Apparatus for the Study of Redox Potential in Biological Systems

The four pieces of apparatus 1 described in this paper have been used in several investigations on biological oxidation-reduction systems. Other apparatus for similar purposes have been described by Ahlgren (5), Lehmann (4), Clark (1), Michaelis (2), Borsook and Schott (3), and Baumberger, Jiirgensen, and BardweU (7). 1. The Modified Thunberg Tube.--Ahlgren (5) has described in detail the use of the Thunberg tube in the study of the reduction of dyes by biological systems. The apparatus shown in Fig. 1 has the advantage that it is cheaper, has no ground glass stopper to be greased and thus involves no special difficulty in cleaning, and will hold a vacuum suitable for the development of extremely low redox potentials such as the complete reduction of rosinduline. The experimental procedure with this tube is to introduce the substrate, buffer, and dye and finally the enzyme, then to apply de Khotinsky cement to the pyrex vacuum tube at point DeK, warm the tip of the soft glass adapter b, and introduce it into the cement so that it rises in the interstices between b and the neck. Cool the cement, attach b to water pump, and evacuate to boiling for a minute. I t is essential to keep the tube warmer than the tap water and to wet the walls with the contents, as thereby the oxygen is more readily displaced. Heat b at the constriction while still evacuating and finally seal off the attached lower half of b and anneal with care. (The introduction