Scanning tunneling microscopic (STM) analysis of the phospholipid bilayer surface characteristics in the P beta phase. Secondary ripples.

Previous investigations have elaborated on the necessity for dimyristoylphosphatidylcholine (DMPC) molecules to conform in a ripple phase at the temperature intermediate between the transition and pretransition in order to protect the hydrophilic-hydrophobic polarity of the bilayer. Present observations, in addition to the asymmetric P beta phase of 11.1 +/- 1.3 nm wave-length, demonstrate orthogonal corrugations perpendicular to the main wave direction. Whether this is a prerequisite for maintaining the molecular order-disorder balance at such specific temperature, or it results from yet unknown source is unclear at present.