摘要:

AbstractAn efficient ‘O‐acyl isopeptide method’ for the synthesis of difficult sequence‐containing peptides was applied successfully to the synthesis of amyloid β peptide (Aβ) 1–42 via a water‐solubleO‐acyl isopeptide of Aβ1–42, i.e. ‘26‐O‐acyl isoAβ1–42’ (6). This paper describes the detailed synthesis of Aβ1–42 focusing on the importance of resin selection and the analysis of side reactions in theO‐acyl isopeptide method. Protected ‘26‐O‐acyl isoAβ1–42’ peptide resin was synthesized using 2‐chlorotrityl chloride resin with minimum side reactions in comparison with other resins and deprotected crude 26‐O‐acyl isoAβ1–42 was easily purified by HPLC due to its relatively good purity and narrow elution with reasonable water solubility. This suggests that only one insertion of the isopeptide structure into the sequence of the 42‐residue peptide can suppress the unfavourable nature of its difficult sequence. The migration ofO‐acyl isopeptide to intact Aβ1–42 under physiological conditions (pH 7.4) viaONintramolecular acyl migration reaction was very rapid and no other by‐product formation was observed while6was stable under storage conditions. These results concluded that our strategy not only overcomes the solubility problem in the synthesis of Aβ1–42 and can provide intact Aβ1–42 efficiently, but is also applicable in the synthesis of large difficult sequence‐containing peptides at least up to 50 amino acids. This synthesis method would provide a biological evaluation system in Alzheimer's disease research, in which 26‐O‐acyl isoAβ1–42 can be stored in a solubilized form before use and then rapidly produces intact Aβ1–42in situduring biologi

ISSN:1075-2617    

DOI:10.1002/psc.649

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractThe conformational properties of the homo oligomers of increasing chain length Boc‐(Asn)n‐NHMe (n= 2, 4, 5), (GlcNAc‐β‐Asn)n‐NHMe (n= 2, 4, 5, 8) and Boc‐[GlcNAc(Ac)3‐β‐Asn]n‐NHMe (n= 2, 4, 5) were studied by using NOE experiments and molecular dynamic calculations (MD). Sequential NOEs and medium range NOEs, including (i,i+2) interactions, were detected by ROESY experiments and quantified. The calculated inter‐proton distances are longer than those characteristic of β‐turn secondary structures. Owing to the large conformational motions expected for linear peptides, MD simulations were performed without NMR constraints, with explicit water and by applying different treatments of the electrostatic interactions. In agreement with the NOE results, the simulations showed, for all peptides, the presence of both folded and unfolded structures. The existence of significant populations of β‐turn structures can be excluded for all the examined compounds, but two families of structures were more often recognized. The first one with sinusoidal or S‐shaped forms, and another family of large turns together with some more extended conformations. Only the glycosylated pentapeptide showsin vacuoa large amount of structures with helical shaped form. The results achieved in water and in DMSO are compared and discussed, together with the effect of the glycosylation. Copyright © 2005 European Peptide So

ISSN:1075-2617    

DOI:10.1002/psc.644

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractGlucagon‐like peptide‐1 (GLP‐1) is a 30‐residue peptide implicated in short‐term appetite regulation. Its analogs are presumed to be potential drugs against obesity and non‐insulin dependent diabetes mellitus (NIDDM or type 2 diabetes). This study examined how the dynamic fingerprints can be used for establishing dynamics–activity relationships in a series of peptides for which the mechanism of action is unknown and in which mutations can cause an increase or decrease in biological activity. The 3D autocorrelation method was used to generate maps of both active and inactive analogs. As the active conformation of GLP‐1 is not yet clearly defined, the dynamic fingerprints of peptides in an aqueous environment were compared to explain the high affinity of the peptide for its receptor. The suggestion that the peptide could bind to the receptor in a folded conformation has been examined. In the case of the GLP‐1 analogs, it was shown that the folding tendency cannot be directly related to affinity values and the results do not favor a folded active conformation model of GLP‐1. Copyright © 2005 European Peptide Society and

