普兰林肽的固相合成

目的:探索普兰林肽的固相合成、氧化条件及纯化方法。方法:采用Fmoc固相多肽合成法,以Rink Amide-AM树脂做载体,HBTU/HOBt/DIEA做缩合剂,逐步缩合得到全保护线性普兰林肽树脂,以TFA/苯甲硫醚/苯酚/H2O/EDT/TIS配比的裂解液脱除保护基团,分别采用空气,二甲基亚砜,双氧水氧化两个半胱氨酸的巯基形成一对二硫键,半制备反相高效液相色谱法纯化。结果:合成含37个氨基酸以及一对二硫键的普兰林肽经RP-HPLC和MALDI-TOF-MS确证,粗品纯度在50.0%以上,粗品经半制备型反相高效液相色谱纯化,所得精肽的纯度大于95.0%,总收率为30.5%。结论:该方法简单,合成的产品成本低,纯度高,可为工业化生产提供借鉴。     

抗肿瘤肽AP-9的固相合成

建立了抗肿瘤肽AP-9的Fmoc固相全合成方法，产品纯度大于98％。着重研究了Fmoc-Arg（Pbf）-OH与H—Pro—Trt树脂的缩合反应。结果表明，以THF-NMP（1：1）为溶剂，于30℃微波辐射反应6min，缩合产率达80．2％。     

奥曲肽固相合成工艺研究

目的优化奥曲肽固相合成工艺。方法本研究采用Fmoc保护基固相合成策略合成奥曲肽直链肽[D-Phe-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr(ol)],并在此基础上进行裂解、成环、纯化、制备奥曲肽。本研究着重对裂解条件进行优化,包括裂解液成分、比例、反应温度和时间等。结果与结论以TFA∶TIS∶H_2O∶DTT=90∶2.5∶2.5∶8为裂解体系,在10℃下反应2～3 h得到纯度92%(HPLC)的直链肽粗品。本文优化的裂解条件提高了奥曲肽直链肽纯度,同时避免了乙二硫醇的使用,使得生产过程对环境更加友好,更适合工业化生产。     

Fmoc法固相合成普兰林肽

以Fmoc保护的氨基酸为原料,Amide Rink MBHA树脂为载体,按照氨基酸序列进行耦合制得普兰林肽,同时考察了裂解条件.应用反相高效液相色谱得到纯度98%以上的样品.     

醋酸奥曲肽的固相合成

目的设计并合成醋酸奥曲肽.方法采用固相多肽合成法,使用逐步缩合的战略合成奥曲肽.结果与结论合成了醋酸奥曲肽,纯品总收率为30%(以连到树脂上的第一个氨基酸计).关键中间体及最终产物的结构经质谱、红外光谱、核磁共振氢谱及碳谱得到确证.     

Fmoc 策略固相合成磷酰化肽研究进展

蛋白质的磷酰化和去磷酰化对多种生命活动的调节起着关键的作用,磷酰化肽是研究这些生命调节过程中一类非常重要的物质。自 20 世纪 40 年代人类首次成功地合成出磷酰化肽以来,磷酰化肽的研究就引起了化学家和生物学家的广泛关注。由于Fmoc 固相合成策略在多肽的合成中被普遍应用,因此,Fmoc 固相合成策略也已经成为目前磷酰化肽最主要的合成手段。该文对近年来采用 Fmoc 固相合成策略进行磷酰化肽合成的方法（包括整体磷酰化法和磷酰化单体合成法）进行了总结,并对各种合成方法的优缺点进行了讨论。     

降钙素基因相关肽抗原决定簇的固相合成

本文采用国内原料用Ｍｅｒｒｉｆｉｅｌｄ固相合成法合成了阵钙素基因相关肽（ＣＧＲＰ）的抗原决定簇Ｔｙｒ°－ＣＧＲＰ（２７～３７）．快原子轰击质谱和氨基酸组分分析与理论值一致。     

