Abstract
Phospholipid behavior in bovine retinal rod outer segment disk membranes and in phosphatidylcholine membranes containing the photopigment rhodopsin is explored. 31P NMR spectra of these systems show two distinguishable resonances. One resembles closely the 31P NMR resonance normally obtained from phospholipid bilayers. The other resonance is much broader. Thus, there appear to be two phospholipid head-group domains in this retinal membrane. Each environment confers different properties on the head groups. Phosphatidylcholine membranes containing the disk photopigment also show two phospholipid domains. Therefore, the environment in the retinal rod outer segment disk membranes characterized by the broad resonance may arise from the influence of the integral membrane protein rhodopsin on the membrane phospholipid bilayer.