Biochemical Equilibrium Research Articles

Biochemical properties of acid soils under native grassland in a temperate humid zone

The biochemical properties of 29 soils under native grassland in a temperate humid zone (Galicia, north‐west Spain) and subject to low intensity management (at least during the last 100 years) were determined with the aim of establishing a reference database to allow future comparative studies of the effect of grassland management on soil quality. Several biochemical properties were quantitatively and qualitatively studied. These properties were: labile carbon, microbial biomass carbon, microbial respiration, metabolic quotient, net nitrogen mineralisation and the potential activities of dehydrogenase, catalase, phosphodiesterase, phosphomonoesterase, case in‐protease, BAA‐protease, urease, cellulase, β‐glucosidase, invertase and arylsulphatase. The values of these properties were generally within the ranges of those reported for grassland soils from other parts of the world, but some properties differed both quantitatively and qualitatively from those of forest climax soils in the same area. An equation showing a balance between soil organic matter content and soil biochemical properties was obtained, indicating the existence of a biochemical equilibrium similar to that previously obtained for Galician (north‐west Spain) forest climax soils.

The impact of kosmotropes and chaotropes on bulk and hydration shell water dynamics in a model peptide solution

Kosmotropic (order-making) and chaotropic (order-breaking) co-solvents influence stability and biochemical equilibrium in aqueous solutions of proteins, acting indirectly through the structure and dynamics of the hydration water that surrounds the protein molecules. We have investigated the influence of kosmotropic and chaotropic co-solvents on the hydrogen bonding network dynamics of both bulk water and hydration water. To this end the evolution of bulk water and hydration water dynamics of a prototypical hydrophobic amino acid with polar backbone, N-acetyl-leucine-methylamide (NALMA), has been studied by quasielastic neutron scattering as a function of solvent composition. The results show that bulk water and hydration water dynamics, apart from a dynamical suppression that depends on the NALMA solute, exhibit the same dependence on addition of co-solvent for all of the co-solvents studied (urea, glycerol, MgSO 4, and dimethyl sulfoxide). The hydrophobic solute and the high concentration water-structuring additive have the same effect on the water hydrogen bonding network. Water remains the preferential hydration of the hydrophobic side chain and backbone. We also find that the reorganization of the bulk water hydrogen bond network, upon addition of kosmotrope and chaotrope additives, is not dynamically perturbed, and that the hydrogen bond lifetime is maintained at 1 ps as in pure bulk water. On the other hand the addition of NALMA to the water/co-solvent binary system causes reorganization of the hydrogen bonds, resulting in an increased hydrogen bond lifetime. Furthermore, the solute’s side chain dynamics is not affected by high concentrations of co-solvent. We shall discuss the hydration dynamics results in the context of protein folding and protein–solvent interactions.

Biochemical properties of vineyard soils in Galicia, Spain

In the present study we investigated changes in soil biochemical activity in vineyard soils. With this aim, soil samples (0-10 cm) from 15 vineyard soils developed on diverse parent materials were collected during winter. All soil samples were analysed for a large number of both general and specific biochemical properties. The values of all of the biochemical parameters analysed were extremely low, between 3 and 39% of the usual values obtained for native Galician soils under climax vegetation. To estimate the level of biochemical quality of vineyard soils, while avoiding the problem of comparing soils with totally different organic matter contents, a biochemical equilibrium equation was used. The results showed that vineyard soils are highly degraded soils, for which in the most extreme cases, the value of the biochemical equilibrium index was 13%, i.e. almost 8 times lower that in high quality soils such as climax soils.

Role of compost, bentonite and lime in recovering the biochemical equilibrium of diesel oil contaminated soil

The aim of the study was to determine how soil contamination with diesel oil affected biochemical properties of soil and to determine whether the application of compost, bentonite or lime could recover the biochemical equilibrium of soil. The experiments were carried out in a greenhouse. Typical Eutric Cambisols soil formed from sandy loam was polluted with the following amounts of diesel oil: 2.5, 5.0 and 10 cm<sup>3</sup>/kg of soil. The results of the tests showed that the contamination of soil with diesel oil at the amount between 2.5 and 10 cm<sup>3</sup>/kg of soil disturbed the biochemical balance of soil. Irrespective of the application of compost, bentonite or lime and regardless which plant species was grown, diesel oil significantly (p = 0.01) stimulated the activity of dehydrogenases, urease, and alkaline phosphatase as well as the nitrification of soil. Enrichment of soil with compost, bentonite or lime stimulated the activity of urease, alkaline phosphatase and nitrification. The activity of dehydrogenases, urease and nitrification of soil, in contrast to the activity of acid phosphatase, was higher in soil under spring oilseed rape than in soil under oats. The activity of dehydrogenases, urease, alkaline phosphatase in soil contaminated with diesel oil was positively correlated with the nitrification of soil. The correlation between the activity of acid phosphatase and soil nitrification was negative.

