Under high light, the rates of photosynthetic CO2 assimilation can be influenced by reductant consumed by both foliar nitrate assimilation and mitochondrial alternative electron transport (mAET). Additionally, nitrate assimilation is dependent on reductant and carbon skeletons generated from both the chloroplast and mitochondria. However, it remains unclear how nitrate assimilation and mAET coo...

The steady-state kinetics of reductant-independent ATP hydrolysis by Klebsiella pneumoniae nitrogenase at 23 degrees C at pH 7.4 were determined as a function of component protein ratio (optimal at an oxidized Fe protein/MoFe protein ratio of 3:1) and MgATP concentration (Km 400 microM). Competitive inhibition was observed for MgADP (Ki 145 microM), [beta gamma-methylene]ATP (Mgp[CH2]ppA) (Ki 1...

In vitro excystment studies on the metacercaria of Acanthoparyphium spinulosum indicated that optimal excystment occurred when the cysts were incubated in either a complete medium containing trypsin and bile salts, or bile salts alone following acid pretreatment, and the reductant (sodium dithionite) at a temperature of 42°C and a pH of 7.8. A relatively lower percentage of excystment was obtai...

Exogenously and endogenously produced reactive oxygen species attack the base and sugar moieties of DNA showing a preference for reaction at 2'-deoxyguanosine (dG) sites. In the present work, dG was oxidized by HO(•) via the Fe(II)-Fenton reaction or by X-ray radiolysis of water. The oxidized lesions observed include the 2'-deoxynucleosides of 8-oxo-7,8-dihydroguanine (dOG), spiroiminodihydanto...

A gas analysis system was built to study the relationship between the reductant cost of NO(3)(-) assimilation and the measured rate of CO(2) and O(2) exchange in roots, leaves, and stems+ petioles of soybean (Glycine max L. Merr. cv Maple glen) plants. The measurements were used to calculate the diverted reductant utilization rate (DRUR = 4*[measured rate of CO(2) + measured rate of O(2)], in m...

Studies on the influence of light on respiration have yielded different results with different organisms. In some instances results were interpreted as evidence for light stimulation of respiration (3, 4, 5, 6), in other cases for photoinhibition (8, 13), and in still other examples for a negligible effect (1). With a given species simultaneous measurements of respiratory and photosynthetic 02 ...

A new type of ferredoxin was isolated from Azotobacter vinelandii cells. The protein was able to replace the native chloroplast ferredoxin in the photoreduction of nicotinamide adenine dinucleotide phosphate (NADP) and functioned as a reductant for the Azotobacter nitrogenase.

Whether reductive dehalogenation proceeds via a one- or a two-electron mechanism has been suggested to affect product distributions, hence potentially influencing the success of engineered treatment systems. In this work, we explore vicinal dibromide stereoisomers as "probes" of the concertedness of electron transfer in reduction by aqueous suspensions of iron and zinc metal. Dibromides consist...

Photosyntlhesis is presently conceived as a cooperation between 2 photoacts, photosystem I generating a strong reductant and a weak oxidant, photosystem II generating a srong oxidant (yielding O2) and a weak reductant. Coupling between the 2 photosteps presumably occurs between the weak reductant and the weak oxidant, a step possibly generating high energy phosphate. A number of means are avail...