聚乙二醇单修饰的重组人粒细胞集落刺激因子突变体的纯化与分析

目的 获得高活性的聚乙二醇定点单修饰的产物PEG-rmhG-CSF-Cys176.方法 用聚乙二醇马来酰亚胺基和高活性的重组人粒细胞集落刺激因子突变体(rmhG-CSF)的半胱氨酸(Cys)基团特异性结合,并用离子交换层析分离纯化修饰产物,通过高效凝胶过滤色谱检测纯度,MTT法检测体外的生物活性.结果 蛋白纯度为97%,体外生物活性为0.8×10~8 IU·mg~(-1).结论 半胱氨酸反应性PEG和游离Cys的结合是在rmhG-CSF活性区以外的位置C末端,修饰后的蛋白活性基本未受影响.     

采用固-液相相结合法合成聚乙二醇化胸腺五肽

目的通过对胸腺五肽(TP5)进行聚乙二醇(PEG)修饰,合成PEG化TP5,以期延长TP5在体内的半衰期。方法采用液相合成和固相合成相结合技术合成PEG化TP5。采用透析、高效液相色谱进行分析和纯化;通过核磁、质谱和氨基酸测序进行产物结构鉴定。结果合成的PEG化TP5结构鉴定与理论值一致。结论采用一种简便的方法成功实现对TP5的PEG化修饰。     

重组L-门冬酰胺酶的聚乙二醇化学修饰及修饰后酶的稳定性研究

目的单甲氧基聚乙二醇 (mPEG)化学修饰大肠杆菌重组L 门冬酰胺酶 (L ASP) ,考察经过修饰的酶的稳定性。方法N 羟基琥珀酰亚胺 (NHS)活化酯法活化mPEG ,生成的单甲氧基聚乙二醇琥珀酰琥珀酸亚胺酯 (SS mPEG)按不同摩尔比例与L ASP偶联 ,确定适合的反应时间和反应pH值。通过聚乙二醇化学修饰后的酶 (L ASP PEG) ,酶活力和纯度通过奈氏法和丙烯酰胺凝胶电泳 (SDS PAGE)检测 ,高效液相色谱检测L ASP PEG相对分子质量并考察了L ASP PEG体外稳定性等。结果SDS PAGE显示mPEG已经偶联到L ASP分子上 ,以两者摩尔比 1 0∶1为最佳 ,反应pH条件为 8.5 ,获得的L ASP PEG平均比活单位为 6 4 .8IU/mg ,相对分子质量为 30 1 80 0 ,体外稳定性高于L ASP。结论此实验确定了mPEG化学修饰L ASP最佳反应条件为 2 5℃反应 30min ,两者投料摩尔比为 1 0∶1 ,获得的L ASP PEG比L ASP稳定性高     

长效胸腺五肽的合成

目的提高长效胸腺五肽(mPEG(10kD)-TP5)——定位单链聚乙二醇化修饰的胸腺五肽的合成产率。方法选用Fmoc-Tyr(tBu)-Wang树脂和Fmoc/t-Butyl策略完成所有氨基酸的缩合,三氟乙酸对Wang树脂、侧链切割脱除。在碱性条件下,单甲氧基聚乙二醇修饰物(mPEG(10kD)-SPA)定点连接到赖氨酸的侧链氨基(ε-NH2)上。中间产物经钯碳催化氢化,得到mPEG(10kD)-TP5。结果目标产物总收率为20%,新合成路线比我们之前报道的方法产率提高了10倍。结论路线操作简单,易于纯化,产率较高。     

