Simultaneous measurements of heat production and optical density in oscillating reactions

Abstract A device is presented which can be inserted into a calorimetric vessel to enable a simultaneous measurement of optical density and heat production. It consists mainly of a quartz rod and a photodiode which is sensitive from the near ultraviolet to the infrared. Specific wavelengths are selected by glass or interference filters placed between the light source and the rod. Homogeneity of the medium in the vessel can be achieved by a gentle but effective pneumatic stirring. The applicability of the whole set-up is demonstrated for two oscillating chemical reactions (Belousov-Zhabotinskii and Briggs-Rauscher reactions) and for the oscillating glycolysis of a cell-free cytoplasmic extract from yeast.