Microcalorimetric method to determine competitive binding action of a psychotropic drug (dipotassium chlorazepate) on L-tryptophan · human serum albumin complex

A mathematical treatment and an original microcalorimetric method are developed to verify an eventual competitive binding between any two substances for the same macromolecule. To apply this method, a competitive binding of L-tryptophan and one benzodiazepin (dipotassium chlorazepate) for human serum albumin is perfectly demonstrated.The association constants and the enthalpy variations are equal to 14 000 ± 2000 M^?1 and ?6.6 ± 0.2 kcal/mol for human serum albumin · tryptophan complex and 13 000 ± 1000 M^?1 and ?10.0 ± 0.2 kcal/mol for human serum albumin · chlorazepate complex. In all cases the stoichiometry is equal to one.The binding of tryptophan to human serum albumin is partially stereospecific; the association constant and the enthalpy variation for D-tryptophan complex are equal, respectively, to 1000 ± 200 M^?1 and ?2.6 ± 0.3 kcal/mol.     

Anthropometric and physiological properties in the determination of biological distances.

The investigation of anthropometric dimensions of the body and head, lung function tests and blood pressure was carried out in 3 separate groups. The analysis of 'distances' between particular pairs of the analyzed groups was performed by Penrose's CH2 and its components CQ2 and (v-l/v)CZ2. It is pointed to various ways of diversification of particular characteristics, which is likely to depend on different selective inertia of particular traits, that is, on different intensity of the effect of genetic and/or ecological factors on their formation. It is shown that as many different biological characteristics of human groups as possible should be taken into consideration for the calculation of 'distances'.     

Specificity of predator-induced neck spine and alteration in life history traits in Daphnia pulex

It has been proposed that the predator-induced defensive neck spine in Daphnia pulex has a demographic cost. Our results show that this cost is not merely an allocation cost related to the formation and maintenance of the neck spine. In a life table experiment, we tested whether spine induction and life history traits in D. pulex are affected by different invertebrate predators: first and third instar Chaoborus, fourth instar Mochlonyx and two size classes of Notonecta and Dytiscus larvae. D. pulex showed sensitivity to the different predators. Predator-exposure affected one or more of the following life history traits of D. pulex: the timing of first reproduction, clutch size, and growth. In some cases, exposure to predators altered life history traits when neck spine induction did not occur. These shifts in life history traits occurring in the absence of spine induction may be caused by behavioral or physiological changes triggered by the predators.     

Comparison of an iterative microcalorimetric method and dialysis equilibrium for calculating thermodynamic parameters of a binding protein which presents a weak affinity for its substrate

An original iterative microcalorimetric method is used to study the interaction of 5-fluorouracil, a cancer chemotherapeutic agent, with human serum albumin. Two equivalent binding sites are demonstrated with an association constant and an enthalpy variation equal to 370 ± 30 m^?1 and ?10 ± 0,5 kcal/mol, respectively. By means of a competitive microcalorimetric method, the partially competitive binding of dipotassium chlorazepate and 5-fluorouracil is shown. This iterative microcalorimetric method can be applied to all techniques involving the measurement of a phenomenon which is proportional to the concentration of the complex.