Conformation and Biological Activity of Cyclic Peptides

Cyclic peptides containing biologically active hormone sequences are suitable models for studying conformation-activity relationships. In such models the usual flexibility of peptide chains is reduced by their cyclic arrangement. However, conformational analysis of such systems by experimental means is possible only if a single conformer predominates at equilibrium, and criteria for this are put forward. NMR spectroscopic methods, including many recent advances, are discussed in relation to their ability to contribute to peptide conformational analysis.     

Engineering of Cardiotoxin by Chemical Synthesis: (I) Rapid Synthesis of Fully Active Cardiotoxin II and IV of Taiwan Cobra Venom

Two 60-residue snake toxins with four disulfide bridges, cardiotoxin II and IV, of Taiwan cobra (Naja naja atra) have been rapidly prepared in overall yields of 3.9% (cardiotoxin II) and 3.7% (cardiotoxin IV) within three weeks using the chemical method. Physicochemical characterization of these synthetic cardiotoxins was carried out by amino acid analysis, mass spectroscopy, capillary electrophoresis, peptide mapping, circular dichroism spectroscopy, and lethal toxicity. As compared with natural cardiotoxins, the results indicated that the synthetic cardiotoxins possessed the same physicochemical properties as those of natural ones. Therefore, in addition to preparation of various important toxins with satisfactory quantities for biochemical and pharmacological studies within a short lime, this rapid method also provides an important route to obtain many interesting toxins and designed toxin analogues for structure/function relationship studies in the near further.     

Novel Antimicrobial Peptides from a Cecropin-Like Region of Heteroscorpine-1 from Heterometrus laoticus Venom with Membrane Disruption Activity

The increasing antimicrobial-resistant prevalence has become a severe health problem. It has led to the invention of a new antimicrobial agent such as antimicrobial peptides. Heteroscorpine-1 is an antimicrobial peptide that has the ability to kill many bacterial strains. It consists of 76 amino acid residues with a cecropin-like region in N-terminal and a defensin-like region in the C-terminal. The cecropin-like region from heteroscorpine-1 (CeHS-1) is similar to cecropin B, but it lost its glycine-proline hinge region. The bioinformatics prediction was used to help the designing of mutant peptides. The addition of glycine-proline hinge and positively charged amino acids, the deletion of negatively charged amino acids, and the optimization of the hydrophobicity of the peptide resulted in two mutant peptides, namely, CeHS-1 GP and CeHS-1 GPK. The new mutant peptide showed higher antimicrobial activity than the native peptide without increasing toxicity. The interaction of the peptides with the membrane showed that the peptides were capable of disrupting both the inner and outer bacterial cell membrane. Furthermore, the SEM analysis showed that the peptides created the pore in the bacterial cell membrane resulted in cell membrane disruption. In conclusion, the mutants of CeHS-1 had the potential to develop as novel antimicrobial peptides.     

新型抗菌肽的设计、活性研究及与磷脂相互作用的计算模拟

设计合成了多个具有2个活性序列的线性和环状多肽及具有单个活性序列的短链多肽, 研究了它们的杀菌活性, 发现其杀菌活性顺序为长链肽>环状肽>短链肽, 特别是线性的Linear-KT和Linear-KS对多种革兰氏阴性菌和阳性菌均具有较高的杀菌活性. 采用MTT法考察了Linear-KT和Linear-KS对正常细胞的毒性, 其中Linear-KS表现出较低的细胞毒性, 优于阳性对照多粘菌素B. 利用计算模拟的方法计算了多肽与细菌细胞膜中磷脂酰甘油(DMPG)的相互作用. 结果表明, 多肽和DMPG的结合能也表现出长链肽>环状肽>短链肽的规律, 特别是Linear-KT和Linear-KS具有较高的结合能. 长链肽含有2个活性序列, 可提供多个荷正电的氨基酸与荷负电的磷脂结合, 结合能较大, 杀菌活性较强. 同时, 柔性的结构及Linear-KT和Linear-KS中丝氨酸和苏氨酸的β碳上的羟基可与磷脂上的羰基形成多个氢键, 进一步增大了结合能. 计算模拟的方法为抗菌肽的杀菌活性从理论上提供了一定的依据.     

