The Extinction Coefficient of Fibrinogen from Man, Dog, Elephant, Sheep, and Goat at 280 mμ

SummaryFibrinogen from the plasma of man, dog, elephant, sheep, and goat was isolated, purified, and dialyzed free of (NH4)2SO4 against 0.005 M sodium citrate. The optical density at 280 mμ and the total nitrogen (micro-Kjeldahl) were determined on serial dilutions from each specie and the extinction coefficient E (0.1%) calculated. In the case of the dog, least square analysis of 38 determinations reveals that the equation y = 1.583x — 0.044 is the line of best fit, with correlation coefficient of 0.998. The extinction coefficient for a 0.1% solution of dog fibrinogen in 0.005 M sodium citrate is thus 1.583. Extinction coefficients, calculated as the ratio of optical density to fibrinogen concentration without least square analysis, for fibrinogen from other species have also been determined. These extinction coefficients show mean values of 1.55 for man, 1.58 for dog, 1.57 for elephant, 1.55 for sheep and 1.56 for goat, with the average value for all five species being 1.56. The use of this average valu...