Linear Oligopeptides Research Articles

Linear oligopeptides — effect of lengthening of the main chain by one tetrahedral carbon atom in the -Aib- l-Ala- sequence: a solid-state conformational analysis of segments of polypeptide antibiotics

The infrared absorption and X-ray diffraction conformational analysis of t-Boc-Aib- l-Ala-Aib-OMe have shown the presence of the type-1 4→1 intramolecularly H-bonded peptide conformation (β-bend) in the solid state. Lengthening of the chain by one tetrahedral carbon atom, as in t-Boc-Aib-βAla-Aib-OMe, has a disruptive effect on this folded structure. It has also been found that two water molecules co-crystallize with each molecule of the l-Ala containing tripeptide. These results are discussed in comparison with those, previously reported, obtained in chloroform solution.

Solid-state conformations of linear oligopeptides and aliphatic amides. A model of chiral perturbation of a conjugated system

A partir de 300 structures cristallines connues, etude de l'effet de la substitution chirale sur l'equilibre conformationnel d'un systeme conjugue plan

Linear oligopeptides. 118. Preferred conformations and modes of self-association of the fluoren-9-ylmethoxycarbonyl amino acid derivatives

An analysis of the preferred conformations and modes of self-association of the N-fluoren-9-methoxycarbonyl derivatives of L-alanine and α-aminoisobutyric acid was performed in solution and in the solid state using infrared absorption, 1H nuclear magnetic resonance, and X-ray diffraction. In a solvent of low polarity (deuterochloroform) non-associated and self-associated species (involving predominantly the hydroxyl and carbonyl groups of the carboxylic acid moiety) simultaneously occur. At high dilution, where self-association is absent, the amount of intramolecularly H-bonded forms, if any, should be extremely small. Z(trans) [Formula: see text]E(cis) isomerism about the amide bond of the secondary urethane moiety was observed only for the less bulky L-alanine derivative. In the solid state all H-bonding donors and acceptors of the L-alanine and α-aminoisobutyric acid derivatives take part to complex schemes of intermolecular H-bonds. In the L-alanine derivative, crystallized as monohydrate, most of the intermolecular H-bonds involve the water molecule. Intramolecular H-bonds are not observed in either compound. The conformation about the secondary urethane CO—NH bond is Z(trans) in both compounds. Both L-alanine and α-aminoisobutyric acid residues are partially folded. The observation of the long C(sp3)—O bond of the fluoren-9-yl-methoxycarbonyl moiety might contribute to explain the unexpected experimental result that this protecting group can be removed by catalytic hydrogenation.

Cyclic peptides

In order to explore the route for cyclization of linear oligopeptide containing a ΔAla (α, β‐dehydroalanine) residue, AM‐toxin II was synthesized. As a preliminary experiment, synthesis of [L‐Phe3] AM‐toxin II, containing L‐Phe in place of L‐App (L‐2‐amino‐5‐phenylpentanoic acid), was attempted. Cyclization of H‐L‐Phe‐ΔAla‐L‐Ala‐L‐Hmb‐ONSu in pyridine at 3 mM concentration yielded a mixture of cyclic dimer and cyclic polymers. Cyclization of H‐L‐App‐ΔAla‐L‐Ala‐L‐Hmb‐ONSu under the same conditions gave similar results; however, cyclization at 0.3 mM concentration yielded a mixture of desired cyclic monomer and cyclic dimer. An appreciable amount of cyclic monomer was isolated from the mixture. Characteristic features of the monomer were identical to those of natural AM‐toxin II.

Linear oligopeptides. 99. An infrared absorption method to titrate quantitatively the extent of self-association in peptides

Linear oligopeptides. 99. An infrared absorption method to titrate quantitatively the extent of self-association in peptides

Linear oligopeptides: c.d. and n.m.r. study of Dnp-pNA derivatives of Aib-containing tetrapeptides in a β-bend conformation

A circular dichroism investigation of two β-bend forming, Aib-containing tetrapeptides, with the -Aib- l-Ala- and - l-Ala-Aib- central sequences, occurring in peptaibol antibiotics, blocked at the N-terminal end with the 2,4-dinitrophenyl group and at the C-terminal end with the p-nitroanilino group, is described. A comparison is made with a tetrapeptide containing the - l-Ala- l-Ala- central sequence, also observed in peptaibol antibiotics. The amount of β-bend conformers, determined from the intensities of the exciton couplets arising from the intramolecular interaction of the p-nitroanilino chromophores, has been assessed as a function of the hydrogen-bonding properties of the solvent. The conformational analysis in dimethylsulphoxide has been extended to 1H nuclear magnetic resonance. Some information on the type of β-bend formed has additionally been obtained. The preparation and characterization of the three chromophoric tetrapeptides, along with some analogues and synthetic precursors, are also reported.

