Difference spectroscopy with respiratory membranes of an H2-oxidizing microorganism layered between two gas-permeable, plastic foils: a procedure that allows measurements in the ultraviolet range.

A method for recording redox difference spectra of respiratory membranes which minimizes light scattering and results in increased sensitivity and spectral range when compared to the traditional technique of recording spectra of respiratory particles in suspension is described. Membranes were sandwiched between two gas-permeable, plastic foils, placed in a sealed cuvette, and gassed with H2 as reductant or O2 as oxidant. The membranes of the H2-oxidizing microorganism (Alcaligenes eutrophus H16) used in this work contain a hydrogenase which is coupled to the electron transport chain, thereby allowing H2 to serve as a source of electrons. With this procedure, spectra of both cytochromes and quinones were recorded. By using mixtures of H2 and O2, spectra of cytochromes between the fully oxidized and fully reduced states were recorded.