Receptor sites

The molecular surface of receptor site regions cannot be derived from the structure infoi mation of the molecule, bth represents the form ofthe active site of a protein surrounded by a ligand. This surface representation is employed in drug design in order to illustrate the volume of the pocket region or the molecular interaction layers [186. ... 

Genetic algorithms can also be used to perform molecular docking [Judson et d. 1994 Jont et d. 1995b Oshiro et d. 1995]. Each chromosome codes not only for the internal conform tion of the ligand as described in Section 9.9.1 but also for the orientation of the ligand withi the receptor site. Both the orientation and the internal conformation will thus vary as th populations evolve. The score of each docked structure within the site acts as the fitnes function used to select the individuals for the next iteration. 

Jones G, P Willett and R C Glen 1995b. Molecular Recognition of Receptor Sites Using a Geneti Algorithm with a Description of Desolvation. Journal of Molecular Biology 245 43-53. 

The difference m odor between (R) and (S) carvone results from their different behavior toward receptor sites m the nose It is believed that volatile molecules occupy only those odor receptors that have the proper shape to accommodate them Because the receptor sites are themselves chiral one enantiomer may fit one kind of receptor while the other enantiomer fits a different kind An analogy that can be drawn is to hands and gloves Your left hand and your right hand are enantiomers You can place your left hand into a left glove but not into a right one The receptor (the glove) can accommodate one enantiomer of a chiral object (your hand) but not the other... 

Section 7 8 Both enantiomers of the same substance are identical m most of then-physical properties The most prominent differences are biological ones such as taste and odor m which the substance interacts with a chiral receptor site m a living system Enantiomers also have important conse quences m medicine m which the two enantiomeric forms of a drug can have much different effects on a patient... 

The compound shown is diethylstilbestrol (DES) it has a number of therapeutic uses in estrogen replacement therapy DES is not a steroid but can adopt a shape that allows it to mimic estrogens such as estradiol (p 1100) and bind to the same receptor sites Construct molecular models of DES and estradiol that illustrate this similanty in molecular size shape and location of polar groups... 

In addition, researchers can survey the surface and clefts of a macromolecule for potential receptor sites based on Hgand distance ranges "use the common distance range of the superimposed atoms" (116) to faciHtate the development of a "pharmacophore" or critical contact assembly besides the Hgand... 

There are three advantages to study molecular recognition on surfaces and interfaces (monolayers, films, membranes or soHds) (175) (/) rigid receptor sites can be designed (2) the synthetic chemistry may be simplified (J) the surface can be attached to transducers which makes analysis easier and may transform the molecular recognition interface to a chemical sensor. And, which is also a typical fact, this kind of molecular recognition involves outside directed interaction sites, ie, exo-receptor function (9) (see Fig. 5b). 

A persistent idea is that there is a very small number of flavor quaUties or characteristics, called primaries, each detected by a different kind of receptor site in the sensory organ. It is thought that each of these primary sites can be excited independently but that some chemicals can react with more than one site producing the perception of several flavor quaUties simultaneously (12). Sweet, sour, salty, bitter, and umami quaUties are generally accepted as five of the primaries for taste sucrose, hydrochloric acid, sodium chloride, quinine, and glutamate, respectively, are compounds that have these primary tastes. Sucrose is only sweet, quinine is only bitter, etc saccharin, however, is slightly bitter as well as sweet and its Stevens law exponent is 0.8, between that for purely sweet (1.5) and purely bitter (0.6) compounds (34). There is evidence that all compounds with the same primary taste characteristic have the same psychophysical exponent even though they may have different threshold values (24). The flavor of a complex food can be described as a combination of a smaller number of flavor primaries, each with an associated intensity. A flavor may be described as a vector in which the primaries make up the coordinates of the flavor space. 

Other auxin-like herbicides (2,48) include the chlorobenzoic acids, eg, dicamba and chloramben, and miscellaneous compounds such as picloram, a substituted picolinic acid, and naptalam (see Table 1). Naptalam is not halogenated and is reported to function as an antiauxin, competitively blocking lAA action (199). TIBA is an antiauxin used in receptor site and other plant growth studies at the molecular level (201). Diclofop-methyl and diclofop are also potent, rapid inhibitors of auxin-stimulated response in monocots (93,94). Diclofop is reported to act as a proton ionophore, dissipating cell membrane potential and perturbing membrane functions. 

Polymer Applications. The reaction of sahcylaldehyde with poly(vinyl alcohol) to form an acetal has been used to provide dye receptor sites on poly(vinyl alcohol) fibers (89) and to improve the light stabihty of blend fibers from vinyl chloride resin and poly(vinyl alcohol) (90) (see Fibers, POLY(VINYL alcohol)). ... 

Pharmacodynamics is the study of dmg action primarily in terms of dmg stmcture, site of action, and the biochemical and physiological consequences of the dmg action. The availabiUty of a dmg at its site of action is deterrnined by several processes (Fig. 1), including absorption, metaboHsm, distribution, and excretion. These processes constitute the pharmacokinetic aspects of dmg action. The onset, intensity, and duration of dmg action are deterrnined by these factors as well as by the avadabihty of the dmg at its receptor site(s) and the events initiated by receptor activation (see Drug delivery). 

Choline functions in fat metaboHsm and transmethylation reactions. Acetylcholine functions as a neurotransmitter in certain portions of the nervous system. Acetylcholine is released by a stimulated nerve cell into the synapse and binds to the receptor site on the next nerve cell, causing propagation of the nerve impulse. 

Transport. Transcobalamin II dehvers the absorbed vitamin 3 2 to cells and is the primary plasma vitamin B22-binding transport protein. It is found in plasma, spinal fluid, semen, and extracellular fluid. Many cells, including the bone marrow, reticulocytes, and the placenta, contain surface receptor sites for the transcobalamin II—cobalamin complex. 

Receptor models are powerful tools for source apportionment of particulates because a vast amount of particulate species characterization data have been collected at many sampling sites worldwide, and because many aerosol species are primary pollutants. Most of the information available is for elemental concentrations, eg, lead, nickel, and alurninum, although more recent measurements have provided data on concentrations of ionic species and carbonaceous compounds. At a sampling (or receptor) site, the aerosol mass concentration of each species i is... 

The essential feature of the AAA is a comparison of active and inactive molecules. A commonly accepted hypothesis to explain the lack of activity of inactive molecules that possess the pharmacophoric conformation is that their molecular volume, when presenting the pharmacophore, exceeds the receptor excluded volume. This additional volume apparently is filled by the receptor and is unavailable for ligand binding this volume is termed the receptor essential volume [3]. Following this approach, the density maps for each of the inactive compounds (in their pharm conformations superimposed with that of active compounds) were constructed the difference between the combined inactive compound density maps and the receptor excluded volume represents the receptor essential volume. These receptor-mapping techniques supplied detailed topographical data that allowed a steric model of the D[ receptor site to be proposed. 

Figure S.21 The hemaggiutinin moiecuie is formed from three subunits. Each of these subunits Is anchored In the membrane of the influenza vims. The globular heads contain the receptor sites that bind to sialic acid residues on the surface of eukaryotic cells. A major part of the subunit interface is formed by the three long intertwining helices, one from each subunit. (Adapted from I. Wilson et al.. Nature 289 366-373, 1981.)...

A coordinate system to identify stack and receptor site positions. 

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