PubMed Health⌕ Search

Biomedical subjects

B A MCFADDEN

Publications and source records attributed to B A MCFADDEN.

8 recordsLinked to original sources
PubMed1965

CHARACTERISTICS AND INTERMEDIATES OF SHORT-TERM C-14-O-2 INCORPORATION DURING RIBOSE OXIDATION BY HYDROGENOMONAS FACILIS.

McFadden, B. A. (Washington State University, Pullman), and H. R. Homann. Characteristics and intermediates of short-term C(14)O(2) incorporation during ribose oxidation by Hydrogenomonas facilis. J. Bacteriol. 89:839-847. 1965.-Ribose-grown cells of Hydrogenomonas facilis, which had been suspended in growth medium and were oxidizing ribose, were exposed to HC(14)O(3) (-) of high specific activity. The uptake was proportional to cell mass. Short-term uptake (less than 2 min) was completely inhibited by 10(-3)m 2,4-dinitrophenol (DNP) or by <4 x 10(-6)mm-chlorocarbonyl cyanide phenylhydrazone, and to the extent of 42% by 5 x 10(-5)m DNP. The following observations were made in kinetic studies (8, 16, 35, 67, 96, and 181 sec) of fixation in the presence of ribose. Glutamate was extensively labeled in periods up to 3 min. It was one of the major early products, containing 30% of the label at 8 sec. The sugar phosphate fraction was not detectably labeled at 8 or 16 sec, but its C(14)-content increased rapidly to 27% at 35 sec and then slowly decreased. Label in phosphoglycerate, phosphoenolpyruvate, and alanine did not appear until 35 sec, and did not exceed about 7, 2, and 3%, respectively, of the total extracted radioactivity. Adenosine triphosphate and adenosine diphosphate were heavily labeled after fixation in a pilot study for 125 sec. Although considerable radioactivity incorporated during the pilot study was intractable by the extraction procedure employed, virtually no C(14) was found in the residue in poly-beta-hydroxybutyric acid. A large number of amino acids and organic acids and some organic phosphates were not detectably labeled in any of the experiments. Omission of ribose greatly diminished incorporation, particularly into glutamate.

2,4-Dinitrophenol↗
PubMed1963

QUANTITATIVE STUDIES OF THE EFFECT OF ORGANIC SUBSTRATES AND 2,4-DINITROPHENOL ON HETEROTROPHIC CARBON DIOXIDE FIXATION IN HYDROGENOMONAS FACILIS.

McFadden, Bruce A. (Washington State University, Pullman), and H. Robert Homann. Quantitative studies of the effect of organic substrates and 2,4-dinitrophenol on heterotrophic carbon dioxide fixation in Hydrogenomonas facilis. J. Bacteriol. 86:971-977. 1963.-Whole cells of Hydrogenomonas facilis under heterotrophic conditions fixed levels of C(14)O(2) which depended upon the nature of the carbon source being oxidized. It was established that oxidative rates varied as a function of p(CO2). Therefore, all studies were conducted in the presence of 1.5 mole% CO(2) in the gas phase. With glucose-grown cells supplied with glucose as substrate, the heterotrophic fixation was curtailed 98% by the addition of 8.3 x 10(-4)m 2,4-dinitrophenol (DNP). A coupling between reductive fixation of CO(2) and heterotrophic oxidation of substrate is consistent with the observed effect of DNP. The efficiency of coupling of fixation with oxidation was studied for acetate, d-glucose, l-glutamate, d,l-lactate, d-ribose, and succinate as substrates. Kinetic studies showed that the efficiency of coupling (expressed as disintegrations per minute of C(14) per microliter of O(2)) was initially time-variable for all substrates; however, it approached a constant value after 30 to 45 min for acetate, glutamate, lactate, and succinate. The initial variation of the ratio with time was due primarily to C(14)O(2) uptake, which was nonlinear with time. Control studies in the absence of exogenous substrate indicated that CO(2) fixation may also be linked to oxidation of endogenous stores accumulated during heterotrophic growth. d-Ribose appears to be the most promising substrate for short-term fixation studies owing to the rapid incorporation of C(14) and the unusually low endogenous fixation rate by cells grown on ribose. Calculations reveal that, after isotopic equilibrium has occurred, the amount of CO(2) utilized during glucose oxidation is almost 50% of O(2) uptake during the same interval. Even during succinate oxidation, which was shown to be coupled much less effectively with CO(2) fixation, the CO(2) utilized during the same interval is 8% of O(2) uptake.

2,4-Dinitrophenol↗