Antiparallel beta-sheets in the crystal structure of the heptapeptide Met-Glu-His-Phe-Arg-Trp-Gly (ACTH 4-10).

The conformation of the molecules in ACTH 4-10 has been determined as part of a study of the conformations of the biologically active N-terminal fragments of the adrenocorticotropic hormone (ACTH). ACTH 4-10 crystallizes in two different superstructures. The substructure considered in the present work, is monoclinic, space group C2, a = 25.75(1) A, b = 27.78(1) A, c = 20.35(1) A, beta = 114.0(1) degrees, Z = 8 molecules ACTH 4-10 plus 22 weight per cent solvent. The crystals contain antiparallel beta-sheets, the orientations of the side groups are not found, because of disorder. The present crystal structure and those of other linear oligopeptides emphasize that antiparallel beta-sheets are energetically favourable. It is very unlikely, however, that the ACTH 4-10 crystals contain the molecules in their biologically active form.

The peptide–urea interaction. Excess enthalpies of ternary aqueous solution of sarcosylsarcosine diketopiperazine and alkylureas at 298.15 K

The excess enthalpies of ternary aqueous solutions of sarcosylsarcosine diketopiperazine and alkylureas have been determined and compared with the properties of other diketopiperazine–urea systems at 298.15 K. A group-contribution analysis shows that cyclic dipeptides are characterized by more favourable peptide–peptide and peptide–urea interactions than the linear oligopeptides. The other contributions, and in particular the cross-interactions between peptides and alkyl chains, seem to assume values equal to those of non-cyclic solutes. The particular properties of sarcosylsarcosine diketopiperazine aqueous solutions are discussed and an unexpected analogy with monosaccharide aqueous solutions is found.

Linear oligopeptides. 81. Solid-state and solution conformation of homooligo(.alpha.-aminoisobutyric acids) from tripeptide to pentapeptide: evidence for a 310 helix

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTLinear oligopeptides. 81. Solid-state and solution conformation of homooligo(.alpha.-aminoisobutyric acids) from tripeptide to pentapeptide: evidence for a 310 helixEttore Benedetti, Alfonso Bavoso, Benedetto Di Blasio, Vincenzo Pavone, Carlo Pedone, Marco Crisma, Gian Maria Bonora, and Claudio TonioloCite this: J. Am. Chem. Soc. 1982, 104, 9, 2437–2444Publication Date (Print):May 1, 1982Publication History Published online1 May 2002Published inissue 1 May 1982https://doi.org/10.1021/ja00373a018RIGHTS & PERMISSIONSArticle Views215Altmetric-Citations165LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (893 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Study of the relationship between conformation and nature of side chains in linear oligopeptides: homologous series derived from β-branched amino acid residues

Conformational analysts of the three homologous series, from dipeptide to heptapeptide of monodisperse, N- and C-protected oligopeptides derived from the β-branched α-amino acid residues L-valine, L-isoleucine, and D-allo-isoleucine is reported. Occurrence of intermolecular β conformations in the higher oligopeptides in the solid state was established by means of infrared absorption. The extent of intramolecularly hydrogen-bonded folded structure formation was assessed as a function of chain length in solvents of low polarity at high dilution. Statistical coil and intermolecular β-conformations were shown to exist in alcohols and aqueous alcoholic mixtures. The results obtained indicate that, branching positions being equal, configuration of the asymmetric carbon atom in the lateral chain, overall bulkiness and lyophobic character of the amino acid side chains are all important factors in determining the stability of the ordered conformations of oligopeptides.

Linear oligopeptides, 70. Study of the relationship between conformation and nature of the side chain: Homologous series derived from α‐amino acid residues with linear hydrocarbon side chains

AbstractA series of N‐ and C‐protected L‐α‐aminobutyric acid homo‐oligopeptides from dipeptide through heptapeptide was synthesized by the dicyclohexylcarbodiimide and acyl azide coupling methods. The monodisperse peptides were characterized and found to be chemically and optically pure. By means of infrared absorption and circular dichroism in the vacuum ultraviolet (150 nm) the occurrence of the intermolecular β‐conformation in the higher oligopeptides in the solid state was ascertained. In solvents of low polarity at high dilution the amount of intramolecularly hydrogen‐bonded folded structure formation was established as a function of peptide chain length. Unordered and intermolecular β‐structures were found in alcohols and in water/2,2,2‐trifluoroethanol mixtures. The results obtained are compared with those already published of other homologous peptide series derived from L‐α‐amino acid residues with linear hydrocarbon side chains, namely alanine, norvaline, and norleucine. Analogies and differences with the series from β‐ and γ‐branched residues are also discussed.

