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By using an amino acid score, it can be indicated if a protein will meet all amino acid needs of the body. If the amino acid score meets the required score it will be a completed or ideal protein. To calculate the amino acid score the formula used is, the milligram of limiting amino acid in 1 gram of test protein/ the milligram of that same ...
The Van Slyke determination is a chemical test for the determination of amino acids containing a primary amine group. It is named after the biochemist Donald Dexter Van Slyke (1883-1971). [1] One of Van Slyke's first professional achievements was the quantification of amino acids by the Van Slyke determination reaction. [2]
Also, amino acid side chain affinity for water was measured using vapor phases. [14] Vapor phases represent the simplest non polar phases, because it has no interaction with the solute. [18] The hydration potential and its correlation to the appearance of amino acids on the surface of proteins was studied by Wolfenden.
Glucogenic amino acids can also be converted into glucose, through gluconeogenesis. [80] Of the 20 standard amino acids, nine (His, Ile, Leu, Lys, Met, Phe, Thr, Trp and Val) are called essential amino acids because the human body cannot synthesize them from other compounds at the level needed for normal growth, so they must be obtained from food.
This requires spectrophotometers capable of measuring in the UV range, which many cannot. Additionally, the absorption maxima at 280 nm requires that proteins contain aromatic amino acids such as tyrosine (Y), phenylalanine (F) and/or tryptophan (W). Not all proteins contain these amino acids, a fact which will skew the concentration measurements.
The xanthoproteic reaction is a method that can be used to detect a presence of protein soluble in a solution, using concentrated nitric acid. The test gives a positive result in amino acids carrying aromatic groups, especially in the presence of tyrosine. If the test is positive the proof is neutralized with an alkali, turning dark yellow.
The biuret reaction can be used to assess the concentration of proteins because peptide bonds occur with the same frequency per amino acid in the peptide. The intensity of the color, and hence the absorption at 540 nm, is directly proportional to the protein concentration, according to the Beer–Lambert law .
A generalised method for N-terminal amino acid analysis follows: React the peptide with a reagent that will selectively label the terminal amino acid. Hydrolyse the protein. Determine the amino acid by chromatography and comparison with standards. There are many different reagents which can be used to label terminal amino acids.