中国东方铃蟾(Bombina orientalis)皮肤中C_(-12-b)肽的分离与鉴定

东方铃蟾鲜皮的甲醇提取液,可引起大鼠离体平滑肌的收缩。此液经碱性氧化铝柱层析分离,其80%乙醇洗脱的 C 组分显示生物活性。C 组分再经葡聚糖凝胶 G-15柱分离,其活性较强的早期洗脱组分 C_(_12),可被糜蛋白酶水解灭活,但其活性并不被5-HT 拮抗剂赛庚啶[2×10~(-6)mol/L]完全拮抗。继用反相高效液相色谱(RP-HPLC)分析,见分离出的 C_(_12_h)峰与铃蟾肽~*(Bombesin,BBS)的出峰时间相同,且具相同的氨基酸组成。上述实验结果提示,C_(_12_h)肽可能就是铃蟾肽。     

Localization and characterization of neuropeptide Y-like peptides in the brain and islet organ of the anglerfish (Lophius americanus)

Summary Results from a previous report demonstrate that more than one molecular form of neuropeptide Y-like peptide may be present in the islet organ of the anglerfish (Lophius americanus). Most of the neuropeptide Y-like immunoreactive material was anglerfish peptide YG, which is expressed in a subset of islet cells, whereas an additional neuropeptide Y-like peptide(s) was localized in islet nerves. To learn more about the neuropeptide Y-like peptides in islet nerves, we have employed immunohistochemical and biochemical methods to compare peptides found in anglerfish islets and brain. Using antisera that selectively react with either mammalian forms of neuropeptide Y or with anglerfish peptide YG, subsets of neurons were found in the brain that labelled with only one or the other of the antisera. In separate sections, other neurons that were labelled with either antiserum exhibited similar morphologies. Peptides from brains and islets were subjected to gel filtration and reverse-phase high performance liquid chromatography. Radioimmunoassays employing either the neuropeptide Y or peptide YG antisera were used to examine chromatographic eluates. Immunoreactive peptides having retention times of human neuropeptide Y and porcine neuropeptide Y were identified in extracts of both brain and islets. This indicates that peptides structurally similar to both of these peptides from the neuropeptide Y-pancreatic polypeptide family are expressed in neurons of anglerfish brain and nerve fibers of anglerfish islets. The predominant form of neuropeptide Y-like peptide in islets was anglerfish peptide YG. Neuropeptide Y-immunoreactive peptides from islet extracts that had chromatographic retention times identical to human neuropeptide Y and porcine neuropeptide Y were present in much smaller quantities. These results are consistent with the hypothesis that peptides having significant sequence homology with human neuropeptide Y and porcine neuropeptide Y are present in the nerve fibers that permeate the islet.     

Synthesis and conformational analysis of aib-containing peptide modelling for N-glycosylation site in N-glycoprotein

A tetrapetide containing an Aib residue, Boc-Asn-Aib-Thr-Aib-OMe, was synthesized as a peptide model for the N-glycosylation site in N-glycoproteins. Backbone conformation of the peptide and possible intramolecular interaction between the Asn and Thr side chains were elucidated by means of n.m.r. spectroscopy. Temperature dependence of NH proton chemical shift and NOE experiments showed that Boc-Asn-Aib-Thr-Aib-OMe has a tendency to form a β-turn structure with a hydrogen bond involving Thr and Aib⁴ NH groups. Incorporation of Aib residues in the peptide model promotes folding of the peptide backbone. With folded backbone conformation, carboxyamide protons of the Asn residue are not involved in hydrogen bond network, while the OH group of the Thr residue is a candidate for a hydrogen bond in DMSO-d₆ solution.     

Isolation and characterization of cDNA clones encoding the 17.9 and 8.1 kDa subunits of Photosystem I from Chlamydomonas reinhardtii

cDNA clones encoding two Photosystem I subunits of Chlamydomonas reinhardtii with apparent molecular masses of 18 and 11 kDa (thylakoid polypeptides 21 and 30; P21 and P30 respectively) were isolated using oligonucleotides, the sequences of which were deduced from the N-terminal amino acid sequences of the proteins. The cDNAs were sequenced and used to probe Southern and Northern blots. The Southern blot analysis indicates that both proteins are encoded by single-copy genes. The mRNA sizes of the two components are 1400 and 740 nucleotides, respectively. Comparison between the open reading frames of the cDNAs and the N-terminal amino acid sequences of the proteins indicates that the molecular masses of the mature proteins are 17.9 (P21) and 8.1 kDa (P30). Analysis of the deduced protein sequences predicts that both subunits are extrinsic membrane proteins with net positive charges. The amino acid sequences of the transit peptides suggest that P21 and P30 are routed towards the lumenal and stromal sides of the thylakoid membranes, respectively.Abbreviations OEE1, 2 and 3 oxygen evolution enhancer proteins 1, 2 and 3 - Rubisco ribulose bisphosphate carboxylase/oxygenase - PS photosystem - P21 and P30 C. reinhardtii thylakoid polypeptides 21 and 30     

Neuromedin U-immunoreactivity in the nervous system of the small intestine of the pig and its coexistence with substance P and CGRP

Summary In the small intestine of the pig, neuromedin U (NMU)-immunoreactivity was mainly confined to the nerve plexus of the inner submucosal and mucosal regions. After colchicine treatment, a high number of immunoreactive nerve cell bodies was observed in the plexus submucosus internus (Meissner), whereas only a low number was found in the plexus submucosus externus (Schabadasch). The plexus myentericus as well as the aganglionic nerve meshworks in the circular and longitudinal smooth muscle layers almost completely lacked NMU-immunoreactivity. Double-labeling experiments demonstrated the occurrence of distinct NMU-containing neuron populations in the plexus submucosus internus: (1) relatively large type-II neurons revealing immunoreactivity for NMU and calcitonin gene-related peptide (CGRP) and/or substance P (SP); (2) a group of small NMU- and SP-immunoreactive neurons; (3) a relatively low number of small neurons displaying immunoreactivity for NMU but not for SP. Based on its distributional pattern, it is concluded that NMU plays an important role in the regulation and control of mucosal functions.     

