyl-4PW作为色谱分离柱,以含0.12%三氟乙酸(TFA)、5%乙腈的水溶液作为A相溶液,以含0.1%TFA的乙腈作为B相溶液,在50℃柱温条件采用分段线性洗脱的方式分离蛋白,并考察CN10蛋白以及PEG化修饰后CN10蛋白的量效关系,根据外标法检测CN10和CN10-PEG的蛋白含量,根据PEG化修饰前后CN10蛋白量效关系的变化推断CN10蛋白的PEG化修饰率。结果 PEG化修饰前后的CN10蛋白经TSKgel Octadecyl-4PW色谱柱层析均能达基线分离,当用214 nm波长检测时,CN10蛋白浓度以及PEG修饰后的CN10蛋白均与其对应峰面积呈现良好的线性关系(r2=0.999 58;r2=0.999 67)。结论建立了一种简单快速的检测CN10蛋白PEG化修饰率的方法 ,此方法具有较高的准确性及专属性,可用于CN10的PEG化修饰工艺的监测。     

集成干扰素突变体IIFN72C的构建及其聚乙二醇定点修饰

目的：设计构建集成干扰素突变体IIFN72C并进行聚乙二醇定点修饰,以获得高活性的长效干扰素分子。方法：利用蛋白质分子同源模建,选择在集成干扰素分子IIFN的第72位引入半胱氨酸残基构成集成干扰素突变体IIFN72C。诱导表达后经包涵体变复性和层析纯化,与单甲氧基聚乙二醇（mPEGMAL）定点偶联。修饰产物经纯化后,以SDSPAGE考察其纯度,用WISHVSV系统进行生物活性测定。结果：IIFN72C以包涵体形式表达,表达量占菌体总蛋白的30%以上,比活性与突变前相当;修饰产物大多数为单修饰体,纯化后纯度大于98%,比活性保留约为修饰前的8%。结论：成功设计并表达IIFN72C用于PEG定点修饰,修饰产物活性保留得以提高。     

聚乙二醇修饰重组溶葡球菌酶的初步研究

目的:探讨聚乙二醇(PEG)修饰重组溶葡球菌酶(lysostaphin)的反应条件以及修饰后产物的纯化方法.方法:采用超声波细胞粉碎机进行菌体破碎,阳离子交换层析、疏水层析进行蛋白纯化;在不同条件下,将活化的单甲氧基聚乙二醇琥珀酰亚胺丙酸酯(mPEG-SPA)与纯化后的lysostaphin反应,以单个PEG-Lysostaphin的比例为指标,用SDS-PAGE、MALDI-TOF-MS方法确定其在修饰产物中的所占比例;采用Sephacryl S-200分子筛凝胶层析法对修饰产物进行分离纯化.结果:mPEG-SPA修饰lysostaphin的反应条件为pH 8.0,温度4℃,lysostaphin与mPEG-SPA的质量比为1∶5,反应时间2.0h;反应产物经一步Sephacryl S-200分子筛凝胶层析纯化后,初步实现分离.结论:初步确定了聚乙二醇修饰lysostaphin的反应条件及修饰产物的纯化方法.     

聚乙二醇定点修饰集成干扰素突变体Ⅱ

目的：用聚乙二醇（PEG）修饰集成干扰素突变体Ⅱ（IFN-Con-m2,IIFNm2）,通过纯化获得新型修饰分子并对该分子进行抗胰蛋白酶水解稳定性及初步药代动力学研究。 方法：将mPEG20000定点偶联到IIFNm2的第86位Cys残基上,修饰后的产物经CM层析后,以SDS-PAGE考察其纯度,用WISH-VSV系统进行生物活性测定;在0.1%胰蛋白酶条件下考察体外抗酶解稳定性;并以SD大鼠进行初步药代动力学研究,绘制血药浓度-时间曲线。采用3P87软件进行数据拟合,分析药物动力学参数。 结果：干扰素修饰率约为50%,且绝大多数以单修饰体（mono-PEG- IIFNm2）形式存在;提纯后mono-PEG-IIFNm2 的纯度大于98%,比活性约为修饰前IIFNm2的1%。抗胰蛋白酶水解试验表明：30min后,IIFNm2抗病毒活性残留为8%,mono-PEG-IIFNm2为41%。初步药代动力学研究显示：IIFNm的消除半衰期为(1.57±0.34)h,mono-PEG-IIFNm2为(18.0±4.0)h。 结论：成功地偶联了PEG和IIFNm2,建立了mono-PEG-IIFNm2的纯化工艺,PEG修饰能增加IIFNm2的体外抗胰蛋白酶水解稳定性,并显著延长体内半衰期。     

