Gramicidin composition

Other workers began to study the structure of gramicidin. Christensen and coworkers12 isolated crystalline tryptophane and leucine from a hydrolysate. They found no evidence for a fatty acid component and established that phenylalanine, proline and hydroxyproline were absent from a hydrolysate. These workers isolated alanine diox-pyridate from a hydrolysate and also established that gramicidin contained a compound with vicinal hydroxy and amino groups. They speculated that this compound might be serine or isoserine and proposed that gramicidin contains two tryptophane, 2 leucine, 2 or 3 alanine and 1 hydroxyamino residues or a multiple of this composition. 

Gordon, Martin and Synge18 utilized their new and elegant technique, chromatography, to establish the amino acid composition of gramicidin. They proposed a 24 unit cyclic peptide consisting of six moles each of leucine, and tryptophane, 5 moles of valine, 3 moles of alanine and 2 moles each of glycine and unknown hydroxyamino compound. 

Shamby et al. described a surface finish that consists of a water-insoluble composite of silver bromide nanoparticles and poly(4-vinylpyridinium) salts. Again, silver is released and the quarternary ammonium groups kill on contact [139], Gyomard et al. incorporated the natural antimicrobial peptide gramicidin A into a LbL matrix and were able to show, that the peptide kills Enterococcus faecalis in the surroundings when released and on the surface in immobilized form [140], It is also possible that the antimicrobial a-poly-L-lysine in the LbL layer helped a little. 

The accurate mass measurement was performed on a Micromass AutoSpec SE mass spectrometer using electrospray ionization on the triply charged ion of a cofactor-containing peptide (sample 2). Doubly charged ions of bradykinin (m/z 530.7885) and gramicidin S (m/z 571.3608) were used as calibration standards. Leu-enkeph in (MH+ at m/z 556.2771) was also included to verify the accuracy of the mass measurement. The monoisotopic molecular mass of this peptide was established by the mean [M-i-3H]3+ value obtained from four separate injections. Elemental compositions of the crosslinked residue were obtained by computer calculations. 

New York) and challenged to find a soil microbe that could destroy a bacteria. ° In 1939, he discovered a substance extracted from a soil bacillns. Tyrothricin (later showed composition of two substances, gramicidin (20%) and tyrocidine (80%), cured mice infected with pnenmococci. It was the first natural antibiotic extracted from soil bacteria, able to arrest the growth of staphylococcns, bnt proved highly toxic. 

The gramicidin family of linear polypeptides represents a biologically viable channel system of related peptides in which specific changes in amino acid composition can be correlated with cation binding selectivity and transport. The parent molecule of this family of polypeptides, gramicidin A, has the amino acid sequence shown in Fig. 1. This relatively simple molecule is probably the best characterized ion channel (both structurally and functionally) and has, to date, been the principal proving-ground for many of our ideas about the molecular nature of ion conduction in membranes. ... 

The ion selectivity of gramicidin channels can be measured either from bi-ionic potentials [21] or from the conductance ratios of single channels [16]. Both approaches give the same selectivity sequence and do not depend either on membrane composition or thickness. The ion sequence is ... 

The nuclear magnetic resonance is the most powerful technique in the composite approach, as proved by the fact that application of NMR spectroscopy has had many important results in the study of detailed spatial structures and conformational dynamics of peptides in solution. These results have had a significant impact on the understanding of physiological mechanism of action of such substances as gramicidins, oxytocin, valinomycin, etc. [for a review, see(l)]. ... 

Another homeomeric basic cyclic peptide was isolated in 1943 by Gause and Brazhnikova (220) from different strains of B. brevis. This peptide, relatively easily isolated, was called Gramicidin S., and is very close, in properties and composition, to the tyrocidine group. Hence it will be discussed with this family of peptides. 

In NMR, upon change of solvent composition from a good amide proton acceptor to trifluoroethanol, intramolecularly hydrogen-bonded or solvent-shielded protons remain unperturbed, whereas solvent-exposed protons shift upfield ( 1 ppm). The dependence on solvent composition of the chemical shifts in the cyclic peptide gramicidin S has been reported... 

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