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Peptide Chain (peptide + chain)
Selected AbstractsQuantifying End-to-End Conformational Communication of Chirality through an Achiral Peptide Chain,ANGEWANDTE CHEMIE, Issue 32 2009Jonathan Clayden Prof. Erfolgreich kommuniziert: Zwei diastereotope Protonen, die mehr als 60 Bindungen vom nächsten Chiralitätszentrum entfernt sind, liefern Signale eines AB-Systems, was für eine gut geordnete Helix der dazwischenliegenden Struktur spricht. Aus der Abnahme der Anisochronie lässt sich die lineare Persistenz einer Helix aus achiralen Aminosäuren quantifizieren: Nur 3.5,% des Chiralitätseinflusses geht pro achiralen Rest verloren. [source] N -(4-Nitrophenylsulfonyl)- and N -(Fluorenylmethoxycarbonyl)- N -ethyl Amino Acid Methyl Esters , A Practical ApproachEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 22 2010Emilia Lucia Belsito Abstract An efficient one-pot preparation of N -ethyl- N -4-nitrophenylsulfonyl (nosyl) amino acid methyl esters was accomplished by a simple N -ethylation reaction by using triethyloxonium tetrafluoroborate in the presence of N,N -diisopropylethylamine. The N -ethylated amino acid methyl esters are obtained with total retention of stereochemistry at the original chiral centers. To further broaden the scope of this methodology, the N -ethylated nosyl-protected compounds are easily converted in the more practical fluorenylmethyloxycarbonyl (Fmoc)-protected derivatives. The cleavage of methyl ester by using a mild and neutral method enables the preparation of N -ethyl amino acids that are building blocks suitable for introduction into a peptide chain. The methodology works well with both nosyl- and Fmoc-based solution-phase peptide synthesis. [source] Arginine-based structures are specific inhibitors of cathepsin CFEBS JOURNAL, Issue 11 2000Application of peptide combinatorial libraries Novel synthetic peptide inhibitors of lysosomal cysteine proteinase cathepsin C have been designed through the use of soluble peptide combinatorial libraries. The uncovered structural inhibitory module consists of the N-terminal cluster of l -arginine residues. Its modification with d -amino acids or arginine derivatives did not increase the inhibition strength. Inhibitory potency of oligoarginines improves with the elongation of peptide chain reaching a maximum for octa- l -arginine. The oligoarginines specifically interact with the cathepsin C active site as shown by competitive-type inhibition kinetics (Ki , 10,5 m) and intrinsic fluorescence measurements. The inhibitory interaction of oligoarginines is established through the specific spatial contact of a net of guanidino groups in the arginine side-chains, as indicated by comparison with inhibitory action of low molecular mass guanidine derivatives (Ki , 10,3 m). Nonarginine polyionic compounds cannot mimic the inhibitory effect of oligoarginines. The arginine-based peptide inhibitors were selective towards cathepsin C among other cysteine proteinases tested. [source] Gas-phase basicities for ions from bradykinin and its des-arginine analoguesJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 8 2001Nigel P. Ewing Abstract Apparent gas-phase basicities (GBapps) for [M + H]+ of bradykinin, des-Arg1 -bradykinin and des-Arg9 -bradykinin have been assigned by deprotonation reactions of [M + 2H]2+ in a Fourier transform ion cyclotron resonance mass spectrometer. With a GBapp of 225.8 ± 4.2 kcal mol,1, bradykinin [M + H]+ is the most basic of the ions studied. Ions from des-Arg1 -bradykinin and des-Arg9 -bradykinin have GBapp values of 222.8 ± 4.3 kcal mol,1 and 214.9 ± 2.3 kcal mol,1, respectively. One purpose of this work was to determine a suitable reaction efficiency ,break point' for assigning GBapp values to peptide ions using the bracketing method. An efficiency value of 0.1 (i.e. approximately 10% of all collisions resulting in a deprotonation reaction) was used to assign GBapps. Support for this criterion is provided by the fact that our GBapp values for des-Arg1 -bradykinin and des-Arg9 -bradykinin are identical, within experimental error, to literature values obtained using a modified kinetic method. However, the GBapps for bradykinin ions from the two studies differ by 10.3 kcal mol,1. The reason for this is not clear, but may involve conformation differences produced by experimental conditions. The results may be influenced by salt-bridge conformers and/or by conformational changes caused by the use of a proton-bound heterodimer in the kinetic method. Factors affecting the basicities of these peptide ions are also discussed, and molecular modeling is used to provide information on protonation sites and conformations. The presence of two highly basic arginine residues on bradykinin results in its high GBapp, while the basicity of des-Arg1 -bradykinin ions is increased by the presence of two proline