Intracellular redox equilibrium and growth phase affect the performance of luciferase-based biosensors

Light emission from the bacterial luciferase operon has been variously exploited during last two decades. The use of convenient inducible promoters has granted significant degrees of specificity to whole cell-based assays for high-throughput screening and environmental monitoring. Nevertheless, unexplained unspecific responses have been repeatedly reported. Here, we show that the impairment of the intracellular biochemical equilibrium interferes with the luminescence produced by Escherichia coli and Staphylococcus aureus strains carrying the lux operon under constitutive or inducible control. Compounds as trimethoprim and methotrexate, by indirectly inducing NADPH accumulation, enhance light emission. Conversely, molecules driving the cell toward an oxidized state, as dimethyl sulfoxide, inhibit luminescence. These findings fit into the accepted biochemical pathway for bioluminescence, where NADPH and reducing equivalents are necessary for the production of luciferase substrates, although they do not directly take part into the light-emitting reaction. Moreover, we investigated the influence of induction timing upon the bioluminescence response from inducible reporter systems and demonstrated a correlation between the emitted light and the growth phase at which induction is performed. Our results provide explanations for some unspecific responses recorded so far in whole cell-based luminescent biosensors and emphasize the intrinsic limitations of this kind of reporting system.

Evaluation of microfluidic blood gas sensors that combine microdialysis and optical monitoring

It is shown that microdialysis-based blood gas (pH, pCO2 and pO2) optical sensors are stable for durations of several hours in blood. This performance is uncommon with many types of membrane sensor. Microdialysis techniques can be designed to ensure that the sweep microflow samples are in biochemical equilibrium with the bulk media, even after hours of exposure to the complex composition of blood. The rate of diffusion through the membrane is not the determining factor in sensor reading, as it is with other sensor techniques that consume the analyte. The sweep fluid 95% equilibration times for microdialysis fibres were approximately double in blood compared with buffer, reflecting slower diffusion of ions. This is in contrast to the equilibration of gases through silicone hollow-fibre membranes in blood, which showed unchanged equilibration times between blood and buffer. Sensor measurements correlate well with a blood gas analyser for up to 9 h in blood, with correlation coefficients of 0.973 for the pO2 sensor 0.974 for the pCO2 sensor and 0.947 for the pH sensor. In blood, the sensors have precisions of 1.7 mmHg, 3.7 mmHg and 0.019 pH units and bias levels of -0.7 mmHg, 1.2 mmHg and 0.002 pH units, for pO2, pCO2 and pH, respectively.

The Role of Hydration on the Mechanism of Allosteric Regulation: In Situ Measurements of the Oxygen-Linked Kinetics of Water Binding to Hemoglobin

We report here the first direct measurements of changes in protein hydration triggered by a functional binding. This task is achieved by weighing hemoglobin (Hb) and myoglobin films exposed to an atmosphere of 98% relative humidity during oxygenation. The binding of the first oxygen molecules to Hb tetramer triggers a change in protein conformation, which increases binding affinity to the remaining empty sites giving rise to the appearance of cooperative phenomena. Although crystallographic data have evidenced that this structural change increases the protein water-accessible surface area, isobaric osmotic stress experiments in aqueous cosolutions have shown that water binding is linked to Hb oxygenation. Now we show that the differential hydration between fully oxygenated and fully deoxygenated states of these proteins, determined by weighing protein films with a quartz crystal microbalance, agree with the ones determined by osmotic stress in aqueous cosolutions, from the linkage between protein oxygen affinity and water activity. The agreements prove that the changes in water activity brought about by adding osmolytes to the buffer solution shift biochemical equilibrium in proportion to the number of water molecules associated with the reaction. The concomitant kinetics of oxygen and of water binding to Hb have been also determined. The data show that the binding of water molecules to the extra protein surface exposed on the transition from the low-affinity T to the high-affinity R conformations of hemoglobin is the rate-limiting step of Hb cooperative reaction. This evidences that water binding is a crucial step on the allosteric mechanism regulating cooperative interactions, and suggests the possibility that environmental water activity might be engaged in the kinetic control of some important reactions in vivo.

