Biological systems modifications

Since you are now familiar with the types of chemical modifications that may be mediated by biological systems, you should be able to answer the following SAQ regarding the modification of prostaglandins. 

The level of DNA modification in any biological system is low, ranging up to about one adduct per 105 bases in the DNA helix. Any methods used to detect such damage must therefore either be very sensitive or involve some method by which the effect of such damage is amplified to measurable levels. 

Many commercially important polymers are produced via emulsion polymerization. This is also one of the most common methods to produce dye-doped beads. A dye is added to the mixture of monomers prior to initiating the polymerization and is either noncovalently entrapped or is copolymerized. The second method ensures that no leaching will occur from the particle but requires modification of the dye (typically by providing it with a double bond). This method is most common for preparation of pH-sensitive beads where a pH indicator is entrapped inside cross-linked polyacrylamide particles. The size of the beads can be tuned over a wide range so that preparation of both nano- and microbeads is possible. Despite thorough washing the surfactants are rather difficult to remove completely and their traces can influence the performance of some biological systems. 

A. Goldbeter and D. E. Koshland, Jr., An amplified sensitivity arising from covalent modification in biological systems, Proc. Natl. Acad. Sci. USA, 78( 11), 6840-6844 (1981). 

The diverse chemical reactivity of HAs makes them potential toxic compounds, either directly, by chemical modification of functional groups of a variety of biological systems, or indirectly, by their conversion to toxic metabolites. In some cases their metabolites are considered to be toxic in humans, animals and plants even at relatively modest levels of exposure. 

Amino acids with modified side-chains are frequently encountered in biological systems. Among all the modifications involving the side-chain of the amino acids, reversible glyco-sylation and phosphorylation play a central role in regulating the biological functionalities of numerous proteins. 

Exact analysis of sialic acid is required in biologieal experiments where the biological role of sialic acid is frequently studied with the aid of sialidases, and the amount of sialic acids released is determined. This is also important for periodate oxidation studies on biological systems, where modification of sialic acids by periodate is only assumed, but chemical analysis of this effect by isolation and analysis of the modified sialic acids is seldom performed. These uncertainties in determinations of sialic acid can be overcome by the purification procedures already described. Furthermore, it must be stressed that unequivocal determination of the structure of a sialic acid, especially... 

Another property characteristic of the evolution of complex systems is their adaptability to external conditions. In other words, complex systems are not only dynamical but also adaptative. Adaptability is an emergent property of major consequence in the evolution of complex systems. As a matter of fact, and just like self-organization from which it is not dissociable, adaptability to external conditions results in a modification of probabilities, as exemplified by ecosystems (Burns, 1994). This is of utmost significance in biology, allowing biological systems to evolve to purposive outcomes. In drug research also, adaptability is of major but as yet... 

In most applications, the input, activation and output functions are the same for all neurons and they do not change during the training process. In other words, learning is the process by which an ANN modifies its weights and bias terms in response to the input information (spectra and concentration values). As for the biological systems, training involves the destruction , modification... 

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