Conformation Of Cyclo Research Articles

Conformational Characterization of (Val-Pro-Gly-Val-Gly)6 with 13C Solid State NMR

The repeated pentapeptide sequence, (Val-Pro-GlyVal-Gly)n, has been considered to be an essential repeated sequence for producing the elastic character of elastin.1 The previous structural studies have been concentrated to clarify whether the unit, Pro-Gly, in the sequence takes β-turn structure.2–4 However, there are very limited structural information on the other parts of the pentapeptide sequence. By employing the mathematical methods of deriving a linear helical correlation structures from a conformation of cyclo-(Val1Pro-Gly-Val-Gly)3 obtained by X-Ray diffraction analysis,3 Urry’s group reported the torsion angles as Val1(φ, ψ) = (−120◦, 100◦), Val4(φ, ψ) = (−120◦, 80◦) and Gly5(φ, ψ) = (−150◦, −130◦) together with the ProGly unit; (Pro2(φ, ψ) = (−60◦, 120◦) and Gly3(φ, ψ) = (120◦, −40◦)). However, in general, cyclo-peptides take limited conformations because of the presence of many constraints such as steric constraints and hydrogen bonding formation as well as “cyclic” without the end groups. The extension of the information on the structures of cyclo-peptides to linear peptide with similar sequence should be performed very carefully. Thus, it is better to obtain the information on the torsion angles directly for the linear pentapeptide sequence in the solid state if it is possible. In our previous papers,5–7 13C solid state NMR such as especially 2D spin-diffusion solid state NMR under off magic angle spinning (OMAS) coupled with 13C isotope double labeling of specific residues has been successfully used to determine the torsion angles of the backbone amino acid residues for the silk model peptides, (Ala-Gly)15 and (Ala-Gly-Gly)10 in the several solid state forms. Especially, a new structural model of (Ala-Gly)15 as a model of Bombyx mori silk fibroin before spinning could be proposed.5 In this paper, we synthesized four kinds of the repeated pentapeptide sequences, (VPGVG)6, (VPGVG)2VP[1-C]G13[1-C]V14G(VPGVG)3, (VPGVG)2VPG[1-C]V14[1-C]G15(VPGVG)3, (VPGVG)2VPGV[1-C]G15[1-C]V16PGVG(VPGVG)2 in order to obtain the information on the torsion angles of the backbone of two Val residues (Val14 and Val16) and one Gly residue (Gly15) using both 2D spin-diffusion NMR under OMAS. Especially, the local conformation of the Gly15 residue was analyzed in detail from the comparison of the calculated and observed 2D spin-diffusion NMR spectra.

The structure and conformation of the tryptophanyl diketopiperazines cyclo(Trp–Trp)·C2H6SO and cyclo(Trp–Pro)

The structure and conformation of the cyclic dipeptides [cyclo(L-Trp–L-Trp)·C2H6SO] and cyclo(L-Trp–L-Pro) have been investigated with X-ray crystallographic and spectroscopic methods. Cyclo(L-tryptophanyl-L-tryptophanyl)·DMSO solvate crystallized in the space group P2 12121 with cell dimensions a = 6.193(2), b = 11.545(3), c = 31.117(4) A. The crystal structure is stabilized by four hydrogen bonds (three intermolecular hydrogen bonds and one intramolecular bond). The first intermolecular bond is between the oxygen of DMSO and the nitrogen of indole ring 2, in contrast to the second intramolecular hydrogen bond between the nitrogen of indole ring 1 and the oxygen of DMSO. The two remaining intermolecular hydrogen bonds are between the nitrogens of the DKP ring and the carbonyl oxygens of the DKP ring. The values of χ1A 1 (−45.764) and χ1A 2 (67.437) indicate an extended side chain conformation for Trp residue 1 (EN) and a folded conformation for Trp residue 2. The DKP ring is more planar than in other cyclic dipeptide compounds (ϕ1 = 11.414, Ψ1 = −7.516, ϕ2 = 12.471, and Ψ2 = −8.256). In cyclo(L-Trp–L-Trp) the Cβ resonance of L-tryptophan (29.88 ppm) is shifted upfield 0.82 ppm when compared with the same resonance in cyclo(L-Trp–L-Gly) (30.7 ppm) and cyclo(L-Leu–L-Trp) (30.7 ppm). Two conformations of cyclo(Trp–Pro) crystallized in the space group P1 with cell dimensions a = 5.422(1), b = 9.902(1), c = 13.443(2) A, α = 80.42(1), β = 78.61(1), and γ = 89.13(1)°. The conformation of the backbone and the orientation of the aromatic side chains for these conformers are very similar. The DKP rings for both conformers adopt a typical boat conformation in contrast to the flattened chair conformation observed for cyclo(Tyr–Pro) and cyclo(Phe–F-Pro). The tryptophan side chains of these conformers are folded towards the diketopiperazine (DKP) ring. The pyrrolidine ring for conformer 1 can be described as an envelope (Cs–Cβ-endo) conformation in contrast to the pyrrolidine ring symmetry for conformer 2 which is an intermediate between Cs and C2 rather than pure Cs for the proline ring with Cβ-endo and Cγ-exo with respect to C′. The two prolyl rings are puckered at the β-carbon atoms which deviate from the best planes defined by the four remaining atoms. The crystal structures are stabilized by four intermolecular hydrogens bonds. An intermolecular bond between the nitrogen of the indole ring (conformer 1) and the carbonyl oxygen of the DKP ring (conformer 2) was observed. The second hydrogen bond is between the nitrogen of the indole ring (conformer 2) and the carbonyl oxygen of the DKP ring (conformer 1). The last two hydrogens involve the carbonyl oxygens of the DKP rings and the nitrogens of the DKP rings [carbonyl oxygen of DKP ring (conformer 1)––––nitrogen of DKP ring (conformer 2); nitrogen of DKP ring (conformer 1)––––––carbonyl oxygen of DKP ring (conformer 2)].

