CD Spectra and Cyclization of Linear Pentapeptides as Gramicidin S Precursors with a Benzyloxycarbonyl Group on the Side Chain of Orn Residue

1993 ◽  
Vol 66 (10) ◽  
pp. 3113-3115 ◽  
Author(s):  
Makoto Tamaki ◽  
Sadatoshi Akabori ◽  
Ichiro Muramatsu
Keyword(s):  
Side Chain ◽  
Cd Spectra ◽  
Gramicidin S

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.

Enzymatic Synthesis of Four Stereoisomers of 7-0xo-biopterin and Determination of the Absolute Structure of Ichthyopterin

Pteridines ◽  
1990 ◽  
Vol 2 (3) ◽  
pp. 151-156 ◽  
Author(s):  
Shin Ichiro Takikawa ◽  
Sadao Matsuura
Keyword(s):  
Enzymatic Synthesis ◽  
Side Chain ◽  
Side Chains ◽  
Enzymatic Conversion ◽  
Cd Spectra ◽  
The Absolute ◽  
Chiral Centers ◽  
Absolute Structure

Summary Enzymatic conversion of stereoisomers of biopterin (3a-d) to the 7-oxo-biopterin isomers (4a-d) was performed with a new pterin 7-oxidase extracted from carp skin. The chiral centers of the 6-side chains of biopterin isomers were preserved during the conversion, and the four possible stereoisomers of 7-oxo-biopterin (4a-d) were obtained from the corresponding biopterin isomers (3a-d). HPLC and CD spectra studies showed that natural ichthyopterin is 2-amino-6-(L-erythro-1',2' -dihydroxypropyl)-4, 7(3H,8H)-pteridinedione (4a) which has the same L-erythro structure at the side chain as natural biopterin (3a). This fact suggests that ichthyopterin is biologically derived from biopterin in these fishes.

Structures and reaction mechanisms of riboflavin synthases of eubacterial and archaeal origin

2005 ◽  
Vol 33 (4) ◽  
pp. 780-784 ◽  
Author(s):  
M. Fischer ◽  
W. Römisch ◽  
B. Illarionov ◽  
W. Eisenreich ◽  
A. Bacher
Keyword(s):  
Escherichia Coli ◽  
Reaction Mechanisms ◽  
Nmr Spectra ◽  
Common Ancestor ◽  
Sequence Similarity ◽  
Side Chain ◽  
Cd Spectra ◽  
Riboflavin Biosynthesis ◽  
Significant Sequence Similarity ◽  
E Coli

The biosynthesis of one riboflavin molecule requires one molecule of GTP and two molecules of ribulose 5-phosphate as substrates. GTP is hydrolytically opened, converted into 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione by a sequence of deamination, side chain reduction and dephosphorylation. Condensation with 3,4-dihydroxy-2-butanone 4-phosphate obtained from ribulose 5-phosphate leads to 6,7-dimethyl-8-ribityllumazine. The dismutation of 6,7-dimethyl-8-ribityllumazine catalysed by riboflavin synthase produces riboflavin and 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione. A pentacyclic adduct of two 6,7-dimethyl-8-ribityllumazines has been identified earlier as a catalytically competent reaction intermediate of the Escherichia coli enzyme. Acid quenching of reaction mixtures of riboflavin synthase of Methanococcus jannaschii, devoid of similarity to riboflavin synthases of eubacteria and eukaryotes, afforded a compound whose optical absorption and NMR spectra resemble that of the pentacyclic E. coli riboflavin synthase intermediate, whereas the CD spectra of the two compounds have similar envelopes but opposite signs. Each of the compounds could serve as a catalytically competent intermediate for the enzyme by which it was produced, but not vice versa. All available data indicate that the respective pentacyclic intermediates of the M. jannaschii and E. coli enzymes are diastereomers. Whereas the riboflavin synthase of M. jannaschii is devoid of similarity with those of eubacteria and eukaryotes, it has significant sequence similarity with 6,7-dimethyl-8-ribityllumazine synthases catalysing the penultimate step of riboflavin biosynthesis. 6,7-Dimethyl-8-ribityllumazine synthase and the archaeal riboflavin synthase appear to have diverged early in the evolution of Archaea from a common ancestor.