Chemical Studies of Formosan Cobra (Naja Naja Atra) Venom: Part II. Isolation and Characterization of Guanosine,Adenosine, and Inosine from Cobra Venom

A non-protein fraction from crude Formosan cobra venom was found to be a nucleoside mixture. The components were identified as guanosine, adenosine and inosine by paper chromatographic and polyamide thin-layer chromatographic correlations and their spectroscopic data. The mole ratio of guanosine/adenosine/inosine was found to be 7:2.5:1.     

计算机辅助设计新型人脂肪酸合酶抑制剂及其抗肿瘤活性

以Orlistat为先导化合物,利用AutoDock进行计算机模拟对接,在对接结果中选择能量较低的6个结构进行合成与抗肿瘤活性筛选。以orlistat为原料,经2步反应制得苄基(2S,3S,5S)-2-己基-3,5-二羟基十六酸酯(2); 再经4步反应获得(3S,4S)-3-己基-4-［(S)-2-羟基十三烷基］氧杂环丁烷-2-酮(5); 5在EDCI作用下与酸经缩合反应合成了4个计新型人脂肪酸合酶抑制剂（6a~6d）,其中6b~6d为新化合物,其结构经¹H NMR, ¹³C NMR 和HR-MS（ESI）表征。体外初步活性测试表明：(S)-1-［(1S,2S)-3-己基-4-氧代氧杂环丁烷-2-基］十三烷-2-烟酸酯（6a）对MDA-MB-231细胞有较好的抑制作用,其IC₅₀为11.72 μmol·mL^-1,优于Orlistat(21.5 μmol·mL^-1)。     

新型化学修饰siRNAs的设计、合成及生物活性研究

以含取代基团的苯酚和氯代环氧丙烷为原料,经多步反应合成了4种含芳香结构的化学修饰单体,针对靶向Mdm2 mRNA序列的siRNA,在其3'末端加入不同化学修饰的单体制备获得9个siRNAs.采用四甲基偶氮唑盐(MTT)法对所合成的siRNAs进行体外抗肿瘤活性、稳定性测试,结果显示化学修饰的siRNA8,siRNA11,siRNA15对人乳腺癌MCF-7细胞的活性和核酸酶稳定性均有显著提高,其中siRNA11体外对RNA水解酶的半衰期提高了10倍.     

Synthesis and Biological Activity of a Novel Pentacyclic Heterocycle

A novel pentacyclic heterocycle has been synthesized starting from D ‐glucose involving two crucial conversions: the intramolecular cycloaddition of O‐allyloxy furanaldoxime derived from D ‐glucose to furanopyran‐2‐isoxazoline and its diastereoselective reductive cleavage to the corresponding cis‐1,3‐amino alcohol. The antibacterial and antifungal activities of the synthesized heterocycle have been examined.     

Chemical Studies of Formosan Cobra (Naja Naja Atra) Venom: Part III. N-Terminal Amino Acid Analysis of Some Purified Protein Components by DNP and DNS Methods

N-Terminal amino acid residues of Fractions IX, X, and XII were reinvestigated by DNP and DNS methods with two-dimensional polyamide thin-layer chromatography. It was found that our previous work¹ had been erroneously concluded. By the present work, it was obvious that all three fractions had Leu as their N-terminal amino acid residues.     

A Novel Antifungal Protein with Lysozyme-Like Activity from Seeds of Clitoria ternatea

An antifungal protein with a molecular mass of 14.3 kDa was isolated from the seeds of butterfly pea (Clitoria ternatea) and designated as Ct protein. The antifungal protein was purified using different methods including ammonium sulphate precipitation, ion exchange chromatography on DEAE-cellulose and gel filtration on Sephadex G-50 column. Ct protein formed a single colourless rod-shaped crystal by hanging drop method after 7 days of sample loading. The protein showed lytic activity against Micrococcus luteus and broad-spectrum, fungicidal activity, particularly against the most clinically relevant yeasts, such as Cryptococcus neoformans, Cryptococcus albidus, Cryptococcus laurentii, Candida albicans and Candida parapsilosis. It also exerted an inhibitory activity on mycelial growth in several mould species including Curvularia sp., Alternaria sp., Cladosporium sp., Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Rhizopus sp., and Sclerotium sp. The present study adds to the literature on novel seed proteins with antifungal activity.     

