摘要:

AbstractThe synthesis and biological evaluation of penicillamine6‐5‐tert‐butylproline7‐oxytocin analogs and comparison with their proline7‐oxytocin counterparts has led to the discovery of two potent oxytocin (OT) antagonists: [dPen1,Pen6]‐oxytocin (1, pA2= 8.22, EC50= 6.0 nM) and [dPen1,Pen6,5‐tBuPro7]‐oxytocin (2, pA2= 8.19, EC50= 6.5 nM). In an attempt to understand the conformational requirements for their biological activity, spectroscopic analyses of1and2were performed using1H NMR, laser Raman and CD techniques. In H2O, oxytocin analogs1and2exhibitedcis‐isomer populations of 7% and 35%, respectively. Measurement of the amide proton temperature coefficients revealed solvent shielded hydrogens for Gln4and Pen6in the majortrans‐conformer of1as well as for Gln4in the minorcis‐conformer of2. Few long‐distance NOEs were observed, suggesting conformational averaging for analogs1and2in water; moreover, a lower barrier (16.6 ± 0.2 kcal/mol) for isomerization of the amideN‐terminal to 5‐tBuPro7relative to OT was calculated from measuring the coalescence temperature of the Gly9backbone NH signals in the NMR spectra of2. Observed bands in the Raman spectra of1and2correspond to Cβ‐S‐S‐Cβdihedral angles of +110–115° and ±90°, respectively. In water, acetonitrile and methanol, the CD spectra for1exhibited a positive maximum around 236–239 nm; in trifluoroethanol, the spectra shifted and a negative maximum was observed at 240 nm. The CD spectra of2were unaffected by solvent changes and exhibited a negative maximum at 236–239 nm. The CD and Raman data both suggested that a conformation having a right‐handed screw sense about the disulfide and a χCS−SCdihedral angle value close to 115° was favored for analog1in water, methanol and acetonitrile, but not trifluoroethanol, where a ±90° angle was favored. Analog2was more resilient to conformational change about the disulfide, and adopted a preferred disulfide geometry corresponding to a ±90° χCS−SCdihedral angle. Monte Carlo conformational analysis of analogs1and2using distance restraints derived from NMR spectroscopy revealed two prominent conformational minima for analog1with disulfide geometries around +114° and +116°. Similar analysis of analog2revealed one conformational minimum with a disulfide geometry around +104°. In sum, the conformation about the disulfide in [dPen1,Pen6]‐OT (1) was shown to be contingent on environment and in TFE, adopted a geometry similar to that of [dPen1,Pen6,5‐tBuPro7]‐OT (2) which appeared to be stabilized by hydrophobic interactions between the 5‐tBuPro7(5R)‐tert‐butyl group, the Leu8isopropyl sidechain and the Pen6β‐methyl substituents. In light of the conformational rigidity of2about the disulfide bond, and the similar geometry adopted by1in TFE, a S‐S dihedral angle close to +110° may be a prerequisite for their binding at t

ISSN:1075-2617    

DOI:10.1002/psc.637

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractThe powerful antimicrobial properties of bovine lactoferricin (LfcinB) make it attractive for the development of new antimicrobial agents. An 11‐residue linear peptide portion of LfcinB has been reported to have similar antimicrobial activity to lactoferricin itself, but with lower hemolytic activity. The membrane‐binding and membrane‐perturbing properties of this peptide were studied together with an amidated synthetic version with an added disulfide bond, which was designed to confer increased stability and possibly activity. The antimicrobial and cytotoxic properties of the peptides were measured againstStaphylococcus aureusandEscherichia coliand by hemolysis assays. The peptides were also tested in an anti‐cancer assay against neuroblastoma cell lines. Vesicle disruption caused by these LfcinB derivatives was studied using the fluorescent reporter molecule calcein. The extent of burial of the two Trp residues in membrane mimetic environments were quantitated by fluorescence. Finally, the solution NMR structures of the peptides bound to SDS micelles were determined to provide insight into their membrane bound state. The cyclic peptide was found to have greater antimicrobial potency than its linear counterpart. Consistent with this property, the two Trp residues of the modified peptide were suggested to be embedded deeper into the membrane. Although both peptides adopt an amphipathic structure without any regular α‐helical or ß‐sheet conformation, the 3D‐structures revealed a clearer partitioning of the cationic and hydrophobic faces for the cyclic peptide. Copyright © 2004 European Peptide Society and John

ISSN:1075-2617    

DOI:10.1002/psc.629

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractLinear and cyclic phosphopeptides related to the pY2267 binding site of the epithelial receptor tyrosine kinase Ros have been synthesized as ligands for the amino‐terminal SH2 (src homology) domain of protein tyrosine phosphatase SHP‐1. The synthesis was accomplished by Fmoc‐based solid‐phase methodology using side‐chain unprotected phosphotyrosine for the linear and mono‐benzyl protected phosphotyrosine for the cyclic peptides. According to molecular modelling, the incorporation of a glycine residue between Lys (position pY−1 relative to phosphotyrosine) and Asp or Glu (position pY+2) was recommended for the cyclic candidates. The preparation of these peptides was successfully performed by the incorporation of a Fmoc‐Xxx(Gly‐OAll)‐OH (Xxx = Asp, Glu) dipeptide building block that was prepared in solution prior to SPPS. The cyclization was achieved with PyBOP following Alloc/OAll‐deprotection. This study demonstrates the usefulness of allyl‐type protecting groups for the generation of side‐chain cyclized phosphopeptides. Alloc/OAll‐deprotection and cyclization are compatible with phosphorylated tyrosine. Copyright © 2004 European Peptide Soci

