Relaxation dynamics of the gel to liquid-crystalline transition of phosphatidylcholine bilayers. Effects of chainlength and vesicle size
| Autor: | Michael L. Johnson, W. W. Van Osdol, Qiang Ye, Rodney L. Biltonen |
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| Rok vydání: | 1991 |
| Předmět: |
Yield (engineering)
Lipid Bilayers Molecular Conformation Analytical chemistry Biophysics Thermodynamics 02 engineering and technology Calorimetry Structure-Activity Relationship 03 medical and health sciences Lipid bilayer 030304 developmental biology 0303 health sciences Bulk modulus Fourier Analysis Chemistry Vesicle Bilayer Relaxation (NMR) Models Theoretical 021001 nanoscience & nanotechnology Kinetics Volume (thermodynamics) Phosphatidylcholines 0210 nano-technology Gels Research Article |
| Zdroj: | Biophysical Journal. 59(4):775-785 |
| ISSN: | 0006-3495 |
| DOI: | 10.1016/s0006-3495(91)82290-1 |
| Popis: | The relaxation kinetics of the gel to liquid-crystalline transition of five phosphatidylcholine (DC14PC to DC18PC) bilayer dispersions have been investigated using volume perturbation calorimetry, a steady-state technique which subjects a sample to sinusoidal changes in volume. Temperature and pressure responses to the volume perturbation are measured to monitor the relaxation to a new equilibrium position. The amplitude demodulation and phase shift of these observables are analyzed with respect to the perturbation frequency to yield relaxation times and amplitudes. In the limit of low perturbation frequency, the temperature and pressure responses are proportional to the equilibrium excess heat capacity and bulk modulus, respectively. At all temperatures, the thermal response data are consistent with a single primary relaxation process of the lipid. The less accurate bulk modulus data exhibit two relaxation times, but it is not clear whether they reflect lipid processes or are characteristic of the instrument. The observed thermal relaxation behavior of all multilamellar vesicles are quantitatively similar. The relaxation times vary from approximately 50 ms to 4 s, with a pronounced maximum at a temperature just greater than Tm, the temperature of the excess heat capacity maximum. Large unilamellar vesicles also exhibit a single relaxation process, but without a pronounced maximum in the relaxation time. Their relaxation time is approximately 80 ms over most of the transition range. |
| Databáze: | OpenAIRE |
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