Amino Acid Analysis Calculations

Types of Calculations

To calculate the amino acid composition expressed as mole fraction

  1. Sum the # of nmoles of the individual amino acids (excluding the internal standard).
  2. Divide the amount of each amino acid by this sum.

To calculate the amino acid composition expressed as mole %

  1. Multiply the mole fractions by 100.

To calculate the amino acid composition expressed as weight %

  1. Multiply the # of nmoles of an amino acid by that amino acid residue’s molecular weight to convert nmoles to ngrams.
  2. Sum the # of ngrams of the individual amino acids (excluding the internal standard).
  3. Divide the weight of each AA by the sum to determine its weight fraction.
  4. Multiply the AA’s weight fraction by 100.

To calculate the sample protein concentration. (Na+)

  1. Multiply all underlined concentrations by the corresponding amino acid’s residue weight (excluding the norleucine standard).
  2. Sum these values.
  3. Multiply the sum by 2.0 (expected amount of internal standard per 50 uL) then divide by the actual amount of norleucine injected.
  4. Multiply by the value from 3.) by the total volume then divide by the injected volume. Concentration is in ngrams/total sample hydrolyzed.
  5. Divide the value from 4.) by the initial transfer volume. Concentration is in ngrams/uL of original sample. Divide by 1000 for mgs/mL.