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Temperature-dependent lateral diffusion of phospholipids in hepatic microsomes as studied by 31P-NMR
Abstract:
The 81 MHz 31P-NMR spectra of isolated rabbit liver microsomes before and after trypsin treatment and of the total microsomal lipid extract were recorded in the 4-40 degrees C temperature range. In both treated and untreated microsomes at 4 degrees C most of the phospholipids gave rise to typical bilayer spectra whereas the lineshape of the latter in the 25-37 degrees C temperature range becomes narrower and more symmetrical. Quasi-elastic light scattering (QELS) measurements revealed that the microsomes maintain their size in the temperature region of the measurements. We interpret the lineshape changes for untreated microsomes above 25 degrees C as being determined by lateral diffusion. This is supported by lineshape calculations as a function of the lateral diffusion coefficient. The different spectral behavior of enzymatically active (untreated) and inactive (treated) microsomes suggests that the membrane proteins influence the lateral diffusion of the phospholipids.
Insights
Phospholipid lateral diffusion in rabbit liver microsomes changes with temperature. Membrane proteins influence this diffusion, impacting phospholipid behavior in intact microsomes.
Area of Science:
- Biochemistry
- Biophysics
- Membrane Biology
Background:
- Rabbit liver microsomes are crucial for cellular metabolism.
- Phospholipids form the bilayer structure of cell membranes.
- Understanding lipid dynamics is key to membrane function.
Purpose of the Study:
- To investigate the temperature-dependent lateral diffusion of phospholipids in rabbit liver microsomes.
- To determine the influence of membrane proteins on phospholipid dynamics.
Main Methods:
- 31P-NMR spectroscopy at 81 MHz to analyze phospholipid spectra.
- Quasi-elastic light scattering (QELS) to assess microsomal size.
- Lipid extraction and analysis.
- Lineshape calculations to model diffusion.
Main Results:
- Phospholipids exhibited typical bilayer spectra at 4°C.
- Above 25°C, spectra became narrower and more symmetrical, indicating increased lateral diffusion.
- Microsome size remained constant across the temperature range.
- Enzymatically active microsomes showed different spectral behavior than treated (inactive) ones.
Conclusions:
- Temperature significantly affects phospholipid lateral diffusion in microsomes.
- Membrane proteins play a role in modulating phospholipid lateral diffusion.
- These findings provide insights into the dynamic nature of the microsomal membrane.