聚乙二醇对生长激素释放肽的化学修饰

目的为得到生长激素释放肽-2(growth hormone releasing peptide-2,GHRP-2)的聚乙二醇(mPEG)修饰产物并考察其稳定性。方法采用mPEG-NHS活性酯,在不同的溶剂条件下,用不同的投料比对GHRP-2进行修饰;HPLC检测反应结果;Sephadex 75凝胶层析法进行分离纯化。结果确定以无水二甲基甲酰胺为溶剂,m(PEG-NHS)∶m(GHRP-2)=1∶1为最佳条件,原料基本消失,主要得到单修饰的GHRP-2。所得产物在pH7.4、pH8.4、pH9.4缓冲液中50 d时的释药率分别为2.1%、7.2%、20.5%。结论无水条件更有利于mPEG-NHS活性酯对GHRP-2的修饰,产物在体外弱碱性条件下较稳定。     

mal-sac-mPEG的制备及对溶菌酶的初步修饰研究

由马来酸酐、6 氨基正己酸及单甲氧基聚乙二醇为原料合成马来酸酐 6 氨基己酸 mPEG酯,用于蛋白质巯基的修饰。对原料的反应比例、柱层析洗脱剂等进行了研究。通过熔点测试、红外光谱分析、1H NMR鉴定和紫外扫描等对中间产物及终产物进行了初步结构鉴定,并以SDS PAGE分析活化mPEG修饰溶菌酶的情况。结果:建立了较简便的合成及分离纯化马来酸酐 6 氨基己酸 mPEG酯的方法。mal sac mPEG的熔点为 55~56℃,紫外吸收光谱在320 nm出现特征吸收峰,红外光谱有典型的特征吸收峰。活化mPEG可修饰溶菌酶。     

聚乙二醇化脑啡肽的镇痛药效和体内分布

目的探讨聚乙二醇(PEG)修饰改善甲硫氨酸脑啡肽(MEK)体内半衰期短和对中枢神经系统(CNS)释放的作用。方法热板致痛小鼠侧脑室注射3.1μmol.kg-1MEK及其mPEG2000和mPEG5000修饰物,醋酸致痛小鼠尾静脉注射31μmol.kg-1同上受试物,比较镇痛活性;小鼠尾静脉注射0.2 ml.(10 g)-1容积5.55～7.40 GBq.L-1浓度的125I标记MEK及其mPEG2000修饰物,比较体内分布。结果 MEK及mPEG修饰物3组间F检验P<0.05或0.01(热板模型15 min除外);mPEG5000修饰物作用强于mPEG2000修饰物及未修饰MEK,镇痛活性可持续至120 min(P<0.01)。mPEG2000修饰物10 min时肝脏分布低于MEK、240 min时血液分布高于MEK(P<0.01),血液半衰期(T12)是原型肽的3倍、清除率(CL)降低2.2倍。结论适当分子量PEG修饰可降低MEK肝脏清除、增强镇痛活性、延长半衰期和镇痛时间,对改善脑啡肽成药性有积极意义;未直接证实mPEG修饰改善MEK的CNS释放。     

聚乙二醇修饰重组人干扰素α-2b修饰产物的初步分析研究

目的 对聚乙二醇(PEG)修饰重组人干扰素α-2b(rhIFNa-2b)的修饰产物进行了初步分析研究。方法以单甲氧基聚乙二醇甲酸琥珀酰亚胺酯对rhIFNα-2b进行修饰,修饰产物以Superdex 75 Highload制备型凝胶色谱柱进行分离、纯化,SDS-PAGE鉴定各组分,采用Mariner电喷雾飞行时间质谱对单修饰IFNα-2b(Inono-PEG-IFNα-2b)进行分析。结果 分别获得了纯化的mono-PEG-IFNα-2b和多修饰IFNα-2b(poly-PEG-IFNα-2b)。ESI-TOF质谱也证明mono-PEG-IFNα-2b分子量比rhIFNα-2b多5 000左右;紫外光谱分析表明,PEG修饰产物的结构没有发生改变。结论获得了纯化的PEG修饰产物。     

