Melanin Concentrating Hormone Analogs: Contraction of the Cyclic Structure. III. CD Spectroscopic Study

1992 ◽  
Vol 57 (3) ◽  
pp. 614-620
Author(s):  
Ivo Frič ◽  
Michal Lebl ◽  
Victor J. Hruby
Keyword(s):  
Amino Acid ◽  
Spectroscopic Study ◽  
Spectral Properties ◽  
Membered Ring ◽  
Helical Conformation ◽  
Amino Acid Residues ◽  
Cyclic Structure ◽  
Cd Spectra ◽  
Melanin Concentrating Hormone ◽  
Hormone Analogs

A comparison of the CD spectra of MCH analogs differing in length but containing a heterodetic ring of the same size (compounds I, IV and VII or III, VI and IX) reveals that a conformational change occurs upon elongating the peptide chain from thirteen to seventeen amino-acid residues. The 5-17 fragments appear to prefer a β-turn conformation, whereas the 1-17 full-sequence peptides prefer α-helical conformation. Peptides containing seventeen-membered ring exhibit greater conformational adaptability (the incorporation of their cyclic moiety into an ordered conformation being easier) than those containing a twenty-six-membered ring. Spectral properties of the twenty-three-membered heterodetic ring in peptides II and V indicate that they do not possess highly ordered conformation.

Synthesis and conformation of sequential basic polypeptides with branched and linear side chains

1985 ◽  
Vol 50 (12) ◽  
pp. 2925-2936 ◽  
Author(s):  
Štěpánka Štokrová ◽  
Jan Pospíšek ◽  
Jaroslav Šponar ◽  
Karel Bláha
Keyword(s):  
Amino Acid ◽  
Salt Concentration ◽  
Salt Solution ◽  
Theoretical Work ◽  
Side Chain ◽  
Amino Acid Residues ◽  
Cd Spectra ◽  
Low Salt ◽  
Conformational Freedom ◽  
Basic Polypeptides

Polypeptides (Lys-X-Ala)n and (Lys-X-Gly)n in which X represents residues of isoleucine and norleucine, respectively, and polypeptide (Tle-Lys-Ala)n, were synthesized via polymerization of 1-hydroxysuccinimidyl esters of the appropriate tripeptides to complete previously studied series. Circular dichroism (CD) spectra of the respective polymers were measured as a function of pH and salt concentration of the medium. The results were correlated with those obtained previously with the same series containing different amino acid residues at the X-position. The helix forming ability of the polypeptides (Lys-X-Ala)n with linear X side chain was found to be independent of the length. In the series (Lys-X-Gly)n the unordered conformation was the most probable one except (Lys-Ile-Gly)n. This polymer assumed the β conformation even in low salt solution at neutral pH. An agreement with some theoretical work concerned with the restriction of conformational freedom of amino acid residue branching at Cβ atom with our experimental results is evident.

scholarly journals Increasing protein stability by engineering the n → π* interaction at the β-turn

2020 ◽  
Vol 11 (35) ◽  
pp. 9480-9487 ◽  
Author(s):  
Bhavesh Khatri ◽  
Puja Majumder ◽  
Jayashree Nagesh ◽  
Aravind Penmatsa ◽  
Jayanta Chatterjee
Keyword(s):  
Amino Acid ◽  
Protein Stability ◽  
Structural Stability ◽  
Direct Consequence ◽  
Helical Conformation ◽  
Amino Acid Residues ◽  
Π Interactions

Amino acid residues adopt a right-handed α-helical conformation with increasing strength of the n → π* interaction. We also demonstrate a direct consequence of n → π* interactions on enhancing the structural stability of proteins.

scholarly journals Conformation of dehydropentapeptides containing four achiral amino acid residues – controlling the role of L-valine

2014 ◽  
Vol 10 ◽  
pp. 660-666 ◽  
Author(s):  
Michał Jewgiński ◽  
Joanna Krzciuk-Gula ◽  
Maciej Makowski ◽  
Rafał Latajka ◽  
Paweł Kafarski
Keyword(s):  
Amino Acid ◽  
Nmr Spectroscopy ◽  
Secondary Structure ◽  
Helical Conformation ◽  
Structural Studies ◽  
Amino Acid Residues ◽  
Terminal Position ◽  
Dehydroamino Acid

Structural studies of pentapeptides containing an achiral block, built from two dehydroamino acid residues (ΔZPhe and ΔAla) and two glycines, as well as one chiral L-Val residue were performed using NMR spectroscopy. The key role of the L-Val residue in the generation of the secondary structure of peptides is discussed. The obtained results suggest that the strongest influence on the conformation of peptides arises from a valine residue inserted at the C-terminal position. The most ordered conformation was found for peptide Boc-Gly-ΔAla-Gly-ΔZPhe-Val-OMe (3), which adopts a right-handed helical conformation.

scholarly journals Capsid Protein C of Tick-Borne Encephalitis Virus Tolerates Large Internal Deletions and Is a Favorable Target for Attenuation of Virulence