ISSN:1075-2617    

DOI:10.1002/psc.631

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractAn ESR investigation of the interaction of spin‐labelled penetratin with heparin, heparansulfates and several phospholipid vesicle formulations is reported. Penetratin is a 16‐aa peptide corresponding to the third helix of the Antennapedia homeodomain and belonging to the cell‐penetrating peptide family. The present study shows that ESR spectroscopy can provide specific and reliable information about the mechanism of interaction of penetratin with polysaccharides and lipids, at a molecular level. The study showed that: (i) heparin and heparansulfates specifically interact with spin‐labelled penetratin and promote peptide aggregation and concentration on their molecular surface; (ii) penetratin does not interact with neutral lipids, whereas it enters negatively charged lipid bilayers; (iii) cholesterol plays a negative effect on the insertion of penetratin into the lipid membrane; (iv) the interaction of penetratin with lipid vesicles is strongly dependent on lipid concentration. In a low lipid regime, penetratin associates with the polar heads of phospholipids and aggregates on the membrane surface; once the lipid concentration attains a threshold, the peptide enters the lipid bilayer. This step is characterized by reduced peptide mobility and partial disaggregation.It has been shown that ESR spectroscopy is a valuable investigation tool in studies related to the still unclear mechanism of the internalization process. Copyright © 2004 European Peptide Society and John Wiley&S

ISSN:1075-2617    

DOI:10.1002/psc.633

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractIn the process of developing a method for the synthesis of membrane proteins, the conditions for native chemical ligation, namely, detergent concentration and the chemical characteristics of the thiol additive were investigated in detail. TheC‐terminal region of the opioid receptor like 1, ORL1(288–370), which containsC‐terminal intracellular and transmembrane domains, was chosen as a model. The building blocks, ORL1(329–370) and ORL1(288–328)‐SR‐Gly‐Arg5‐Leu (‐SR‐ : ‐SCH2CH2CO‐) were most effectively condensed slightly below the critical micelle concentration of SDS and in the presence of mercaptoethanesulfonic acid as a thiol additive. The results showed that the concentration of SDS and the charge on the thiol additive are crucial factors for the effective synthesis of a membrane protein by native chemical ligation. Copyright © 2004 European Peptide Societ

ISSN:1075-2617    

DOI:10.1002/psc.634

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractAnthraquinone peptide derivatives have previously been shown to inhibit the enzyme topoisomerase I (topo I), a pharmaceutical target for the prevention of malignant carcinomas. A highly efficient procedure for the attachment of the anthraquinone moiety to theN‐terminus of a peptide on a solid support is reported. This methodology provides a convenient method for the synthesis of labelled peptides, with potential applications for chemotherapy, DNA detection and protein purification. As the synthetic strategy utilizes the solid phase, it should also be amenable to the generation of combinatorial libraries. The utility of the method by synthesizing a pool of peptides and assaying for topo I inhibition is demonstrated. Copyright © 2005 European Peptide Society and John Wiley&Sons, L

ISSN:1075-2617    

DOI:10.1002/psc.635

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractThe synthesis of glyoxylyl peptides by coupling the masked glyoxylic acid derivative (FmocNH)2CHCO2H,1, to a peptidyl resin assembled using Fmoc/tert‐butyl chemistry has been described recently. Deprotection and cleavage of the peptide from the solid support using TFA was followed by unmasking of the glyoxylyl group in solution in the presence of DBU. [] The glyoxylyl peptide was thus generated using non‐oxidizing conditions by comparison with the method based on the periodic oxidation of a seryl‐precursor. However, base treatment of the (FmocNH)2CHCO2‐peptide led to the formation of a byproduct besides the desired glyoxylyl peptide. This paper describes an optimized procedure for unmasking the Fmoc‐protected α,α′‐diaminoacetic acid moiety in solution which suppressed byproduct formation. Also presented is a series of experiments that permitted a structure and a mechanism of formation for the byproduct to be suggested. Copyright © 2005 European Peptide Society and John

ISSN:1075-2617    

DOI:10.1002/psc.632

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

Abstract2‐Oxoamides based on long chain β‐amino acids were synthesized. 1‐Benzyl substituted long chain amines, needed for such synthesis, were synthesized starting from Boc‐phenylalaninol. The oxidative conversion of a phenyl group to a carboxyl group was used as the key transformation synthetic step. The compounds synthesized were studied for their activity against GIVA PLA2, and were proven to be weak inhibitors. Copyright © 2004 European Peptide Society and John Wiley&

ISSN:1075-2617    

DOI:10.1002/psc.628

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractIt was previously reported that acylation of theN‐terminus of several known B2antagonists with various types of bulky acyl groups consistently improved their antagonistic potency in the rat blood pressure assay. On the other hand, earlier results seem to suggest that the effects of acylation on the contractility of isolated rat uterus depend substantially on the chemical character of the acyl group, as it was observed that this modification may either change the range of antagonism or even transform it into agonism.Bearing all this in mind, three new analogues of bradykinin were designed by modifying the moderately potent B2antagonist, previously synthesized by Stewart's group,D‐Arg‐Arg‐Pro‐Hyp‐Gly‐Thr‐Ser‐D‐Phe‐Thi‐Arg. New analogues were obtained by acylation of theN‐terminus of the above peptide with succinic acid, 12‐aminododecanoic acid and 4‐aminobenzoic acid in order to confirm whether either the positive or the negative charge on theN‐terminal end of the peptide is responsible for the transformation of activity. The activity of analogues was assessed on blood pressure and in uterotonicin vitrotests. The modifications proposed either preserved or increased the antagonistic potency in the rat blood pressure test. On the other hand, the three substituents, depending on their chemical character, differently influenced the interaction with the rat uterine receptors. The results may be of value in the design of new B2agonists and antagonists. Copyright © 2005 European Peptide

ISSN:1075-2617    

DOI:10.1002/psc.646

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY