Structural specificity

Quinidine, however, would appear to exhibit a certain degree of structural specificity with respect to its action on the heart [260, 861]. This action would seem to result from a binding to the cardiac cell membranes (possibly through interaction with histidine units [862, 863]) which inhibits the active transport of calcium ions into the cells [864] and so produces the characteristic reduction 

Other representatives of the complex indole alkaloid group also tend to veer more towards the structurally specific type, and the more important of these will, in fact, be briefly discussed under the general heading of structurally specific agents. 

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D. J. Cram (Los Angeles), J.-M. Lebn (Strasbourg) and C. J. Pedersen (Wilmington, Delaware) development and use of molecules with structure specific interactions of high selectivity. 

The mechanisms of the electrophilic substitutions in the isoxazole nucleus have not yet been studied. They should not differ fundamentally from those usually accepted for the substitution of aromatic systems but the structural specificity of the isoxazole ring might give rise to some peculiarities, as recently specially discussed.One important point is that isoxazole shows a clearcut tendency to form coordination compounds. Just as pyridine and other azoles, isoxazoles coordinate with halogens and the salts of heavy metals, for example of cadmium,mercury,zinc. Such coordination... 

The low structural specificity in the local anesthetic sell cs is perhaps best illustrated by phenacalne (91), a local an-I -.lhetic that lacks not only the traditional ester or amide func-I ion but the basic aliphatic nitrogen as well. First prepared at I lie turn of the century, a more recent synthesis starts by con-ili iusation of p-ethoxyaniline with ethyl orthoacetate to afford I he imino ether (90), Reaction of that intermediate with a sec-I liil mole of the aniline results in a net displacement of ethanol, iiobably by an addition-elimination scheme. There is thus ob-I.lined the amidine, 91, phenacalne. 

Cyclization of the side chain onto the nitrogen atom leads to compounds with sedative and tranquilizing activity. The lack of structural specificity, that is, the fact that both positional isomers (41,43) show the same activity, is notable. Thus, condensation of the Grignard reagent from 2-bromopyridine with ben-zophenone affords the tertiary carbinol, 40. Catalytic reduction... 

Further illustration for the lack of structural specificity required for antihistaminic activity comes from the finding that ethylenediamines carrying both a benzylamine and an additional aromatic substituent on one of the nitrogens afford a series of useful therapeutic agents. Alkylation of benzylaniline with JV-... 

The low order of structural specificity required for classical antihistaminic activity was noted earlier. It has been found possible to substitute an indene nucleus for one of the two aromatic rings that most of these agents possess. The basic side chain may be present as either dimethylaminoethyl or itself cyc-lized to provide an additional fused ring. 

The lack of structural specificity among sedative-hypnotic drugs has been alluded to before. It is perhaps not too surprising that quinazolones, too, show this activity. The prototype, methaqualone (149), is obtained in a single step from the condensation of the"anthranilamide, 148, with o-toluidine.(The reaction may well involve first formation of the bisamide cycli-zation will then give the quinazolone ring system.) Condensation... 

Gcfrorene, n. something frozen, ice cream, ice. Gefiige, n. structure texture, bed, stratum system, order, -art, /. kind or type of structure. -bestandteil, m. structural constituent, -lehre, /. science of structure, specif, metallography. 

Since we will be dealing with finite graphs, we can analyze the behavior of random Boolean nets in the familiar fashion of looking at their attractor (or cycle) state structure. Specifically, we choose to look at (1) the number of attractor state cycles, (2) the average cyclic state length, (3) the sizes of the basins of attraction, (4) the stability of attractors with respect to minimal perturbations, and (4) the changes in the attractor states and basins of attraction induced by mutations in the lattice structure and/or the set of Boolean rules. 

Supporting particles Size (pm) Structure Specific surface area (m /g) Yield (mol%) Size of... 

S. Chabot, R. Bel-Rhlid, R. Chenevert, and Y. Piche. Hyphal growth promotion in vitro of the VA mycorrhizal fungus Gigaspora nuirgarila by the activity of structurally specific flavonoid compounds under CO enrichment conditions. New Phy-lol. /22-.461 (1992). 