ISSN:1075-2617    

DOI:10.1002/psc.636

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractAccurate rate constants were calculated from HPLC kinetic measurements of the selective acidolysis of theC‐terminal amide bond of eightN‐acyl‐N‐(4‐methoxybenzyl)‐α,α‐trialkyl glycine amides in TFA at 25.00 °C. The results were in all cases consistent with a first order behaviour with respect to the substrate and, apparently, also to the acid, and a clear relationship between reactivity and structure could be observed. The data collected also allowed experimental evidence to be obtained for the first time in support of the previously postulated formation of an intermediate oxazolonium salt. In the case of the more crowded species this intermediate compound undergoes slow hydrolytic ring opening, which takes place in competition with cleavage of theN‐alkyl group to give another oxazolonium derivative that hydrolysed still more slowly. The stability of the intermediate cyclic compounds may result either from conjugation of the phenyl group with the oxazolonium ring in the case ofN‐benzoyl derivatives, or from conformational assistance imparted by the bulky amino acid side chains of the α,α‐dialkyl glycine species, or both. The loss of theN‐alkyl group also seems to be assisted by the bulkiness of the amino acid side chains, which thus tends to decrease the selectivity of cleavage. Copyright © 2005 European Peptide Socie

ISSN:1075-2617    

DOI:10.1002/psc.640

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractRecently the discovery of a novel 87 amino acid influenza A virus (IAV) protein, named PB1‐F2, has been reported that originates from an alternative reading frame in the PB1 polymerase gene and is encoded in most of the known human IAV isolates. Using optimized protocols, full length biologically activesPB1‐F2 and a number of fragments have been synthesized by following either the standard elongation SPPS method or by native chemical ligation of unprotectedN‐ andC‐terminal peptide fragments at the histidine and cysteine residues located in position 41 and 42 of the native sequence, respectively. The ligation procedure afforded the most efficient synthesis ofsPB1‐F2 and facilitated the generation of various mutants ofsPB1‐F2 from pre‐synthesized peptide fragments. During the synthesis ofsPB1‐F2, the formation of succinimide and subsequent conversion to the piperidine derivative at the aspartic acid residue in position 23 was observed. This reaction was forestalled by applying specific modifications to the SPPS protocol. The chain‐elongation SPPS protocol is optimal for producing small peptides ofsPB1‐F2, their derivatives and precursors for a subsequent ligation protocol, while the full length protein, mutants and labelled derivatives are more conveniently and efficiently synthesized by SPPS protocols that include native chemical ligation. The molecular identity ofsPB1‐F2 was confirmed by peptide mapping, mass spectrometry,N‐terminal sequencing,1H NMR spectroscopy and Western blot analysis. The latter analysis afforded direct evidence of the inherent tendency ofsPB1‐F2 to undergo oligomerization, a phenomenon observed both for full lengthsPB1‐F2 and fragments thereof, as well as for its full length viral counterpart. Our synthesis protocols open the field for multiple biological and structural studies onsPB1‐F2 that, similar to the molecule expressed in an IAV context, induces apoptosis and interacts with membranesin vitroandin vivo, as shown in previous studies. Copyright © 2005 European Peptide So

ISSN:1075-2617    

DOI:10.1002/psc.641

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractFor the first time tripeptides, Z‐AA1‐Xaa‐AA3‐OMe (AA1and AA3= Gly or Aib, Xaa = 2Pmg and 2Pyg) were prepared containing α‐methyl‐α‐(2‐pyridyl)glycine (2Pmg) and α‐(2‐pyridyl)glycine (2Pyg) by solid‐phase Ugi reaction. These results clearly indicate that for the preparation of tripeptides containing an amino acid with a pyridine ring, the solid‐phase Ugi reaction is very useful.NMR analysis clarified that 2Pmg‐containing tripeptides adopt a unique conformation with an intramolecular hydrogen bond between 2Pmg‐NH and the pyridine nitrogen. However, in the case of Z‐Gly‐2Pyg‐Gly‐OMe, the intramolecular hydrogen bonding between 2Pyg‐NH and the pyridine nitrogen was not observed, whereas Z‐Aib‐2Pyg‐Aib‐OMe adopts a unique conformation with an intramolecular hydrogen bond between 2Pyg‐NH and a pyridine nitrogen. Conformational analysis of the tripeptides, Z‐AA1‐Xaa‐AA3‐OMe (AA1, AA3= Gly or Aib, Xaa = α,α‐di(2‐pyridyl)glycine (2Dpy), α‐phenyl‐α‐(2‐pyridyl)glycine (2Ppg), 2Pmg and 2Pyg), clarified that when an α,α‐disubstituted glycine with a 2‐pyridyl group at an α‐carbon atom is introduced into any peptide, an intramolecular hydrogen bond between a pyridine nitrogen and an amide proton is formed and conformational mobility of the peptide backbon

