Caged compounds kinetic applications

In a chapter primarily intended to illustrate the use of caged compounds for kinetic studies it is more important to use some selected examples to discuss principles in some detail, rather than to survey all the available compounds and their applications, which are being constantly extended. The future emphasis is likely to be on compounds permitting more rapid release of a wider range of substrates for kinetic studies of muscle contraction, excitation contraction coupling and neuroreceptors (see for instance figure 8.4). The potential of the use of caged compounds for transient kinetic studies on enzyme reactions has not yet been tapped. 

The time resolution of the photochemical release of caged substrates depends on two factors the energy/time profile of the light source used for photolysis and the effective rate of liberation of active substrate. It should be remembered that the time scale of the potential application of a kinetic technique depends critically on the accuracy of the determination of zero time. Some practical details of the investigation of different parameters are illustrated below. Suffice it to say for the moment that the range of compounds presently available for different systems have time constants from 10 ms to 10 ps for the liberation of phosphates and amino derivatives (neurotransmitters). 

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