Separation of lipid-free egg yolk proteins by high-pressure liquid chromatography using solvents containing formic acid

A method for obtaining total protein patterns from lipid-containing systems, in particular egg yolk, is described. After dispersion of the yolk in 8 M guanidine hydrochloride solution, lipid is removed by extraction with chloroform-methanol and petrol. The protein solution is applied to a high-pressure liquid chromatograph and eluted with a gradient of formic acid, isopropanol, and acetonitrile. In measurements on a known yolk protein, duck apovitellenin I, the method did not cause irreversible formylation of N-terminal or other residues. The method was used (1) to compare protein patterns of whole yolk from hen and quail eggs; (2) to isolate and partially sequence quail apovitellenin I; and (3) to compare protein patterns of "white yolk" and "yellow yolk."