Conformational Study of Structurally Constrained 18-Membered Cyclic Peptide Containing N,N′-Ethylene-Bridged-(S)-Alanyl-(S)-Alanine

Abstract The conformation of cyclo[(2S,3′S)-2-(3′-benzyl-2′-oxopiperazin-1′-yl)-3-phenyl-propanoyl-glycyl]2 crystallized with two water molecules (C44H46N6O6 2H2O) is compared with its solution structure and those of cyclo[(2S, 3′S)-2-(3′-methyl-2′-oxopiperazin-1′-yl)-propanoyl-glycyl]2.

Solution conformation of c-[Gln-Trp-Phe-Gly-Leu-Met], a NK-2 tachykinin antagonist.

The conformation of cyclo-[Gln-Trp-Phe-Gly-Leu-Met], a potent tachykinin antagonist selective for the NK-2 receptor, has been studied by 1H NMR spectroscopy in DMSO-d6 and in a DMSO-d6/H2O cryoprotective mixture in the temperature range 280-320 K. The NMR data cannot be interpreted on the basis of a single ordered conformation. An exhaustive search, based mainly on missing NOEs among skeleton protons, yields a description of the conformational state in solution consisting of a few interconverting structures that can explain all observed NMR parameters. The relative position of the side chains of key residues may be interpreted in terms of bioactive conformations.

The conformation of cyclo-[(R)-cysteinyl-(R)-cysteine] in solution

Cyclo[( R)-Cysteinyl-( R)-Cysteine]; Conformation; Molecular Modelling; NMR; Peptide The conformation in solution of the conformationally constrained cyclic dipeptide N-BOC-[cyclo-(R)-cysteinyl-(R)-cysteine] t-butyl ester is investigated by NMR and molecular mechanics techniques. The compound is found to exist as two slowly interconverting conformations in chloroform, both of which have a cis amide bond.

Cyclodipeptides: Structure and conformation of cyclo(tyrosyl-prolyl)

The structure and conformation of the cyclodipeptide, cyclo(Tyrosyl-Prolyl), cyclo(Tyr-Pro) have been investigated with X-ray crystallographic and spectroscopic methods. Two conformations of cyclo(Tyr-Pro) crystallized in the space groupP21212 with cell dimensionsa=11.890(3),b=12.057(1),c=18.528(4). Both these conformations are uncommon for cyclodipeptides containing a proline residue. The tyrosyl side chains of these conformers are folded towards the diketopiperazine (DKP) ring. The DKP ring adopts a flattened chair conformation in contrast to the typical boat conformation generally observed for DKP rings. The conformation of the pyrrolidine ring can be described as a pseudo C2 symmetrical twist. One intermolecular hydrogen bond was observed for each of the two conformations of cyclo(Tyr-Pro). The hydrogen of the hydroxyl group of the tyrosyl residue is hydrogen bonded to the oxygen of the carbonyl group of the diketopiperazine ring, i.e., the carbonyl group originating from the tyrosyl residue. NMR spectroscopic studies indicated a different conformation for cyclo(Tyr-Pro) in solution similar to the generally observed conformation of cyclodipeptides, i.e., extended aromatic side chain and boat conformation for the DKP ring.