单甲氧聚乙二醇/牛血清白蛋白/5-氟尿嘧啶的制备及其抑瘤活性初探

目的:制备单甲氧聚乙二醇/牛血清白蛋白/5-氟尿嘧啶(mPEG/BSA/5-FU)偶联物,以延长5-FU的半衰期并降低其达峰浓度,同时初步探讨偶联物的抑瘤活性。方法:通过在5-FU的N-1处引入乙酸基后再制成活性酯并与BSA偶联,用mPEG修饰偶联物而得mPEG/BSA/5-FU。60只小鼠皮下注射H22肝癌细胞腹水建立实体瘤模型后随机分为生理盐水组、5-FU(25 mg·kg-1.d-1)组、BSA/5-FU组(以5-FU计25 mg·kg-1·d-1)及mPEG/BSA/5-FU(以5-FU计50、25、12.5 mg·kg-1·d-1)剂量组共6组,分别腹腔注射相应试药10 d后处死,计算各组抑瘤率等。结果:得到了偶联率为32.89%的BSA/5-FU,修饰度为48.37%的mPEG/BSA/5-FU。同等5-FU剂量下mPEG/BSA/5-FU组、5-FU组、BSA/5-FU组的抑瘤率分别为40.51%、33.63%、20.54%(P<0.01)。结论:制备mPEG/BSA/5-FU偶联物的偶联反应及修饰反应的工艺简单,抑瘤实验显示所得目标产物的抑瘤率明显高于5-FU组和BSA/5-FU组。     

甲氧基聚乙二醇苯并三唑修饰对淋巴细胞功能的影响

目的　研究甲氧基聚乙二醇 苯并三唑 (mPEG BTC)修饰淋巴细胞表面人类白细胞抗原 (HLA)对细胞有无损伤。方法　利用微量淋巴细胞毒性实验和单向混合淋巴细胞培养来检测mPEG BTC的修饰效果 ;利用电镜观察修饰前后淋巴细胞的形态 ;通过淋巴细胞转化实验及培养上清液的IL 2含量的检测对淋巴细胞的增殖、分化及分泌功能进行评价 ;检测淋巴细胞表面CD分子评价淋巴细胞的抗原识别功能 ;体外保存淋巴细胞检测其寿命 ;对淋巴细胞染色体进行分析 ,评价mPEG对细胞遗传物质的影响。结果修饰后淋巴细胞的微量淋巴细胞毒性实验结果 ,淋巴细胞转化率 ,淋巴细胞相对转化指数 ,IL 2分泌含量分别由修饰前的 (8.0± 0 )分 ,(6 3.6± 7.8) % ,(1.0 7±0 .2 9) ,(38± 11)ng·L- 1降至 (1.1± 0 .3)分 ,(0 .2±1.6 ) % ,(0 .3± 0 .11) ,(11± 3)ng·L- 1。CD2 +,CD4 +,CD8+,CD5 8+分子荧光强度亦有不同程度降低 ,而mPEG BTC修饰对淋巴细胞的形态、寿命及遗传物质无明显改变。结论　mPEG BTC修饰可阻断HLA介导的特异性免疫反应 ,降低淋巴细胞的增殖、抗原分泌能力及分泌 ,但对其形态、结构、遗传物质及寿命无明显影响。     

Pharmacokinetics and hepatic extraction of recombinant human parathyroid hormone, hPTH (1-34), in rat, dog, and monkey

The pharmacokinetics (PK) and hepatic extraction (E(H)) of human PTH (1-34), hPTH (1-34), were characterized in rat, dog, and monkey, following intraportal (IPO) and intravenous (IV) bolus administration. hPTH (1-34) was administered to Sprague-Dawley rats (2, 10, 100 microg/kg), beagle dogs (3, 6 microg/kg), and rhesus monkeys (6, 30 microg/kg). Serum concentrations of immunoreactive hPTH (1-34) were used to derive PK parameters. IPO bioavailability (F(IPO)) was determined by comparing dose-normalized serum exposure (i.e., AUC(IPO)/AUC(IV)). E(H) was estimated as 1-F(IPO). In all species, greater than dose-proportional increases in exposure (i.e., C(max) and AUC) were observed for both routes. Dose-dependent disposition (i.e., time-average clearance (CL) and half-life (t(1/2)) were observed in all three species. In rats, E(H) values of 71% (2 microg/kg), 35% (10 microg/kg), and <1% (100 microg/kg) were obtained. In dogs, E(H) values of 90% (3 microg/kg) and 66% (6 microg/kg) were obtained. In monkeys, E(H) values of 25% (6 microg/kg) and <1% (30 microg/kg) were observed. In conclusion, hPTH (1-34) is subject to hepatic first pass extraction in rat, dog, and monkey with evidence of saturation in the rat. Saturable hepatic extraction in dog and monkey is inconclusive due to the limited dose range investigated.     

