Common names, 1/8, VIII

Only in rare cases is it possible to solve the master equation explicitly. For instance, we have seen that one-step master equations can be solved when the step probabilities rn and gn are constant or linear in n, but not otherwise. It is therefore important to find approximation methods, of which the Fokker-Planck approximation is the best known. Many other methods have been suggested in the literature, usually consisting of ad hoc prescriptions for cutting off higher moments of the fluctuations, and often determined by the needs or taste of the author rather than by logic. As a consequence they have led to the unreliable and contradictory results mentioned in VIII. 1. One thing they have in common, however, namely the idea that somehow the fluctuations are small. 

Rubiae Radbc is made up of locally common Rubiaceous plants Rubia akane in Japan, R. cordifolia in China, and R. tinctorum in Europe. The former two showed antineoplastic activity, but the latter did not. Because the extract of Rubiae Radix showed antineoplastic activity against sarcoma 180A, isolation was pursued for the active principles. After repeated fractionation and purification of the extract, oligopeptides were obtained as active principles against P388 leukemia. The extract was partitioned with water and benzene, and water and ethyl acetate. From both fractions, eight components were isolated as crystals, and named as RA-I-VIII (160-167) after Rubia akane 124-128). 

In all cases the systems were heterogeneous and the active initiators are now known by the genraal name Ziegler-Natta catalysts. This encompasses a vast number of substances prepared from different combinations of organometaUic compounds where the metal comes from the main Groups I, II, or III and is combined with the halide or esto of a transition metal (Groups IV to VIII). Table 7.1 contains a number of the common components of the Ziegler-Natta catalysts, but this list is far from exhaustive. 

For the sake of comparing the stored free energies in such compounds as ATP, acyl-CoA, and others, it has become conventional to refer to one common reaction partner, namely water. In effect, the free energies of hydrolysis are compared. The values for several importaiit compounds have been compiled in Table VIII. The accuracy of the values is not very good, since they are based on rather complicated measurements. 

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