Conformational study of cyclo[D-Trp-D-Asp-Pro-D-Val-Leu], an endothelin-A receptor-selective antagonist

The conformation of cyclo[D-Trp-D-Asp-Pro-D-Val-Leu], (BQ123), an endothelin-A receptor-selective antagonist, has been studied in 20% acetonitrile in water by CD and NMR spectroscopy. CD studies showed the peptide adopted a similar, constrained conformation in both water alone and 20% acetonitrile in water. NMR spectra showed the proline residue to be in the trans conformation and 2 of the NH protons to exchange slowly with the solvent, indicating hydrogen bonding. Structural constraints derived from the NMR spectra were used to define the conformation in molecular dynamics simulations. A single backbone conformation is observed for the cycle, comprising a β type II turn and a γ′ turn.

Structure and conformation of peptides containing the sulfonamide junction II. Synthesis and conformation of cyclo[‐MeTau‐Phe‐DPro‐

By applying the method of amino-acyl incorporation to sulfonamido peptides, cyclo(-MeTau-Phe-DPro-) 3 has been synthesized in high yield starting from Z-MeTau-Phe-Pro-OH. The crystal structure and the molecular conformation of 3 have been determined. Crystals are orthorhombic, s.g. P2(1)2(1)2(1), with a = 5.454, b = 13.486, c = 24.025 A. The structure has been solved by direct methods and refined to R = 0.039 for 1974 reflections with I greater than 1.5 sigma (I). The 10-measured cyclopeptide adopts a backbone conformation in the crystals characterized by Phe-DPro and DPro-MeTau peptide bonds in trans and cis conformation, respectively. Both the peptide bonds deviate significantly from planarity and the corresponding [delta omega[ values are ca. 12 degrees. The sulfonamide SO2NH junction adopts a cisoidal conformation with a C alpha 1-S1-N2-C alpha 2 torsion angle of 70.8 degrees. 13C n.m.r. data show that the trans geometry at the Phe-DPro junction found in the crystals is retained in DMSO solution. The 10-membered ring of 3 is characterized by a pseudo mirror-plane passing through the Phe nitrogen and the DPro carbonylic carbon. The DPro ring adopts a half-chair conformation. The Phe side chain conformation corresponds to the statistically most favored g- rotamer (chi 1 = -68.6 degrees). The crystal packing is characterized by a weak intermolecular hydrogen bond between NH group and the MeTau O1' oxygen.

N.m.r studies of internal mobility in a cyclic tetrapeptide.

The conformation of cyclo(D-Phe-D-Pro-Ala-Pro) is reported. Measurements of spin-lattice relaxation in the rotating frame indicate that this peptide is conformationally less mobile on the microsecond time scale than larger cyclic peptides previously studied. Libration of the Pro-Ala and Pro-Phe peptide bond planes is suggested as the source of the small exchange contributions to 1/T1p.

N.m.r. studies on the conformation of cyclo(‐l‐Trp‐l‐His) in solutions

N.m.r. studies on the conformations of cyclo(‐l‐Trp‐l‐His) in acidic and basic D2O and DMSO solutions are presented here. The detailed conformational analysis of the cyclodipeptide molecule is based on 1H chemical shifts, spin‐spin coupling constants and NOE measurements. The conformational analysis consists of the following steps: 1) Calculations of the allowed {χn} states of the peptide molecule, (an allowed {χn} state is characterized by defining the two torsional angles χ1 and χ2 for each amino acid residue, which does not violate the excluded volume criteria). 2) Calculations of the induced chemical shifts of the His H5 and Hβ resonances arising from the indole and imidazole ring current effects, in the various allowed {χn} states and the comparison of the calculated and measured chemical shifts of the above resonances. 3) The conformation of the DKP ring and the distribution of the relative populations among the three rotational isomers of each of the side chains were estimated from the measured coupling constants. Finally, the NOE measurements enabled us to determine the various pairs of protons which are spatially in close proximity to each other.