Iontophoretic pulsatile transdermal delivery of human parathyroid hormone (1-34)

Iontophoretic pulsatile transdermal delivery of hPTH(1-34) was examined in Sprague-Dawley (SD) rats, hairless rats and beagle dogs. Application for 60 min (200 microg; 0.1 mA cm(-2)) showed current-responsive increases in serum hPTH(1-34) levels in all the animals. In SD rats, the area under the curves of serum hPTH(1-34) levels (AUCs) were proportional to the doses (40, 120, 200, 400 and 1000 microg) and current densities (0.05, 0.1 and 0.15mA cm(-2)) applied. The absorption rates per 200-microg dose, calculated by a deconvolution method, were 6.7, 2.4 and 3.7 microg h(-1) for SD rats, hairless rats and beagle dogs, respectively. These values correlated well with the ratios of the skin porosity to the dermal thickness reported for these animals, which are believed to represent the reciprocal of the electrical resistance of the aqueous channels formed by the hair follicles. From this correlation, we suggested that absorption of hPTH(1-34) occurs mainly via the hair-follicle route, and that the absorption rate in man might be intermediate between those in hairless rats and beagle dogs. Three-fold repetitions of 30 min current with various rest intervals produced current-responsive triple pulses in serum hPTH(1-34) levels in SD rats. Seven-fold repetitions of current also produced similar current-responsive pulsatile serum hPTH(1-34) levels. However, peak serum hPTH(1-34) levels tended to decrease gradually after the fourth current application, possibly due to consumption of the electrodes, suggesting that three-fold repetitions of current might be optimal. These findings suggest that this iontophoretic administration system could create a repeated-pulsatile pattern of serum hPTH(1-34) levels without the necessity for frequent injections, and may be useful for the treatment of osteoporosis with hPTH(1-34).     

Electronically facilitated transdermal delivery of human parathyroid hormone (1-34)

Electronically facilitated transdermal delivery of human parathyroid hormone (1-34), hPTH (1-34), was investigated in vitro, using dermatomed porcine skin. The effect of iontophoretic current density, electroporative pulse voltages and also electroporation followed by iontophoresis was investigated on the in vitro percutaneous absorption of hPTH (1-34). Iontophoresis at 0.5 mA/cm2 current density significantly enhanced (P<0.05) the flux of hPTH (1-34) in comparison to passive flux. Electroporation pulses of 100, 200 and 300 V significantly increased (P<0.05) the flux of hPTH (1-34) in comparison with the passive as well as iontophoretic flux at 0.5 mA/cm2. The electroporative flux of hPTH (1-34) was found to vary linearly (R2 = 0.97) with the pulse amplitude. The principal barrier of the skin, stratum corneum, was found perturbed following the pulses as evident by light microscopy studies. The application of electroporation pulses followed by iontophoresis further increased the flux by several fold. The flux of hPTH (1-34) with the electroporation pulses of 100 and 300 V followed by iontophoresis at 0.2 mA/cm2 was 10- and 5-fold higher, respectively, in comparison to the flux with corresponding pulses alone. This shows the synergistic effect of iontophoresis in combination with electroporation on skin permeability of hPTH (1-34). The results indicate the possibility of designing controlled transdermal delivery systems for hPTH (1-34) using electroporation followed by iontophoresis.     