Calibration of the calcium dissociation constant of Rhod2in the perfused mouse heartusing manganese quenching

Both theoretical and experimental results are presented for in vivo calibration of the dissociation constant KCadof the calcium-sensitive fluorescent dye Rhod2in the perfused mouse heart, using manganese quenching of fluorescence transients. An analytical model is derived, based on the biochemical equilibrium of manganese competition with calcium for Rhod2binding. Expressing the differential of the changes between systole and diastole in fluorescence transient (δΔ Fsys-dia). δΔFsys-diain a beating heart as a function of the perfusate manganese concentration [Mn2+]pallows correlation of the measured differential transient changes δΔ Fsys-diawith the calcium dissociation constant KCadof Rhod2and the calcium concentration in the heart. Numerical modeling indicates that the KCadpredominantly affects the asymptotic slope of the δΔ Fsys-diaversus [Mn2+]pcurve at certain manganese concentrations, which suggests that the KCadcan be inversely calculated by partially fitting the δΔ Fsys-diadistribution as a function of the perfusate manganese concentration. The feasibility of this approach is confirmed by quenching of calcium transients by manganese infusion into isolated perfused beating mouse hearts. The resulting calculated dissociation constant KCadof Rhod2is 720nM. Using the same approach, we are able to also estimate intracellular calcium concentrations of 700nM at peak systole and 300nM in diastole. This is in good agreement with values obtained by calibration of fluorescence values with a calcium saturation tetanization procedure in the same perfused mouse heart model.

Defining the validity of a biochemical index of soil quality

The native soils of Galicia (NW Spain) exhibit a biochemical equilibrium such that total soil N is a function of five biochemical and microbiological parameters: microbial biomass C, mineralized N, phosphomonoesterase, β-glucosidase and urease activities. To investigate whether the ratio of the total N calculated from biochemical soil properties (Nc) and the total N as measured by the Kjeldahl method (Nk; Nc/Nk) can be used as an index of soil quality, we determined these variables and consequently the ratio in three kinds of disturbed soils: an artificially Cu-contaminated soil, two lignite mine soils, and a number of arable soils. In none of the studied soils did the individual biochemical parameters respond consistently to the factors influencing soil quality, but in all cases soil degradation was reflected by the Nc/Nk value, which differed more or less markedly from 100%. Nc/Nk can therefore be used for the rapid evaluation of soil degradation, since it distinguishes among biochemically balanced soils, soils in a transient state of high microbiological and biochemical activity and degraded soils. It can also serve as a reliable basis for the rapid calculation of the "ecological dose" (ED50) of soil pollutants. The use of Nc/Nk as an objective index of the biochemical quality of soils is recommended.

In disperse solution, "osmotic stress" is a restricted case of preferential interactions.

In the practice of "osmotic stress," the effect of excluded cosolvents on a biochemical equilibrium is interpreted as the number of water molecules participating in the reaction. This action is attributed to lowering of solvent water activity by the cosolvent. This concept of osmotic stress in disperse solution is erroneous: (i) A cosolvent cannot be both excluded and inert, i.e., noninteracting, because exclusion requires a positive free energy change; (ii) a decrease in water activity alone by addition of solute cannot affect an equilibrium when the reacting surface is in contact with the solvent; and (iii) osmotic stress in disperse solution is a restricted case of preferential interactions; the reaction is driven by the free energy of cosolvent exclusion, and the derived number of water molecules is solely a measure of the mutual perturbations of the chemical potentials of the cosolvent and the protein.

Membrane reactors in chemical production processes and the application to the pervaporation‐assisted esterification

AbstractWhen appropriate membrane was used for the assistance of chemical and biochemical equilibrium reactions, it is possible to enhance the yield and the purity of the reaction product by selectively adding educts or selectively removing products and to a lower the energy input and the reaction time compared to conventional process.In this paper a review on membrane reactors with special emphasis on membrane‐assistance of esterification reactions and a continuous tube membrane reactor for the pervaporation‐assistance of the esterification are presented. The heterogeneously catalyzed esterification of ethanol and acetic acid to ethyl acetate and water was investigated as a typical chemical equilibrium reaction.The selective and simultaneous water separation from the reaction mixture of the esterification with polyvinyl alcohol pervaporation membranes is considered to be an interesting process alternative to the conventional distillation process. Compared to the distillation process, for the pervaporation‐assisted process a decrease of the energy input of over 75% and of the investment and operating coasts of over 50% each was calculated.

