Abstract
1. Changes in pH of rhodopsin solution was induced following illumination with the least color changes.
2. Changes in pH of rhodopsin solution on exposure to a dim green light might be clarified into 3 components, D1, D2 and R.
3. Isoionic point (P0) might be affected with temperature. At lower temperatures (6°C, 19°C) P0 was found in a neutral range, but the higher the temperature (19°C-30°C) the smaller the Po. Relations between temperature (t°C) and P0 may be expressed as (41-t)(7-P0) =28.
4. At 19°C to 30°C, element R was observed on the alkaline side of P0-curve.
5. Element R might be the summation of immediate changes in pH evoked by successive illumination.
6. Origin of element R might be a photo-release of oxygen from rhodopsin solution following illumination.