Prevention of bone loss in ovariectomized rats by pulsatile transdermal iontophoretic administration of human PTH(1-34)

Serum human parathyroid hormone (1-34)[hPTH(1-34)] levels and the anabolic effect of hPTH(1-34) were compared after administration using multiple pulses of iontophoresis or subcutaneous (sc) intermittent injections to ovariectomized (OVX) Sprague Dawley rats. Triple-pulse iontophoretic administration of hPTH(1-34) (doses: 40-400 microg/patch), achieved by repeated 30-min applications of a 0.1 mA/cm(2) current separated by 45-min rest intervals, produced three sharp peaks in the serum hPTH(1-34) level in response to application of the current. Each peak appeared at the end of the 30-min current application period and was proportional to the hPTH(1-34) dose. Compared with once-daily sc injections (7 pulses/week), triple-pulses iontophoretic administered 3 times/week (9 pulses/week) for 4 weeks produced dose-related increases in the bone mineral density (BMD) of the distal 1/3 femur. For the sc administration, the relative BMD values using the vehicle injection as a reference standard for 1, 5, and 25 microg/kg/day were 104, 114, and 121%, respectively. For iontophoretic administration, the relative BMD values using the placebo patch as a reference standard for 40, 120, and 400 microg/patch were 104, 110, and 116%, respectively. The increase in the BMD plotted against the area under the hPTH(1-34) serum level-time curve (AUC) over 1 week resulted in similar straight lines in the 9 pulses/week iontophoretic administration and the 7 pulses/week sc administration groups. The estimated iontophoretic dose giving an equivalent BMD to once-daily sc administration at 5 microg/kg/day was 120 microg/patch. These findings strongly suggest that three iontophoretic pulses administered on alternate days will exert an anabolic effect equivalent to that of daily sc administration at doses giving the same weekly AUC. Furthermore, this method of administering hPTH(1-34) might enable self-medication, a useful advance in the treatment of osteoporosis.     

Osteoporosis-treating parathyroid hormone peptides: What are they? What do they do? How might they do it?

The first experiments demonstrating parathyroid hormone's (PTH's) dramatic bone-building activity in rat pups, using a bovine parathyroid extract called parathormone were reported 74 years ago. Over the next decades, the native parathyroid hormone (human (h)PTH(1-84)) was purified and two of its fragments (hPTH(1-34) and (Leu27)cycloGlu22-Lys26hPTH(1-31)NH2) have been developed for the treatment of osteoporosis. One of these, recombinant (r)hPTH(1-34), is now on the market under the trade name of Forteo. The native hormone has also completed clinical trials and (Leu27)cycloGlu22-Lys26hPTH(1-31)NH2 is in phase II clinical trials under the trade name Ostabolin-C. All three of these peptides potently stimulate bone growth, reinforce bone microstructure weakened by estrogen deprivation and reduce further fracturing. Furthermore, future studies may demonstrate that these peptides also promote the repair of existing fractures and implant anchorage in both healthy and osteoporotic humans. PTHs have the potential to become more successful by using cost-cutting, but still effective, cyclical treatment regimens and by formulating them for non-injectable delivery. This review will discuss the identification of PTH peptides, how they function and their future role in the treatment of osteoporosis.     

Design and synthesis of conformationally constrained glucagon-like peptide-1 derivatives with increased plasma stability and prolonged in vivo activity