一类新型酰基脲化合物的设计,合成及生物活性

设计并合成了２１个新型含呋喃环的双酰基脲化合物，经ＩＲ，＾１ＨＮＭＲ、ＭＳ和元素分析确证其结构，初步生物活性测定结果表明，该类化合物具有几丁质抑制活性。     

Design,Synthesis, and Biological Activity of Novel Triazole Sulfonamide Derivatives Containing a Benzylamine Moiety

The triazole sulfonamide played a very important role in the field of research of new agrochemical compounds as a novel heterocyclic compound with lack of reported resistance. For the research on the innovative triazole sulfonamide fungicide effective against cucumber downy mildew (CDM), the present article designed an array of 1,2,4‐triazole‐1,3‐disulfonamide derivatives. The derivatives were synthesized via coupling multiple benzylamine with triazole sulfonamide groups. ¹H‐NMR, ¹³C‐NMR, and LC–MS spectrometry were used to characterize these synthesized compounds. Most of these derivatives exhibited better fungicidal activities than that of the commercial cyanosole using bioassays. In particular, compounds 6g and 6h showed the best fungicidal activity against CDM (EC₅₀ = 6.91 and 10.62 mg/L). Comparative experiments demonstrated that the fungicidal activity of 6g and 6h was better than the commercial pesticides amisulbrom and cyanosole. According to the study, the compound 6g had a giant application potential on fungicide against CDM.     

Design,Synthesis and Biological Activity of Novel Chalcone Derivatives as Anti-influenza Agents

A series of novel chalcone derivatives was designed and synthesized via a suitable synthetic strategy in good yields using commercially available 2-amino-4-nitrophenol as an initiator. The structures of the target compounds were confirmed by means of ¹H NMR, ¹³C NMR and high-resolution mass spectrometry(HRMS). And the ability of the target compounds to inhibit influenza viruses was evaluated. These compounds showed moderate inhibitory activity against influenza A(H9N2 and H5N1) viruses. Within this series, compounds S14 and S15 with good potency(IC₅₀=40.3-51.5μmol/L) could be used as lead compounds in the future.     

新型取代苯基噁唑类化合物的设计、合成及生物活性

通过活性亚结构拼接方法,将具有生物活性的噁唑基团与咪唑烷或噻唑烷拼接,设计合成了一系列新型取代苯基噁唑类化合物.以取代的苯甲酸为原料,经过3步反应制得目标化合物,其结构经核磁共振及元素分析确证.初步生物测定结果表明,部分化合物对小麦赤霉病、水稻纹枯病、黄瓜灰霉病和番茄早疫病表现出明显的抑制活性,尤其是化合物5q表现出较广的杀菌谱,且活性与多氧霉素相当.初步构效关系分析发现,苯环上取代基的类别和位置对活性有影响,其中卤素取代基对活性有利,邻位取代优于对位和间位取代.     

具有双活性序列的新型抗菌肽的设计及性质

设计合成了具有2个活性序列的线性和环状多肽及具有单个活性序列的短链多肽, 研究了它们的杀菌活性、 细胞毒性及溶血性. 结果表明, 线性肽和环状肽的杀菌活性高于短链肽. 利用计算模拟的方法计算了多肽与细菌细胞膜中一种重要的成分磷脂酰甘油(DMPG)的结合能. 结果表明, 多肽-DMPG的结合能与多肽的杀菌活性具有较高的相关性, 线性和环状多肽与DMPG的结合能大于短链肽. 线性和环状多肽均含有2个活性序列, 可提供多个荷正电氨基酸与荷负电的磷脂结合, 结合能较大, 杀菌活性较强. 采用模拟生物膜对其中几条多肽的作用机理进行了初步研究. 结果表明, 该类多肽有可能使正常哺乳动物细胞的细胞膜产生孔洞; 而对于细菌细胞膜, 多肽并未在膜上产生明显孔洞, 而是引起了细菌细胞膜的聚集.     

