Cyclic Peptides of Sarcosine. Syntheses and Conformation.

Titlestad, Kirsten

doi:10.3891/acta.chem.scand.29b-0153

Cited by 39 publications

(24 citation statements)

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“…[17, 21a, b] The distorted boat-like conformer observedi nt he crystal structure of cyclo(d-Phe-Pro-Sar-Gly) is similar to that observed for cyclotetrasarcosyl and cyclo(Sar-Gly) 2 ,i nw hich a cis-peptide bond is present at each end. [23] Again, as imilarc onformation is observed for the recently isolated Endolide A, albeit the two trans-peptide bonds are of the opposite orientation. [24] Examples of 13-membered CTPs bearing non-cyclic b-AAs, more flexible than 2-Abz, have provenc onformationally homogeneous in some instances, but heterogeneous in others.…”

Section: Resultsmentioning

confidence: 58%

Crystal and NMR Structures of a Peptidomimetic β‐Turn That Provides Facile Synthesis of 13‐Membered Cyclic Tetrapeptides

Cameron

Squire

Edwards

et al. 2017

Chemistry An Asian Journal

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Herein we report the unique conformations adopted by linear and cyclic tetrapeptides (CTPs) containing 2-aminobenzoic acid (2-Abz) in solution and as single crystals. The crystal structure of the linear tetrapeptide H N-d-Leu-d-Phe-2-Abz-d-Ala-COOH (1) reveals a novel planar peptidomimetic β-turn stabilized by three hydrogen bonds and is in agreement with its NMR structure in solution. While CTPs are often synthetically inaccessible or cyclize in poor yield, both 1 and its N-Me-d-Phe analogue (2) adopt pseudo-cyclic frameworks enabling near quantitative conversion to the corresponding CTPs 3 and 4. The crystal structure of the N-methylated peptide (4) is the first reported for a CTP containing 2-Abz and reveals a distinctly planar 13-membered ring, which is also evident in solution. The N-methylation of d-Phe results in a peptide bond inversion compared to the conformation of 3 in solution.

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Section: Resultsmentioning

confidence: 58%

Crystal and NMR Structures of a Peptidomimetic β‐Turn That Provides Facile Synthesis of 13‐Membered Cyclic Tetrapeptides

Cameron

Squire

Edwards

et al. 2017

Chemistry An Asian Journal

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“…We will see thereafter that this approach (analysis of bonded and electrostatic terms) is also validated by three other experimental and theoretical conformationals studies. These rules successfully predict the reported conformations of cyclotetrapeptides such as cyclo(Sar) 4 and cyclo(SarGly) 2 , which both contain N-methylations and which are found as TCTC according to Titlestad 39 (Table IV).…”

Section: Backbone Conformation As Determined From Molecular Mechanicsmentioning

confidence: 97%

Predicting the conformational states of cyclic tetrapeptides

et al. 2003

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Biologically active cyclic tetrapeptides, usually found among fungi metabolites, exhibit phytotoxic or cytostatic activities that are likely to be governed by specific conformations adopted in solution. For conformational studies and drug design, there is a strong interest in using fast and reliable methods to determine correctly the conformational population of cyclotetrapeptides. We show here that standard molecular mechanics computational approach gives satisfactory results. The method was validated step by step by experimental data either obtained after synthesis and NMR analysis, or found in the literature. The cyclo(Gly)(4), cyclo(Ala)(4), cyclo(Sar)(4), and cyclo(SarGly)(2) peptides were used to evaluate the prediction of the peptide backbone conformation, and the detailed conformational analysis of tentoxin, a natural phytotoxic cyclotetrapeptide in which N-alkylated peptide bonds alternate with regular secondary ones, was used to validate the computation of conformers proportions. From the knowledge of an initial cyclic primary structure and of the D or L configuration of the amino acids, we show that it is possible to determine the exact orientation of carbonyl groups and to predict the nature of conformers present in solution. The proportion of each conformer can be inferred from a statistical thermodynamics approach by using the potential energy values of each conformer, computed by molecular mechanics methods with the TRIPOS force field, which allowed us to account for the solvent. The solvent contribution was processed by two different methods according to the nature of the interactions: whether through the dielectric constant introduced in the electrostatic potential, when interaction with solute molecules are weak or negligible, or through the computation of free energy of solvation using the algorithm SILVERWARE for solvents explicitly interacting with the solute. When applied to tentoxin, this conformational analysis yielded results in very good agreement with the experimental data reported by Pinet et al. (Biopolymers, 1995, Vol. 36, pp. 135-152), on both the nature of existing conformers and their relative proportions, whatever the nature of the considered solvent.