A series of conformationally constrained derivatives of glucagon-like peptide-1 (GLP-1) were designed and evaluated. By use of [Gly (8)]GLP-1(7-37)-NH2 (2) peptide as a starting point, 17 cyclic derivatives possessing i to i + 4, i to i + 5, or i to i + 7 side chain to side chain lactam bridges from positions 18 to 30 were prepared. The effect of a helix-promoting alpha-amino-isobutyric acid (Aib) substitution at position 22 was also evaluated. The introduction of i to i + 4 glutamic acid-lysine lactam constraints in c[Glu (18)-Lys (22)][Gly (8)]GLP-1(7-37)-NH2 (6), c[Glu (22)-Lys (26)][Gly (8)]GLP-1(7-37)-NH2 (10), and c[Glu (23)-Lys (27)][Gly (8)]GLP-1(7-37)-NH2 (11) resulted in potent functional activity and receptor affinities comparable to native GLP-1. Selected GLP-1 peptides were chemoselectively PEGylated in order to prolong their in vivo activity. PEGylated peptides [Gly (8),Aib (22)]GLP-1(7-37)-Cys ((PEG))-Ala-NH2 (23) and c[Glu (22)-Lys (26)][Gly (8)]GLP-1(7-37)-Cys ((PEG))-Ser-Gly-NH2 (24) retained picomolar functional potency and avid receptor binding properties. Importantly, PEGylated GLP-1 peptide 23 exhibited sustained in vivo efficacy with respect to blood glucose reduction and decreased body weight for several days in nonhuman primates.     

The role of the liver and kidneys in the pharmacokinetics of subcutaneously administered teriparatide acetate in rats

Teriparatide acetate, a synthetic polypeptide fragment consisting of human parathyroid hormone residues 1-34 [hPTH(1-34)], is a bone anabolic agent used to treat osteoporosis. The present study was conducted to characterise the pharmacokinetics of teriparatide acetate in rats after subcutaneous administration. Teriparatide was rapidly absorbed into the circulation and eliminated immediately. No intact teriparatide was detected in the urine. To elucidate the mechanism of teriparatide metabolism, we performed in vivo and in vitro studies using the radiolabelled bioactive analogue, [(125)I]-[Nle(8,18),Tyr(34)]-hPTH(1-34). After subcutaneous administration, the concentration of analogue metabolites increased in the plasma time-dependently. The concentration in the kidneys was more than 3-fold the concentration in the liver. In vitro analyses suggested that kidney radioactivity was associated with degraded bioactive analogue. In model rats, renal failure, but not hepatic failure, affected the pharmacokinetics of teriparatide acetate, which accounted for the decrease in the clearance of teriparatide. In conclusion, our results suggest that after subcutaneous administration of teriparatide acetate, teriparatide is rapidly absorbed and distributed to the liver or kidneys, where it is immediately degraded. The kidneys play a particularly important role in the distribution and metabolism of teriparatide, but not its excretion.     

Comparing the incidence of bone tumors in rats chronically exposed to the selective PTH type 1 receptor agonist abaloparatide or PTH(1–34)

Prolonged treatment with human parathyroid hormone (hPTH) in rats results in development of bone tumors, though this finding has not been supported by clinical experience. The PTH type 1 receptor agonist abaloparatide, selected for its bone anabolic activity, is under clinical development to treat postmenopausal women with osteoporosis. To determine the carcinogenic potential of abaloparatide, Fischer (F344) rats were administered SC daily abaloparatide at doses of 0, 10, 25, and 50 μg/kg or 30 μg/kg hPTH(1–34) as a positive control for up to 2 years. Robust increases in bone density were achieved at all abaloparatide doses and with hPTH(1–34). Comprehensive histopathological analysis reflected a comparable continuum of proliferative changes in bone, mostly osteosarcoma, in both abaloparatide and hPTH(1–34) treated rats. Comparing the effects of abaloparatide and hPTH(1–34) at the 25 and 30 μg/kg respective doses, representing similar exposure multiples to the human therapeutic doses, revealed similar osteosarcoma-associated mortality, tumor incidence, age at first occurrence, and metastatic potential. There were no increases in the incidence of non-bone tumors with abaloparatide compared to vehicle. Thus, near life-long treatment with abaloparatide in rats resulted in dose and time dependent formation of osteosarcomas, with a comparable response to hPTH(1–34) at similar exposure.     