residues at the N-terminus. The proline residue in the second position folds the peptide chain in a manner that increases intramolecular hydrogen bonding to the protonated N-terminal amino group of the proline at the first position. Copyright © 2001 John Wiley & Sons, Ltd. [source] Design and synthesis of new trehalose-conjugated pentapeptides as inhibitors of A,(1,42) fibrillogenesis and toxicity,JOURNAL OF PEPTIDE SCIENCE, Issue 3 2009Paolo De Bona Abstract Aggregation of the amyloid A, peptide and its accumulation into insoluble deposits (plaques) are believed to be the main cause of neuronal dysfunction associated with Alzheimer's disease (AD); small molecules that can interfere with the A, amyloid fibril formation are therefore of interest for a potential therapeutic strategy. Three new trehalose-conjugated peptides of the well known ,-sheet breaker peptide iA,5p, were synthesized. The disaccharide was covalently attached to different sites of the LPFFD peptide chain, i.e. at the N-terminus, C-terminus or at the Asp side chain. CD spectroscopy in different solvents was used to assess changes in the peptide conformation of these compounds. The effects of these glycopeptides on the self-assembly and morphology of A, aggregates were investigated by ThT fluorescence assay and dynamic Scanning Force Microscopy, respectively. All the synthesized compounds were tested as inhibitors of A, toxicity toward pure cultures of rat cortical neurons. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd. [source] Synthesis and biological activity of homoarginine-containing opioid peptidesJOURNAL OF PEPTIDE SCIENCE, Issue 1 2007Jan Izdebski Abstract Two tris-alkoxycarbonyl homoarginine derivatives, Boc-Har{,,,,-[Z(2Br)]2}-OH and Boc-Har{,,,,-[Z(2Cl)]2}-OH, were prepared by guanidinylation of Boc-Lys-OH, and used for the synthesis of neo-endorphins and dynorphins. The results were compared with that obtained in the synthesis in which Boc-Lys(Fmoc)-OH was incorporated into the peptide chain, and after removing Fmoc protection, the resulting peptide-resin was guanidinylated with N,N,-[Z(2Br)]2 - or N,N,-[Z(2Cl)]2 - S -methylisourea. The peptides were tested in the guinea-pig ileum (GPI) and mouse vas deferens (MVD) assays. The results indicated that replacement of Arg by Har may be a good avenue for the design of biologically active peptides with increased resistance to degradation by trypsin-like enzymes. Copyright © 2006 European Peptide Society and John Wiley & Sons, Ltd. [source] Structure,activity relationship of an antibacterial peptide, maculatin 1.1, from the skin glands of the tree frog, Litoria genimaculataJOURNAL OF PEPTIDE SCIENCE, Issue 7 2004Takuro Niidome Abstract Maculatin 1.1 (Mac) is a cationic antibacterial peptide isolated from the dorsal glands of the tree frog, Litoria genimaculata, and has a sequence of GLFGVLAKVAAHVVPAIAEHF-NH2. A short peptide lacking the N -terminal two residues of Mac was reported to have no activity. To investigate the structure,activity relationship in detail, several analogs and related short peptides of Mac were synthesized. CD measurement showed that all the peptides took more or less an ,-helical structure in the presence of anionic lipid vesicles. Analogs which are more basic than Mac had strong antibacterial and hemolytic activities, while short peptides lacking one or two terminal residues exhibited weak or no activity. Outer and inner membrane permeabilization activities of the peptides were also reduced with shortening of the peptide chain. These results indicate that the entire chain length of Mac is necessary for full activity, and the basicity of the peptides greatly affects the activity. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd. [source] Nanomechanics of single keratin fibres: A Raman study of the ,-helix ,,-sheet transition and the effect of waterJOURNAL OF RAMAN SPECTROSCOPY, Issue 5 2007Raphaël Paquin Abstract The use of micro-Raman spectroscopy, through chemical-bond, nano-scale probes, allows the changes in conformations (,-helix ,,-sheet), chain orientation, breakage of disulfide bonds (20%) and the increase of intra- and inter-chain distances during the application of stress to be distinguished. The combination of micro-Raman spectroscopy and a Universal Fibre Tester allows a quantitative measurement of the extension of chemical bonds in the peptide chain during loading. The nano-structural transformations of keratin during strain of human hair in a dry environment (40,60% relative humidity) and saturated with water have been studied. Water permits the sliding of the chains and decreases the bond energy of the hair. Spectral analyses and 2D correlation are two coherent and independent methods to follow the structural nano-mechanical (Raman) and micro-mechanical (strain/stress) analyses, and confirm the validity of the experimental results, tools and principles used, as well as the agreement with the structural model of keratin fibres described by Chapman and Hearle. Copyright © 2006 John Wiley & Sons, Ltd. [source] 15N relaxation study of the amyloid ,-peptide: structural propensities and persistence lengthMAGNETIC RESONANCE IN CHEMISTRY, Issue S1 2006Jens Danielsson Abstract The dynamics of monomeric Alzheimer A,(1,40) in aqueous solution was studied using heteronuclear NMR experiments. 15N NMR relaxation rates of amide groups report on the dynamics in the peptide chain and make it possible to estimate structural propensities from temperature-dependent relaxation data and chemical shifts change analysis. The persistence length of the polypeptide chain was determined using a model in which the influence of neighboring residue relaxation is assumed to decay exponentially as a function of distance. The persistence length of the A,(1,40) monomer was found to decrease from eight to three residues when temperature was increased from 3 to 18 °C. At 3 °C the peptide shows structural propensities that correlate well with the suggested secondary structure regions of the peptide to be present in the fibrils, and with the ,-helical structure in membrane-mimicking systems. Our data leads to a structural model for the monomeric soluble ,-peptide with six different regions of secondary structure propensities. The peptide has two regions with ,-strand propensity (residues 16,24 and 31,40), two regions with high PII-helix propensity (residues 1,4 and 11,15) and two unstructured regions with higher mobility (residues 5,10 and 25,30) connecting the structural elements. Copyright © 2006 John Wiley & Sons, Ltd. [source] GAG Mimetic Libraries: Sulphated Peptide as Heparin-like Glycosaminoglycan Mimics in Their Interaction with FGF-1MOLECULAR INFORMATICS, Issue 8 2005Socorro Vázquez-Campos Abstract Heparin and heparan sulphate (HS) are heterogenous, linear, polysulphated polysaccharides that are important in the regulation of a wide variety of biological processes including blood coagulation, in cell differentiation, adhesion, invasion, migration and development, and in tumor-related cellular events such as growth regulation and metastasis. In general, heparin/HS interacts with proteins mainly through ionic interactions between its negatively charged groups and positively charged groups on the proteins. From a mechanistic or therapeutic standpoint, it is attractive to design less complex charged molecules, other than oligosaccharides, as mimics of heparin. In an attempt to improve the accessibility of heparin mimics, it was assumed, provided that the correct charge topography could be achieved, that sulphated peptides might also act as mimics. Therefore, sulphated peptide combinatorial libraries were generated on solid support to identify novel polyanionic structures that mimic the role of heparin/HS in its binding to fibroblast growth factors (FGFs). Libraries were synthesised by direct sulphation of the peptide on solid phase or by using O- sulphonated building blocks during peptide synthesis. Quantitative solid-phase O -sulphonation of hydroxy amino acid residues in a peptide chain was effected by sulphur trioxide pyridine (SO3 -Pyr) complex in anhydrous pyridine at 65,°C for 4,h. O- Sulphonated building blocks were successfully synthesised in solution and, after stabilisation of the sulphate group by complexion with tetrabutyl ammonium ions, were employed in the synthesis of sulphated peptide libraries, similar to those generated by direct O- sulphonation on solid supports. The libraries were incubated with fluorescent-labelled FGF-1, and analysis and sequence determination of active compounds was carried out using Edman degradation. Selected sulphated peptides from the screening were resynthesised and their affinity for FGF-1 (acidic FGF) was studied in solution competition assays using surface plasmon resonance. These studies showed that sulphated decapeptides do bind to FGF-1 and inhibit its binding to immobilised heparin in the low micromolar concentration range. [source] The role of irregular unit, GAAS, on the secondary structure of Bombyx mori silk fibroin studied with 13C CP/MAS NMR and wide-angle X-ray scatteringPROTEIN SCIENCE, Issue 8 2002Tetsuo Asakura Abstract Bombyx mori silk fibroin is a fibrous protein whose fiber is extremely strong and tough, although it is produced by the silkworm at room temperature and from an aqueous solution. The primary structure is mainly Ala-Gly alternative copolypeptide, but Gly-Ala-Ala-Ser units appear frequently and periodically. Thus, this study aims at elucidating the role of such Gly-Ala-Ala-Ser units on the secondary structure. The sequential model peptides containing Gly-Ala-Ala-Ser units selected from the primary structure of B. mori silk fibroin were synthesized, and their secondary structure was studied with 13C CP/MAS NMR and wide-angle