Magnetic field effects in phospholipid vesicles measured by light scattering
Magnetic field effects in phospholipid vesicles measured by light scattering
The aim of this research is to develop an understanding of the mechanism of the magnetic field effect on biological membrane. Unilamellar lipid vesicles may be regarded as the simplest model for biological membranes. They are composed of weakly diamagnetic anisotropic molecules which show magnetic birefringence. Vesicle suspensions of Dipalmitoyl Phosphatidyl-Choline (DDPC), Dimyristoyl Phosphatidyl-Choline (DMPC) and 50% mole fraction mixtures were prepared by reverse phase evaporation and detergent dialysis techniques. The nonionic n- octyl- β- D- glucoside detergent was used in the preparation with different lipid/detergent molar ratios. An angular light scattering apparatus, previously designed and constructed, has been developed to be controlled by a BBC microcomputer. Measurements of optical turbidity and 90^o light scattering, as a function of temperature, were made in fields of 3.25T and 1.65T respectively, and in zero field. The turbidity measurements showed an increase in transmitted light, i.e. a decrease in turbidity, due to the field effect. The change was greater in the liquid crystal phase than in the gel phase and also greater for DPPC than for DMPC. A significant field-induced reduction in the intensity of 90^o scattered light was observed at temperatures above the main transition (T_m) of the bilayer, with a response time of 0.20 ± 0.05 seconds. Isothermal angular light scattering experiments were carried out in near zero and 1.65T fields. The measurements were made over a range of scattering angles from θ= 5o to 35o in steps of 1o and at temperatures below and above Tm. The size distributions were calculated using an angular light scattering data analysis technique based upon a maximum entropy fitting criterion. The optical anisotropy ratios of the bilayer wall were estimated from fitting the experimental data to Rayleigh-Debye scattering theory. The magnetic effect is modelled in terms of the orientation of superdiamagnetic clusters in the bilayer membrane.
University of Southampton
1989
Eleiwa, Moein Mohammed
(1989)
Magnetic field effects in phospholipid vesicles measured by light scattering.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The aim of this research is to develop an understanding of the mechanism of the magnetic field effect on biological membrane. Unilamellar lipid vesicles may be regarded as the simplest model for biological membranes. They are composed of weakly diamagnetic anisotropic molecules which show magnetic birefringence. Vesicle suspensions of Dipalmitoyl Phosphatidyl-Choline (DDPC), Dimyristoyl Phosphatidyl-Choline (DMPC) and 50% mole fraction mixtures were prepared by reverse phase evaporation and detergent dialysis techniques. The nonionic n- octyl- β- D- glucoside detergent was used in the preparation with different lipid/detergent molar ratios. An angular light scattering apparatus, previously designed and constructed, has been developed to be controlled by a BBC microcomputer. Measurements of optical turbidity and 90^o light scattering, as a function of temperature, were made in fields of 3.25T and 1.65T respectively, and in zero field. The turbidity measurements showed an increase in transmitted light, i.e. a decrease in turbidity, due to the field effect. The change was greater in the liquid crystal phase than in the gel phase and also greater for DPPC than for DMPC. A significant field-induced reduction in the intensity of 90^o scattered light was observed at temperatures above the main transition (T_m) of the bilayer, with a response time of 0.20 ± 0.05 seconds. Isothermal angular light scattering experiments were carried out in near zero and 1.65T fields. The measurements were made over a range of scattering angles from θ= 5o to 35o in steps of 1o and at temperatures below and above Tm. The size distributions were calculated using an angular light scattering data analysis technique based upon a maximum entropy fitting criterion. The optical anisotropy ratios of the bilayer wall were estimated from fitting the experimental data to Rayleigh-Debye scattering theory. The magnetic effect is modelled in terms of the orientation of superdiamagnetic clusters in the bilayer membrane.
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Published date: 1989
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Local EPrints ID: 461083
URI: http://eprints.soton.ac.uk/id/eprint/461083
PURE UUID: 89c6976f-8894-4c57-a6af-d86d84a495b1
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Date deposited: 04 Jul 2022 18:35
Last modified: 04 Jul 2022 18:35
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Author:
Moein Mohammed Eleiwa
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