反相高效液相色谱法分析聚乙二醇修饰的水蛭素

目的：采用反相高效液相色谱法（RP-HPLC）对聚乙二醇（PEG）修饰的水蛭素进行分析分离,用以分析修饰产物中不同修饰度水蛭素的组成和比例。方法：色谱柱为Hypersil C18,5μm,4.6mm×150mm;流动相A为H2O＋0.01％的三氟乙酸,流动相B为乙腈＋0.01％的三氟乙酸。40min内由10％-50％流动相B进行梯度洗脱,洗脱流速1mL／min,上样量50μL,检测波长为214nm。结果：在单甲基化PEG-丙酸琥珀酰亚胺和水蛭素摩尔比不同的的反应产物中,PEG1-水蛭素、PEG2-水蛭素均可以达到基线分离,且不同批次的反应产物进行RP-HPLC的重复性良好。结论：RP-HPLC可以有效地对PEG修饰的水蛭素产物进行分析分离,为PEG化水蛭素的长效、缓释剂型的开发提供技术支持。     

聚乙二醇单修饰重组人粒细胞集落刺激因子的研究

制备单修饰的PEG蛋白偶联物,对获得重复性好的修饰产品,减少后续分离步骤具有重要的意义。用N-羟基琥珀酰亚胺活化法对单甲氧基聚乙二醇 (mPEG,分子量20000) 进行活化,红外光谱分析, 并考察了其水解动力学性质。对重组人粒细胞集落刺激因子(rhG-CSF)进行化学修饰,通过正交试验结合SDS-PAGE电泳检测建立了单条PEG链修饰rhG-CSF的条件,单修饰PEG-rhG-CSF的收率为90%。离子交换层析对修饰产物进行分离纯化,高效凝胶过滤色谱(SEC-HPLC)检测纯度达到97%。     

pH调控双水相萃取色素蛋白复合体及其分配行为研究

为发展色素蛋白复合体分离纯化新方法,探究pH调控PEG1000/柠檬酸钾双水相系统萃取分离纯化色素蛋白复合体。优化萃取条件,光谱法研究其分配行为,检测产物纯度和生物活性。结果表明,最佳萃取条件为调节pH9.0,相组成CPEG100019.0%/C柠檬酸钾20.0%,蛋白质加量3.42 mg/g,K和萃取率达到最大,分别为8.8及86.0%。响应面分析法揭示,PEG1000和柠檬酸钾质量浓度及pH对分配系数和萃取率影响显著。调节pH7.0,反萃取分配系数和反萃取率最小为0.15及86.6%。蛋白质总回收率为74.2%。pH对色素蛋白复合体分配行为具有调控作用,pH大于8.5体系,色素蛋白趋于分配上相,反之分配于下相,PEG1000/柠檬酸钾以及蛋白质加入量不影响色素蛋白复合体分配于上相。电泳表征发现,萃取(pH9.0)上相存在2个蛋白质组分,相对分子量(MW)为7.0 kD及14.0 kD。反萃取(pH7.0)使相对分子量7.0 kD蛋白质组分分配于下相,该组分为LH2β亚基,经萃取和反萃取产物生物活性稳定。pH可调控PEG1000/柠檬酸钾双水相系统萃取分离色素蛋白复合体,产物纯度高,生物活性稳定。     

