Calorimetric biological

Calorimetry is an important technique in biology as well as in chemistry. The inventor of the calorimeter was Antoine Lavoisier, who is shown in the illustration. Lavoisier was a founder of modem chemistry, but he also carried out calorimetric measurements on biological materials. Lavoisier and Pierre Laplace reported in 1783 that respiration is a very slow form of combustion. Thus, calorimetry has been applied to biology virtually from its invention. 

Despite Lavoisier s early work on the link between energy and life, calorimetric measurements played a relatively minor role in biology until recent years, primarily because of practical obstacles. Every organism must take in and give off matter as part of its normal function, and it is very difficult to make accurate heat-flow measurements when matter is transferred. Moreover, the sizes of many organisms are poorly matched to the sizes of calorimeters. Although a chemist can adjust the amount of a substance on which to carry out calorimetry, a biologist often cannot. 

These are just some of the ways in which calorimetry is used in contemporary biological research. Our examples highlight studies at the cellular level, but ecologists also use calorimetry to explore the energy balances In ecosystems, and whole-organism biologists have found ways to carry out calorimetric measurements on fish, birds, reptiles, and mammals. Including humans. 

I. Wadso. Some Problems in Calorimetric Measurements on Cellular Systems. In Biological Microcalorimetry A. E. Beezer, Ed. Academic Press London, 1980 247-274. 

Spectroscopic and Calorimetric Studies of Biological Membrane Structure... 

For biological membranes the situation is more complex. The results from erythrocyte ghosts and lipids (13) suggest nonpolar association through lipid hydrocarbon chains. As a test of the technique a membrane in which the bilayer conformation has been demonstrated by some independent technique is desirable. I have argued earlier from calorimetric evidence that the membrane of M. laidlawii is such a system. NMR spectra of M. laidlawii membranes taken in this laboratory do not, however, show discernible hydrocarbon proton resonance. We must consider, then, why the two techniques of calorimetry and NMR do not agree. 

The principle of calorimetry is very interesting for biological applications. Calorimetric biosensors are based on the detection of the heat production of biological reactions which is caused by enthalpy changes. The micro calorimetric sensing principle is very versatile because of the exothermic nature of nearly all enzymatic reactions [8] and was introduced as a conventionally constructed device very early [9] ... 

The experimental study of heat produced or absorbed in chemical reactions is usually called thermochemistry. Such investigations are often best conducted by direct calorimetric measurements, but values for heat quantities and their time and temperature derivatives can also be obtained from other kinds of thermodynamic experiments. A heat quantity, Q, which is lost or gained in a process conducted under constant pressure, p (in chemistry and biology most frequently the atmospheric pressure), is defined as the enthalpy change, AH, accompanying the process. 

Randzio, S. Suurkuusk, J. (1980). Interpretation of calorimetric thermograms and their dynamic corrections. In Biological Microcalorimetry (Beezer, A.E., ed.), pp. 311-341, Academic Press, London. 

Wadso, I. (1987). Calorimetric techniques. In Thermal and Energetic Studies of Cellular Biological Systems (James, A.M., ed.), pp. 34-67, Wright, Bristol. 

Kemp, R.B., Schaarschmidt, B. (Eds.) (1995). Calorimetric and Thermodynamic Studies in Biology Special Issue. Thermochim. Acta 251,1-402. 

One of the earliest decisions was to calibrate the GRID force field whenever possible by using experimental measurements rather than theoretical computations, and calorimetric measurements were therefore needed for the initial calibration in order to differentiate the enthalpic and entropic contributions to the overall free energy. However, only a very little calorimetric data was readily available at that time, about well characterised biological systems in which the structures of the interacting ligand and macromolecule were both known, and so a different approach was initially needed. 

Although studies of the thermotropic phase behavior of singlecomponent multilamellar phospholipid vesicles are necessary and valuable, these systems are not realistic models for biological membranes that normally contain at least several different types of phospholipids and a variety of fatty acyl chains. As a first step toward understanding the interactions of both the polar and apolar portions of different lipids in mixtures, DSC studies of various binary and ternary phospholipid systems have been carried out. Phase diagrams can be constructed by specifying the onset and completion temperatures for the phase transition of a series of mixtures and by an inspection of the shapes of the calorimetric traces. A comparison of the observed transition curves with the theoretical curves supports... 

The occurrence of cholesterol and related sterols in the membranes of eukaryotic cells has prompted many investigations of the effect of cholesterol on the thermotropic phase behavior of phospholipids (see References 23-25). Studies using calorimetric and other physical techniques have established that cholesterol can have profound effects on the physical properties of phospholipid bilayers and plays an important role in controlling the fluidity of biological membranes. Cholesterol induces an intermediate state in phospholipid molecules with which it interacts and, thus, increases the fluidity of the hydrocarbon chains below and decreases the fluidity above the gel-to-liquid-crystalline phase transition temperature. The reader should consult some recent reviews for a more detailed treatment of cholesterol incorporation on the structure and organization of lipid bilayers (23-25). 

An enzyme biosensor consists of an enzyme as a biological sensing element and a transducer, which may be amperometric, potentiometric, conductimetric, optical, calorimetric, etc. Enzyme biosensors have been applied to detecting various substrates (Table 3.1), which are selectively oxidized or reduced in enzyme-catalyzed processes depending on the nature of substrates and enzymes used (oxidases or reductases) to construct sensors. 

Miller DP, de Pablo JJ. Calorimetric solution properties of simple saccharides and their significance for the stabilization of biological structure and function. ] Phys Chem 2000 B104 8876-8883. 

Thermometric sensors are based on the measurement of the heat effects of a specific chemical reaction or an adsorption process that involves the analyte. In this group of sensors the heat effects may be measured in various ways, for example in catalytic sensors the heat of a combustion reaction or an enzymatic reaction is measured by use of a thermistor. Calorimetric biosensors detect variations of heat during a biological reaction. 

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