scholarly journals Diastereoisomeric analogues of gramicidin S: structure, biological activity and interaction with lipid bilayers

2000 ◽  
Vol 349 (3) ◽  
pp. 747-755 ◽  
Author(s):  
Masood JELOKHANI-NIARAKI ◽  
Leslie H. KONDEJEWSKI ◽  
Susan W. FARMER ◽  
Robert E. W. HANCOCK ◽  
Cyril M. KAY ◽  
...  
Keyword(s):  
Biological Activity ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Cyclic Peptides ◽  
Cyclic Peptide ◽  
Cd Spectra ◽  
Gramicidin S ◽  
Sds Micelles ◽  
Related Approach ◽  
Relationship Of

Analogues of a structurally equivalent version of the antimicrobial decameric cyclic peptide gramicidin S, GS10 [cyclo-(Val-Lys-Leu-D-Tyr-Pro)2], were designed to study the effect of distortion in the β-sheet/β-turn structure of the cyclic peptide on its biological activity. In one approach, the hydrophobic nature of GS10 was conserved, and single amino acids in its backbone were replaced systematically with their corresponding enantiomers to give five diastereoisomeric analogues. In a related approach, a more basic and hydrophilic analogue of GS10 [cyclo-(Lys-Val-Lys-D-Tyr-Pro5-Lys-Leu-Lys-D-Tyr-Pro10)], together with two of its monosubstituted diastereoisomeric analogues (featuring D-Lys1 or D-Val2 respectively), were synthesized. CD spectra were measured in a variety of environments, i.e. aqueous, aqueous trifluoroethanol and those containing SDS micelles or phospholipid vesicles. In comparison with GS10 spectra, CD spectra of both groups of analogues in these environments exhibited structural distortion. Moreover, compared with GS10, antimicrobial and haemolytic activities of the analogues were drastically decreased, implying the existence of a threshold minimum amphipathicity for effective biological activity. However, in both groups of analogues, there was a correlation between amphipathicity and antimicrobial and haemolytic activities. In the second group of analogues, both electrostatic and hydrophobic factors were related to their antimicrobial and haemolytic activities. In order to gain an insight into the nature of the biological activity of the two classes of cyclic peptides, the relationship of their structure to interaction with lipid membranes, and the implied mechanisms, were analysed in some detail in the present study.

Circular Dichroism, Self Interaction and Side Chain Conformation of Riboflavin and Riboflavin Analogues

1972 ◽  
Vol 27 (9) ◽  
pp. 1044-1046 ◽  
Author(s):  
G. Scola-Nagelschneider ◽  
P. Hemmerich
Keyword(s):  
Circular Dichroism ◽  
Ionic Strength ◽  
Aqueous Solutions ◽  
Chain Conformation ◽  
Side Chain ◽  
Cd Spectra ◽  
Polar Solvents ◽  
Side Chain Conformation ◽  
Vibronic Transitions ◽  
Circular Dichroïsm

The CD-spectra of riboflavin and riboflavin analogues in aqueous solutions differ very little depending on pH and ionic strength, but are extremely sensitive upon solvent changes. The two bands in the region of 300 —500 nm seen in aqueous solutions are split into seven bands in less polar solvents, which can be assigned to seven vibronic transitions. The spectra may be interpreted by “through space” and “through chain” interactions of the sidechain centers of chirality with the flavin chromophore, which influence the two first π —π* transitions in different manner.

scholarly journals CD Spectra of 2,4-Dinitrophenyl Derivatives of α-Amino Acids Having Polynuclear Aromatic Group in the Side Chain. Absolute Configuration of 3-(9-Anthryl)alanine

1985 ◽  
Vol 58 (10) ◽  
pp. 3047-3048 ◽  
Author(s):  
Masao Kawai ◽  
Taketoshi Matsuura ◽  
Yasuo Butsugan ◽  
Syun Egusa ◽  
Masahiko Sisido ◽  
...  
Keyword(s):  
Amino Acids ◽  
Absolute Configuration ◽  
Side Chain ◽  
Cd Spectra ◽  
Aromatic Group ◽  
Derivatives Of
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