STUDY OF THE EFFECT OF HYPOURICAEMIC THERAPY ON SERUM LIPID LEVELS IN GOUT PATIENTS: 47

25 patients with primary gout had fasting serum uric acid and lipid levels determined before hypouricaemic therapy. These uric acid and lipid levels were repeated after biochemical equilibrium had occurred on allopurinol or probenecid and in the absence of significant changes in weight. No significant changes occurred in cholesterol, triglyceride or high density lipoprotein cholesterol levels (paired 't' tests - p > 0.05). There were no significant correlations of serum lipid levels with each other, with uric acid values or with weight. These findings suggest that hypouricaemic therapy in gout patients has no effect on serum lipid levels.

The Use of Exponentially Damped Polynomials for Biological Recovery Data

SUMMARY Exponentially damped polynomial regression models are applied to data arising from the return to biochemical equilibrium after an induced disturbance. Computation and statistical analyses are outlined, and illustrated with human blood glucose levels after alcohol consumption.

Recommendations for measurement and presentation of biochemical equilibrium data

Recommendations for measurement and presentation of biochemical equilibrium data

Recommendations for measurement and presentation of biochemical equilibrium data

Recommendations for measurement and presentation of biochemical equilibrium data

Recommendations for Measurement and Presentation of Biochemical Equilibrium Data*

Recommendations for Measurement and Presentation of Biochemical Equilibrium Data*

Recommendations for measurement and presentation of biochemical equilibrium data. Prepared by the Interunion Commission on Biothermodynamics.

Recommendations for measurement and presentation of biochemical equilibrium data. Prepared by the Interunion Commission on Biothermodynamics.

Recommendations for measurement and presentation of biochemical equilibrium data

Equilibrium data are of importance in describing and understanding of biochemical systems. At present there is marked variation among different investigators in the choice of experimental conditions for the study of similar or identical reactions and in the manner of reporting the data. In many cases the description of the system does not provide all the essential information that would permit reproduction of the experiments. This can lead to confusion and difficulties in correlating the results of different workers.Equilibrium studies in biochemistry involve special problems that are not encountered in general chemistry. The attainment of biochemical equilibria commonly involves the addition of a specific enzyme to the system to catalyse the reaction studied; sometimes two or more enzymes must be added. In addition the enzyme may require the presence of certain cofactors, such as metal ions. The reactants, or products, or both, may bind or release protons or other ions during the reaction under study.

Vitamin-responsive inborn errors of metabolism

Vitamins are essential precursors of coenzymes. The dietary intake, or exogenous supply that is sufficient to maintain normal metabolic and biochemical equilibrium, defines the requirement of a vitamin for man. Interindividual variation exists in the latter, the large part of which is accomodated by intakes conforming to the recommended dietary allowances (RDA) for individual vitamins. Deficient supply of a vitamin eventually affects all functions dependent on the presence of its coenzyme form; the deficiency state is usually corrected by replacement of the vitamin at the RDA level. Some individuals have a requirement for a particular vitamin that is met only by doses well above the RDA (i.e. at pharmacologic levels of intake). This type of aberration is usually inherited. The mutant gene product impedes some step in the sequence of events that makes the coenzyme form of the vitamin accessible to its apoenzyme(s). A mutation that imposes an exaggerated requirement for a vitamin may alter its transport across membranes, or its conversion into coenzyme (“biosynthetic defect”); alternatively, the mutation may affect an apoenzyme so that the steric relationships between coenzyme and protein are no longer favorable (“binding defect”). In the former, all apoenzymes served by the product of biosynthesis (coenzyme) will be perturbed; in the latter, only the specific apoenzyme is affected. Vitamin responsiveness, either biochemical or clinical indicates that a block in biosynthesis is “leaky”, or that an unfavorable relationship between enzyme and coenzyme can be overcome. It has also been suggested that saturation of a mutant apoenzyme by its coenzyme may cause posttranscriptional induction, by attenuating the rate of enzyme degradation; or the coenzyme may augment an alternate route of metabolism by induction of the enzyme at the first committed step. The mechanisms by which mutations permit vitamin responsiveness among the inborn errors of metabolism, while imposing an inherited aberration in vitamin requirement, are of more than theoretical interest. Individuals, with vitamin-responsive hereditary metabolic disease, in general, have milder variants of the classical (Garrodian) phenotype; moreover, their treatment is relatively simple and the response to it is often dramatic.

Models Describing Sex Ratio Data in Heterodera Rostochiensis

The model is based upon an assumption that the sex of a larva is irreversibly determined by its nutrient status early in its feeding phase. This dependence involves a biochemical equilibrium of nutrient molecules with target sites in the larva. The model is economical in that only a single parameter is involved; the equations are simple, easy to apply to data, and give a good description of the data considered here. The model suggests useful approaches to further experimentation in this field.