The conformation of cyclo[l-pro-l-leu-l-val-(gly)thz-(gly)thz], a dolastatin 3 analog, in the crystalline and solution states

Cyclo[L-Pro-L-Leu-L-Val-(gly)Thz-(gly)Thz], (1), has been prepared in high yield using pentafluorophenol in the ring closure reaction. This dolastatin 3 analog has been subjected to crystal structure analysis (space-group P6 5, a = b = 34.897(9), c = 24.611(10)Å, asymmetric unit contents:(C 26H 35N 7O 5S 2)4·(C 7H 8)7·(CH 30H) 4, ϱ calc = 1.202gcm-3.) and solution (CDCl 3 and DMSO-d 6) studies using 1H- and 13C-NMR techniques. The molecule has been found to adopt a clearly preferred conformation both in the crystal and in solution. The conformation contains a cis (gly)Thz-Pro peptide bond and two intramolecular hydrogen bonds, one from Leu-NH to a thiazole endocyclic nitrogen atom and the other from a (gly)Thz-NH to the Leu-C=O. The results of this study not only demonstrate that the conformation of (1) is very similar in the crystal and solution, but also provide conclusive evidence that the conformation proposed by Bernier, et al 4. earlier is incorrect. The crystal packing demonstrates that (1) is a very hydrophobic cyclopeptide with a tendency to self associate. In the crystal (1) associates via systematic hydrogen bonding to form a network of interlocking hydrophobic tubes filled with toluene molecules. The solvent molecules migrate out of the crystals on exposure to air resulting in fragmentation.

Structure and conformation of cyclo(-L-phenylalanyl-L-prolyl-D-alanyl-), form II of a synthetic cyclic hexapeptide

Structure and conformation of cyclo(-L-phenylalanyl-L-prolyl-D-alanyl-), form II of a synthetic cyclic hexapeptide

Cyclic dipeptides containing proline, the crystal structure and conformation of cyclo(-L-Phe-L-Pro-)

Cyclic dipeptides containing proline, the crystal structure and conformation of cyclo(-<scp>L</scp>-Phe-<scp>L</scp>-Pro-)

ChemInform Abstract: PEPTIDE CONFORMATIONS. 22. THE CONFORMATION OF CYCLO(PRO2‐(NB)GLY) IN CRYSTAL AND SOLUTION BY X‐RAY ANALYSIS AND ONE‐ AND TWO‐DIMENSIONAL NMR SPECTROSCOPY

Chemischer InformationsdienstVolume 14, Issue 18 Physical Organic Chemistry ChemInform Abstract: PEPTIDE CONFORMATIONS. 22. THE CONFORMATION OF CYCLO(PRO2-(NB)GLY) IN CRYSTAL AND SOLUTION BY X-RAY ANALYSIS AND ONE- AND TWO-DIMENSIONAL NMR SPECTROSCOPY H. KESSLER, Search for more papers by this authorR. SCHUCK, Search for more papers by this authorR. SIEGMEIER, Search for more papers by this authorJ. W. BATS, Search for more papers by this authorH. FUESS, Search for more papers by this authorH. + FOERSTER, Search for more papers by this author H. KESSLER, Search for more papers by this authorR. SCHUCK, Search for more papers by this authorR. SIEGMEIER, Search for more papers by this authorJ. W. BATS, Search for more papers by this authorH. FUESS, Search for more papers by this authorH. + FOERSTER, Search for more papers by this author First published: May 3, 1983 https://doi.org/10.1002/chin.198318061Read the full textAboutPDF 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 Share a linkShare onEmailFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume14, Issue18May 3, 1983 RelatedInformation

ChemInform Abstract: PEPTIDE CONFORMATION. 12. CONFORMATION OF CYCLO‐(L‐PRO3) IN SOLUTION

Chemischer InformationsdienstVolume 13, Issue 6 Natural Products ChemInform Abstract: PEPTIDE CONFORMATION. 12. CONFORMATION OF CYCLO-(L-PRO3) IN SOLUTION H. KESSLER, H. KESSLERSearch for more papers by this authorA. FRIEDRICH, A. FRIEDRICHSearch for more papers by this authorW. E. HULL, W. E. HULLSearch for more papers by this author H. KESSLER, H. KESSLERSearch for more papers by this authorA. FRIEDRICH, A. FRIEDRICHSearch for more papers by this authorW. E. HULL, W. E. HULLSearch for more papers by this author First published: February 9, 1982 https://doi.org/10.1002/chin.198206326AboutPDF 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 Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume13, Issue6February 9, 1982 RelatedInformation