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“…Like TBCN, cyclic peptides are also attractive candidates for artificial receptors because they have a rigid peptide backbone that forms a cavity and provides binding sites suitable for guest molecules. N ‐methylated cyclic triglicine has a C 3 symmetry conformation (crown form) elucidated by NMR30, 31 and X‐ray crystallography studies 32. Hioki et al33 reported the synthesis of N‐substituted cyclic triglycines using N , N ′, N ″‐triallyl‐cyclo‐triglicine as a scaffold.…”

Section: Introductionmentioning

confidence: 99%

Identification of a NCR⁺/NKG2D⁺/LFA‐1^low/CD94⁻ immature human NK cell subset

et al. 2009

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CD56bright natural killer (NK) cells, generated in vitro from CD34 1 hematopoietic progenitor cells, were characterized after a 30-day culture with flt3 ligand plus IL-15. Virtually, all CD56 bright cells expressed CD117, CD25, natural cytotoxicity receptors (NCRs), NKG2D, CD161, and CD244, while only a subset expressed CD18-CD11a (LFA-1), and CD94 molecule, defining an immature CD56 and activatory function that finely control their functional activities. In particular, they express inhibitory receptors for MHC class I (MHC-I) molecules, named killer cell immunoglobulin (Ig)-like receptors (KIRs) and C-type lectin CD94-CD159a, and many triggering molecules like NKp30, NKp44, NKp46, (called natural cytotoxicity receptors, NCRs), NKG2D, CD161, and CD244 (1-4). The majority of peripheral blood (PB) human NK cells are characterized by a phenotype with a low density expression of CD56 (CD56 dim ) and a high expression of CD16 (CD16 bright ), whereas a minority (approximately 5-10%) shows a bright expression of CD56 (CD56 bright ). This latter NK subset presents relatively high expression of some cytokine receptors (CD117 and CD25), lymph node homing receptors (CD62L and CCR7) and the CD94-CD159a heterodimeric inhibitory receptor. Moreover, differently from the well-known CD56 dim /CD16 bright cells, only a small percentage of the CD56 bright subset expresses KIR inhibitory receptors (5-10%) and CD16 dim (20-30%) while, in the majority, these antigens are not expressed (5). On the other hand, CD56bright NK cells are widely expressed in lymphoid tissues (6) and can be generated from CD34 1 cells when cultured with combinations of flt-3 ligand (FL) or stem cell factor plus IL-15 or IL-2 (7-10). During their development, NK cells sequentially acquire many different antigens and some of them allow to distinguish intermediate stages of NK cell differentiation. We had already taken advantage of CD161 antigen expression to define an immature CD161 1 /CD56 2 subset able to kill Jurkat cells via a TRAIL-dependent mechanism (3,11). When cultured with IL-12, this NK cell subset began to express CD56 molecule and became cytotoxic against K562 cells, thus suggesting a

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Cyclic Peptides of Sarcosine. Syntheses and Conformation.

Cited by 39 publications

References 0 publications

Crystal and NMR Structures of a Peptidomimetic β‐Turn That Provides Facile Synthesis of 13‐Membered Cyclic Tetrapeptides

Crystal and NMR Structures of a Peptidomimetic β‐Turn That Provides Facile Synthesis of 13‐Membered Cyclic Tetrapeptides

Predicting the conformational states of cyclic tetrapeptides

Identification of a NCR⁺/NKG2D⁺/LFA‐1^low/CD94⁻ immature human NK cell subset

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Cyclic Peptides of Sarcosine. Syntheses and Conformation.

Cited by 39 publications

References 0 publications

Crystal and NMR Structures of a Peptidomimetic β‐Turn That Provides Facile Synthesis of 13‐Membered Cyclic Tetrapeptides

Crystal and NMR Structures of a Peptidomimetic β‐Turn That Provides Facile Synthesis of 13‐Membered Cyclic Tetrapeptides

Predicting the conformational states of cyclic tetrapeptides

Identification of a NCR+/NKG2D+/LFA‐1low/CD94− immature human NK cell subset

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Identification of a NCR⁺/NKG2D⁺/LFA‐1^low/CD94⁻ immature human NK cell subset