ISSN:1075-2617    

DOI:10.1002/psc.639

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractThe conformational properties in DMSO of two head‐to‐tail cyclic analogues of kallidin ([Lys0]‐bradykinin, KL) as well as those of the corresponding linear peptides were studied by NMR and molecular dynamics (MD) simulations. The modifications in the sequence were introduced at position 6, resulting in the four peptides, [Tyr6]‐KL (YKL), [Trp6]‐KL (WKL), cyclo‐([Tyr6]‐KL) (YCKL) and cyclo‐([Trp6]‐KL) (WCKL).The linearWKLanalogue was significantly more potent than kallidin on rat duodenum preparations, whereasYKLwas significantly less potent. Both cyclic peptides,YCKLandWCKLdisplayed similar activity, lower than that of the linear analogues and also of cyclo‐KL.The two linear analogues display high conformational flexibility in DMSO. In the predominant conformer, for both peptides, all three X‐Pro bonds adopt atransconfiguration. Three out of four conformers present inYCKLandWCKLwere completely assigned. The configurations at the X‐Pro bonds are the same for the two analogues. All cyclic conformers show acisconfiguration in at least one X‐Pro bond and always opposite configuration for the two consecutive X‐Pro bonds.The NOE‐restrained MD calculations resulted in the detection of several elements of secondary structure in each of the conformers. Such elements are described and their possible relevance to biological activity is discussed. Copyright © 2004 European Peptide So

ISSN:1075-2617    

DOI:10.1002/psc.586

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractThe Gly‐ and Arg‐richC‐terminal region of human nucleolin is a 61‐residue long domain involved in a number of protein–protein and protein–nucleic acid interactions. This domain contains 10 aDma residues in the form of aDma‐GG repeats interspersed with Phe residues. The exact role of Arg dimethylation is not known, partly because of the lack of efficient synthetic methods. This work describes an effective synthetic strategy, generally applicable to long RGG peptides, based on side‐chain protected aDma and backbone protected dipeptide Fmoc‐Gly‐(Dmob)Gly‐OH. This strategy allowed us to synthesize both the unmodified (N61Arg) and the dimethylated (N61aDma) peptides with high yield (∼26%) and purity. As detected by NMR spectroscopy, N61Arg does not possess any stable secondary or tertiary structure in solution and Nω,Nω‐dimethylation of the guanidino group does not alter the overall conformational propensity of this peptide. While both peptides bind single‐stranded nucleic acids with similar affinities (Kd= 1.5 × 10−7M), they exhibit a different behaviour in ssDNA affinity chromatography consistent with the difference in pKavalues. It has been previously shown that N61Arg inhibits HIV infection at the stage of HIV attachment to cells. This study demonstrates that Arg‐dimethylatedC‐terminal domain lacks any inhibition activity, raising the question of whether nucleolin expressed on the cell‐surface is indeed dimethylated. Copyright © 2004 European P

ISSN:1075-2617    

DOI:10.1002/psc.577

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractBacteriocin AS‐48 is a 70‐residue cyclic polypeptide fromEnterococcus faecalisthat shows a broad antimicrobial spectrum against both Gram‐positive and Gram‐negative bacteria. The structure of bacteriocin AS‐48 consists of a globular arrangement of five helices with a high positive electrostatic potential in the region comprising helix 4, the turn linking helix 4 and 5, and theN‐terminus of helix 5. This region has been considered to participate in its biological activity and in particular in membrane permeation. To understand the mechanism of the antibacterial activity of AS‐48 and to discriminate the several mechanisms proposed, a simplified bacteriocin was designed consisting of 21 residues and containing the high positively charged region. A disulfide bridge was introduced at an appropriate position to stabilize the peptide and to conserve the helix‐turn‐helix arrangement in the parent molecule. According to1H and13C NMR data, the designed simplified bacteriocin fragment adopts a significant population of a native‐like helical hairpin conformation in aqueous solution, which is further stabilized in 30% TFE. The designed peptide does not show any antibacterial activity, though it is shown to compete with the intact native bacteriocin AS‐48. These results suggest that the mechanism of membrane disruption by bacteriocin is not as simple as being driven by a deposition of positively charged molecules on the plane of the bacterial membrane. Some other regions of the protein must be present such as, for instance, hydrophobic regions so as to enhance the accumulation of the peptide and favour membrane permeation. Copyright © 2004 European Peptide Society an

ISSN:1075-2617    

DOI:10.1002/psc.589

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractThe IgG‐derived immunomodulating peptide tuftsin, Thr‐Lys‐Pro‐Arg, is recognized by specific receptors on phagocytic cells, notably macrophages, and is capable of targeting proteins and peptides to these sites. Aiming to target 3′‐azido‐3′‐deoxythymidine (AZT) to HIV‐infected macrophages, a conjugate of AZT with tuftsin was synthesized. The AZT‐tuftsin chimera possesses the characteristic capacities of its two components. Thus, like AZT, it inhibits reverse transcriptase activity and HIV‐antigen expression, and similarly to tuftsin, it stimulates IL‐1 release from mouse macrophages and augments the immunogenic function of the cells. Importantly, the conjugate is not cytotoxic to T‐cells. The results suggest that the AZT‐tuftsin conjugate might have potential use in AIDS therapy. Copyright © 2004 European Peptide So

ISSN:1075-2617    

DOI:10.1002/psc.587

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractWith the aim of producing long‐acting analogs of gonadotropin releasing hormone (GnRH), four analogs, containing ‐X6aaψ(CH2SO2NH)‐Leu7building unit (XaaGly, Ala, Val or Phe), and a reduced‐size analog [Des‐Tyr5]‐GnRH which includes the unit Phe5ψ(CH2SO2NH)‐Leu6, and [β‐Ala6]‐GnRH were synthesized. The peptides were evaluated for their capacity to induce LH‐release from rat pituitary cells and to withstand proteolysis by pituitary‐derived enzymes, compared with the parent peptide GnRH. Albeit stable toward enzymatic degradation, the sulfonamido containing peptides were only marginally bioactive. [β‐Ala6]‐GnRH, however, induced LH‐release and bound to pituitary receptors nearly as efficiently as GnRH. This analog was also highly stable toward proteolysis suggesting that it may serve as a long‐acting GnRH‐analog. Copyright © 2004 European Pe

ISSN:1075-2617    

DOI:10.1002/psc.596

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractIn contrast to the RGD‐peptides, head to tail cyclization of LNGRV and LNGRv caused only a marginal change in their integrin receptor affinity as shown by the limited effect and selectivity on the adhesion of endothelial cells to ECM components. Structure determination of the two cyclopeptides by NMR and MD, semiempirical andab initiomethods revealed that both are very flexible and take on multiple stable conformers in solution. This structural diversity, along with the presence of the Asn‐Gly peptide bond, enhances succinimide ring formation leading to the hydrolysis of Asn. It has been demonstrated that c(LNGRV) suffers deamidation with time both in solution and during storage. As the isoaspartyl‐peptide may co‐elute with the asparginyl‐peptide in the course of HPLC analysis, MS measurement is necessary to check the purity of peptides containing the NGR sequence. Our stability investigations raise the question whether the NGR motif or its hydrolysis product is effective inin vivoexperiments. Copyright © 2004 European Peptide Society and John Wiley

ISSN:1075-2617    

DOI:10.1002/psc.588

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

Abstractα‐Alkoxycarbonyl protected ornithines were treated withN,N′‐[Z(2Cl)]2‐S‐methylisothiourea andN,N′‐[Z(2Br)]2‐S‐methylisothiourea,N,N′‐Z2‐S‐methylisothiourea andN,N′‐Boc2‐S‐methylisothiourea to formNα, ω, ω′‐tris‐alkoxycarbonyl arginines. Two of them, Boc‐Arg‐{ω,ω′‐[Z(2Br)]2}‐OH and Boc‐Arg‐{ω,ω′‐[Z(2Cl)]2}‐OH, were used for the synthesis of dermorphin fragments containing two or three arginine residues. Examination of the products by HPLC and ESI‐MS revealed that the purity of the materials obtained with the use of the new derivatives was higher than that obtained in concurrent syntheses in which Boc‐Arg(Tos) was u

ISSN:1075-2617    

DOI:10.1002/psc.585

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY