Hydrogen gas evolution and carbon dioxide fixation with visible light by chlorophyllin coupled with polyethylene glycol

Chlorophyllin a was conjugated with alpha-(3-aminopropyl)-omega-methoxypoly (oxyethylene), PEG-NH2, to form the PEG-chlorophyllin conjugate through aci d-amide bonds. The PEG-chloraphyllin conjugate was stable toward light illu mination under anaerobic condition in comparison with chlorophyllin a. The conjugate catalyzed the reduction of methyl viologen in the presence of 2-m ercaptoethanol and the evolution of hydrogen gas in the presence of methyl viologen (an electron carrier), 2-mercaptoethanol (an electron donor) and h ydrogenase (Scheme 1). Furthermore, the PEG-chlorophyllin conjugate catalyz ed the photoreduction of NADP(+) or NAD(+) in the presence of ascorbate as an electron donor and ferredoxin-NADP(+) reductase as the coupling enzyme. Utilizing the reducing power of NADPH generated by the PEG-chlorophyllin co njugate under the illumination, CO2 fixation was accomplished by the synthe sis of malate (C-4) from pyruvate (C-3) and CO2 in the presence of malic en zyme (Scheme 2). These reactions mentioned above did never proceed in dark or without each emzyme.