Aspects of cyclic and linear oligopeptides

Aspects of cyclic and linear oligopeptides

Linear oligopeptides, 78. The effect of the insertion of the proline residue on the solution conformation of host peptides

AbstractThe conformational properties of three series of monodispersed, chemically and optically pure, PEGThe following abbreviations have been used in the text: PEG, poly(ethylene glycol); ‐NHPEG, “amino‐PEG”; ‐NHPEG‐M, “amino‐PEG” ‐monomethyl ether; t‐Boc, tert‐butyloxycarbonyl; Z, benzyloxycarbonyl; Ala, alanine; Met, methionine; Gly, glycine; Glu, glutamic acid; Pro, proline; OBzl, benzyloxy; OEt, ethoxy; CD, circular dichroism; MeOH, methanol; TFE, 2,2,2‐trifluoroethanol; HFIP, 1,1,1,3,3,3‐hexafluoro‐2‐propanol. ‐bound linear host oligopeptides of the general formula \documentclass{article}\pagestyle{empty}\begin{document}$ t{\rm - Boc\rlap{--} (L - Met\rlap{--} )}_n {\rm NHPEG} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ t{\rm - Boc\rlap{--} (L - X\rlap{--} )}_n {\rm NHPEG - M} $\end{document} [X = Ala, Glu(OBzl)] containing a single guest L‐Pro residue at different positions in the main chain have been investigated in aqueous and alcoholic solutions as a function of concentration, temperature, and added salts using CD. The corresponding N‐deblocked peptides have also been examined. The incorporation of the L‐Pro residue into a host petide chain blocks the extension of the α‐helical conformation at the level of the segment containing the guest residue at its N‐terminal end. The investigations reveal asymmetric helixnucleation properties of the L‐Pro residue as predicted by theory. In β‐structure‐forming oligopeptides, the insertion of a L‐Pro residue results in a significant destabilization of the ordered conformation. Thus, aggregation of peptide chains is less pronounced in these co‐oligopeptides.

Linear oligopeptides, 77. The effect of the insertion of a proline residue on the solid‐state conformation of host peptides

AbstractThe conformational properties of two series of monodispersed, chemically and optically pure, PEGThe following abbreviations have been used in the text: PEG, poly(ethylene glycol); ‐NHPEG, “amino‐PEG”; ‐NHPEG‐M, “amino‐PEG” monomethyl ether; NPS, o‐nitrophenylsulfenyl; t‐Boc, tert‐butoxycarbonyl; Z, benzyloxycarbonyl; Met, methionine; Pro, proline; OBzl, benzyloxy; OMe, methoxy; OEt, ethoxy; NHEt, ethylamino; Glu, glutamic acid; IR, infrared; MeOH, methanol; TFE, 2,2,2‐trifluoroethanol. ‐bound linear host oligopeptides of the general formula \documentclass{article}\pagestyle{empty}\begin{document}$ t{\rm - Boc\rlap{--} (L - Met\rlap{--} )}_n {\rm NHPEG} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ t{\rm - Boc\rlap{--} [L - Glu(OBl)\rlap{--} ]}_n {\rm NHPEG - M} $\end{document} containing a single guest L‐Pro residue at different positions in the main chain have been investigated in the solid state using IR absorption. The corresponding N‐deblocked peptides have also been examined. The incorporation of a L‐Pro residue in a central position of a β‐conformation appears to induce the onset of a structural irregularity characterized by IR absorption bands in the vicinity of 3 325 cm−1 and 1 575 cm−1.

Linear oligopeptides. LXXVI. Effect of lateral chains on the circular dichroism spectra of protonated peptides

Journal of Polymer Science: Polymer Chemistry EditionVolume 18, Issue 9 p. 2883-2885 Note Linear oligopeptides. LXXVI. Effect of lateral chains on the circular dichroism spectra of protonated peptides C. Toniolo, C. Toniolo Biopolyrmer Research Centre, CNR, Institute of Organic Chemistry, University of Padova, 35100 Radova, ItalySearch for more papers by this authorG. M. Bonora, G. M. Bonora Biopolyrmer Research Centre, CNR, Institute of Organic Chemistry, University of Padova, 35100 Radova, ItalySearch for more papers by this author C. Toniolo, C. Toniolo Biopolyrmer Research Centre, CNR, Institute of Organic Chemistry, University of Padova, 35100 Radova, ItalySearch for more papers by this authorG. M. Bonora, G. M. Bonora Biopolyrmer Research Centre, CNR, Institute of Organic Chemistry, University of Padova, 35100 Radova, ItalySearch for more papers by this author First published: September 1980 https://doi.org/10.1002/pol.1980.170180913AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Volume18, Issue9September 1980Pages 2883-2885 RelatedInformation