For the confirmatory procedure, it is recommended that the sponsor develop spectral data based on at least three structurally specific ions that completely define the marker residue molecule. These ions may or may not include the molecular ion. The use of water loss and isotopic ions is usually unacceptable and CVM concurrence should be sought when water loss ions or isotopic ions are selected for the confirmatory analysis. The proposed fragment ion structures should be consistent with the fragmentation pattern, and justification for specificity of selected ions or scan range should be included. All confirmation criteria should be specified in the standard operating procedure. 

Spectral data based on at least three structurally specific ions fhaf completely define the parent molecule (may or may not include the molecular ion), or more if nonspecific ions are included. Use of water loss and isotopic ions is discouraged. 

The structures of [TpMe2]2Zn (80) and [Tpph]2Zn (85) have been determined by x-ray diffraction (Fig. 28). Interestingly, [TpMe2]2Zn and [TpPh]2Zn do not possess similar structures. Specifically, whereas the zinc center in [TpMe2]2Zn is six-coordinate and octahedral, the zinc center in [TpPh]2Zn is only four-coordinate and tetrahedral. Thus, the potentially tridentate [TpPh] ligand acts only as a bidentate ligand in [i72-TpPh]2Zn. However, it should be noted that the Fe in the related complex [TpPh]2Fe is octahedrally coordinated (90). 

Beeck at Shell Laboratories in Emeryville, USA, had in 1940 studied chemisorption and catalysis at polycrystalline and gas-induced (110) oriented porous nickel films with ethene hydrogenation found to be 10 times more active than at polycrystalline surfaces. It was one of the first experiments to establish the existence of structural specificity of metal surfaces in catalysis. Eley suggested that good agreement with experiment could be obtained for heats of chemisorption on metals by assuming that the bonds are covalent and that Pauling s equation is applicable to the process 2M + H2 -> 2M-H. 

While the activity and the structural specificity of the xenognosins were very encouraging, Astragalus gummifer is native to the Middle East and would not be expected to have co-evolved as a host for the southeastern U.S. native, Agalinis purpurea. The questions of whether molecules of this type were actually exuded from host roots in sufficient quantities to constitute host selection still remained. For that reason, John Steffens switched his attention to Lespedeza... 

Non-informative spectra from nonpolar compounds (contain low-mass structurally specific ions but no molecular species)... 

Unlike mass transport across membranes, which relates to chemical structure in predictable ways, the potencies of drugs as seen in pharmacological, pharmacodynamic, or other tests are highly structurally specific within a class of drugs and are without commonality across classes. A drug s activity involves a complex merging of these separate structural influences, with bioavailability always one of the concerns. Such concern is minimal when a truly superficial effect is involved, however. For example, the most potent antiseptic as measured in the test tube is likely to have... 

A complex ion is one that contains more than one ion. Because of its effect on mobility, complexation, the process by which complex ions form in solution, is very important for heavy metals and may be significant for organic wastes. Heavy metals are particularly prone to complexation because their atomic structure (specifically the presence of unfilled d-orbitals) favors the formation of strong bonds with polar molecules, such as water and ammonia (NH3), and anions, such as chloride (CO and cyanide (CN ). Depending on the chemistry of an injected waste and existing conditions, complexation can increase or decrease the waste s mobility. 

JPF Bai, GL Amidon. Structural specificity of mucosal-cell transport and metabolism of peptide drugs. J Pharm Sci 9 969-978, 1992. 

The purpose of this experiment was to investigate the extent and the structural specificity of hydrogen exchange during the extraction of bituminous coal with naphthalene. Table I includes the data of an extraction experiment (E20) conducted with naphtha-lene-d8 using nitrogen as the cover gas. In the experiment, the reactants were heated at 380°C for 1 hour at 2200 psi the same apparatus was applied as in E19. After the run, the spent solvent was separated from the coal by distillation, and the coal and solvent were examined for deuterium and protium incorporation. 

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