含RGD序列假肽及其模拟物的合成研究概况

通过文献检索,综述含RGD序列假肽及肽模拟物的合成研究概况。     

肽核酸的固相合成方法

肽核酸（PNA）作为一类很有发展前景的非天然的反义核酸，其高效合成是将其广泛应用的基础。本文从PNA单体的合成和PNA寡聚体的合成两方面对近几年PNA的固相合成作了系统的介绍。     

NMR and molecular modeling characterization of RGD containing peptides

The tripeptide sequence arginine-glycine-aspartic acid (RGD) has been shown to be the key recognition segment in numerous cell adhesion proteins. The solution conformation and dynamics in DMSO-d₆ of the cyclic pentapeptides, Ac-Cys-Arg-Gly-Asp-Cys-OH (CRGDC), a potent fibrinogen receptor antagonist, and Ac-Cys-Arg-Gly-D-Asp-Cys-OH (CRGdC), a weak fibrinogen receptor antagonist, have been characterized by nuclear magnetic resonance (NMR) spectroscopy and molecular modeling. ¹H-¹H distance constraints derived from two-dimensional NOE spectroscopy and torsional angle constraints obtained from ³JNH-h α coupling constants, combined with computer-assisted modeling using conformational searching algorithms and energy minimization have allowed several low energy conformations of the peptides to be determined. Low temperature studies in combination with molecular dynamics simulations suggest that each peptide does not exist in a single, well-defined conformation, but as an equilibrating mixture of conformers in fast exchange on the NMR timescale. The experimental results can be fit by considering pairs of low energy conformers. Despite this inherent flexibility, distinct conformational preferences were found which may be related to the biological activity of the peptides.     

RGD肽聚乳酸微球的制备

目的制备RGD肽聚乳酸(RGD-PLA)微球,并初步研究其性质。方法采用溶剂挥发法制备RGD-PLA微球,以包封率为考察目标,采用正交设计优化制备工艺,并初步考察了其性质。结果优化工艺后制备的RGD-PLA微球,形态均匀,粒径范围在10～32μm,包封率在74%以上。结论所得RGD-PLA微球,包封率高,稳定性良好,有一定的缓释效果。     

两种RGD模拟肽抗兔血小板聚集活性研究

目的研究两种RGD模拟肽(NB05和NB06)的抗兔血小板聚集活性.方法体外检测RGD肽抑制家兔ADP诱导血小板聚集率,计算RGD肽对血小板聚集的抑制率.体内颈动静脉旁路血栓模型检测两种RGD肽对形成血栓湿重的影响.结果NB05和NB06体外抗家兔血小板聚集的IC50值分别为(33.34±3.58)和(8.69±1.34)μmol·L-1;NB05和NB06均使血栓湿重显著减小(P＜0.01),NB06的抗血栓活性较NB05高(P＜0.05).结论NB05和NB06均具有较强的抗血小板聚集和抗血栓形成活性.     

Use of iminodiacetic acid for the synthesis of piperazinyl peptides related to leu-enkephalin. II.

Piperazinyl peptides related to Leu-enkephalin were obtained using as intermediates condensation products with iminodiacetic acid. The products are devoid of analgesic activity.     

Design, synthesis, and evaluation of near infrared fluorescent multimeric RGD peptides for targeting tumors

