Among various photosensitizing dyes, 4, 4'-dimethyl 3, 3'-di-n-heptyl-8- {2-(4-methyl-3-n-heptylthiazole) }-2, 2'-dicarbocyanin diiodide (abb. NK19), even in an extremely low concentration, is known to inhibit the proliferation
of bacteria and tissue culture cells (1, 2, 3). With respect to the mechanism of such inhibitory action no other property of this NKl9 is known except that it has a marked adsorptive property to protein (4). As a step
toward the elucidation of the mode of biological effect, the author studied
the effect of NK19 on the energy transfer reaction of Irat liver mitochondria, followed by comparison with the mode of actions of various other inhibitors of the oxidative phosphorylation (5). NK19. NKl9 can be prepared by letting 2, 4-dimethylthiazole heptyliodide react with ethylorthoformate in anhydrous acetic acid. We used
NKI9, a product of Nihon Kanko Shikiso Research Laboratories. The molecular structure is as in the following and in its MeOH state it has maximum absorbancy at 590 m,a. For the use in experiment it was made into 1 mg/ml of MeOH and was stored in the dark until used.</p