Novel Lanthanide(III) Ternary Complexes with Naphthoyltrifluoroacetone: A Synthetic and Spectroscopic Study

A series of lanthanide complexes with general formula [Ln(NTA)₃X] were prapared [Ln = Y ( a ), Er ( b ), Eu ( c ), NTA = naphthoyltrifluoroacetone, X = H₂O ( 1 ), phen = phenanthroline ( 2 ), bpyO1 = 2, 2′‐bipyridine N‐oxide ( 3 ), and bpyO2 = 2, 2′‐bipyridine‐N,N′‐dioxide ( 4 )]. The crystal structures of [Eu(NTA)₃bpyO2] ( 4b ), [Er(NTA)₃bpyO1] ( 3c ), and [Er(NTA)₃phen] ( 2c ) were determined. X‐ray crystallographic analysis reveals that the complexes are of mononuclear structure with three NTA and one ancillary ligand. The photoluminescence spectra of 3c and 4b exhibit strong characteristic emissions arising from Eu³⁺ central ion due to the efficient sensitization of bpyO1 and bpyO2, respectively.     

取代噻吩双酰胺类化合物的设计、 合成及生物活性

利用中间体衍生化方法, 将噻吩环引入到双酰胺类化合物中, 合成了一系列取代噻吩双酰胺类化合物1~3; 目标化合物的结构经核磁共振波谱、 红外光谱及元素分析确认. 生物活性测试结果表明, 化合物1在600 mg/L剂量下对小菜蛾具有良好的杀虫效果, 致死率均为100%, 其中化合物1a和1e在20 mg/L剂量下对小菜蛾的致死率仍达到60%以上; 改变双酰胺结构中的吡唑环得到化合物2和3, 其杀虫活性消失, 说明该类化合物中吡唑环结构对杀虫活性具有关键作用.     

模拟宿主防御肽的尼龙3抗菌聚合物结构设计、合成及活性研究

微生物感染一直是人类健康的严峻挑战,传统抗生素几乎不可避免地使微生物产生耐药性,因此亟待开发既对耐药细菌、真菌有活性,又不易使微生物产生耐药性的新型抗菌剂.宿主防御肽(host defense peptide,HDP)几乎存在于各种生命形式中并表现出广谱抗菌活性和不易使微生物产生耐药性的特点,近年来作为对抗微生物耐药性的新途径被广泛研究.为解决HDP自身稳定性差(容易被蛋白酶水解)的缺点,多个研究组相继开展HDP模拟物的研究,希望在改善抗菌剂稳定性的同时保持抗菌活性.尼龙3聚合物(β-多肽)是模拟HDP的一类代表性抗菌聚合物.尼龙3聚合物通常由一个亲水性/正电荷亚基和一个疏水性亚基通过不同比例组合来模拟HDP的2个关键性结构特点:正电荷和两亲性结构.通过优化端基基团和聚合物长度、变化亚基的化学结构、探索优化的亲水性/正电荷与疏水性亚基组合以及调节亚基在聚合物中的比例,发现了对多个耐药菌菌株具有高活性和高选择性的尼龙3聚合物.尼龙3对细菌营养细胞和稳定的孢子都显示了活性,同时尼龙3也对游离真菌细胞和真菌生物膜都表现出选择性抗菌活性.这些发现提示了尼龙3对抗微生物耐药性的潜力以及尼龙3作为新型抗菌剂的可能应用.     

新型抗糖尿病铬(III)配合物的合成和生物活性及机理探究

为了寻找新型的抗糖尿病分子,以苯乙双胍为前体,制备了苯乙双胍铬（III）配合物.通过元素分析、摩尔电导率、电喷雾质谱、红外光谱、紫外可见光谱和核磁共振波谱对配合物的结构进行了表征,并研究了配合物在不同温度、不同pH值下溶液的稳定性、与H₂O₂的反应性和形貌.同时,构建了糖尿病C57小鼠模型,研究了其生物活性和毒性.结果证明,配合物对其活性指标均有好的抑制作用,保留了苯乙双胍的降糖性质,对机体是无毒的,并且通过MTT（3-（4,5-二甲基噻唑-2）-2,5-二苯基四氮唑溴盐）实验说明配合物的生物相容性较好,实现了金属配合物降糖与控脂的多功能化应用.在此基础上,通过光谱法研究了配合物与胰高血糖素的相互作用,表明配合物对胰高血糖素是静态猝灭以较强的作用力结合,条件结合常数为1.29×10⁵ L·mol^-1,结合位点数约为1,初步提出了配合物的新的降糖机制.