Molecular interactions between RGD peptides and integrins are known to mediate many biological and pathological processes. This has led to an increased interest in the development of RGD compounds with high affinity and improved selectivity for integrin receptors. In this study, we synthesized and evaluated a series of multimeric RGD compounds constructed on a dicarboxylic acid-containing near-infrared (NIR) fluorescent dye (cypate) for tumor targeting. An array of NIR fluorescent RGD compounds was prepared efficiently, including one RGD monomer (cypate-(RGD)(2)-NH(2)), two RGD dimers (cypate-(RGD)(2)-NH(2) and cypate-(RGD-NH(2))(2)), one trimer (cypate-(RGD)(3)-NH(2)), two tetramers (cypate-(RGD)(4)-NH(2) and cypate-[(RGD)(2)-NH(2)](2)), one hexamer (cypate-[(RGD)(3)-NH(2)](2)), and one octamer (cypate-[(RGD)(4)-NH(2)](2)). The binding affinity of the multimeric RGD compounds for alpha(v)beta(3) integrin receptor (ABIR) showed a remarkable increase relative to the monomer cypate-RGD-NH(2). Generally, the divalent linear arrays of the multimeric RGD units bound the ABIR with slightly higher affinity than their monovalent analogues. These results suggest that the receptor binding affinity was not only dependent on the number of RGD moieties but also on the spatial alignments of the pendant peptides. Internalization of the compounds by ABIR-positive tumor cells (A549) was monitored by NIR fluorescence microscopy. The data showed that endocytosis of the octameric RGD derivative was significantly higher by comparison to other compounds in this study. In vivo noninvasive optical imaging and biodistribution data showed that the compounds were retained in A549 tumor tissue. These results clearly demonstrated that an array of simple RGD tripeptides on a NIR fluorescent dye core can be recognized by ABIR. Optimization of the spatial alignment of the RGD moieties through careful molecular design and library construction could induce multivalent ligand-receptor interactions useful for in vivo tumor imaging and tumor-targeted therapy.     

Study on the synthesis and characterization of peptides containing phosphorylated tyrosine

Phosphorylation and dephosphorylation are key events in receptor-mediated and post-receptor-mediated signal transduction. Synthetic phosphopeptides have been shown to have dramatic agonist or antagonist effects in several of these signaling pathways. For its 1997 study, the Association of Biomolecular Resource Facilities (ABRF) Peptide Synthesis Research Group assessed the ability of member laboratories to synthesize phosphotyrosine peptides. Participating laboratories were requested to synthesize and submit the following crude peptide, H–Glu–Asp–Tyr–Glu–Tyr(PO₃H₂)–Thr–Ala–Arg–Phe–NH₂, for evaluation by amino acid analysis, sequence analysis, RP-HPLC, MALDI-TOF and ESI mass spectrometry. Prior to analysis of submitted peptides from ABRF members, the Peptide Synthesis Research Group synthesized and characterized the nonphosphorylated form of the peptide, the doubly phosphorylated form and the peptides singly phosphorylated on either the first or the second tyrosine. These peptide standards were separated easily by HPLC and capillary electrophoresis and the phosphotyrosine was detected readily by Edman degradation sequence analysis. No differences were seen by amino acid analysis and the expected masses were observed by mass spectrometry. The two singly phosphorylated peptides were easily distinguished by MALDI-PSD. Analysis of the peptides submitted from member facilities revealed that all but four of the 33 samples contained the correct product as determined by HPLC and mass spectrometry. HPLC analysis indicated that 20 of the 33 submitted samples contained greater than 75% correct product, five contained less than 50% correct product and four did not contain any correct product. By ESI/MS, an additional singly charged ion at m/z 535.5 was detected in five of the 33 submitted samples; this ion was subsequently shown to represent Ac-TARF-NH₂. No correlation was found to exist between coupling time and percentage correct product; however, a correlation may exist between a greater percentage of correct product and the use of non-protected phosphotyrosine.     