X-ray scattering. The 13C isotope labeling of the peptides and the 13C conformation-dependent chemical shifts were used for the purpose. The Ala-Ala units take antiparallel ,-sheet structure locally, and the introduction of one Ala-Ala unit in (Ala-Gly)15 chain promotes dramatical structural changes from silk I (repeated ,-turn type II structure) to silk II (antiparallel ,-sheet structure). Thus, the presence of Ala-Ala units in B. mori silk fibroin chain will be one of the inducing factors of the structural transition for silk fiber formation. The role of Tyr residue in the peptide chain was also studied and clarified to induce "locally nonordered structure." [source] Sugar-complex structures of the C-half domain of the galactose-binding lectin EW29 from the earthworm Lumbricus terrestrisACTA CRYSTALLOGRAPHICA SECTION D, Issue 1 2009Ryuichiro Suzuki R-type lectins are one of the most prominent types of lectin; they exist ubiquitously in nature and mainly bind to the galactose unit of sugar chains. The galactose-binding lectin EW29 from the earthworm Lumbricus terrestris belongs to the R-type lectin family as represented by the plant lectin ricin. It shows haemagglutination activity and is composed of a single peptide chain that includes two homologous domains: N-terminal and C-terminal domains. A truncated mutant of EW29 comprising the C-terminal domain (rC-half) has haemagglutination activity by itself. In order to clarify how rC-half recognizes ligands and shows haemagglutination activity, X-ray crystal structures of rC-half in complex with d -lactose and N -acetyl- d -galactosamine have been determined. The structure of rC-half is similar to that of the ricin B chain and consists of a ,-trefoil fold; the fold is further divided into three similar subdomains referred to as subdomains ,, , and ,, which are gathered around the pseudo-threefold axis. The structures of sugar complexes demonstrated that subdomains , and , of rC-half bind terminal galactosyl and N -acetylgalactosaminyl glycans. The sugar-binding properties are common to both ligands in both subdomains and are quite similar to those of ricin B chain,lactose complexes. These results indicate that the C-terminal domain of EW29 uses these two galactose-binding sites for its function as a single-domain-type haemagglutinin. [source] Investigation of molecular structure of bombesin and its modified analogues nonadsorbed and adsorbed on electrochemically roughened silver surfaceBIOPOLYMERS, Issue 6 2008Edyta Podstawka Abstract This work describes the molecular structure of bombesin (BN) and its analogs on the basis of the absorption infrared and Raman results described below. In these analogues is replaced one ([D-Phe12]BN, [Tyr4]BN, and [Lys3]BN) or two ([Tyr4,D-Phe12]BN, [D-Phe12,Leu14]BN, and [Leu13 -®-Leu14]BN) amino acid residues within the peptide chain with a synthetic amino acid, creating antagonists to bombesin, which are useful in the treatment of cancer. It is also used surface enhanced Raman scattering (SERS) to study the differences and changes in the vibrational spectra of BN and its analogs, which were attached to an electrochemically roughened silver surface as these peptides interacted with target proteins. This work explores the use of SERS for molecules anchored to a macroscopic silver surface to interrogate the interaction of these peptides with protein receptors. The results presented here show that all peptides coordinate to the macroscopic silver surface through an indole ring and the methylene group of Trp8, the CO fragment, and an amide bond; however, the orientation of these fragments on the electrochemically roughened silver surface and the strength of the interactions with this surface is slightly different for each peptide. For example, the interaction of CH2 of [D-Phe12]BN, [Tyr4,D-Phe12]BN, [D-Phe12,Leu14]BN, [Leu13 -®-Leu14]BN, and [Lys3]BN with the silver surface perturbed the vertical orientation of the Trp8 indole ring on this surface. Hence, the indole ring adopted a close to perpendicular orientation on the silver surface for BN and [Tyr4]BN, only. © 2007 Wiley Periodicals, Inc. Biopolymers 89: 506,521, 2008. