Thermodynamics of Nath's 2-ion model for ATP synthesis.

A major finding of studies of organic acid ionization was that substituents on an aliphatic chain attached to a carboxyl group have large effects on the equilibrium constant but very little effect on ΔH which is in the range 0 ± 4 kJ/mol for all carboxylic acids of this type. According to Nath's 2-ion mechanism for ATP synthesis, succinic acid was selected by biological evolution because an acid that could be ionized with no energy input was required, i.e.

Germination of L. Seeds Is Associated with the Alternative Respiratory Pathway.

The alternative oxidase (AOX) is a ubiquinol oxidase with a crucial role in the mitochondrial alternative respiratory pathway, which is associated with various processes in plants. In this study, the activity of AOX in pea seed germination was determined in two pea cultivars, 'Maravilha d'América' (MA) and 'Torta de Quebrar' (TQ), during a germination trial using cytochrome oxidase (COX) and AOX inhibitors [rotenone (RT) and salicylic hydroxamic acid (SHAM), respectively]. Calorespirometry was used to assess respiratory changes during germination.

Modification of the structural stability of human serum albumin in rheumatoid arthritis.

Differential scanning calorimetry (DSC) can indicate changes in structure and/or concentration of the most abundant proteins in a biological sample via heat denaturation curves (HDCs). In blood serum for example, HDC changes result from either concentration changes or altered thermal stabilities for 7-10 proteins and has previously been shown capable of differentiating between sick and healthy human subjects. Here, we compare HDCs and proteomic profiles of 50 patients experiencing joint-inflammatory symptoms, 27 of which were clinically diagnosed with rheumatoid arthritis (RA).

Temperature Response of Metabolic Activity of an Antarctic Nematode.

Because of climate change, the McMurdo Dry Valleys of Antarctica (MCM) have experienced an increase in the frequency and magnitude of summer pulse warming and surface ice and snow melting events. In response to these environmental changes, some nematode species in the MCM have experienced steady population declines over the last three decades, but , a mesophilic nematode species, has responded with a steady increase in range and abundance. To determine how responds to increasing temperatures, we measured metabolic heat and CO production rates and calculated O consumption rates as a function of temperature at 5 °C intervals from 5 to 50 °C.

Exploring the Applicability of Calorespirometry to Assess Seed Metabolic Stability Upon Temperature Stress Conditions- L. Used as a Case Study.

The availability of phenotyping tools to assist breeding programs in the selection of high-quality crop seeds is of obvious interest with consequences for both seed producers and consumers. Seed germination involves the activation of several metabolic pathways, such as cellular respiration to provide the required ATP and reducing power. This work tested the applicability of calorespirometry, the simultaneous measurement of heat and CO rates, as a phenotyping tool to assess seed respiratory properties as a function of temperature.

Transformation of matter in living organisms during growth and evolution.

Growth of an organism involves transformations of the state of matter from unstructured food or photosynthate into the highly organized matter in the living organism. Biological evolution involves random changes in the structure of DNA that lead to changes in the organization of the matter in an organism. Thermodynamic data show the organized biomass in living organisms has the same thermodynamic properties as a random mixture of the same elemental composition and is not in an energetically metastable, low entropy state.

Proposing a minimal set of metrics and methods to predict probabilities of amyloidosis disease and onset age in individuals.

Many amyloid-driven pathologies have both genetic and stochastic components where assessing risk of disease development requires a multifactorial assessment where many of the variables are poorly understood. Risk of transthyretin-mediated amyloidosis is enhanced by age and mutation of the transthyretin (TTR) gene, but amyloidosis is not directly initiated by mutated TTR proteins. Nearly all of the 150+ known mutations increase dissociation of the homotetrameric protein structure and increase the probability of an individual developing a TTR amyloid disease late in life.

Response of Mycorrhizal 'Touriga Nacional' Variety Grapevines to High Temperatures Measured by Calorespirometry and Near-Infrared Spectroscopy.

Heat stress negatively affects several physiological and biochemical processes in grapevine plants. In this work, two new methods, calorespirometry, which has been used to determine temperature adaptation in plants, and near-infrared (NIR) spectroscopy, which has been used to determine several grapevine-related traits and to discriminate among varieties, were tested to evaluate grapevine response to high temperatures. 'Touriga Nacional' variety grapevines, inoculated or not with or were used in this study.

Obtaining precise and accurate results by ITC.

Acquisition of precise and accurate results by isothermal titration calorimetry (ITC) can be achieved through thoughtful experimental design and modeling and careful experimental operations. Large reported errors in ITC results in determinations of stoichiometries, equilibrium constants and enthalpy changes for ligand binding to proteins are the consequence of poor experiment design, failure to properly calibrate and test instruments and protocols, lack of controls, errors in solution preparation, and incorrect data analyses. Analysis of a recent report that claimed to have determined the "repeatability, precision, and accuracy of the enthalpies and Gibbs energies of a protein-ligand binding reaction" by ITC is used to illustrate how to improve ITC operations and results.

Enzyme Kinetics Determined by Single-Injection Isothermal Titration Calorimetry.

This chapter describes how to collect Michaelis-Menten kinetic data on an enzyme-catalyzed reaction with the isothermal titration calorimetry (ITC) and the single-injection method. ITC measures the heat rate which is directly proportional to the reaction rate. The enthalpy change (ΔH), K, k, and v are determined in a single assay that does not require labeling or immobilization.

Calorimetric Methods for Measuring Stability and Reusability of Membrane Immobilized Enzymes.

Unlabelled: The aim of this work is to develop calorimetric methods for characterizing the activity and stability of membrane immobilized enzymes. Invertase immobilized on a nylon-6 nanofiber membrane is used as a test case. The stability of both immobilized and free invertase activity was measured by spectrophotometry and isothermal titration calorimetry (ITC).

Effect of soil storage at 4 °C on the calorespirometric measurements of soil microbial metabolism.

Soil samples must usually be stored for a time between collection and measurements of microbial metabolic properties. However, little is known about the influence of storage conditions on microbial metabolism when studied by calorespirometry. Calorespirometry measures the heat rate and the CO rate of microbial metabolism, where the ratio of heat and CO released, the calorespirometric ratio, informs about the nature of substrates being used by microorganisms.

Enzyme-catalyzed and binding reaction kinetics determined by titration calorimetry.

Background: Isothermal calorimetry allows monitoring of reaction rates via direct measurement of the rate of heat produced by the reaction. Calorimetry is one of very few techniques that can be used to measure rates without taking a derivative of the primary data. Because heat is a universal indicator of chemical reactions, calorimetry can be used to measure kinetics in opaque solutions, suspensions, and multiple phase systems and does not require chemical labeling.

Calorespirometry, oxygen isotope analysis and functional-marker-assisted selection ('CalOxy-FMAS') for genotype screening: A novel concept and tool kit for predicting stable plant growth performance and functional marker identification.

We propose a novel concept and tool kit for predictive phenotyping. The proposed technology measures respiration properties as functions of growth conditions to identify genotypes with higher plasticity via homeostasis and adaptive morphophysiology. Combining calorespirometry, oxygen isotope analysis and functional-marker-assisted selection ('CalOxy-FMAS') for genotype screening will enable predicting the genetic potential for stable plant growth performance.

Enzyme kinetics determined by single-injection isothermal titration calorimetry.

The purposes of this paper are (a) to examine the effect of calorimeter time constant (τ) on heat rate data from a single enzyme injection into substrate in an isothermal titration calorimeter (ITC), (b) to provide information that can be used to predict the optimum experimental conditions for determining the rate constant (k2), Michaelis constant (KM), and enthalpy change of the reaction (ΔRH), and (c) to describe methods for evaluating these parameters. We find that KM, k2 and ΔRH can be accurately estimated without correcting for the calorimeter time constant, τ, if (k2E/KM), where E is the total active enzyme concentration, is between 0.1/τ and 1/τ and the reaction goes to at least 99% completion.

Calorespirometry of terrestrial organisms and ecosystems.

Calorespirometry is the simultaneous measurement of heat and gas exchange from biological systems. Such measurements can be used to assess fundamental properties of many different types of systems from small ecosystems to isolated tissues. Techniques for calorespirometric measurements on terrestrial (non-aquatic) samples are described.

Phenotyping carrot (Daucus carota L.) for yield-determining temperature response by calorespirometry.

Calorespirometric measurements proved to be useful for phenotyping temperature response in terms of optimum temperatures for growth and low temperature limits for growth respiration in diverse carrot genotypes. High and low-temperature tolerance is an important trait in many breeding programs, but to date, improvement strategies have had limited success. Developing new, cost efficient and reliable screening tools to identify and select the most tolerant crop plant genotypes is necessary to assist plant breeding on cold and heat tolerance, and calorespirometry is proposed for this.

Effects of temperature and modified atmospheres on diapausing 5th instar codling moth metabolism.

The oxygen and capacity limitation of thermal tolerance (OCLTT) has been established in aquatic insect larvae, but OCLTT has not been shown to generally apply to terrestrial insects. Previous research indicates that heat treatments in combination with high concentrations of carbon dioxide and low concentrations of oxygen may be effective for controlling diapausing codling moth, a quarantine pest in walnuts, but treatment requires long times and the killing mechanism is unknown. In this study, the effects of temperature and modified atmospheres on metabolism in diapausing 5th instar codling moth (Cydia pomonella) was investigated with multi-channel differential scanning calorimeters, one equipped with an oxygen sensor.

Differential scanning calorimetry of gliomas: a new tool in brain cancer diagnostics?

Background: Thermal stability signatures of complex molecular interactions in biological fluids can be measured using differential scanning calorimetry (DSC). Evaluating the thermal stability of plasma proteomes offers a method of producing a disease-specific "signature" (thermogram) in neoplastic and autoimmune diseases.

Objective: The authors describe the use of DSC with human brain tumor tissue to create unique thermograms for correlation with histological tumor classification.

Determining enzyme kinetics via isothermal titration calorimetry.

Isothermal titration calorimetry (ITC) has emerged as a powerful tool for determining the thermodynamic properties of chemical or physical equilibria such as protein-protein, ligand-receptor, and protein-DNA binding interactions. The utility of ITC for determining kinetic information, however, has not been fully recognized. Methods for collecting and analyzing data on enzyme kinetics are discussed here.

Calorimetric determination of rate constants and enthalpy changes for zero-order reactions.

Calorimetry is a general method for determination of the rates of zero-order processes, but analysis of the data for the rate constant and reaction enthalpy is difficult because these occur as a product in the rate equation so evaluation of one requires knowledge of the other. Three methods for evaluation of both parameters, without prior knowledge, are illustrated with examples and compared with literature data. Method 1 requires the reaction to be studied in two buffers with different enthalpies of ionization.