人Leptin基因在大肠杆菌中的高效表达、纯化及其生物学活性研究

将人Leptin表达质粒pBV220-OB转化E.coliJM109,经热诱导获得了目的蛋白的表达。经SDS-PAGE鉴定分析,表达产物以包涵体形式存在,目的蛋白表达量占菌体总蛋白的40%以上。通过包涵体分离,Sephacryl S200HR凝胶和DEAE52离子交换层析及Hypersil C18柱反相色谱纯化,获得纯度在95%以上,内毒素含量小于10EU/mg的高纯度的重组人Leptin。Western-blot鉴定表明,纯化表达产物能和抗Leptin抗体特异性结合;蛋白质N端15个氨基酸序列分析结果和预期的序列一致。纯化产物经复性处理,其分子中Cys96和Cys146形成二硫键。体内活性检测显示,纯化和复性的rh-Leptin明显抑制BALB/c小鼠的进食和体重增长,提示其具有明显的生物学活性。     

无标签鼠疫耶尔森菌V抗原突变体在大肠杆菌中的表达、纯化及免疫原性分析

目的：在大肠杆菌中表达、纯化无标签鼠疫耶尔森菌低钙反应Ｖ抗原突变体,并对其免疫原性进行研究。方法：采用融合ＰＣＲ方法将Ｖ抗原基因中编码半胱氨酸的碱基缺失突变,将获得得Ｖ抗原突变体基因克隆到原核表达载体ｐＥＴ３２ａ（＋）后转化大肠杆菌ＢＬ２１（ＤＥ３）,用ＩＰＴＧ诱导表达并进行柱层析纯化,纯化产物以Ｗｅｓｔｅｒｎ印迹进行鉴定并免疫ＢＡＬＢ／ｃ小鼠,通过ＥＬＩＳＡ检测免疫血清效价。结果：目的蛋白在大肠杆菌中获得了可溶性高表达,经三步柱层析后纯度高于９５％,经Ｗｅｓｔｅｒｎ印迹检测可与野生型Ｖ抗原单克隆抗体特异性结合,免疫小鼠后获得高效价免疫血清。结论：获得了无标签的鼠疫耶尔森菌Ｖ抗原突变体蛋白,并证实其具有免疫原性,将对Ｖ抗原结构和功能的研究提供帮助。     

PEGylation of lysine residues improves the proteolytic stability of fibronectin while retaining biological activity

Excessive proteolysis of fibronectin (FN) impairs tissue repair in chronic wounds. Since FN is essential in wound healing, our goal is to improve its proteolytic stability and at the same time preserve its biological activity. We have previously shown that reduced FN conjugated with polyethylene glycol (PEG) at cysteine residues is more proteolytically stable than native FN. Cysteine‐PEGylated FN supported cell adhesion and migration to the same extent as native FN. However, unlike native FN, cysteine‐PEGylated FN was not assembled into an extracellular matrix (ECM) when immobilized. Here, we present an alternative approach in which FN is preferentially PEGylated at lysine residues using different molecular weight PEGs. We show that lysine PEGylation does not perturb FN secondary structure. PEG molecular weight, from 2 to 10 kDa, positively correlates with FN–PEG proteolytic stability. Cell adhesion, cell spreading, and gelatin binding decrease with increasing molecular weight of PEG. The 2‐kDa FN–PEG conjugate shows comparable cell adhesion to native FN and binds gelatin. Moreover, immobilized FN–PEG is assembled into ECM fibrils. In summary, lysine PEGylation of FN can be used to stabilize FN against proteolytic degradation with minimal perturbation to FN structure and retained biological activity.     

Proteolytically stabilizing fibronectin without compromising cell and gelatin binding activity

Excessive proteolytic degradation of fibronectin (FN) has been implicated in impaired tissue repair in chronic wounds. We previously reported two strategies for stabilizing FN against proteolytic degradation; the first conjugated polyethylene glycol (PEG) through cysteine residues and the second conjugated PEG chains of varying molecular weight on lysine residues. PEGylation of FN via lysine residues resulted in increased resistance to proteolysis with increasing PEG size, but an overall decrease in biological activity, as characterized by cell and gelatin binding. Our latest method to stabilize FN against proteolysis masks functional regions in the protein during lysine PEGylation. FN is PEGylated while it is bound to gelatin Sepharose beads with 2, 5, and 10 kDa PEG precursors. This results in partially PEGylated FN that is more stable than native FN and whose proteolytic stability increases with PEG molecular weight. Unlike completely PEGylated FN, partially PEGylated FN has cell adhesion, gelatin binding, and matrix assembly responses that are comparable to native FN. This is new evidence of how PEGylation variables can be used to stabilize FN while retaining its activity. The conjugates developed herein can be used to dissect molecular mechanisms mediated by FN stability and functionality, and address the problem of FN degradation in chronic wounds. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 31:277–288, 2015     