2002 ◽  
Vol 76 (7) ◽  
pp. 3534-3543 ◽  
Author(s):  
Regina M. Kofler ◽  
Franz X. Heinz ◽  
Christian W. Mandl
Keyword(s):  
Amino Acid ◽  
Capsid Protein ◽  
Protein C ◽  
Alpha Helix ◽  
Helical Conformation ◽  
Amino Acid Residues ◽  
Structural Class ◽  
Hydrophobic Domain ◽  
Tick Borne Encephalitis ◽  
Subviral Particles

ABSTRACT Deletions ranging in size from 4 to 21 amino acid residues were introduced into the capsid protein of the flavivirus tick-borne encephalitis (TBE) virus. These deletions incrementally affected a hydrophobic domain which is present at the center of all flavivirus capsid protein sequences and part of which may form an amphipathic alpha-helix. In the context of the full-length TBE genome, the deletions did not measurably affect protein expression and up to a deletion length of 16 amino acid residues, corresponding to almost 17% of mature protein C, viable virus was recovered. This virus was strongly attenuated but highly immunogenic in adult mice, revealing capsid protein C as a new and attractive target for the directed attenuation of flaviviruses. Apparently, the larger deletions interfered with the correct assembly of infectious virus particles, and this disturbance of virion assembly is likely to be the molecular basis of attenuation. However, all of the mutants carrying large deletions produced substantial amounts of subviral particles, which as judged from density gradient analyses were identical to recombinant subviral particles as obtained by the expression of the surface proteins prM and E alone. The structural and functional flexibility of protein C revealed in this study and its predicted largely alpha-helical conformation are reminiscent of capsid proteins of other enveloped viruses, such as alphaviruses (N-terminal domain of the capsid protein), retroviruses, and hepadnaviruses and suggest that all of these may belong to a common structural class, which is fundamentally distinct from the classical β-barrel structures of many icosahedral viral capsids. The possibility of attenuating flaviviruses by disturbing virus assembly and favoring the production of noninfectious but highly immunogenic subviral particles opens up a promising new avenue for the development of live flavivirus vaccines.

Melanin concentrating hormone analogs: contraction of the cyclic structure. 1. Agonist activity

1988 ◽  
Vol 31 (5) ◽  
pp. 949-954 ◽  
Author(s):  
Michal Lebl ◽  
Victor J. Hruby ◽  
Ana M. de L. Castrucci ◽  
Maria A. Visconti ◽  
Mac E. Hadley
Keyword(s):  
Agonist Activity ◽  
Cyclic Structure ◽  
Melanin Concentrating Hormone ◽  
Hormone Analogs

Fine tuning of the spectral properties of LH2 by single amino acid residues

2008 ◽  
Vol 96 (2) ◽  
pp. 145-151 ◽  
Author(s):  
Martina V. Silber ◽  
Günther Gabriel ◽  
Brigitte Strohmann ◽  
Adela Garcia-Martin ◽  
Bruno Robert ◽  
...  
Keyword(s):  
Amino Acid ◽  
Spectral Properties ◽  
Fine Tuning ◽  
Single Amino Acid ◽  
Amino Acid Residues

Alkaloids of the Australian Rutaceae: Evodia xanthoxyloides F.Muell. V. A note on the constitution of evolidine

1955 ◽  
Vol 8 (4) ◽  
pp. 552 ◽  
Author(s):  
RM Curtis
Keyword(s):  
Amino Acid ◽  
Amino Acid Residues ◽  
Cyclic Structure ◽  
New Formula

Evolidine, formerly described as an alkaloid, is shown to be a peptide. A new formula C38H58O9N8 having a cyclic structure and containing seven amino acid residues is proposed.

Conformation of branched polypeptides based on poly(L-lysine): The effect of terminal amino acids in the branches

1985 ◽  
Vol 50 (1) ◽  
pp. 228-244 ◽  
Author(s):  
Hana Votavová ◽  
Ferenc Hudecz ◽  
Judit Kajtár ◽  
Jaroslav Šponar ◽  
Karel Bláha ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Ionic Strength ◽  
Glutamic Acid ◽  
Amino Acid Residues ◽  
Ordered Structure ◽  
Cd Spectra ◽  
Helix Formation ◽  
Terminal Amino ◽  
Α Helix

CD Spectra of branched polypeptides based on poly(L-lysine) and containing three DL-alanine residues and one to three other L- or D-amino acid residues in the branches were measured in water, water-methanol and water-trifluoroethanol mixtures. In aqueous solutions dependence of the CD spectra on pH and ionic strength was studied. The effect of branch elongation was followed mainly with compounds containing glutamic acid. One terminal D-amino acid residue and also an extension by two L- or D-amino acid residues does not hinder the α-helix formation in the backbone but affects the conditions of its formation. In polypeptides with three L- or D-amino acids additional α-helical segments in the branches are assumed to be formed. For branches with L-amino acids the CD curves express additively the contributions of both helical components, in the case of D-amino acids the increasing population of the ordered structure in branches is manifested by compensation of dichroic contribution of the L-amino acid backbone leading even to enantiomorphous curves.

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