The secondary structure of porin, maltoporin, and OmpA protein reconstituted in lipid membranes was detd. by Raman spectroscopy. The 3 proteins have similar structures consisting of 50-60% b-strand, .apprx.20% b-turn, and <15% a-helix. By using a method for structural prediction that accounts for amphipathic b-strands, folding models were developed for porin and for the segment of OmpA protein incorporated into the membrane. In the model, the OmpA fragment consists of 8 amphipathic membrane-spanning b-strands that form a b-barrel. Similarly, porin is folded into 10 amphipathic membrane-spanning b-strands that are located at the surface of the trimer towards the lipids and 8 predominantly hydrophilic strands in the interior. [on SciFinder (R)]