From biochemistry to physiology: the calorimetry connection

Titration calorimetry standards and the precision of isothermal titration calorimetry data

Current Isothermal Titration Calorimetry (ITC) data in the literature have relatively high errors in the measured enthalpies of protein-ligand binding reactions. There is a need for universal validation standards for titration calorimeters. Several inorganic salt co-precipitation and buffer protonation reactions have been suggested as possible enthalpy standards. The performances of several commercial calorimeters, including the VP-ITC, ITC200, and Nano ITC-III, were validated using these suggested standard reactions.

Integrating two physiological approaches helps relate respiration to growth of Pinus radiata

Correlation methods originating in the growth and maintenance paradigm (GMP) are traditionally used to calculate a 'growth coefficient' (g) or the 'growth potential' (1/g) of entire plants. The enthalpy balance approach is usually applied to plant organs and relies on determination of both CO(2) release and O(2) reduction to provide a measure of instantaneous rates of enthalpic growth (R(SG)DeltaH(B)). Aspects of both the approaches to explore physiological mechanisms that govern enthalpic growth (variation in rates of CO(2) release versus rates of O(2) reduction) were combined. Respiration and growth rates of apical buds of Pinus radiata were affected strongly by canopy position, and moderately by branching order. A linear relation between enthalpic growth and CO(2) respiration explained 69% of the observed variation. Despite faster rates of growth, enthalpic growth potential (1/g(H)) was comparatively low in the upper canopy. Low enthalpic growth potential entailed comparatively low enthalpy conversion efficiency (eta(H), ratio of R(SG)DeltaH(B) to R(CO(2)) DeltaH(CO(2)); proportional to CO(2):O(2) and to carbon conversion efficiency epsilon) at large R(SG)DeltaH(B). Maximizing enthalpic growth requires a large capacity for O(2) reduction. Relations between R(SG)DeltaH(B) and eta(H) could be described by hyperbolae using two parameters. One parameter, P(1), is equivalent to enthalpic growth potential (1/g(H)).