The Arrangement of Amino Acids in Proteins

Growth of rhizobia in protein hydrolysates

Sixteen nitrogen-rich agricultural and industrial wastes and by-products, such as vegetable waste, lasora (Cordia myxa L.), meat waste, water-hyacinth (Eichhornia crassipes), and pea (Pisum sativum L.) husks were partially hydrolysed to amino acids with the help of acetic acid of 1, 5, 10, 15, and 20% concentration. In general, 10-20% acetic acid gave the highest amounts of amino acids. Each protein hydrolysate, separately or/and in proper combination, was substituted with the nutrient yeast extract in equal concentration (mg/ml) in yeast extract mannitol (YEM) medium. The growth of Rhizobium spp. was observed over a period of 5 or 7 days with determination of turbidity at 700 nm. High optical densities, but somewhat inferior to the control, were obtained in the case of medium consisting of hydrolysate of water-hyacinth, vegetable waste, pea husk, mixed leaves, and corn steep liquor substrates separately at different concentration of acid, but the medium consisting of hydrolysates of pea husk and water-hyacinth (5% acetic acid) in equal proportions showed similar growth to that with the YEM medium in the case of both Rhizobium spp.

An investigation of hydrolytic techniques for the amino acid analysis of foodstuffs

A survey of hydrolytic methods for the amino acid analysis of foods is presented and the advantages and disadvantages of the methods are discussed. Amino acids were determined after hydrolysis of the proteins with hydrochloric acid, sulphuric acid, perchloric acid, p‐toluene sulphonic acid and sodium hydroxide. The results are shown graphically using as examples a pure protein (casein) and a potential food protein of microfungal origin (Fusarium graminearum). The addition of some cation exchange resin to acids catalysed the hydrolysis of some peptide bonds containing aspartic acid, threonine, serine, glutamic acid, valine and isoleucine. Whilst several methods gave close agreement for the analysis of a pure protein, hydrolysis with 6 N‐hydrochloric acid gave the largest yield of most amino acids in food proteins. With the exception of extracted soya meal, protection of cystine prior to hydrolysis gave higher values than direct hydrolysis.

Quantitative chemical composition of peptidoglycan of Listeria monocytogenes

The qualitative and quantitative chemical composition of the peptidoglycan layer of Listeria monocytogenes cell walls was determined. The peptidoglycan layer was isolated from intact cells after treatment with sodium lauryl sulfate and digestion with Pronase. The isolated peptidoglycan contained carbohydrates which included hexose, rhamnose, and amino sugars. The amino sugar was identified as glucosamine which was present in very high micromole concentration, as compared with the amino acids, muramic acid, or diaminopimelic acid. In addition, protein and phosphorus were also present. However, the presence of teichoic acid was not detected in the peptidoglycan. Protein moiety contained a total of 18 amino acids with lysine as the N-terminal amino acid.

Comparison of Chemical Components of Cell Walls of Brucella abortus Strains of Low and High Virulence

Amino acid, carbohydrate, and lipid components of cell walls of Brucella abortus strain 19A (low virulence) and strain 2308 (high virulence) were compared by thin layer chromatography (TLC) and by use of an amino acid analyzer. A total of 15 amino acids were detected by both chromatographic methods. Each amino acid was present in greater amounts in strain 2308 than in strain 19A when equal amounts of hydrolysates of cell wall and endotoxin-containing preparations were analyzed. A component with the same R F value as ethanolamine was present in strain 2308 cell wall hydrolysates but was not revealed by TLC of strain 19A cell wall hydrolysates. This component was not detected with the amino acid analyzer. TLC of cell walls tagged with 2,4-dinitrofluorobenzene prior to hydrolysis showed that phenylalanine was a terminal amino acid in cell walls of B. abortus strains 19A and 2308, B. suis strain 1776, and B. melitensis strain 2500. Carbohydrates detected in cell walls of strains 19A and 2308 by TLC were tentatively identified as glucose, mannose, rhamnose, and galactose. Colorimetric tests were also positive for 2-keto-3-deoxy-octulosonic acid, heptose, and dideoxyhexose. At least seven lipid components were detected by TLC of ether extracts of cell walls of strains 19A and 2308. It is suggested that one or more lipids is important in maintaining cell wall structure, because isolated cell walls rapidly became fragmented after exposure to ether.

Steric Factors in the Chemistry of Polypeptides, Poly-agr-Amino Acids and Proteins

An application of the rule of six for the estimation of steric hindrance in reactions of dipeptides and polypeptides, and conformational preferences of polypeptides and proteins, is described.