Molecular specificity

Mention was made in Section XVIII-2E of programmed desorption this technique gives specific information about both the adsorption and the desorption of specific molecular states, at least when applied to single-crystal surfaces. The kinetic theory involved is essentially that used in Section XVI-3A. It will be recalled that the adsorption rate was there taken to be simply the rate at which molecules from the gas phase would strike a site area times the fraction of unoccupied sites. If the adsorption is activated, the fraction of molecules hitting and sticking that can proceed to a chemisorbed state is given by exp(-E /RT). The adsorption rate constant of Eq. XVII-13 becomes... 

The third alternative is a more robust, sensitive and specialized fonn of the first, in that only hydrogen nuclei indirectly spin-spin coupled to in a specific molecular configuration are imaged. In achieving selectivity, the technique exploits the much wider chemical shift dispersion of compared to H. The metliod involves cyclic transfer from selected H nuclei to indirectly spin-spin coupled C nuclei and back according to the sequence... 

Many phenomena ask for local, site-specific properties of a molecule such as the partial charge on a specific atom in a molecule or the hydrogen bond donor ability of a certain OH group. It would be highly desirable to have methods as simple as an additivity model to estimate such site-specific molecular properties. 

Finally, engineered surfaces may contribute to the understanding of adhesion (172). Control of adhesion is essential to a large number of industrial processes and is often associated with various problems, but currendy (ca 1997) there is Htde if any understanding of how specific molecular ordering and interactions at the surface may affect adhesion. 

Kamlet-Taft Linear Solvation Energy Relationships. Most recent works on LSERs are based on a powerfiil predictive model, known as the Kamlet-Taft model (257), which has provided a framework for numerous studies into specific molecular thermodynamic properties of solvent—solute systems. This model is based on an equation having three conceptually expHcit terms (258). 

The specific molecular mechanisms by which PCDDs and PCDFs are initially formed and become part of the PIC remain largely unknown and are theoretical. The theoretical basis for conjecture is derived primarily from direct observations in municipal solid waste incinerators. The emissions of... 

Chapter 2, Single Point Energy Calculations, discusses computing energies at specific molecular structures, as well as the related molecular properties that may be predicted at the same time. 

The Role of Molecular Shape Similarity in Specific Molecular Recognition... 

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. 

Not all cell-based functional assays are directed against a specific molecular target. Indeed many drugs... 

Common to all three aims is that silico-derived predictions can rationalize experimental efforts either by well-directed very specific molecular biological experiments like site directed mutations or e.g., by reducing the number of compounds to screen experimentally for drug design. 

There are several hundred reported NF-kB inhibitors (see www.nf-kb.org for a complete and updated list). These inhibitors include natural products, chemicals, metabolites, and synthetic compounds. A large majority of these products, in particular commonly used antiinflammatory drugs such as corticosteroids and the nonsteroidal antiinflammatory drugs (NSADDs) aspirin, sulindac, ibuprofen and sulphasalazine, have the ability to partially inhibit NF-kB activity in cell culture. However, the precise mechanism of action and the specific molecular targets of most of these inhibitors remain unclear. 

In 1922, Evans and Bishop named the animal nutritional factor essential of reproduction Vitamin E . In the 1960s, vitamin E was associated with antioxidant function. Twenty-five years later, vitamin E has been found to possess functions that are independent of its antioxidant and free radical scavenging ability. a-Tocopherol specific molecular mechanisms were discovered which are still under investigation. 

A specific role for vitamin E in a required metabolic function has not been found. In addition to its direct antioxidant effects, a-tocopherol has been reported to have specific molecular functions. 

Most disease-specific molecular and cellular processes involve low concentrations and have low capacities. Therefore, molecular imaging requires highly sensitive imaging modalities to detect and quantify the imaging probes as it is done with short-lived radioisotopes. Optical imaging and ultrasound are next in sensitivity. MRI would require too high contrast agent concentrations... 

When the same monomer is used to build up a polymer, it is termed a homopolymer. Copolymers have two different monomers or functional groups, and terpolymers have three groups. There are even tetrapolymers available. These polymers may be further classified, for example, as random, graft, or block copolymers. Block copolymers, which have alternating sections of specific molecular chains, are used in BW formulations (but are more commonly found in CW programs). 

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