The utility calculates protein molecular and weight coefficients of extinction at 280 nm, basing on the amount of tryptophane (Trp), tyrosine (Tyr) and cysteine (Cys) residues in the structure of a protein molecule. Calculations are founded on method represented by Gill S.C., von Hippel P.H. (Anal. Biochem. 182, pp. 319-326, 1989). Example: given that a protein molecule contains 4 tryptophanes (Trp), 4 tyrosines (Tyr) and 8 cysteines (Cys) residues one needs to determine molecular and weight coefficients of extinction for a-Lactalbumin (bovine). The protein's molecular weight is 14186 Da (for details see Help).