天花粉蛋白的定点聚乙二醇修饰

用一种定点修饰天花粉蛋白（ｔｒｉｃｈｏｓａｎｔｈｉｎ,ＴＣＳ）的方法,将聚乙二醇（ＰＥＧ）偶联到预先选定的位点．利用ｎＴＣＳ无半胱氨酸（Ｃｙｓ）残基这一特点,通过定点突变将一个Ｃｙｓ残基引入ＴＣＳ以取代第７位的丝氨酸（Ｓｅｒ）残基．然后,与巯基反应的ＰＥＧ－ｍ ａｌｅｉｍ ｉｄｅ 即可偶联到新引入的Ｃｙｓ 残基上．经纯化得到均一的ＰＥＧ－ＴＣＳ复合物,在ＳＤＳ－ＰＡＧＥ上显示一条区带,表观分子量为３８ ｋＤ．复合物的体外致核糖体失活活性降低了６倍,但其体内引产活性与ｎＴＣＳ相同．定点ＰＥＧ修饰方法为改造ＴＣＳ提供了新途径．     

Genetic PEGylation

Polyethylene glycol (PEG) was genetically incorporated into a polypeptide. Stop-anticodon-containing tRNAs were acylated with PEG-containing amino acids and were then translated into polypeptides corresponding to DNA sequences containing the stop codons. The molecular weights of the PEG used were 170, 500, 700, 1000, and 2000 Da, and the translation was confirmed by mass spectrometry. The PEG incorporation ratio decreased as the molecular weight of PEG increased, and PEG with a molecular weight of 1000 Da was only slightly incorporated. Although improvement is required to increase the efficiency of the process, this study demonstrates the possibility of genetic PEGylation.     

Solid-phase PEGylation of recombinant interferon alpha-2a for site-specific modification: process performance, characterization, and in vitro bioactivity

'Solid-phase' PEGylation, in which a conjugation reaction attaches proteins to a solid matrix, has distinct advantages over the conventional, solution-phase process. We report a case study in which recombinant interferon (rhIFN) alpha-2a was adsorbed to a cation-exchange resin and PEGylated at the N-terminus by 5, 10, and 20 kDa mPEG aldehydes through reductive alkylation. After PEGylation, a salt gradient elution efficiently purified the mono-PEGylate of unwanted species such as unmodified IFN and unreacted PEG. Mono-PEGylation and purification were integrated into a single, chromatographic step. Depending on the molecular weight of the mPEG aldehyde, the mono-PEGylation yield ranged from 50 to 65%. Major problems associated with the solution-phase process such as random or uncontrollable multi-PEGylation and post-PEGylation purification difficulties were overcome. N-terminus sequencing and MALDI-TOF mass spectrophometry confirmed that the PEG molecule was conjugated only to the N-terminus. A cell proliferation study indicated reduced antiviral activity of the mono-PEGylate compared to that of the unmodified IFN. As higher molecular weight PEG was conjugated, in vitro bioactivity and antibody binding activity, as measured by a surface plasmon resonance biosensor, decreased. Nevertheless, trypsin resistance and thermal stability were considerably improved .     

Molecular Insight into the Steric Shielding Effect of PEG on the Conjugated Staphylokinase: Biochemical Characterization and Molecular Dynamics Simulation

