OMPs were prepared with N-lauryl-sarcosine using a modification of the method of Sawai et al. 8 Samples were subjected to denaturing- PAGE using the discontinuous Tris–glycine buffer system in 12% polyacrylamide gels. LPS extracts were prepared by boiling bacterial OMP preparations for 10 min in sample buffer. After cooling, 50 mg of proteinase K was added and samples were incubated overnight at 55C and boiled at 100C for 10 min.