Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Chemical modulation

In order to improve the properties of the well-known adrenergic antagonist, two chemical modulations on classical drugs including NO-donor moiety have been described. On the one hand, chemical modifications on Prazosin, an a 1-adrenergic antagonist, including furoxanyl moieties have been reported [70,182,183]. hi this approach, the 2-furanylcarbonyl moiety of Pra-... [Pg.291]

The Jamieson paper reports the results of a number of studies, some successful, others not. Failures can be ascribed to the difficulties encountered in log P control. The first evident trouble concerns the choice of the lipophilicity descriptor many prefer log P, but this choice is questionable as has been outlined by Lombardo (see Chapter 16). Secondly, variations in lipophilicity profile influence not only hERG activity, but also target selectivity and also ADMET properties. Lipophilicity is a bulk property and its modification can involve different moieties of the molecules. Once the chemical modulation has been designed, but before moving to the bench, the research group should predict the consequences of this change on each step of the drug s action, but unfortunately this is not always done. [Pg.328]

Blackwell, L., Norris, J., Suto, C.M. and Janzen, W.P. (2008) The use of diversity profiling to characterize chemical modulators of the histone deacetylases. Life Sciences, 82, 1050-1058. [Pg.115]

The structural diversity of MAO A and B-selective inhibitors clearly indicates that a relationship between the structural features of a given molecule and its selective recognition by either MAO A or B cannot be established a priori [83], However, there are many examples showing that the affinity of any active molecule can markedly be improved by chemical modulation of the lead structure [64]. As an example the mode of interaction of befloxatone (30) was investigated [84],... [Pg.674]

Chemical genomics profiling of environmental chemical modulation of hmnan nuclear receptors. Environ Health Perspect 119 1142-1148... [Pg.372]

FIGURE 16.17 (a) Elements of a typical airshed model (from McRae et al., 1982a). (b) Elements of the chemical module (from D. Dabdub and J. Seinfeld, personal communication, 1996). [Pg.888]

Fig. 11. The mechanical valves can be replaced by thermal or chemical modulating devices. In principle, this modification circumvents the need of reliable mechanical valves and offers a more flexible system s . An example is the thermal oxidative modulation of methane in air. Figure 12 shows a concentration profile during 8 days, determined with an experimental modulation CC set up... Fig. 11. The mechanical valves can be replaced by thermal or chemical modulating devices. In principle, this modification circumvents the need of reliable mechanical valves and offers a more flexible system s . An example is the thermal oxidative modulation of methane in air. Figure 12 shows a concentration profile during 8 days, determined with an experimental modulation CC set up...
The situation is substantially different in the case of chemical modulation of the work function (Janata, 1991). When electrically neutral molecular hydrogen dissociates at the surface and dissolves in palladium, it partially donates charge density to the free electrons in the metal and changes the position of the Fermi level and thus its work function. Consequently, the contact potential between palladium and copper changes as well. The origin of the contact potential is again the distribution of electrons between Pd and Cu, but the cause of this distribution is the interaction between palladium and hydrogen. [Pg.183]

Fig. 8.1 General chemiresistors and their equivalent circuits (a) lateral configuration in which any of the five resistances can be modulated by chemical interaction (b) impedimetric chemiresistor in which capacitance Cg is chemically modulated... Fig. 8.1 General chemiresistors and their equivalent circuits (a) lateral configuration in which any of the five resistances can be modulated by chemical interaction (b) impedimetric chemiresistor in which capacitance Cg is chemically modulated...
Here V is the applied voltage, 0b is the average barrier height, d is the insulator thickness, h is Planck s constant, m is the mass, e is the charge of electron, and B is a constant dependent on barrier height and thickness. Both barrier height and the thickness of the oxide can be chemically modulated, giving rise to chemiresistive behavior. Such barrier junctions apparently exist in most chemiresistors, which do not use noble metals for the contact. [Pg.245]

Different complications arise if the selective layer is a solid-state ionic conductor. At such an interface, a net electrochemical reaction, governed by Faraday s law, takes place and the mass transport of the electroactive ionic species within the contact region and formation of a depletion layer must be considered. In general, when the response of the sensor depends on the chemical modulation of the contact resistance by one of the above mechanisms it will be a strongly nonlinear function of concentration. Furthermore, because Rc is always dependent on the applied voltage, the optimization of the response must be done by examining the voltage-current characteristics of the contact. [Pg.246]