PEGylation is a successful approach to improve potency of a therapeutic protein. The improved therapeutic potency is mainly due to the steric shielding effect of PEG. However, the underlying mechanism of this effect on the protein is not well understood, especially on the protein interaction with its high molecular weight substrate or receptor. Here, experimental study and molecular dynamics simulation were used to provide molecular insight into the interaction between the PEGylated protein and its receptor. Staphylokinase (Sak), a therapeutic protein for coronary thrombolysis, was used as a model protein. Four PEGylated Saks were prepared by site-specific conjugation of 5 kDa/20 kDa PEG to N-terminus and C-terminus of Sak, respectively. Experimental study suggests that the native conformation of Sak is essentially not altered by PEGylation. In contrast, the bioactivity, the hydrodynamic volume and the molecular symmetric shape of the PEGylated Sak are altered and dependent on the PEG chain length and the PEGylation site. Molecular modeling of the PEGylated Saks suggests that the PEG chain remains highly flexible and can form a distinctive hydrated layer, thereby resulting in the steric shielding effect of PEG. Docking analyses indicate that the binding affinity of Sak to its receptor is dependent on the PEG chain length and the PEGylation site. Computational simulation results explain experimental data well. Our present study clarifies molecular details of PEG chain on protein surface and may be essential to the rational design, fabrication and clinical application of PEGylated proteins.     

The inhibitory potencies of monoclonal antibodies to the macrophage adhesion molecule sialoadhesin are greatly increased following PEGylation

PEGylation of antibodies is known to increase their half-life in systemic circulation, but nothing is known regarding whether PEGylation can improve the inhibitory potency of antibodies against target receptors. In this paper, we have examined this question using antibodies directed to Sialoadhesin (Sn), a macrophage-restricted adhesion molecule that mediates sialic acid dependent binding to different cells. Anti-Sn monoclonal antibodies (mAbs), SER-4 and 3D6, were conjugated to PEG 5 kDa or and PEG 20 kDa, resulting in the incorporation of up to 3 molecules of PEG per mAb molecule. Following purification of PEGylated mAbs by anion exchange chromatography, it was shown that PEGylation had little or no effect on antigen binding activity but led to a dramatic increase in inhibitory potency that was proportional to both the size of the PEG and the degree of derivatization. Thus, PEGylation of antibodies directed to cell surface receptors could be a powerful approach to improve the therapeutic efficacy of antibodies, not only by increasing their half-life in vivo, but also by increasing their inhibitory potency for blocking receptor-ligand interactions.     

聚乙二醇修饰重组人干扰素α-2b的碘染色法

目的：建立检测聚乙二醇位点特异性修饰重组人干扰素α-2b反应的方法。方法：采用分子量20000的甲氧基聚乙二醇马来酰亚胺修饰重组人干扰素α-2b,反应混合物样品经十二烷基硫酸钠聚丙烯酰胺凝胶电泳（SDS-PAGE）后,碘染色法判断反应产物组成。结果：该修饰反应产物除含有单PEG化的干扰素α-2b外,还有不同修饰程度的多PEG化干扰素。结论：本方法方便快捷、分辨率高、特异性强,同时可用于其它聚乙二醇修饰蛋白质的分析研究。     

PEGylation of cholecystokinin prolongs its anorectic effect in rats

The anorectic compound CCK-9 was coupled to polyethylene glycol 5 kDa, 10 kDa, 20 kDa and 30 kDa, under different reaction conditions. Conjugates were purified by HPLC and characterized by MALDI-TOF MS. A 96% PEGylation yield was obtained in buffer pH 7.5 after 6h reaction at 20 degrees C. The anorectic activity was tested in vivo in rats. A single bolus intra-peritoneal injection of non-modified CCK-9 resulted in a significant initial food intake reduction 30 min after food presentation (87% compared to paired control group). When PEG-CCK-9 conjugates modified with polymers of molecular weight up to 20 kDa were injected, lower but statistically significant initial food intake reductions were obtained (76% for PEG 10 kDa-CCK-9 conjugate compared to control group). The cumulative food intake reduction of non-modified CCK-9 is normalized within 1-2h, whereas the PEG-CCK-9 molecules showed a prolonged anorectic activity lasting for 6h for PEG 5 kDa-CCK-9; 23 h for PEG 10 kDa-CCK-9 and between 8h and 23 h for PEG 20 kDa-CCK-9. For PEG 30 kDa-CCK-9 conjugate, neither an initial nor a cumulative FI reduction was observed. PEG-CCK-9 conjugates show a significantly prolonged anorectic activity in comparison to the non-modified peptide. This effect is most evident for the PEG 10 kDa-CCK-9 conjugate.