Functional group activation bioactivation

Radiation grafting for various biomedical applications remains an extremely active field of development. The grafted side chains can contain functional groups to which bioactive materials can be attached. These include amine, carboxylic, and hydroxyl groups, which can be considered as a center for further modifications. 

Once inside the body, extremely hydrophilic compounds tend to be excreted more readily by the kidney. That could be useful, because it lowers toxicity. Additionally, chemical classes and functional groups known to be toxic—as well as those that can be bioactivated into toxic substances—should be avoided when designing chemical products. Chemicals can also be designed to shield active toxic sites or to facilitate metabolic degradation to nontoxic metabolites. 

A second major area of interest in the design of bioactive molecules is that of the process of molecular recognition which is vital to the formation of the bas-rep complex. The functional groups required for recognition and activity, in their appropriate arrangement in space, or conformation, constitute the pharmacophore of a bas. The study of the possible conformations of a bas may be carried out by molecular mechanics or quantum chemical calculations. Another important factor is the nature and geometry of the receptor site. 

However, it was immediately recognized by peptide chemists that, even in the cases where a direct (backbone)peptide -protein(backbone) interaction is not operative, the backbone conformation may dramatically influence the biological response. It is evident that the introduction of new, promising peptidomimetics is based primarily on the combined knowledge of the complementary conformational, topochemical, and electronic properties of the native peptide and of its address (in other words, of the receptor or the active site of the enzyme with which it interacts). Then, the design of peptidomimetics as potential bioactive compounds must take into particular account two structural factors (i) a favorable fit (tertiary structure) with respect to the corresponding complementary spatial situation at the active site (ii) the placement of structural elements (e.g., functional groups, polar and... 

Molecular modelling of ecdysteroids (7) and brassinosteroids is still in its infancy. A comparison of the three dimensional (3D-) structures of the two biologically most active representatives of brassinosteroids and ecdysteroids, i.e. of brassinolide and 20-hydroxyecdysone, suggests that functional groups relevant for bioactivity are found at similar positions in both molecules in spite of the structural differences mentioned above. More detailed comparative studies of the 3D-structures of ecdysteroids and brassinosteroids are eagerly awaited. 

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