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Chiral interaction in peptide molecules: Effects of chiral peptide species on helix-sense induction in an N-terminal-free achiral peptideBIOPOLYMERS, Issue 5 2006Yoshihito Inai Abstract Noncovalent chiral domino effect (NCDE) has been proposed as terminal-specific interaction upon a 310 -helical peptide chain, of which the helix sense is manipulated by an external chiral stimulus (mainly amino acid derivatives) operating on the N-terminus (Inai, Y., et al. J Am Chem Soc 2000, 122, 11731,11732; ibid., 2002, 124, 2466,2473; ibid., 2003, 125, 8151,8162). We have investigated here a helix-sense induction in an optically inactive N-terminal-free nonapeptide (1) through the screening of several peptide species that differ in chiral sequence, chain length, and C-terminal group. Helix-sense induction in peptide 1 depends largely on both the C-terminal chirality and carboxyl group in the external peptide, in which N-carbonyl-blocked amino acids, "monopeptide acids," should be the minimum requirement for effective induction. N-Protected mono- to tetrapeptides of L -Leu residue commonly induce a right-handed helix. NMR study and theoretical computation reveal that the N-terminal segment of peptide 1 binds the N-protected dipeptide molecule through multipoint coordination to induce a right-handed helix preferentially. The present findings not only will improve our understanding of the chiral roles in peptide or protein helical termini, but also might demonstrate potential applications to chirality-responsive materials based on peptide helical fragments. © 2006 Wiley Periodicals, Inc. Biopolymers 82: 471,481, 2006 This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Melectin: A Novel Antimicrobial Peptide from the Venom of the Cleptoparasitic Bee Melecta albifronsCHEMBIOCHEM, Issue 17 2008Václav, ovský Dr. Abstract A novel antimicrobial peptide designated melectin was isolated from the venom of the cleptoparasitic bee Melecta albifrons. Its primary sequence was established as H-Gly-Phe-Leu-Ser-Ile-Leu-Lys-Lys-Val-Leu-Pro-Lys-Val-Met-Ala-His-Met-Lys-NH2 by Edman degradation and ESI-QTOF mass spectrometry. Synthetic melectin exhibited antimicrobial activity against both Gram-positive and -negative bacteria and it degranulated rat peritoneal mast cells, but its hemolytic activity was low. The CD spectra of melectin measured in the presence of trifluoroethanol and sodium dodecyl sulfate showed a high content ,-helices, which indicates that melectin can adopt an amphipathic ,-helical secondary structure in an anisotropic environment such as the bacterial cell membrane. To envisage the role of the proline residue located in the middle of the peptide chain on biological activity and secondary structure, we prepared several melectin analogues in which the Pro11 residue was either replaced by other amino acid residues or was omitted. The results of biological testing suggest that a Pro kink in the ,-helical structure of melectin plays an important role in selectivity for bacterial cells. In addition, a series of N- and C-terminal-shortened analogues was synthesized to examine which region of the peptide is related to antimicrobial activity. [source] Solution Structure and Stability of Tryptophan-Containing Nucleopeptide DuplexesCHEMBIOCHEM, Issue 1 2003Irene Gómez-Pinto Abstract Covalently linked peptide,oligonucleotide hybrids were used as models for studying tryptophan,DNA interactions. The structure and stability of several hybrids in which peptides and oligonucleotides are linked through a phosphodiester bond between the hydroxy group of a homoserine (Hse) side chain and the 3,-end of the oligonucleotide, have been studied by both NMR and CD spectroscopy and by restrained molecular dynamics methods. The three-dimensional solution structure of the complex between Ac-Lys-Trp-Lys-Hse(p3,dGCATCG)-Ala-OH (p=phosphate, Ac=acetyl) and its complementary strand 5,dCGTAGC has been determined from a set of 276 experimental NOE distances and 33 dihedral angle constraints. The oligonucleotide structure is a well-defined duplex that belongs to the B-form family of DNA structures. The covalently linked peptide adopts a folded structure in which the tryptophan side chain stacks against the 3,-terminal guanine moiety, which forms a cap at the end of the duplex. This stacking interaction, which resembles other tryptophan,nucleobase interactions observed in some protein,DNA complexes, is not observed in the single-stranded form of Ac-Lys-Trp-Lys-Hse(p3,dGCATCG)-Ala-OH, where the peptide chain is completely disordered. A comparison with the pure DNA duplex, d(5,GCTACG3,),(5,CGTAGC3,), indicates that the interaction between the peptide and the DNA contributes to the stability of the nucleopeptide duplex. The different contributions that stabilize this complex have been evaluated by studying other nucleopeptide compounds with related sequences. [source] Solvent effects on coupling yields during rapid solid-phase synthesis of CGRP(8-37) employing in situ neutralization,CHEMICAL BIOLOGY & DRUG DESIGN, Issue 1 2005C.K. Taylor Abstract:, The success of solid-phase peptide synthesis is often dependent upon solvation of the resin and the growing resin-bound peptide chain. We investigated the relationship between solvent properties and solvation of the resin and peptide-resin in order to obtain satisfactory coupling yields for the rapid solid-phase peptide synthesis, using butyloxycarbonyl-(Boc)-amino acid derivatives, of human-,-calcitonin gene-related peptide(8-37) (CGRP(8-37)). Solvation of (p -methylbenzhydrylamine)copoly(styrene,1% divinylbenzene (DVB) (resin) and resin covalently bound to the fully protected amino acid sequence of CGRP(8-37) (peptide,resin) was correlated to solvent Hildebrand solubility (,) and hydrogen-bonding (,h) parameters. Contour solvation plots of ,h vs. , revealed maximum solvation regions of resin and peptide,resin. Maximum resin solvation occurred with N-methylpyrrolidinone (NMP), NMP : dimethylsulfoxide (DMSO) (8 : 2) and DMSO. Inefficient solvation of the peptide,resin occurred with these solvents and resulted in poor syntheses with average coupling yields of 78.1, 88.9 and 91.8%, respectively. Superior peptide,resin solvation was obtained using dimethylacetamide (DMA) and dimethylformamide (DMF), resulting in significantly higher average coupling yields of 98.0 and 99.5%, respectively. Thus, the region of maximum peptide,resin solvation shifts to solvents with higher ,h values. DMF provided the most effective peptide,resin solvation and was the only solvent from which CGRP(8-37) was obtained as a single major product in the crude cleaved material. [source] Solid-Phase Synthesis of DOTA,PeptidesCHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2004Luis M. De León-Rodriguez Dr. Abstract A general synthetic route to two DOTA-linked N -Fmoc amino acids (DOTA-F and DOTA-K) is described that allows insertion of DOTA at any endo -position within a peptide sequence. Three model pentapeptides were prepared to test the general utility of these derivatives in solid-phase peptide synthesis. Both DOTA derivatives reacted smoothly by means of standard HBTU activation chemistry to the point of insertion of the DOTA amino acid, but extension of the peptide chain beyond the DOTA-amino acid insertion required the use of pre-activated C -pentafluorophenyl ester N - , -Fmoc amino acids. Three Gal-80 binding peptides (12-mers) were then prepared by using this methodology with DOTA positioned either at the N terminus or at one of two different internal positions;the binding of the resulting GdDOTA-12-mers to Gal-80 were compared. The methodology described here allows versatile, controlled introduction of DOTA into any location within a peptide sequence. This provides a potential method for the screening of libraries of DOTA-linked peptides for optimal targeting properties. [source] Palladium-Catalysed Amination of Electron-Deficient or Relatively Electron-Rich Benzo[b]thienyl Bromides , Preliminary Studies of Antimicrobial Activity and SARsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2004Maria-João R. P. Queiroz Abstract Several diarylamines in the benzo[b]thiophene series were prepared in good to high yields by palladium-catalysed amination of ethyl 3-bromobenzo[b]thiophene-2-carboxylate with anilines and 5-aminoindole in the presence of Pd(OAc)2, BINAP and Cs2CO3 in toluene. The presence of the ester group at the 2-position of the benzo[b]thiophene moiety increases the yields and lowers the heating times relative to the reactions performed with 3-bromobenzo[b]thiophene. When aminopyridines were used instead of anilines, the ligand and the solvent need to be changed to XANTHPHOS and dioxane in the amination reaction. With 2-aminopyridine a one-pot C,N coupling and intramolecular cyclization involving the nitrogen atom of the pyridine ring occurred, with loss of ethanol, giving an interesting fluorescent tetracyclic heteroaromatic compound. The antimicrobial activity, the minimal inhibitory concentrations (MICs) and the structure-activity relationships (SARs) were evaluated. A selectivity with low MICs was observed against Bacillus Cereus, and good results were also obtained against Candida albicans. The acids obtained by hydrolysis of the ester group, as non-proteinogenic ,,,-unsaturated ,-amino acids, can be incorporated into peptide chains to induce conformational constraints. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Thiocarbamate-linked peptides by chemoselective peptide ligationJOURNAL OF PEPTIDE SCIENCE, Issue 12 2008Soizic Besret Abstract Peptide chemical ligation chemistries, which allow the chemoselective coupling of unprotected peptide fragments, are useful tools for synthesizing native polypeptides or unnatural peptide-based macromolecules. We show here that the phenylthiocarbonyl group can be easily introduced into peptides on , or , amino groups using phenylthiochloroformate and standard solid-phase method. It reacts chemoselectively with cysteinyl peptides to give an alkylthiocarbamate bond. S,N -shift of the alkylaminocarbonyl group from the Cys side chain to the ,-amino group did not occur. The method was used for linking two peptide chains through their N -termini, for the synthesis of a cyclic peptide or for the synthesis of di- or tetravalent multiple antigenic peptides (MAPs). Thiocarbamate ligation is thus complementary to thioether, thioester or disulfide ligation methods. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd. [source] Microwave-assisted Boc-solid phase peptide synthesis of cyclic cysteine-rich peptidesJOURNAL OF PEPTIDE SCIENCE, Issue 6 2008Abstract In this study we describe the first protocols for the synthesis of cystine-rich peptides in the presence of microwave radiation with Boc-solid phase peptide synthesis (SPPS). This method is exemplified for macrocyclic peptides known as cyclotides, which comprise ,30 amino acids and incorporate a cystine knot arrangement of their three disulfide bonds. However, the method is broadly applicable for a wide range of peptides using Boc-SPPS, especially for SPPS of large peptides via native chemical ligation. Microwave radiation produces peptides in high yield and with high purity, and we were able to reduce the time for the assembly of ,30 mer peptide chains to an overnight reaction in the automated microwave-assisted synthesis. Copyright © 2007 European Peptide Society and John Wiley & Sons, Ltd. [source] Synthesis of A,[1-42] and its derivatives with improved efficiencyJOURNAL OF PEPTIDE SCIENCE, Issue 2 2007Márta Zarándi Abstract It has been proved that the principal component of senile plaques is aggregates of ,-amyloid peptide (A,) in cases of one of the most common forms of age-related neurodegenerative disorders, Alzheimer's disease (AD). Although the synthetic methods for the synthesis of A, peptides have been developed since their first syntheses, A,[1-42] is still problematic to prepare. The highly hydrophobic composition of A,[1-42] results in aggregation between resin-bound peptide chains or intrachain aggregation which leads to a decrease in the rates of deprotection and repetitive incomplete coupling reactions during 9-flurenylmethoxycarbonyl (Fmoc) synthesis. In order to avoid aggregation and/or disrupt internal aggregation during stepwise Fmoc solid phase synthesis and to improve the quality of crude products, several attempts have been made. Since highly pure A, peptides in large quantities are used in biological experiments, we wanted to develop a method for a rational synthesis of human A,[1-42] with high purity and adequate yield. This paper reports a convenient methodology with a novel solvent system for the synthesis of A,[1-42], its N -terminally truncated derivatives A,[4-42] and A,[5-42], and A,[1-42] labeled with 7-amino-4-methyl-3-coumarinylacetic acid (AMCA) at the N -terminus using Fmoc strategy. The use of 10% anisole in Dimethylformamide/Dichloromethane (DMF/DCM) can substantially improve the purity and yield of crude A,[1-42] and has been shown to be an optimal coupling condition for the synthesis of A,[1-42]. Anisole is a cheap and simple aid in the synthesis of ,difficult sequences' where other solvents are less successful in the prevention of aggregation during the synthesis. Copyright © 2006 European Peptide Society and John Wiley & Sons, Ltd. [source] Principles of carbopeptoid folding: a molecular dynamics simulation studyJOURNAL OF PEPTIDE SCIENCE, Issue 2 2005Riccardo Baron Abstract The conformational spaces of five oligomers of tetrahydrofuran-based carbopeptoids in chloroform and dimethyl sulfoxide were investigated through nine molecular dynamics simulations. Prompted by nuclear magnetic resonance experiments that indicated various stable folds for some but not all of these carbopeptoids, their folding behaviour was investigated as a function of stereochemistry, chain length and solvent. The conformational distributions of these molecules were analysed in terms of occurrence of hydrogen bonds, backbone torsional-angle distributions, conformational clustering and solute configurational entropy. While a cis -linkage across the tetrahydrofuran ring favours right-handed helical structures, a trans -linkage results in a larger conformational variability. Intra-solute hydrogen bonding is reduced with increasing chain length and with increasing solvent polarity. Solute configurational entropies confirm the picture obtained: they are smaller for cis - than for trans -linked peptides, for chloroform than for dimethyl sulfoxide as solvent and for shorter peptide chains. The simulations provide an atomic picture of molecular conformational variability that is consistent with the available experimental data. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd. [source] SPPS of protected peptidyl aminoalkyl amidesJOURNAL OF PEPTIDE SCIENCE, Issue 11 2002Manolis Karavoltsos Abstract Monophthaloyl diamines derived from naturally occurring amino acids were attached through their free amino functions to resins of the trityl type. The phthaloyl groups were removed by hydrazinolysis, and peptide chains were assembled using Fmoc/tBu-amino acids on the liberated amino functions. The peptidyl aminoalkyl amides obtained were cleaved from the resins by mild acidolysis, with the tBu-side chain protection remaining intact. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd. [source] Insulins in equine urine: qualitative analysis by immunoaffinity purification and liquid chromatography/tandem mass spectrometry for doping control purposes in horse-racingRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 3 2008Tiia Kuuranne Insulin is a peptide hormone consisting of two peptide chains (A- and B-chain) that are cross-linked by two disulfide bonds. To obtain improved pharmacokinetic onset of action profiles of insulin treatment in diabetic patients, recombinant long-, intermediate-, and rapid-acting insulin analogs are produced, in which the C-terminal end of the B-chain plays an especially important role. A review of the veterinary literature reveals the low prevalence of equine type I diabetes mellitus, which indicates that the therapeutic use of insulin in racing horses is unlikely. Although there is no unequivocal evidence of an overall performance-enhancing effect of insulin, in human sports the misuse of insulin preparations is reported among elite athletes. The desired effects of insulin include the increase of muscular glycogen prior to sports event or during the recovery phase, in addition to a chalonic action, which increases the muscle size by inhibiting protein breakdown. In the present study urinary insulin was detected in equine samples and differences between equine insulin, human insulin, as well as rapidly acting recombinant insulin variants were examined. The method was based on sample purification by solid-phase extraction (SPE) and immunoaffinity chromatography (IAC), and subsequent analysis by microbore liquid chromatography (LC) and tandem mass spectrometry (MS/MS) using top-down sequencing for the determination of various insulins. Product ion scan experiments of intact proteins and B-chains enabled the differentiation between endogenously produced equine insulin, its DesB30 metabolite, human insulin and recombinant insulin analogs, and the assay allowed the assignment of individual product ions, especially those originating from modified C-termini of B-chains. Copyright © 2008 John Wiley & Sons, Ltd. [source] Determination of the disulfide bond pattern of the endogenous and recombinant angiogenesis inhibitor endostatin by mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2001Harald John Endostatin, a C-terminal fragment of collagen XVIII, is a promising protein drug which is in development for cancer therapy due to its anti-angiogenic activity. Although several endogenous molecular forms of human endostatin differing in their N-terminal length and their post-translational modifications (18.5,22,kDa) have been discovered, only one recombinant form of 20,kDa is used in clinical trials. This protein, recombinantly expressed in Pichia pastoris, contains four cysteines forming two disulfide bonds (Cys1-Cys4 and Cys2-Cys3). In contrast, there are conflicting data about the disulfide pattern of endogenous material. This report presents the disulfide analyses of both the endogenous circulating endostatins isolated from human hemofiltrate and the recombinant protein. The determination of the disulfide pattern was performed by Edman degradation, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and electrospray ionization ion trap mass spectrometry (ESI-ITMS) performed in the off-line nanospray mode. All native and recombinant endostatins exhibited a Cys1-Cys4 (Cys162 -Cys302) and Cys2-Cys3 (Cys264 -Cys294) linkage. For a clear discussion of fragmented disulfide-bridged peptide chains obtained from MSn experiments, a modified general nomenclature is proposed. Copyright © 2001 John Wiley & Sons, Ltd. [source] Chemoselective synthesis of peptides containing major advanced glycation end-products of lysine and arginineCHEMICAL BIOLOGY & DRUG DESIGN, Issue 3 2005P. Gruber Abstract:, Useful methodologies have been developed, enabling the straightforward synthesis of peptides containing N, -(carboxymethyl)- l -lysine (CML) and N, -(carboxyethyl)- l -lysine (CEL), the major glycation end-products of lysine. These lysine derivatives were successfully incorporated into growing peptide chains via standard Fmoc/Ot -Bu peptide synthesis procedures. For the synthesis of peptides containing major glycation end-products of arginine, synthetic routes have been developed enabling the transformation of ornithine residues in peptides into the well-known arginine-derived advanced glycation end-products (AGEs) Glarg, carboxymethyl- l -arginine (CMA), MG-H1, MG-H2, MG-H3, and carboxyethyl- l -arginine (CEA), respectively, by means of special modifying agents. Furthermore, it was shown that Glarg-containing peptides become quantitatively hydrolyzed into CMA-peptides under physiologic conditions. A similar reaction was observed in case of a MG-H3-peptide, which turned into a CEA-peptide under these conditions. [source] | ||||||||||||||||||||||