nitrogenase and cadmium-sulfide

This study investigated the abilities of a purple non-sulfur bacterium, Rhodopseudomonas palustris TN110 to bioremediate cadmium through the biosynthesis of CdS nanoparticles and to fix nitrogen simultaneously. Under microaerobic-light conditions, R. palustris TN110 synthesized CdS nanoparticles. The produced CdS nanoparticles had a spherical shape and an average size of 4.85 nm. The Fourier transform infrared spectrum of the nanoparticles reveals the carbonyl groups, bending vibrations of the amide I and II bands of proteins, and CN stretching vibrations of aromatic and aliphatic amines. These bands and groups suggest protein capping/binding on the surface of the nanoparticles. R. palustris TN110 converted 25.61% of 0.2 mM CdCl

Topics: Biodegradation, Environmental; Cadmium; Cadmium Compounds; Chemical Precipitation; Gene Expression Regulation, Enzymologic; Nanoparticles; Nitrogen Fixation; Nitrogenase; Rhodopseudomonas; Sulfides

The splitting of dinitrogen (N2) and reduction to ammonia (NH3) is a kinetically complex and energetically challenging multistep reaction. In the Haber-Bosch process, N2 reduction is accomplished at high temperature and pressure, whereas N2 fixation by the enzyme nitrogenase occurs under ambient conditions using chemical energy from adenosine 5'-triphosphate (ATP) hydrolysis. We show that cadmium sulfide (CdS) nanocrystals can be used to photosensitize the nitrogenase molybdenum-iron (MoFe) protein, where light harvesting replaces ATP hydrolysis to drive the enzymatic reduction of N2 into NH3 The turnover rate was 75 per minute, 63% of the ATP-coupled reaction rate for the nitrogenase complex under optimal conditions. Inhibitors of nitrogenase (i.e., acetylene, carbon monoxide, and dihydrogen) suppressed N2 reduction. The CdS:MoFe protein biohybrids provide a photochemical model for achieving light-driven N2 reduction to NH3.

Topics: Adenosine Triphosphate; Ammonia; Cadmium Compounds; Catalysis; Hydrolysis; Light; Molybdoferredoxin; Nanoparticles; Nitrogen; Nitrogen Fixation; Nitrogenase; Oxidation-Reduction; Sulfides