Development of a Joliot-electrode for the detection of photosynthetically produced oxygen in cyanobacterial cells

Abstract

The instrument I constructed in this project was a bare platinum electrode based on the original electrode by Pierre Joliot (Joliot P. (1972). Methods in Enzymology 24, 123–124) and the design by Johannes Messinger (Messinger J. (1993). Ph.D. thesis, Technische Universität Berlin). This electrode has the ability to detect the changes of oxygen tension with a high temporal resolution, enabling the exact measurement of the oxygen output from different photosynthetically active samples, such as thylakoid membranes and cyanobacterial cells. The sample was illuminated by an array of LEDs. The instrument also has the ability to keep the sample at a constant temperature, to reduce temperature related effects. A 3D-model and blueprints of the instrument were created and modified as necessary, before and after it was built. Special materials were acquired and the parts were manufactured in two workshops. New circuit diagrams for the detection circuit were planned based on original diagrams. A separate trigger circuit was also planned and built. Different analog-to-digital converters were acquired and tested. Corresponding programs for the handling, display and storage of data were programmed. The instrument was tested for basic functionality and flaws were corrected. Further tests were performed with different types of samples. As errors occurred they were eliminated or circumvented and the performance of the instrument was steadily improved. Several limitations with the current design were identified and additional improvements are recommended to enhance the utility of the electrode for determination of oxygen evolution by cyanobacterial cells.