Solution stability of linear vs. cyclic RGD peptides

Abstract: Arg-Gly-Asp (RGD) peptides contain an aspartic acid residue that is highly susceptible to chemical degradation and leads to the loss of biological activity. Our hypothesis is that cyclization of RGD peptides via disulphide bond linkage can induce structural rigidity, thereby preventing degradation mediated by the aspartic acid residue. In this paper, we compared the solution stability of a linear peptide (Arg-Gly-Asp-Phe-OH; 1 ) and a cyclic peptide (cyclo-(1, 6)-Ac-Cys-Arg-Gly-Asp-Phe-Pen-NH_2; 2 ) as a function of pH and buffer concentration. The decomposition of both peptides was studied in buffers ranging from pH 2–12 at 50°C. Reversed-phase HPLC was used as the main tool in determining the degradation rates and pathways of both peptides. Fast atom bombardment mass spectrometry (FAB-MS), electrospray ionization mass spectrometry (ESI-MS), matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry, liquid chromatography-mass spectrometry (LC-MS), and one- and two-dimensional nuclear magnetic resonance spectroscopy (NMR) were used to characterize peptides 1 and 2 and their degradation products. In addition, co-elution with authentic samples was used to identify degradation products. Both peptides displayed pseudo-first-order kinetics at all pH values studied. The cyclic peptide 2 appeared to be 30-fold more stable than the linear peptide 1 at pH 7. The degradation mechanisms of linear ( 1 ) and cyclic ( 2 ) peptides primarily involved the aspartic acid residue. However, above pH 8 the stability of the cyclic peptide decreased dramatically due to disulphide bond degradation. Both peptides also exhibited a change in degradation mechanism upon an increase in pH. The increase in stability of cyclic peptide 2 compared to linear peptide 1 , especially at neutral pH, may be due to decreased structural flexibility imposed by the ring. This rigidity would prevent the Asp side chain carboxylic acid from orientating itself in the appropriate position for attack on the peptide backbone.     

含RGD多肽的构象研究

血小板活化时，表面ＧＰⅡｂ／Ⅲａ受体变构，与纤维蛋白结合形成血栓，纤维蛋白识别ＧＰⅡｂ／Ⅲａ受体时，ＲＧＤ（Ａｒｇ＝Ｇｌｙ－Ａｓｐ）是关键序列，含ＲＧＤ多肽可以竞争ＧＰⅡｂ／Ⅲａ受体，进而阻断血栓形成进程，作者注意到，含ＲＧＤ多肽的抗血栓活构象关系密切，采用Ｂｉｏｓｙｍ公司设计的Ｄｉｓｃｏｖｅｒ程序，计算了ＲＧＤＳ，ＲＧＤＶ和ＲＧＤＦ在真空下，在水中的和在正辛醇中的右手螺旋、左手螺旋及β伸展构象，     

Multivalent effects of RGD peptides obtained by nanoparticle display

The binding of RGD peptides to integrins offers an excellent system to study the multivalent mediated changes in affinity that arise when peptides, displayed on the surface of a nanoparticle carrier, bind to integrins displayed on the cell membrane. The IC50 of an RGD nanoparticle for endothelial adhesion was 1.0 nM nanoparticle or 20 nM peptide (20 peptide/nanoparticle) and was associated with strong multivalent effects, defined as a multivalent enhancement factor (MVE) of 38 (MVE=IC50 (peptide)/IC50 (peptide when displayed by nanoparticle)). The attachment of RGD peptides to nanoparticles resulted in an extension of the peptide blood half-life from 13 to 180 min. Based on the multivalent enhancement of affinity and extension of blood half-life, multivalent RGD nanoparticle-sized materials should be potent inhibitors of the alpha(V)beta(3) function on endothelial cells in vivo.     

小分子靶向肽RGD的合成工艺改进

目的优化细胞黏附肽精氨酸-甘氨酸-天冬氨酸(RGD)三肽的合成路线。方法以天冬氨酸和苯甲醇为原料,经成酯、成酰胺、脱保护基等多步反应合成目标化合物。结果在制备RGD过程中采用分步纯化的方法,对反应溶剂、反应产物的纯化方法等进行优化;在制备中间体甘氨酸-天冬氨酸二苄酯(GD二肽)时采用液相合成法,GD二肽的纯度为99. 0%,一步收率约为91. 9%; GD二肽与Nα-Boc-Nω-NO2-精氨酸经液相合成法和脱保护,得到目标化合物三肽RGD,其纯度为97. 0%,一步收率约为90. 5%。结论优化工艺后制得各重要中间体及目标物的结构均经MS、1H-NM R、IR谱确证,优化后的路线总收率为38. 7%(以Boc-Arg(NO2)-OH计)。该RGD的合成工艺反应条件温和、反应易于控制、成本低、收率高,可为RGD肽的工业化生产提供参考。