ISSN:1075-2617    

DOI:10.1002/psc.647

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractTenNε‐glycylornithineamide derivatives have been synthesized containing variousNα‐linked pyrimidine‐1‐ylacetyl groups which can undergo (2π + 2π) photodimerization on irradiation with UV light at 254 nm. The dimerization efficiency of the free and bound pyrimidine groups was compared in aqueous solution: it was dependent on the substitution of the pyrimidine ring.Nα,Nα′‐bis‐(uracil‐1‐ylacetyl)‐(Nε‐glycylornithineamide) andNα,Nα′‐bis‐(5‐bromouracil‐1‐ylacetyl)‐(Nε‐glycylornithineamide) were identified as possible candidates for optical data storage. Copyright © 2005 E

ISSN:1075-2617    

DOI:10.1002/psc.645

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractStudies with cultured tumour cell lines are widely usedin vitroto evaluate peptide‐induced cytotoxicity as well as molecular and biochemical interactions. The objectives of this study were to investigate the influence of the cell culture medium on peptide metabolic stability andin vitroantitumour activity. The degradation kinetics of the model peptide methionine enkephalin (Met‐E, Tyr‐Gly‐Gly‐Phe‐Met), demonstrated recently to play an important role in the rate of proliferation of tumour cellsin vitroandin vivo, were investigated in cell culture systems containing different amounts of fetal bovine serum (FBS). The influence of enzyme inhibitors (bestatin, captopril, thiorphan) on the Met‐E degradation was also investigated. The results obtained in the Dulbecco's modified Eagle medium containing 10% FBS indicated a rapid degradation of Met‐E (t1/2= 2.8 h). Preincubation of the medium with a mixture of peptidase inhibitors reduced the hydrolysis of Met‐E, as shown by the increased half‐life to 10 h. Thein vitroactivity of Met‐E against poorly differentiated cells from lymph node metastasis of colon carcinoma (SW620) and human larynx carcinoma (HEp‐2) cells was determined. Tumour cells were grown for 3 weeks prior to the experiment in a medium supplemented with 10%, 5% or 2% FBS. Statistically significant to mild or no suppression of cell proliferation was observed in all cultures. In both cell lines, a significant suppression of cell growth by a combination of peptidase inhibitors and Met‐E, compared with cells exposed to the peptide alone and cells grown in the absence of Met‐E, was observed. This study indicated that caution must be exercised in interpreting the antiproliferative effects of peptide compounds in conventional drug‐response assays. Copyright © 2005 European Peptide So

ISSN:1075-2617    

DOI:10.1002/psc.643

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY

摘要:

AbstractIn peptide synthesis, the use ofNα‐tert‐butyloxycarbonyl‐Nπ‐benzyloxymethylhistidine [Boc‐His(π‐Bom)] raises the problem of the Bom group generating formaldehyde during the hydrogen fluoride (HF) cleavage reaction. This can lead to modification of the functional groups on amino acids in the peptide chain. Besides this side reaction, the failure ofNα‐Boc deprotection from the His(π‐Bom) residue occurs during TFA treatment for the standard solid‐phase peptide synthesis (SPPS) even in the case of a non ‘difficult sequence’. This gives amino acid deletion products generated at theN‐terminus of the His(π‐Bom) residues. Reviewing the removability of the Boc group on amino acid derivatives showed that the group on the His(π‐Bom) residue was much more resistant under the deprotecting conditions than expected. To circumvent this problem, special precautions, i.e. prolonged deprotection steps and/or increased concentrations of TFA, should be taken for a successful SPPS. Copyright © 2005 European Pepti

ISSN:1075-2617    

DOI:10.1002/psc.657

出版商:John Wiley&Sons, Ltd.    

年代:2005

数据来源: WILEY