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Membrane dynamics in the intact PM2 phage and its host cells as monitored by T1rho(H)
T Odahara1, Y Kyogoku, H Akutsu
1National Institute of Bioscience and Human-Technology, 1-1, Higashi, Tsukuba 305, Japan.
Abstract:
Temperature dependence of the spin-lattice relaxation time of proton in the rotating frame (T1rho(H)) was examined for the membranes of the intact PM2 phage, its host bacterial cells, and the phospholipids extracted from the cells. The relevant motions of the phospholipid molecules in all lipid membranes were found in the fast-motional regime (tauc < 1.7 x 10(-6) s) in the temperature range from 0 to 34 degrees C. The motions responsible for the relaxation in the intact biomembranes are more suppressed than those of the extracted phospholipid bilayers, suggesting that the lipid-protein interactions induce slow motions of the phospholipids in the membrane. Especially, the membrane of the intact PM2 phage showed a cooperative change in the motional state, being consistent with the reported change in the phosphorus chemical shift anisotropies of DNA and phospholipids of the phage particle.
Insights
Proton spin-lattice relaxation studies reveal that lipid-protein interactions in biomembranes suppress phospholipid motion compared to extracted lipids. Intact PM2 phage membranes exhibit cooperative changes in molecular motion.
Area of Science:
- Biophysics
- Membrane Biophysics
- Molecular Dynamics
Background:
- Cellular membranes are complex structures with dynamic lipid and protein components.
- Understanding molecular motion within membranes is crucial for elucidating biological function.
- Lipid-protein interactions are known to influence membrane fluidity and dynamics.
Purpose of the Study:
- To investigate the temperature dependence of proton spin-lattice relaxation in the rotating frame (T1rho(H)).
- To compare the motional dynamics of phospholipids in intact viral and bacterial membranes versus extracted phospholipids.
- To determine the role of lipid-protein interactions in modulating phospholipid dynamics.
Main Methods:
- Nuclear Magnetic Resonance (NMR) spectroscopy was employed to measure T1rho(H).
- Experiments were conducted on intact PM2 phage membranes, host bacterial cell membranes, and extracted phospholipids.
- Temperature dependence studies were performed in the range of 0 to 34 degrees C.
Main Results:
- Phospholipid molecular motions in all studied membranes were in the fast-motional regime (tauc < 1.7 x 10(-6) s).
- Motions in intact biomembranes were significantly more suppressed than in extracted phospholipid bilayers.
- The intact PM2 phage membrane displayed a cooperative change in its motional state.
Conclusions:
- Lipid-protein interactions significantly hinder phospholipid motion in native biomembranes.
- The observed cooperative motion in PM2 phage membranes aligns with previous findings on DNA and phospholipid chemical shift anisotropies.
- NMR relaxation measurements provide insights into the complex dynamics of membrane molecular interactions.