The regulation of oat coleoptile phosphoenolpyruvate carboxylase and malic enzyme by Hâ ½ and metabolites : kinetic evidence for and against a cytosolic pH-stat

Phosphoenolpyruvate carboxylase (PEPC) and malic enzyme activities in soluble protein extracts of Avena coleoptiles were investigated to determine whether their kinetics were consistent with a role in cytosol pH regulation. Malic enzyme activity was specific for NADP+ and Mn2+. Maximal labelled product formation from [14C]-substrates required the presence of all coenzymes, cofactors and substrates. Plots of rate versus malate concentration, and linear transformations there- 2 of, indicated typical Michaelis-Menten kinetics at non-saturating malate levels and substrate inhibition at higher malate levels. pH increases between 6.5 and 7.25 increased near-optimal activity, decreased the degree of substrate inhibition and the Kmapp(Mn2+) but did not affect the Vmax or Kmapp(malate). Transformed data of PEPC activity demonstrated non-linear plots indicative of non-Michaelian kinetics. pH increases between 7.0 and 7.6 increased the Vmax and decreased the Km app (Mg2+) but did not affect the Kmapp(PEP). Various carboxylic acids and phosphorylated sugars inhibited PEPC and malic enzyme activities, and these effects decreased with pH increases. Metabolite inhibited malic enzyme activity was non-competitive and resulted mainly from Mn2+ chelation. In contrast, metabolite inhibited PEPC activity was unique for each compound tested, being variously dependent on the PEP concentration and the pH employed. These results indicate that fluctuations in pH and metabolite levels affect PEPC and malic enzyme activities similarly and that 3 the in vitro properties of PEPC are consistent with its proposed role in a pH-stat, whereas the in vitro properties of the malic enzyme cannot be interpreted in terms of a role in pH regulation.

The utility of sedimentary diatoms as a measure of historical lake ph

As a result of increased acid precipitation, the pH of a large number of Canadian Shield lakes has been falling. Prior to this study there was no documentation available to explain the history of lake acidification for the Algoma area lakes. In order to obtain this information the diatom inferred pH technique was developed in this study. During two field seasons, July 1981 and July 1982, short sediment cores (circa 25-30 cm) were collected from 28 study lakes located north of Lake Superior, District Algoma, Ontario. The surface sediment diatoms (0-1 cm) from each of these lakes were carefully identified, enumerated, and classified in terms of their pH indicator status. The surface sediment diatom analysis indicated that lake pH is one of the most important factors affecting the species composition and relative abundance of diatom populations. Thus diatom assemblages can be sensitive indicators of lake acidification. When Nygaard's index alpha was plotted against observed lake pH, a statistically significant relationship resulted (r=-0.89; p=pha regression equation was used to construct the pH histories of 4 lakes (lakes X4, CS, U3, and WI). The repeatability of this technique was confirmed by comparing two downcore paleo-pH profiles of Lake WI. These two paleo-pH profiles represented almost identical paleo-pH patterns for Lake WI. The paleo-pH study of Lake X4 revealed that the lake has been rather acidic (pH <5.6) for the last 200 years. It appears that the recent increase in acid precipitation 3 over the last 30 years has not altered the water pH compared to the lake's pH history. However, the paleo-pH study of another acidic lake (Lake CS) indicated that its pH has significantl}* dropped over the last 30 years . During this time the Lake CS pH has dropped almost 2 pH units (7.1 to 5.2). The other two lakes studied for downcore pH were circumneutral in nature . One of these lakes (Lake U3) displayed a relatively stable pH history while the other lake (Lake WI) displayed significant pH fluctuations over post-Ambrosia time. The variable pH history of Lake WI was probably associated with the Algoma sintering plant plume and forest fires. A significant relationship between surface sediment diatoms and observed lake pH and secondly a statistically significant relationship between index alpha and observed pH suggested that diatoms are one of the best indicators of lake pH. Thus diatom inferred pH technique has great potential in explaining the rate of lake acidification.