Linear oligopeptides: 65′. Conformational analysis of the N-protected aromatic α-amino acid [formula omitted] by X-ray diffraction and infrared absorption

The X-ray diffraction and i.r. absorption conformational analysis of N -tert-butyloxycarbonyl- l-phenylalanine has showed the absence of intramolecularly hydrogen-bonded peptide conformations in the solid state. The molecules are held together in rows of ‘cyclic dimer’ motifs through intermolecular N H … O C (acid) and O H … O C {urethane} hydrogen bonds, the secondary amide-like group of the urethane moiety being in the unusual cis conformation, whereas the carboxylic acid group in the common syn conformation. The two molecules in the unit cell present a centrosymmetric set of ϕ, ψ 1, and ψ 2 values. In polar solvents solvated species largely predominate. In saturated hydrocarbon solution non-associated and associated (mostly involving the carboxylic acid CO as the proton acceptor) species simultaneously occur. The extent of association decreases with dilution. The amount of intramolecularly hydrogen-bonded oxy- C 7 and C 5 forms if any, should be extremely small. The type of association at saturation seems to differ from that found in the crystalline compound obtained by precipitation with saturated aliphatic hydrocarbons (from a diethyl ether solution).

Linear oligopeptides. 56. Critical size for development of β-and α-helical structures of monodispersed homo- l-oligomethionines in the solid state

The infrared absorption properties of monodispersed, chemically and optically pure ‘amino-PEG’-bound linear homooligopeptides having the general formula t- Bx( l-Met) n NHPEG , n = 1–15 and H 2 +( l-Met) nNHPEG, n = 1–14 have been investigated in the solid state. The critical sizes for development of the β-structure and α-helix ( n = 3 and n = 13, respectively), and the effect, on the latter, of the solvent from which the solid samples are cast, have been established.

Linear oligopeptides, 60. Synthesis by the liquid‐phase method and characterization by amino acid analyses of two complete monodispersed homologous series derived from L‐alanine (to the octapeptide) and L‐valine (to the hexapeptide)

AbstractThe synthesis by the liquid‐phase method of the two complete, monodispersed homo‐oligopeptide series having the general formula t‐Boc\documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--}(\ {\rm L} - {\rm X}\rlap{---} )$\end{document}nGly‐OPEG (I:X=Ala, n=1‐8; II: X = Val, n = 1–6) is described. The chemical purity of the various products was assessed by thin layer chromatography and amino acid analyses. The influence of chain length and steric effects on the formation of peptide bonds and their stability to acid hydrolysis is also illustrated.

Linear Oligopeptides. 57. A Circular Dichroism Study of α-Helix and β-Structure Formation in Solution by Homooligo-L-methionines

Linear Oligopeptides. 57. A Circular Dichroism Study of α-Helix and β-Structure Formation in Solution by Homooligo-L-methionines

Linear oligopeptides, 55. Infrared conformational analysis of polyethyleneglycol‐bound alanine and valine homo‐L‐oligopeptides in the solid state and in solution

AbstractThe IR absorption properties of three series of monodisperse, chemically and optically pure, PEG‐bound linear homo‐oligopeptides having the general formula t‐Boc‐(L‐Ala‐)1–8Gly‐OPEG, t‐Boc‐(L‐Val‐)1–7Gly‐OPEG and t‐Boc‐(L‐Val‐)2–8Gly‐OPEG‐M were investigated in the solid state and in solution. In the latter case the study was extended to solvents of largely different polarity and different concentrations. In the solid state the Ala and Val peptides from n = 5 to n = 8 assume essentially a β‐structure. The occurrence of the unusual parallel‐chain β‐conformation was suggested for the N‐deblocked Val highest peptides. The conformational analysis in deuterochloroform at high dilution showed that a much higher content of intramolecularly H‐bonded forms exist in Ala4 than in the Val4 peptides. At higher concentrations chain length, solvent, and side chain effects are all operative in determining the extent of peptide association. The influence of the bi‐ and monofunctional polymeric supports on the conformational properties of the Ala and Val homo‐oligopeptide series is also discussed. Finally, preliminary results on the relationship between reactivity of the polymer‐bound growing peptide chain during the step‐by‐step synthesis and peptide conformation are reported.