Synthetic study of peptide neurotoxins isolated from animals in South East Asia

(1)新螺芋螺毒素的合成及二硫键配对测定本论文合成了三种从珍珠螺中分离得到的新型芋螺毒素CMRⅡ、CMR III和CMR V。它们都有三个分子内二硫键。为了确定二硫键的配对，我们采用选择性二步二硫键形成法合成了CMRII。与天然多肽的高效液相共洗脱表明，Cmr II具有C1-C4、C2-C5和C3-C6的结合。然而，有人认为CmrV具有不同的二硫键模式。4种新的芋螺毒素AmIV、AmVIIA、AmVIIB和AMix是由国外合作者从Amadis中分离得到的。分别为AmIV和AMix合成了C端酰胺化和游离肽。高效液相共洗脱实验表明，AmIV和AMix分别含有游离端和酰胺化的C-末端。合成的AmVIIA和AmVIIB具有游离的C-末端。(2)sc…的二硫键构型、三维结构与活性的关系更多的蛇毒毒素。从蝎子Heterometus fuIvipe中分离出的Hefu毒素-1采用了独特的两个平行螺旋的三维折叠，通过两个二硫键连接，而不需要任何β片断。我们合成了两个肝毒素-1类似物，在中心环区缺失了一个或两个氨基酸残基。对缺失类似物的酶切分析表明，两者具有与天然多肽相同的二硫键配对。合成了几个氨基酸取代的类似物用于构效关系研究。从蝎子H、刺蛇蛇毒中分离得到5个新的多肽毒素HS2388、HS2404、HS2620、HS3019和HS3700。我们合成了它们，证实HS2388和HS2404具有酰胺化的C-末端，而其他的则具有游离的C-末端。圆二色谱和酶消化比较表明，HS2388、HS2404、HS2620和HS3019与肝毒素-1具有相同的二硫键模式。HS2620的合成类似物表明，第20位的碱性残基干扰了该毒素与K通道的相互作用。较少

(1)Synthesis and disulfide pairing determination of novel conotoxins from cone snail.We synthesized three novel conotoxins CMrII, CMrIII, and CMrV isolated from Cones marmoreus. All of them have three intramolecular disulfide bonds. In order to determine the disulfide pairings, we synthesized CMrII by selective two-step disulfide bond formation method. HPLC co-elution with native peptide suggested that CMrII has C1-C4, C2-C5, and C3-C6 combinations. Whereas, it was suggested that CMrV has different disulfide patterns. Re-examination is in progress for CMrV.Four novel conotoxins, AmIV, AmVIIA, AmVIIB, and AmIX were isolated from C. amadis by foreign collaborators. Both C-terminal amidated and free peptides were synthesized for AmIV and AmIX. HPLC co-elution indicated that AmIV and AmIX had free and amidated C-terminals, respectively. AmVIIA and AmVIIB were synthesized and shown to have free C-terminals.(2)Relationships of disulfide pattern, three-dimensional structure and activity of sc … More orpion toxins.Hefutoxin-1 isolated from scorpion Heterometrus fuIvipes adopts a unique three-dimensional fold of two parallel helices linked by two disulfide bridges without any βsheets. We synthesized two analogs of hefutoxin-1 with deletion of one or two amino acid residues at the central loop region. Enzymatic digestion of deletion analogs showed that both of them have the same disulfide pairings as native peptides. Several analogs with amino acid substitution were synthesized for structure-activity relationship study.Five novel peptide toxins HS2388, HS2404, HS2620, HS3019, and HS3700 were isolated from scorpion H, spinifer venom. We synthesized all of them and confirmed that HS2388 and HS2404 have amidated C-terminals, whereas others have free C-terminals. Comparison of CD spectra and enzymatic digestion suggested that HS2388, HS2404, HS2620, and HS3019 have the same disulfide pattern as that of hefutoxin-1. Synthetic analogs of HS2620 suggested that the basic residue at the 20th position interfere the interaction of this toxin to K channels. Less