Beckman Hall construction

Digging the foundation of the Arnold and Mabel Beckman Business and Technology Hall, Chapman University, Orange, California, 1997. Architect: Dworsky Associates; Contractor: Turner Construction.

Architectural drawing for Beckman Hall

Architectural drawing of the site for the Arnold and Mabel Beckman Business and Technology Hall, Chapman University, Orange, California, ca. 1997.

Digging Beckman Hall foundation, Chapman University, Orange, California

Digging the foundation for the Arnold and Mabel Beckman Business and Technology Hall, Chapman University, Orange, California, ca. 1997. Turner Construction, contractor.

Beckman Hall construction

Digging the foundation for the Arnold and Mabel Beckman Business and Technology Hall, Chapman University, Orange, California, ca. 1997. Turner Construction, contractor.

Digging the foundation for Beckman Hall, Chapman University, Orange, California

Digging the foundation for the Arnold and Mabel Beckman Business and Technology Hall, Chapman University, Orange, California, ca. 1997. Turner Construction, contractor.

Beckman Hall construction

Digging the foundation for the Arnold and Mabel Beckman Business and Technology Hall, Chapman University, Orange, California, ca. 1997. Turner Construction, contractor.

Building foundation of Beckman Hall

Digging the foundation for the Arnold and Mabel Beckman Business and Technology Hall, Chapman University, Orange, California, ca. 1997. Turner Construction, contractor.

Effect of pH on non-photochemical quenching in spinach photsystem 2 particles as measured by picosecond fluorescence decay kinetics

Single photon timing was used to study picosecond chlorophyll a fluorescence decay kinetics of pH induced non-photochemical quenching in spinach photosystem 2 particles. The characteristics of this quenching are a decrease in chlorophyll a fluorescence yield as well as a decrease in photochemistry at low pH. Picosecond kinetics of room temperature fluorescence temporally resolve the individual components of the steady state fluorescence yield into components that are related to primary energy conversion processes in photosystem 2. Four components were resolved for dark adapted (Fo), light saturated (Fm), and chemically reduced (Nadithionite) photosystem 2 reaction centres. The fastest and slowest components, indicative of energy transfer to and energy capture by the photosystem 2 reaction centre and uncoupled ("dead") chlorophyll, respectively, were not affected by changing pH from 6.5 to 4.0. The two intermediate components, indicative of electron transfer processes within the reaction centre of photosystem 2, were affected by the pH change. Results indicate that the decrease in the steady state fluorescence yield at low pH was primarily due to the decrease in lifetime and amplitude of the slower of the intermediate components. These results imply that the decrease in steady state fluorescence yield at low pH is not due to changes in energy transfer to and energy capture by the photosystem 2 reaction centre, but is related to changes in charge stabilization and charge recombination in the photosystem 2 reaction centre.

Estudio de la variación del pH a nivel de reactor biológico, sobre la remoción de dietilenglicol de agua residual industrial [por] Ricardo Carreño Andrade

Tesis (Maestría en Ciencias con Especialidad en Ingeniería Ambiental) U.A.N.L.

Estudios de la ductilidad en caliente de un acero inoxidable martensítico 17-4 PH endurecido por precipitación.

Tesis (Maestría en Ciencias de la Ingeniería Mecánica con Especialidad en Materiales) UANL, 2012.

pH salival en pacientes con hipofunción de glándulas salivales y con neuroelectroestimulación.

Tesis (Maestría en Ciencias con Especialidad en Periodoncia) UANL, 2013.

Comparar el nivel de pH salival en las diferentes etapas de la enfermedad periodontal.

Tesis (Maestría en Ciencias Odontológicas con Especialidad en Periodoncia) UANL, 2013.

Degradación de pirazinamida mediante el proceso foto-fenton utilizando FeC?O? como fuente de hierro a pH 3, 4.5 y 6.

Tesis (Maestría en Ciencias con orientación en Química Analítica Ambiental) UANL, 2014.