Corroborative models, definition

Hill introduced two useful definitions for model compounds of metalloproteins, — speculative models and corroborative models, Speculative models are prepared when the structure of the microenvironment of the metallobiosite is unknown and the objective is to reproduce some physico-chemical property of the system in a small molecule complex. When the structure of the metallobiosite is known a corroborative model can be prepared. This is usually a small molecule complex in which the environment of the metal is reproduced as accurately as possible. It then becomes possible to determine whether the observed properties of the metal in the protein are dominated by the first coordination sphere and can give insights into the relationship between structural features of the metallobiosite and its physical properties. 

Thus the data in fig. 8.16 corroborate the results obtained in the simpler receptor model as in fig. 8.13, there exists a pattern of periodic stimulation that maximizes cell responsiveness measured here by the capability of generating the largest amount of intracellular cAMP in a given amount of time, in response to pulsatile stimulation. The values Ti = 2.70 min, To = 4.75 min obtained for the optimal pattern of periodic stimulation match those observed in the experiments and are close to those obtained in fig. 8.13 in the general model for similar parameter values. Very similar results are obtained when other definitions of cellular responsiveness are chosen, or when the excitable properties of D. discoideum cells are taken into account (Li Goldbeter, 1990). 

It must be emphasized that a component whose lifetime is exponentially distributed cannot be improved by maintenance. For an improvement would imply a reduction of its failure rate. In the present model it is ensured that the unavailability is equal to zero after every functional test. This is achieved by determining in the first place whether it is still capable of functioning or has failed. In the latter case the component is either repaired or replaced. If it is still capable of functioning it is as good as new because components with a constant failure rate do not age by definition. If it has to be repaired, as good as new is a hypothesis usually corroborated in plants with a good safety culture. 

The definition of resistant starch is based on its physiological behavior in the human small intestine, i.e., resistant starch is a heterogeneous group of molecules from small monosaccharides to large polymers with different molecular weight, degree of polymerization, and supramolecular architecture. This complexity makes it difficult to quantify accurately. All in vitro methods therefore need to be corroborated against in vivo models however, in vivo models are also very difficult to validate. 

---