Molecular function examples

Cless Functional Group Molecular Formule Example Compound Name... 

Nonadiabatic transitions definitely play crucial roles for molecules to manifest various functions. The theory of nonadiabatic transition is very helpful not only to comprehend the mechanisms, but also to design new molecular functions and enhance their efficiencies. The photochromism that is expected to be applicable to molecular switches and memories is a good example [130]. Photoisomerization of retinal is well known to be a basic mechanism of vision. In these processes, the NT type of nonadiabatic transitions play essential roles. There must be many other similar examples. Utilization of the complete reflection phenomenon can also be another candidate, as discussed in Section V.C. In this section, the following two examples are cosidered (1) photochromism due to photoisomerization between cyclohexadiene (CHD) and hexatriene (HT) as an example of photoswitching molecular functions, and (2) hydrogen transmission through a five-membered carbon ring. 

The secondary structure describes the molecular shape or conformation of the polymer chain. For most linear polymers this shape approaches a helical or pleated skirt (or sheet) arrangement depending on the nature of the polymer, treatment, and function. Examples of secondary structures appear in Figure 2.13. 

Level II methods are those that are not unequivocal but are used to determine the concentration of an analyte at the level of interest, and to provide some structural information. For example, these methods may employ molecular, functional-group, or immunochemical properties as the basis of the analytical scheme. Hence, these methods are often reliable enough to be used as reference methods. Level II methods commonly separate the determinative from the identification procedures, and may also be used to corroborate the presence of a compound or class of compounds. Tims, a combination of two level II methods may provide attributes suitable for a level I method. The majority of analytical methods presently available and used by regulatory control agencies are level II methods. 

Protein function can be described on three levels. Phenotypic function describes the effects of a protein on the entire organism. For example, the loss of the protein may lead to slower growth of the organism, an altered development pattern, or even death. Cellular function is a description of the network of interactions engaged in by a protein at the cellular level. Interactions with other proteins in the cell can help define the lands of metabolic processes in which the protein participates. Finally, molecular function refers to the precise biochemical activity of a protein, including details such as the reactions an enzyme catalyzes or the ligands a receptor binds. 

Probably the most convincing evidence that crystalline structures can safely be used to draw conclusions about molecular function is the observation that many macromolecules are still functional in the crystalline state. For example, substrates added to suspensions of crystalline enzymes are converted to product, albeit at reduced rates, suggesting that the enzyme s catalytic and binding sites are intact. The lower rates of catalysis can be accounted for by the reduced accessibility of active sites within the crystal, in comparison to solution. 

A primitive approach to molecular speciation involves identification of the molecular functionalities through the binding energies (BE s) of their constituent elements. This approach has been used to identify electropolymerized poly-pyrrole (9) and N-(0-hydroxybenzyl)anillne/tyrosine (84) films. In the latter case the identification was confirmed with multi-reflection IR spectroscopy. Both examples used either monomers or model compounds as references to generate known comparison spectra. The BE s and peak shapes have also been used to identify the presence of the ferricinium ion on freshly prepared surfaces (85). In this way the identification is similar to fingerprinting. 

Through the vehicle of partition functions expressions can be derived for macroscopic quantities from molecular parameters. Examples of such qucintities cire the surface pressure, and, for Gibbs monolayers, the adsorbed amount. Fluctuations in extensive quantities, like the number density or the interfacial excess energy, may also be obtained (sec. 1.3.7). 

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