Inaccessible domain

They reported that C02-diluted flames had much higher HL, up to four times more, than N2-diluted flames [22]. For clarity, the accessible and inaccessible domains for pure CH4/air, CH4/N2/air, and CH4/C02/air flames from Figure 6.2.3a, b, and c, respectively, were plotted together on Figure 6.2.3d, where the values of Ka ,a at both the leanest and richest sides of these diluted flames were also indicated. For example, at = 0.6, the values of Ka ,a increased from about 60 to 320 when CH4 fuel was diluted with 60% CO2 (Figure 6.2.3d). Thus, the accessible domain for CH4/CO2/air flames can be significantly expanded. 

The critical element for differentiating between endogenous and exogenous drugs is the distribution of drugs between the semiaccessible and inaccessible domains. This distribution is quantitatively defined by the extended safety zone ratio (Resz) ... 

These results are in striking contrast to those obtained with the hair from heroin users (Figure 3). Essentially perfect plateau wash kinetics were obtained for 6-MAM, morphine, and codeine. Most important, the amounts of 6-MAM released from the inaccessible domain by digestion easily meets the R sz criterion of heroin use. It should also be mentioned that had the alcohol washes been continued, then the alcohol wash kinetics would have been similar to curve AB in Figure 1. 

One noteworthy and common feature of these historic hair samples was the abnormally high porosity of the specimens. That virtually all of the inaccessible domain had been degraded was demonstrated by methylene blue staining procedures and by the complete extraction of the drugs by the aqueous wash solutions. 

Macroporous Suspension Polymers (DVB-5, 20, 50-S-T). Copolymeri-zation in the presence of diluents results in formation of macro-porous materials. As can be seen in Figure 5, raacroporosity exerts a dramatic effect upon the quenching rate. Not surprisingly, EPS is quenched "instantly" upon addition of electrophile, what is most interesting however, is that for all practical purposes, there is no difference in quenching rate between DVB-5-S-T and DVB-20-S-T macroporous materials. Quite remarkably, all domains are readily accessible since the fluorescence emission is completely quenched in these materials. The leveling off of fluorescence emission Intensity for the 50% crosslinked material (DVB-50-S-T) reveals kinetically Inaccessible domains under the conditions of the experiment. 

The large impact of ultramicroelectrodes is rooted in their ability to support very useful extensions of electrochemical methodology into previously inaccessible domains of time, medium, and space. That is, UMEs allow one to investigate chemical systems on time scales that could not previously be reached, in media that could not previously be employed, or in microstructures where spatial relationships are important on a distance scale relevant to molecular events. 

FIGURE 8.14 Activation of nonreceptor PTKs. Lck is held in an inaccessible compact state through phosphorylation of residue Y505, which interacts with the intramolecular SH2 domain. Upon activation of CD45 (ligand unknown), the pY505 is removed and the molecule opens up. Autophosphorylation at theY-394 residue in the catalytic domain constitutes the activation of the PTK. 

The identification of excited states in strong field interactions with molecules has lead to some novel forms of molecular spectroscopy, allowing previously inaccessible states to be studied. For the most part, this comes from the ability to do transient spectroscopy in the time domain with ultrashort pulses. But, the strong field interaction also allows for new population mechanisms. 

Detailed pictures of the iron-binding sites in transferrins have been provided by the crystal structures of lactoferrin (Anderson et ai, 1987, 1989 Baker etai, 1987) and serum transferrin (Bailey etal., 1988). Each structure is organized into two lobes of similar structure (the amino- and carboxy-terminal lobes) that exhibit internal sequence homology. Each lobe, in turn, is organized into two domains separated by a cleft (Fig. 3 and 10). The domains have similar folding patterns of the a//3 type. One iron site is present in each lobe, which occupies equivalent positions in the interdomain cleft. The same sets of residues serve as iron ligands to the two sites two tyrosines, one histidine, and one aspartate. Additional extra density completes the octahedral coordination of the iron and presumably corresponds to an anion and/or bound water. The iron sites are buried about 10 A below the protein surface and are inaccessible to solvent. 

Similarly, when rhombic red a-sulfur is heated above 100°C, it usually fails to exhibit the expected thermodynamic conversion to yellow /3-sulfur at 96°C. Instead, it persists as a superheated metastable phase up to 114°C (dashed line), where it exhibits an apparently normal melting point to the liquid form (unless extreme patience or a nucleating seed crystal of /3-sulfur is employed). The dashed lines in Fig. 7.5 therefore mark out metastable phase transition boundaries between forms of sulfur that are not true Gibbs free energy minima at the cited temperature and pressure (e.g., superheated a-sulfur and supercooled liquid sulfur at 114°C, 1 atm). The metastable phase domains can overlap stable phase domains in a quite complex and confusing manner. A kinetically facile metastable phase boundary will often appear more real and relevant to actual chemical phenomena than will the idealized boundary between (kinetically inaccessible) phases of lowest Gibbs free energy. 

Certain orientations may make a specific site on the protein inaccessible to ligand, substrate, or antigen. For example, consider the adsorptive immobilization of a specific IgG for a solid-phase immunoassay. The procedure will be optimal if the Fab domains are free to bind antigen (Figs. 1 and 16). 

In summary, information about the interactions between layers allowed one to identify the domains where the lamellar phase is unstable. A positive derivative off with respect to di or d2 implies that the region is inaccessible to a lamellar phase. In this case, a water or oil phase will separate until the allowed values for dj and 82 will be reached. In addition, a negative surface tension indicates that another phase (cubic,hexagonal, microemulsion, etc.) is stable. It should be, however, emphasized that when y > 0, a phase other than the lamellar one may be the thermodynamically stable one. 

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