369. Determination of the free amino-nitrogen of casein and of fresh and deteriorated milk protein by the Van Slyke method

1948 ◽  
Vol 15 (3) ◽  
pp. 364-368 ◽  
Author(s):  
C. H. Lea
Keyword(s):  
Constant Temperature ◽  
Nitrous Acid ◽  
Free Amino ◽  
Milk Protein ◽  
Technical Assistance ◽  
Milk Powder ◽  
Amino Nitrogen ◽  
Industrial Research ◽  
Simplified Procedures

The reaction of casein and of fresh and deteriorated milk protein with nitrous acid has been followed at constant temperature for 4 hr. in the manometric apparatus of Van Slyke, and simplified procedures suggested whereby the method can be utilized for investigation of the deterioration of the protein of separated milk powder during storage.Technical assistance in this work was given by Mr L. J. Parr: The work was carried out as part of the programme of the Food Investigation Board of the Department of Scientific and Industrial Research.

Studies on soil humic acids II: Observations on the estimation of free amino groups. Reactions of humic acid and lignin preparations with nitrous acid

1957 ◽  
Vol 48 (3) ◽  
pp. 352-360 ◽  
Author(s):  
J. M. Bremner
Keyword(s):  
Nitric Acid ◽  
Reaction Time ◽  
Humic Acid ◽  
Acid Hydrolysis ◽  
Sodium Hydroxide ◽  
Total Nitrogen ◽  
Nitrous Acid ◽  
Free Amino ◽  
Amino Nitrogen ◽  
Amino Groups

1. Free amino groups in humic acid preparations isolated from 0·5M-sodium hydroxide and 0·1M-sodium pyrophosphate (pH 7·0) extracts of various soils have been estimated by the nitrous acid method of Van Slyke (1929) and the fluorodinitrobenzene technique of Sanger (1945).2. The results obtained by the Van Slyke method using a reaction time of 15min. indicated that from 12 to 30% of the total nitrogen in the preparations examined was in the form of free amino groups. No free amino groups could be detected by the fluorodinitrobenzene technique.3. It is shown that lignin interferes with the estimation of amino groups by the Van Slyke method, and it is suggested that lignin or ligninderived material may be largely responsible for the high apparent amino-nitrogen values obtained with humic acid preparations by this method.4. The reaction of humic acid with nitrous acid resembles the reaction of lignin with nitrous acid in that it is accompanied by the fixation of nitrogen and the destruction of methoxyl groups. The reaction of lignin with nitrous acid is similar in many respects to its reaction with nitric acid.5. Only about one-third of the nitrogen fixed by lignin in its reaction with nitrous acid is removed by prolonged hydrolysis with 6N-HC1, and most of the nitrogen so released is in the form of ammonia. A small amount of the nitrogen liberated by acid hydrolysis is in the form of hydroxylamine.

Methods for Determining Free Amino Nitrogen in Wort and Beer and Viscosity of Wort and Beer

1977 ◽  
Vol 60 (4) ◽  
pp. 805-806
Author(s):  
Dwight B West
Keyword(s):  
Free Amino ◽  
Amino Nitrogen ◽  
New Methods ◽  
Test Materials ◽  
American Society ◽  
Colorimetric Reaction

Abstract The American Society of Brewing Chemists (ASBC) has released new methods for the determination of free amino nitrogen in wort and beer and for viscosity of wort and beer. The 4 procedures have been collaboratively tested by ASBC and the European Brewing Convention and adopted as official by both organizations. The free amino nitrogen methods use ninhydrin in the colorimetric reaction. The viscosity procedures measure flow times of the test materials against water. The methods have been adopted as official first action.

scholarly journals CELLULAR MECHANISMS OF PROTEIN METABOLISM IN THE NEPHRON

1954 ◽  
Vol 99 (6) ◽  
pp. 637-646 ◽  
Author(s):  
N. Kretchmer ◽  
Francis J. Cherot
Keyword(s):  
Amino Acid ◽  
Protein Metabolism ◽  
Free Amino ◽  
Renal Cortex ◽  
Concentration Level ◽  
Amino Nitrogen ◽  
Maximal Concentration ◽  
Cellular Mechanisms ◽  
Tubule Cells

Parenteral injection of amino acids resulted in the formation of Gram-positive droplets in the cytoplasm of the proximal convoluted tubule cells of the kidney of the rat within 15 minutes after intravenous administration. At this time the free alpha amino nitrogen in the cortex of the kidney had increased 2-fold. At the end of 1 hour this level was still somewhat higher than that of the control animals. The administration of increasing amounts of the amino acid disclosed the existence of a maximal concentration level in the renal cortex. When it was reached droplets appeared. Fractionation of the cells 15 minutes after the injection of lysine resulted in the recovery of free amino acid in the supernatant fluid but 1 hour after the injection lysine was contained within the particulate protein of the fractions which contain droplets. The increase in lysine was of the order of 2- 3-fold. It is concluded that the mitochondria-droplet complex is a locus of amino acid concentration and metabolism within the cytoplasm of the renal cell. A method is described for the determination of lysine in micro quantities.

scholarly journals The behaviour of some uramido-acids in the nitrous acid method for the determination of amino-nitrogen

1940 ◽  
Vol 34 (2) ◽  
pp. 192-197 ◽  
Author(s):  
Allan Godfrey Gornall ◽  
Andrew Hunter
Keyword(s):  
Nitrous Acid ◽  
Amino Nitrogen ◽  
Acid Method
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