Direct quantitative determination of peptides and proteins in PVDF transfer membrane using a computing densitometer.

In this paper we describe a method that makes it possible to quantify bands or spots directly on membranes using a computing densitometer. The method is based on the fact that polyvinylidene difluoride (PVDF) membrane is translucent when immersed in solutions containing > 50% methanol. Peptide markers (2.512-16.949 kDa), as well as purified Neuropeptide Y, have been used to optimize direct densitometry of PVDF membrane. For all peptides and proteins analyzed, the optical response of the instrument to peptide and protein bands in PVDF membrane wetted in 50% methanol was linear and highly reproducible. The method described here is useful for a rapid quantification of peptides and proteins on PVDF membrane and is an alternative to RIA, ELISA or bioassay.