Chemical modulation of the surface conductivity is the principle of operation of some of the most commercially successful chemical sensors, the high temperature semiconducting oxide sensors. They are known by their brand name Figaro sensors. They are discussed in detail in Section 8.2.2.1. The reason for their commercial success lies in the fact that their performance and cost match exactly the specific practical needs of many applications, particularly those of the automotive industry. They have been described in great detail, from the point of view of both the underlying physics and chemistry (Morrison, 1994 Logothetis, 1987). [Pg.247]

When a periodically changing excitation signal is chosen for the operation of chemiresistors, they can be used to detect changes of capacitance (Fig. 8.1b). Therefore, the dielectrometric sensors rely on the chemical modulation of one or more equivalent circuit capacitors, either through the change of the dielectric constant of the chemically sensitive layer or through the chemical modulation of the interfacial charge. [Pg.260]

From the viewpoint of the chemist, the brain presents an almost limitless frontier. The brain, as a center for communication control, has been shown by anatomists and physiologists to be composed of a network of neurons that make contact with one another mostly by release of chemicals at synaptic junctions (neurotransmission). There are astronomical numbers of these synaptic junctions,and there 1s also a complex array of chemical transmitters and chemical modulators Involved 1n neurotransmission. Many of these transmitters and modulators have not yet been identified. The physiological actions of these substances are diverse (they both excite and depress activity) so we must also postulate that many different molecular structures are Involved 1n receptor functions even for the very same transmitter or modulator. [Pg.407]

The foregoing discussion has focused on self-assembled monolayers formed on essentially flat electrode surfaces whose areas are vastly larger than those occupied by a single adsorbate. This field has now achieved a significant level of sophistication in terms of their structural characterization as well as their rational design for specific functions, e.g. chemically modulated switches. Although somewhat outside the scope of this book, another important area that exploits the unique properties of self-assembled monolayers is monolayer-protected metal clusters or nanoparticles. [Pg.194]

Janata J, Josowicz M. Chemical modulation of work function as a transduction mechanism for chemical sensors. Acc Chem Res 1998 31 241-8. [Pg.291]

Binding via synchronicity occurs in milliseconds to seconds. Binding via chemical modulation occurs in minutes to hours. We need both, and we must make the best of both until we understand the mother of all questions how does the synchronous and chemically coherent activation of brain cells result in conscious experience in the first place How, after all, is the nervous system involved in subjective experience - what the philosophers call qualia - and what David Chalmers dubs the hard problem Chalmers asserts that neuroscience has not yet, and may never, solve the hard problem. If you love a mystery, and want to avoid the implications of what neuroscience is saying, you have a way out here. Neuroscientists are no more believable than anyone who waves his hands and says And then a miracle happens . The brain is a colony of neurons it thinks and therefore it is. [Pg.123]


See other pages where Chemical modulation is mentioned: [Pg.451]    [Pg.14]    [Pg.412]    [Pg.61]    [Pg.447]    [Pg.167]    [Pg.45]    [Pg.177]    [Pg.123]    [Pg.351]    [Pg.352]    [Pg.359]    [Pg.360]    [Pg.362]    [Pg.363]    [Pg.365]    [Pg.370]    [Pg.100]    [Pg.181]    [Pg.244]    [Pg.244]    [Pg.245]    [Pg.263]    [Pg.289]    [Pg.113]    [Pg.70]    [Pg.153]    [Pg.3]    [Pg.198]    [Pg.23]    [Pg.521]    [Pg.526]   
See also in sourсe #XX -- [ Pg.152 ]




SEARCH



A Chemical Genomics Approach for Ion Channel Modulators

Chemical Modulation of WF

Chemical modulators for enzymatic reactions

Chemical space modulators

Designing safer chemicals module

Fluorescence modulation, chemical

Fluorescence modulation, chemical mechanisms

Oriented Synthesis Developing New Chemical Tools to Probe and Modulate Biological Systems

Thermal Module for Chemically Reactive System

© 2024 chempedia.info