title: Proton spin-lattice relaxation of retinal rod outer segment membranes and liposomes of extracted phospholipids.
abstract: A large fraction of the phospholipid protons of bovine retinal rod outer segment (ROS) disc membrane vesicles yield well-resolved nuclear magnetic resonance lines near physiological temperature. The spin-lattice (T1) relaxation rates of the resolved sharp resonance of ROS disc membranes appear biphasic above 10 degrees C. The rate of the more rapidly relaxing component of each resonance matches closely the relaxation rate of the corresponding resonances of liposomes of purified ROS phospholipids. The slowly relaxing component of each disc membrane resonance is most likely due to phospholipids whose motion is affected by rhodopsin. The primary difference in the relaxation behavior of phospholipids in the ROS membrane vesicles and ROS liposomes appears to be in T1, rather than T2, since the corresponding sharp resonances of both preparations have similar linewidths. These observations suggest that the interaction of rhodopsin with the more fluid membrane phospholipids predominantly affects relatively high frequency segmental motions, which determine T1, while having minimal effects on the lower frequency segmental motions, which influence T2. This conclusion can be rationalized by assuming that a substantial fraction of the interacting phospholipids are relatively fluid with respect to less frequent, larger amplitude segmental motions, but that the more frequent segmental motions (such as beta-coupled trans-gauche isomerizations) are significantly restricted by interaction with protein.
mesh_terms: D000818:Animals; D002417:Cattle; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D008081:Liposomes; D009682:Magnetic Resonance Spectroscopy; D008563:Membrane Lipids; D008565:Membrane Proteins; D008566:Membranes / Q000648:ultrastructure; D010743:Phospholipids; D010786:Photoreceptor Cells / Q000648:ultrastructure*; D012168:Retinal Pigments; D012243:Rhodopsin; D013696:Temperature
chemical_list: D008081:Liposomes; D008563:Membrane Lipids; D008565:Membrane Proteins; D010743:Phospholipids; D012168:Retinal Pigments; D012243:Rhodopsin
references.citation: FEBS Lett. 1976 Nov;70(1):56-60
references.pmid: 992076
references.citation: Biochim Biophys Acta. 1976 Sep 7;443(3):556-70
references.pmid: 963069
references.citation: Biochim Biophys Acta. 1972 Jan 17;255(1):43-56
references.pmid: 4334686
references.citation: Proc Natl Acad Sci U S A. 1972 Mar;69(3):590-3
references.pmid: 4501575
references.citation: Ann N Y Acad Sci. 1973 Dec 31;222:468-88
references.pmid: 4594297
references.citation: J Am Chem Soc. 1974 Mar 6;96(5):1312-9
references.pmid: 4814752
references.citation: Arch Biochem Biophys. 1972 Jul;151(1):270-6
references.pmid: 5044519
references.citation: Biochemistry. 1974 May 21;13(11):2438-44
references.pmid: 4545509
references.citation: Vision Res. 1974 May;14(5):335-7
references.pmid: 4830685
references.citation: J Am Chem Soc. 1972 Jun 28;94(13):4475-81
references.pmid: 4338553
references.citation: Biochim Biophys Acta. 1976 Feb 6;419(3):395-403
references.pmid: 1247567