A Method for High-Performance Sequence Analysis Using Polyvinylidene Difluoride Membranes with a Biphasic Reaction Column Sequencer

Abstract

Methods have been developed for high-sensitivity sequence analysis of proteins electroblotted onto polyvinylidene difluoride (PVDF) membranes using a Hewlett-Packard G1005A protein sequencer. This sequencer normally uses a biphasic (hydrophobic/hydrophilic) reaction column which was designed to accommodate loading and cleanup of samples from diverse solutions. However, the standard column, programs, and chemistry were not designed to accommodate PVDF, which has become a common sequencing support. In this study, a systematic evaluation of the suitability of this sequencer for analysis using PVDF bound samples was performed and included evaluation of: different wash and extraction solvents, multiple programming changes, two alternative formulations of coupling reagents, and the effect of direction for solvent and reagent deliveries. High-performance analysis of PVDF bound samples was achieved by: using a modified reaction column with an empty hydrophobic (top) half of the column module, program modifications for the reaction column and converter, substitution of ethyl acetate for the standard S2/3 extraction solvent and using prototype Version 2.0 formulations of the coupling reagents, R1 and R2. High-performance sequence analyses of experimental samples electroblotted from either 1D or 2D gels onto high-retention PVDF membranes were obtained with a 41-min cycle time, including experimental samples with initial coupling yields <2 pmol. Routine sequencer performance was comparable to, or slightly better than, a conventional gas-phase sequencer which had been previously optimized by us for high-performance sequence analysis of electroblotted samples in the low pmol range.