Interactions of cyclic hexapeptide cyclo(Pro-Sar-Sar) 2 with small molecules

N.m.r. and c.d. spectroscopy have been used to study the interactions of cyclic hexapeptide cyclo(Pro-Sar-Sar) 2 with metal ions and ammonium ions. Cyclo(Pro-Sar-Sar) 2 was found to form complexes with Li +, K −, Ba 2+ and Cu 2+, accompanying the conformational change into a single conformer, and the conformation of cyclo(Pro-Sar-Sar) 2 in the Li +-complex was different from that in the Cu 2+-complex. These findings indicate conformational flexibility of cyclo(Pro-Sar-Sar) 2. The equilibrium constant for the complexation with Li + was 2.3 × 10 2l mol −1, and cyclo(Pro-Sar-Sar) 2 adopted an asymmetric conformation in the complex. The addition of α-amino acid ester hydrochloride also caused the conformational change of cyclo(Pro-Sar-Sar) 2), but in this case it did not converge into a single conformation. This type of interaction was strengthened with aromatic α-amino acid ester hydrochloride due to the aromatic-amide interactions. Finally, the rates of exchange between unbound α-amino acid ester hydrochlorides and those complexed with cyclo(Pro-Sar-Sar) 2 were found to be different, according to the nature of α-amino acid.

Crystal structure and conformation of cyclo-(glycyl-D-leucyl-L-leucyl)2

Crystal structure and conformation of cyclo-(glycyl-D-leucyl-L-leucyl)2

Crystal structure and conformation of the cyclic hexapeptide cyclo-(Gly-L-Pro-D-Ala)2

The crystal structure and conformation of cyclo-(Gly-L-Pro-D-Ala)/sub 2/, C/sub 20/H/sub 30/N/sub 6/O/sub 6/, has been determined by single-crystal x-ray diffraction analysis. The crystals have the symmetry of the orthorhombic space group P2/sub l/2/sub l/2/sub l/ with a = 9.389 (6), b = 10.379 (8), and c = 22.006 (16) A. The structure was solved by direct methods and refined to a final R of 0.055 on 1575 unique reflections. The hexapeptide shows significant deviation from internal twofold symmetry. This asymmetric conformer apparently optimized one single 4 ..-->.. l transannular hydrogen bond at the expense of other possible interactions. Conformation angles are compared with those obtained by CD and NMR techniques, and bond distances are discussed. This hexapeptide contains two type II ..beta.. turns. All of the peptide bonds are in the transconformation and the C/sub ..gamma../ atom in one of the proline rings is disordered. 5 tables, 3 figures.

Solution conformation and hydrolytic activity of cyclo(D‐leu‐L‐His)

AbstractIt has been reported previously that a cyclic dipeptide, cyclo(D‐Leu‐L‐His), showed a high hydrolytic activity toward a hydrophobic ester, p‐nitrophenyl laurate. In order to determine the reason for the high catalytic activity, the conformation of cyclo(D‐Leu‐L‐His) in aqueous solution was investigated by nuclear magnetic resonance and circular dichroism spectroscopy and compared with the conformation of cyclo(L‐Leu‐L‐His), which was nearly inactive in otherwise the same conditions for the hydrolysis. It was demonstrated that the spatial arrangement of the hydrophobic isobutyl group of the D‐leucyl residue and of the nucleophilic imidazolyl group of the L‐histidyl residue in cyclo(D‐Leu‐L‐His) matches very well with the long acyl chain and the active ester function of p‐nitrophenyl laurate. On the other hand, in cyclo(L‐Leu‐L‐His) the hydrophobic and the nucleophilic pendant groups are too close with each other to cooperate intramolecularly for the hydrolysis. It was concluded that the different steric structures of the diastereomers can explain the large difference of the catalytic activities.

Structure and conformation of cyclo(tri-L-prolyl) in the crystalline state

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStructure and conformation of cyclo(tri-L-prolyl) in the crystalline stateMary E. Druyan, Charles L. Coulter, Roderich Walter, G. Kartha, and G. K. AmbadyCite this: J. Am. Chem. Soc. 1976, 98, 18, 5496–5502Publication Date (Print):September 1, 1976Publication History Published online1 May 2002Published inissue 1 September 1976https://doi.org/10.1021/ja00434a016RIGHTS & PERMISSIONSArticle Views54Altmetric-Citations50LEARN 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 (779 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts