Optical and electrical gradients in photosynthesis

Light-gradient photovoltage measurements can be performed on whole chloro-plasts, EDTA-treated thylakoids, on osmotically swollen thylakoids (blebs), both spherical symmetry but of different size, on photosynthetic bacteria and electrically aligned pices of photosynthetic membranes. Depending on the wavelength of the ecitation light, a negative or positive polarity of the photovoltage is observed. Different approach is adapted for a theoretical description of these membrane systems, and the light intensity distribution and the photovoltage in such systems can be calculated. Fits to the photovoltage amplitudes measured as a function of light wavelength enable the values of the optical, electrical and geometrical parameters of the membrane to be derived.