Biological systems, examples

Structural features that promote biological activity are sometimes called biophores. They are divisible into pharmacophores and toxicophores. Pharmacophores impart desirable properties on a molecule (e.g., pharmacological activity or a particular fragrance). Toxicophores are responsible for undesirable effects such as toxicity (e.g., mutagenicity and skin sensitization). The same molecule can have more than one descriptor that can act as both a pharmacophore and a toxicophore in the same or different biological systems. Examples here are the toxic side effects of anti-cancer drugs and the use of Warfarin, a commercially available rat poison, to help reduce the formation of blood clots in human heart disease. 

Barnett, J. E. G. Fluorine as a Substituent for Oxygen in Biological Systems Examples in Mammalian Membrane Transport and Glycosidase Action. Amsterdam Ciba Foundation Symposium Associated Scientific Publishers, 1972, pp. 95-115. 

Hydrogen transfer is one of the most pervasive and fundamental processes that occur in biological systems. Examples include the prevalent role of acid-base catalysis in enzyme and ribozyme function, the activation of C-H bonds leading to structural transformations among a myriad of carbon-based metabolites, and the transfer of protons across membrane bilayers to generate gradients capable of driving substrate transport and ATP biosynthesis. 

Phosphate is a part of many high-energy compoimds in biological systems. Examples include ATP (adenosine triphosphate)) and GTP (guanosine triphosphate). 

Dendritic patterns are one of the most frequently observed forms in both abiotic systems and biological systems. Examples include the roots and branches of trees, snow crystals, neurons, and capillary vessels. Dendrimers are macromolecules, which are based on repeatedly branched building blocks from a core molecule. The name dendrimer, comes from the Greek dendron, meaning... 

NADH and NAD play critical roles in biological systems. Examples include the citric acid cycle and ATP synthesis. 

Heterogeneous monomolecular layers are an important class of samples relevant for, e.g., biological systems. Examples are mixtures of different lipids or lipids and proteins etc., which can form monomolecular layers built from domains of, say, a lipid in a 2D-crystalIine ordered phase immersed in a liquid phase, or crystalline domains of protein among islands of disordered material. A GIXD experiment will probe the crystalline domains only and the rest of the sample will contribute to the background intensity. XR, by contrast, will provide information about an average structure projected onto the vertical z axis. As discussed above. 

The association process discussed in section 8.7 can be easily extended to the association or aggregation of any number of monomers. The aggregation of biomolecules to form larger structures is very common in biological systems. Examples are the association of subunits to form a multisubunit enzyme, the formation of membranes, the recombination of both the small and large subunits of ribosomes, the assembly of subunits and RNA to form the tobacco mosaic virus, and many others. 

In this paper, bioactivity will be considered to be the interaction of some chemical agent on a biological system. Examples of bioactivity would include (1) the action of a drug on a disease center, (2) the action of a herbicide on weeds, (3) the action of an insecticide on insects, and (4) the prevention of conception by a chemical agent. In this sense, an applied bioactive polymeric system is one that utilizes any kind of polymeric material in producing, enhancing or controlling bioactivity. 

This interface is critically important in many applications, as well as in biological systems. For example, the movement of pollutants tln-ough the enviromnent involves a series of chemical reactions of aqueous groundwater solutions with mineral surfaces. Although the liquid-solid interface has been studied for many years, it is only recently that the tools have been developed for interrogating this interface at the atomic level. This interface is particularly complex, as the interactions of ions dissolved in solution with a surface are affected not only by the surface structure, but also by the solution chemistry and by the effects of the electrical double layer [31]. It has been found, for example, that some surface reconstructions present in UHV persist under solution, while others do not. 

In biological systems molecular assemblies connected by non-covalent interactions are as common as biopolymers. Examples arc protein and DNA helices, enzyme-substrate and multienzyme complexes, bilayer lipid membranes (BLMs), and aggregates of biopolymers forming various aqueous gels, e.g, the eye lens. About 50% of the organic substances in humans are accounted for by the membrane structures of cells, which constitute the medium for the vast majority of biochemical reactions. Evidently organic synthesis should also develop tools to mimic the Structure and propertiesof biopolymer, biomembrane, and gel structures in aqueous media. 

Table 2. Examples of Metabolic Detoxification and Metabolic Activation of Chemicals by Biological Systems...

The molecular structure and dynamics of the ice/water interface are of interest, for example, in understanding phenomena like frost heaving, freezing (and the inhibition of freezing) in biological systems, and the growth mechanisms of ice crystals. In a series of simulations, Haymet and coworkers (see Refs. 193-196) studied the density variation, the orientational order and the layer-dependence of the mobilitity of water molecules. The ice/water basal interface is found to be a relatively broad interface of about... 

The similarity recognition hypothesis presented here would be applicable to the specific and precise discrimination in chemical and biological systems. It is hoped that this review will serve to stimulate further work on the physicochemical origin of the shape-similarity effect on specific molecular recognition, for example, work on weak interactions specific for the three-dimensional shape of interacting groups. 

By the end of the text you should appredate the enormous potential that biological systems have for making a wide range of products and to achieve a variety of objectives. You should also have knowledge and be able to dte specific examples, of how economic, sodal and political attitudes may impinge upon the adoption of the technology. 

When compared to traditional chemical synthesis, processes based on biocatalysts are generally less reliable. This is due, in part, to the fact that biological systems are inherently complex. In bioprocesses involving whole cells, it is essential to use the same strain from the same culture collection to minimise problems of reproducibility. If cell free enzymes are used the reliability can depend on the purity of the enzyme preparation, for example iso-enzyme composition or the presence of other proteins. It is, therefore, important to consider the commercial source of the enzyme and the precise specifications of the biocatalyst employed. 

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