Prospective type 1 and type 2 disulfides of Keap1 protein

Experiments were carried out to detect cysteine residues on human Keap1 protein that may be sensors of oxidative stress that gives rise to changes in the GSH/GSSG redox couple. Human Keap1 protein, at a final concentration of 6 microM, was incubated for two hours in aqueous buffer containing 0.010 M GSH, pH 8, in an argon atmosphere. Subsequently, excess iodoacetamide and trypsin were added to generate a peptide map effected by LCMS analysis. Peptides containing all 27 carboxamidomethylated cysteines were identified. Replacement of GSH by 0.010 M GSSG yielded a map in which 13 of the original carboxamidomethylated peptides were unperturbed, while other caboxamidomethylated cysteine-containing peptides were undetected, and a number of new cysteine-containing peptide peaks were observed. By mass analysis, and in some cases, by isolation, reduction, carboxamidomethylation, and reanalysis, these were identified as S-glutathionylated (Type 1) or Cys-Cys (Type 2) disulfides. Such peptides derived from the N-terminal, dimerization, central linker, Kelch repeat and C-terminal domains of Keap1. Experiments were carried out in which Keap1 was incubated similarly but in the presence of various GSH/GSSG ratios between 100 and 1 ([GSH + GSSG] = 0.010 M), with subsequent caraboxamidomethylation and trypsinolysis to determine differences in sensitivities of the different cysteines to the type 1 and type 2 modifications. Cysteines most sensitive to S-glutathionylation include Cys77, Cys297, Cys319, Cys368, and Cys434, while cysteine disulfides most readily formed are Cys23-Cys38 and Cys257-Cys297. The most reducing conditions at which these modifications are at GSH/GSSG = 10, which computes to an oxidation potential of E h = -268.5 mV, a physiologically relevant value. Under somewhat more oxidizing, but still physiologically relevant, conditions, GSH/GSSG = 1 ( E h = -231.1 mV), a Cys319-Cys319 disulfide is detected far from the dimerization domain of the Keap1 homodimer. The potential impact on protein structure of the glutathionylation of Cys434 and Cys368, the two modified residues in the Kelch repeat domain, was analyzed by docking and energy minimizations of glutathione residues attached to the Kelch repeat domain, whose coordinates are known. The energy minimizations indicated marked alterations in structure with a substantial constriction of Neh2 binding domain of the Keap1 Kelch repeat domain. This alteration appears to be enforced by an extended hydrogen-bonding network between residues on the glutathione moiety attached to Cys434 and amino acid side chains that have been shown to be essential for repression of Nrf2 by Keap1. The modifications of Keap1 detected in the present study are discussed in the context of previous work of others who have examined the sensitivity of cysteines on Keap1 to electrophile assault.     

Complete mapping of disulfide linkages for etanercept products by multi-enzyme digestion coupled with LC-MS/MS using multi-fragmentations including CID and ETD

The disulfide linkages of two etanercept products, Enbrel® (innovator drug) and TuNEX®, were characterized and compared using a multi-fragmentation approach consisting of electron transfer dissociation (ETD) and collision induced dissociation (CID) in combination with multi-enzyme digestion protocols (from Lys-C, trypsin, Glu-C, and PNGase F). Multi-fragmentation approach allowed multi-disulfide linkages contained in a peptide to be un-ambiguously assigned based on the cleavage of both the disulfide and the backbone linkages in a MS³ schedule. New insights gained using this approach were discussed. A total of 29 disulfides, Cys18-Cys31, Cys32-Cys45, Cys35-Cys53, Cys56-Cys71, Cys74-Cys88, Cys78-Cys-96, Cys98-Cys104, Cys112-Cys121, Cys115-Cys139, Cys-142-Cys157, Cys163-Cys178 in TNFR portion and Cys240-Cys240, Cys246-Cys246, Cys249-Cys249, Cys281-Cys341, Cys387-Cys445 in IgG1 Fc domain, were completely assigned with the demonstration of the same disulfide linkages between the Enbrel® and TuNEX® products. The data showed the higher order structure was preserved throughout the recombinant manufacturing processes and consistent between the two products.