Selective affinity

Negative efficacy, by definition, efficacy is that property of a molecule that causes the receptor to change its behavior toward the biological host. Negative efficacy refers to the property of selective affinity of the molecule for the inactive state of the receptor this results in inverse agonism. Negative efficacy causes the active antagonism of constitutive receptor activity but is only observed in systems that have a measurably elevated basal response due to constitutive activity. It is a property of the molecule and not the system. 

Two-state model, a model of proteins that coexists in two states controlled by an equilibrium constant. Molecules with selective affinity for one of the states will produce a bias in that state upon binding to the system. Two-state theory was conceived to describe the function of ion channels but also has relevance to receptors (see Chapter 3.7). 

Adenosine Receptors. Figure 1 Structures of widely used AR agonists, both nonselective and selective. Affinities/potencies at the ARs are found in Table 2. (a) Nucleoside derivatives that are either nonselective or selective for A receptors (1-12). (b) Nucleoside derivatives that are selective for A2a. A2a/A2b (mixed), or A3 receptors (13-19). 

Table 8.3 Examples of amino acid selective affinity labels...

Rickettsia are more difficult to produce in quantity than bacteria. Similar to viruses, they are strict obligate parasites and require living cells for growth. They cannot survive long outside a host. They also have a selective affinity for specific types of cells in the body. They are normally transmitted by an arthropod vector (i.e., ticks, lice, fleas, mites), which also serves as either the primary or intermediate host. 

Resins can also be prepared with chelating functional groups which show selective affinities for certain metals. Iminodiacetic acid, vinylacetylacetone, glyoxal-thiophenol and 8-hydroxy quinoline have all been used to produce these so-called chelating resins. Their selectivities are similar to those of the free reagent. 

An alternative efficient approach to disperse CNTs relies on the use of synthetic peptides. Peptides were designed to coat and solubilise the CNTs by exploiting a noncovalent interaction between the hydrophobic face of amphiphilic helical peptides and the graphitic surface of CNTs (Dieckmann et al., 2003 Zoibas et al., 2004 Dalton et al., 2004 Arnold et al., 2005). Peptides showed also selective affinity for CNTs and therefore may provide them with specifically labelled chemical handles (Wang et al., 2003). Other biomolecules, such as Gum Arabic (GA) (Bandyopadhyaya et al., 2002), salmon sperm DNA, chondroitin sulphate sodium salt and chitosan (Zhang et al., 2004 Moulton et al., 2005), were selected as surfactants to disperse CNTs (Scheme 2.1). 

Wang SQ, Humphreys ES, Chung SY, Delduco DF, Lustig SR, Wang H, Parker KN, Rizzo NW, Subramoney S, Chiang YM, Jagota A (2003) Peptides with selective affinity for carbon nanotubes. Nature Mater. 2 196-200. 

CNTs can be functionalized with protein via non-covalent bond (Li et al., 2005 Kim et al., 2003 Mitchell et al., 2002). For example, (beta-lactamase I, that can be immobilized inside or outside CNTs, doesn t change enzyme s activity (Vinuesa and Goodnow, 2002). Taq enzyme can attach to the outside of CNT, and doesn t change its activity (Cui et al., 2004). Peptide with Histidine and Tryptophan can have selective affinity for CNT(Guo et al., 1998). Monoclonal antibody can attach to SWNTs. Protein-modified CNTs can be used to improve its biocompatibility and biomolecular recognition capabilities (Um et al., 2006). For example, CNTs functionalized with PEG and Triton X-100 can prevent nonspecific binding of protein and CNTs. Biotin moiety is attached to the PEG chains Streptavidin can bind specifically with biotin-CNT (Shim et al., 2002). 

The process depends on the existence, or development, of a selective affinity of one of the constituents for the envelopes of the gas bubbles. In general, this affinity must be induced, and the reagents which increase the angle of contact between the liquid and one of the materials are known as promoters and collectors. Promoters are selectively adsorbed on the surface of one material and form a monomolecular layer. The use of excess material destroys the effect. Concentrations of the order of 0.05 kg/Mg of solids are usually required. A commonly used promoter is sodium ethyl xanthate ... 

For example, Escherichia coli have six PBP. PBP-la and -lb, which are transpepfidases, are involved in the synthesis of peptidoglycan. PBP-2 is necessary for supporting the rodshaped form of bacteria. Selective inhibition of this enzyme causes production of other non-rod-shaped forms of bacteria, which eventually undergo lysis. PBP-3 is necessary to form the partition during division. Selective inhibition of this enzyme leads to the formation of a fibrous form of bacteria containing many units of rod-shaped bacteria unable to separate one from another, which results in their death. Various beta-lactam antibiotics have a selective affinity to one or a few PBP. Inactivation of certain PBP (PBP-la, -lb, -2, or -3) causes cell death. Unlike these, inactivaition of low-molecular PBP (PBP-4, -5, and -6) is not lethal to bacteria. 

These gels are based on immobilised alkyl boronic acids. They have a selective affinity for 1,2- or 1,3-diol groupings such as those found in catechol-containing molecules such as dopamine and in sugars or glycosides. 

This mechanism is also consistent with models of fear and anxiety that are primarily based upon pharmacologically derived data. The cumulative reduction in serotonergic impiflse flow to septohippocampal and other Hmbic and cortical areas involved in the control of anxiety is believed to explain the anxiolytic effects of Hgands with selective affinity for the 5-HTia receptor in... 

In the search for a new FP receptor agonist having more potent lOP-reducing activity and weaker side effects, our research group has recently discovered a 15-deoxy-15,15-difluoro-PGF2a derivative, tafluprost (AFP-168), which shows highly potent and selective affinity to the FP receptor [71],... 

Amine groups in the polymer provide selective affinity for heavy metals in both cationic and anionic states and preferentially form coordination complexes with transition-group heavy... 

Strong and selective affinity of crown ethers to metal cations have been applied in so-called liquid membranes (which are completely different from... 

What is the exact influence of water and organic molecules on the enzyme structure Could its effects on properties such as selectivity, affinity, binding constants, and catalytic constants be predictable by controlling the hydration/solvation state ... 

Kettner C, Shaw E. d-PHE-PRO-ARGCH2C1-1 selective affinity label for thrombin. Thrombosis Research 1979 14 969-973. 

There are numerous studies of metal complexation by whole cells indicating that complexation depends on the bacterium, the metal, and pH. It has been found that at low pH, cationic metal complexation is reduced however, binding of anionic metals such as chromate (Cr042 ) and selenate (Se042 ) is increased. Bacteria seem to show selective affinities for different metals. This was demonstrated by a study of the complexation of four metals by four different bacterial genera that... 

Ion exchange processes function by replacing undesirable ions of a liquid with ions such as H+ or OH- from a solid material in which the ions are sufficiently mobile, usually some synthetic resin. Eventually the resin becomes exhausted and may be regenerated by contact with a small amount of solution with a high content of the desired ion. Resins can be tailored to have selective affinities for... 

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