Extracellular polysaccharides of cowpea rhizobia: compositional and functional studies

Polysaccharides excreted by cowpea Rhizobium strains JLn(c) and RA-1 were mixtures of complex acidic exopolysaccharides and low molecular weight neutral glucans. These polymers were fractionated using gel filtration chromatography. Purified fractions of the acidic heteropolymer reacted with peanut agglutinin to give precipitin bands when subjected to Ouchterlony gel diffusion. The acidic exopolysaccharide was found to contain mainly glucose, galactose, glucuronic acid, mannose and fucose. The non-carbohydrate substituents of the acidic heteropolymer were pyruvate, acetate and uronate which were identified by infrared and proton nuclear magnetic resonance spectroscopy as well as by chemical analysis.Abbreviations EPS Extracellular polysaccharide - YEM yeast extract mannitol - PNA peanut agglutination - ¹H-NMR proton nuclear magnetic resonance     

A cDNA clone encoding the precursor for a 10.2 kDa photosystem I polypeptide of barley

Two cDNA clones for the barley photosystem I polypeptide which migrates with an apparent molecular mass of 9.5 kDa on SDS-polyacrylamide gels have been isolated using antibodies and an oligonucleotide probe. The determined N-terminal amino acid sequence for the mature polypeptide confirms the identification of the clones. The 644 base-pair sequence of one of the clones contains one large open reading frame coding for a 14 882 Da precursor polypeptide. The molecular mass of the mature polypeptide is 10 193 Da. The hydropathy plot of the polypeptide shows one membrane-spanning region with a predicted -helix secondary structure. The gene for the 9.5 kDa polypeptide has been designated PsaH.     

Immunoreactivity to the pancreatic polypeptide family in the nervous system of the adult human blood fluke,Schistosoma mansoni

Summary The presence and distribution of neuropeptides belonging to the pancreatic polypeptide family have been demonstrated by an indirect immunofluorescence technique in the nervous systems of adult male and female Schistosoma mansoni. Seven antisera of differing regional specificity to pancreatic polypeptide (PP), peptide YY (PYY) and neuropeptide Y (NPY) were employed on both whole-mount and cryostat-sectioned material. Positive immunoreactivity (IR) was obtained with all antisera except an N-terminally-directed antiserum to NPY. In the CNS, immunoreactivity was restricted to cell bodies and nerve fibres in the anterior ganglia, central commissure and dorsal and ventral nerve cords of both sexes, whereas, in the PNS, positive-IR was present in the plexuses innervating the subtegumental musculature and the oral and ventral suckers. Intense immunoreactivity was observed in a plexus of nerve fibres and cell bodies in the lining of the gynaecophoric canal and in fine nerve fibres innervating the dorsal tubercles of the male. In contrast, in the female, strong immunoreactivity was evident in nerve plexuses innervating the lining of the ovovitelline duct and in the wall of the ootype, but most notably in a cluster of cells in the region of Mehlis' gland. Results suggest that molecules with C-terminal homology to the PP-family are present in S. mansoni. These peptides would appear to be important regulatory molecules in the parasite's nervous system and may play a role in the control of egg production.     

蜚蠊灭菌肽的诱导及初步分离分析

昆虫经诱导盾产生灭菌肽的研究近年来已有很大进展,有关这方面的研究工作绝大多数都是以有翅亚纲内生翅类鳞翅目(主要是蚕类)昆虫和少数双翅目昆虫为材料.本文首次以有翅亚纲外生翅类蜚蠊目的美洲蜚蠊(Ptriplaneta americana L.)为实验昆虫,用Escherichia coil K₁₂ strain D₃₁作诱导源,对不同发育期、不同性别、不同成虫期的蜚蠊进行诱导后,采用含菌培养基平板测活方法,就存在个体数及能产生抗菌物质的个体数进行了初步的研究.发现成虫日龄在10天之内的雄性蜚蠊能够产生抗菌物质的个体百分比最高.抗菌物质出现的高峰期是在诱导后第三、四天.用滴滴涕和溴氰菊酯作诱导源对雄性蜚蠊的诱导实验表明,杀虫剂也能诱导蜚蠊产生抗菌物质,而且所诱导产生抗菌物质的活性强度(用抑菌圈直径表示)高于大肠杆菌所诱导的.滴滴涕和溴氰菊酯的重复诱导可提高蜚蠊产生抗菌物质个体百分比.蜚蠊经诱导后产生的抗菌物质具有广谱性,对苏云金杆菌、金黄色葡萄球菌、枯草杆菌及绿脓杆菌等有较强的抗菌活性,而对大肠杆菌D₃₁、大肠杆菌、粘质沙雷氏杆菌和溶壁微球菌等有较弱的抗菌活性.用肽类物质的指纹图谱法分离蜚蠊血淋巴抗菌物质,发现经诱导后血淋巴中确有新的肽类物质产生,该物质具抗菌活性,用DABITC法分析,其N-末端氨基酸为赖氨酸.