186 CHEMICAL NATURE OF ANTIBIOTIC SUBSTANCES 



The specific rotation of gramicidin in 95 per cent alcohol solution is 

 approximately [a]^5 _ _|_ ^o^ Qj^ analysis, it gives 62.7 per cent C, 

 7.5 per cent H, and 13.9 per cent N. The molecular weight, as 

 determined in camphor, is about 1,400. The empirical formula of 

 C74H106O14N14 has been suggested. On further study, the molecular 

 weight of gramicidin was found (911) to present an anomaly in that it 

 appeared to depend on the nature of the solvent and on the concentra- 

 tion of the solute, giving values from 600 to 1,200 j isothermal distil- 

 lation in methanol, however, indicated a molecular weight of 2,700 

 to 3,100, with an approximate formula of C146H000O2N30. It gave 

 neither free amino nor carboxyl groups j it contained 10 molecules of 

 a-amino acids, of which two or three were tryptophane residues. These 

 and a saturated aliphatic acid, with 14 to 16 carbons, account for about 

 85 to 90 per cent of the weight of the substance. Amino acids that have 

 definitely been identified are /-tryptophane, /^-leucine, /-alanine, dl- 

 valine, and glycine (345, 892). A study of the configuration of the di- 

 peptide valyvaline separated from gramicidin brought out the fact that 

 only valines of like configuration have been joined together by the bac- 

 terium (137). About 45 per cent of the a-amino acids gave the d con- 

 figuration (449, 450). An unknown hydroxyamino compound has also 

 been indicated. 



The presence of ethanolamine (2-aminoethanol-l) as a component of 

 gramicidin hydrolysates, which reacts with periodate to yield formal- 

 dehyde and NHo, has been definitely indicated (893). Actually two 

 ethanolamine residues may occur in gramicidin, since their destruction 

 during acid hydrolysis of gramicidin is considerable. The liberation of 

 some of these amino acids during hydrolysis, such as valine and trypto- 

 phane, can be measured by their availability to L. arah'mosus (139). 



Tyrocidine hydrochloride is moderately soluble in alcohol, acetic 

 acid, and pyridine ; it is sparingly soluble in water, acetone, and dioxane, 

 and is insoluble in ether and hydrocarbon solvents. An alcohol solution 

 can be diluted with water to give a clear solution containing 5 to 10 mg. 

 per milliliter; electrolytes produce an immediate precipitate. A solu- 

 tion in distilled water containing i mg. or even less per milliliter has a 

 low surface tension and behaves like a soap or detergent solution. Un- 



