Abstract
1. When a rhodopsin solution was exposed to a continuous illumination of dim green light, the element R was observed. On the other hand, when a rhodopsin solution was exposed to a flash of bright light, the immediate rise of pH was observed.
2. Both the element R and the immediate rise of pH were secondary reactions having scanty of physiological meaning.
3. It is likely that the primary reaction, induced on exposure of rhodopsin solution to light, is the photo-release of oxygen from rhodopsin molecules.
4. The volume of released oxygen on illumination may be calculated from the values of Δ[H+], as follows:
ΩR=Δ[H+] R/5·106 [H+] +9·1015 [H+] 2,
and
ΩI=Δ[H+] I/5·106 [H+] +9·1015 [H+] 2.
where ΩR is mole density of the oxygen molecules released from 10-8 mol/ml rhodopsin on a 10-minute illumination of dim green light, and ΩI is mole density of released oxygen molecules from 10-8 mol/ml rhodopsin in 10 seconds on exposure to a flash of bright light.
5. Both the maximums of ΩR and ΩI were found at pH 6.60.
6. Process I, which was reported by R. HARA, may be the uptake of H ions by the oxygen atoms released from rhodopsin molecules on illumination.
