Site separation

In the above expressions, RT stands for restricted totalistic rules which maximally subdivide the local neighborhood. The inclusion of an ij in the expressions for tp assures that only those sites already linked can be decoupled and the 6 Dij,2) in the equations defining uj are put in to malce sure that only sites separated by distance=2 may be dynamically coupled. 

Hexaammonium macrocycles [32]aneN6 and [38]aneN6 were designed as selective ditopic receptor molecules for dicarboxylates -02C—R—C02- such as succinate, glutarate, or adipate 51). Highest stability of the complex corresponds to the best fit between the substrate R length and the site separation of the receptor II. 

If the ligand aliosterically affects the affinity of the receptor (antagonist binds to a site separate from that for the tracer ligand) to produce a change in receptor conformation to affect the affinity of the tracer (vide infra) for the tracer ligand (see Chapter 6 for more detail), the displacement curve is given by (see Section 4.6.3)... 

It is assumed that the radioligand [A ] binds to a site separate from one binding an allosteric antagonist [B]. 

An essential step of NR action is the interaction of these receptors with the specific DNA sequence HREs. Indeed, HREs position the receptors, and the transcriptional complexes recruited by them, close to the target genes. HREs are bipartite elements that are composed of two hexameric core half-site motifs. These consensus nucleotide sequences form direct, indirect, or inverted repeats, which consist of two half-sites separated... 

Peroxisome Proliferator-Activated Receptors. Figure 2 Binding of PPAR RXR heterodimers to DR1 PPRE-responsive elements. Abbreviations DR1, a direct repeat organization of the A/GGGTCA hexamer half-site separated by a single nucleotide spacer. 

Stabilizers bind at a site separate from those of traditional activators and of ciguatoxin-brevetoxin, but they exert a synergistic action on both types of activators (J5, 42). This action potentiates the activators and generally increases their efficacy, yielding larger depolarizations at lower doses 42) it occurs uniquely with the peptide stabilizers and not with ions or oxidants that also slow the inactivation of Na current 37). 

The third paper in this set Zavarin and Snajberk (1976) described their efforts to detect chemical races within big cone Douglas fir. Analysis of the cortical monoterpenoid fraction of 33 trees revealed that the major component was a-pinene, with P-pinene, 3-carene, and limonene present in lesser amounts. The monoterpene profiles of different populations varied somewhat from each other, but the overall profile of big cone Douglas fir was clearly different from that of Douglas fir. There was no evidence for gene flow between the southernmost population of Douglas fir at Lompoc and the closest population of big cone Douglas fir at Figueroa, sites separated by only 34 km. 

Fig. 56. Partial ORTEP drawings for [TpB l]Zn(CN)09Io 1 with disordered site refined as (CN)0.906(4)Io.094(4> Center superposition of CN and I groups at the disordered site. Left and right disordered site separated into composite molecules. Reprinted with permission from Ref. (213). Copyright 1992 American Chemical Society.

Rotational-echo double-resonance (REDOR)(75,79) is a new solid-state NMR technique which is sensitive to through-space carbon-nitrogen interactions between selectively 13C and 15N-enriched sites separated by up to 5A (20-22). The parameter directly measured in a REDOR experiment is the heteronuclear dipolar coupling constant DCN, which is in itself proportional to the inverse third power of the intemuclear distance, rCN. It is this dependence on (icn)3 which accounts both for REDOR s ability to accurately measure short distances and its insensitivity to longer-range interactions. As a technique which can probe, in detail, intermolecular interactions over a distance range of 5A, REDOR is well suited to studying the distribution of small selectively-labeled molecules in polymer delivery systems. 

Our data provide a ratio of 1 0.2 0.1 for reactivity at G, GG, and GGG sites on a per-G basis. These relationships are summarized in Table 2. The small difference in G vs GG vs GGG hole stability and lower reactivity of the more stable sites is, of course, precisely the combination of stability and reactivity that is required for the observation of hole transport over long distances containing multiple G and GG sites. Hole transport between two GGG sites separated by a TTGTT sequence appears to be somewhat slower than cleavage at the initially oxidized GGG site [12]. To our knowledge, the efficiency of strand cleavage in duplexes possessing more than two GGG sites has not been studied. 

Figure 5.2 The use of hollow PDMS thimbles to achieve site separation ofGrubbs catalyst and an osmium dihydroxylation catalyst [34], The solution of the Grubbs catalyst was placed on the interior of the PDMS thimble in which a metathesis reaction was then performed. After...

Figure 5.20 Energy barriers during atomic diffusion (a) an atom diffusing in a sodium chloride structure or similar passes through octahedral and tetrahedral sites separated by triangular bottlenecks and (b) a schematic energy barrier with a periodicity equal to a, rising to a maximum when the diffusing atom has to pass a bottleneck between two stationary atoms.

The temperature dependent T data are shown in Fig. 9. 7j values decrease from 28 ms at 21°C with increasing temperature, and show a minimum of 6.4 ms at 80° C. These results indicate the presence of the motion with a Larmor frequency of 30 MHz at this temperature. This minimum was found to be attributed to the flipping motion of a phenyl ring from the result of our other experiments discussed in later section.13 The jump rates of the flipping motion were estimated with a two-site jump model that a C-2H bond jumps between two equivalent sites separated by 180°, and that the angle made by the C-2H bond and the rotational axis is 60°. The quadrupole coupling constant of 180 kHz and the asymmetry parameter approximated to zero were used in the calculation. The calculated values for fitting with the... 

Consider two identical acceptor or donor sites separated by a long, separated, saturated chain (Scheme 1.3) that allows the interactions between the two sites to be negligible. The first electron transfer may involve two sites, while the second necessarily involves a single site. This is the reason... 

The situation is quite different for oxygen adsorption. The Oad atoms form the relatively open mesh of a 2 x 2 structure (Fig. 4.9b) where these are located in threefold coordinated sites separated from each other by 2a0 = 0.56 nm. At this stage further uptake of oxygen is pronouncedly slowed down, but the surface is still read-... 

Fig. 3.6 (a) Definition of bottleneck shortest distance and variation of mobile-ion potential with position with (solid line) and without (dotted line) relaxation of host structure, (h) Variation of mobile-ion potential for occupied sites separated by an array of inequivalent, empty sites, (c) Smoothing of the potential of (b) by introduction of mobile ions into second array of sites. 

Fig. 4.25 Elastic and inelastic contribution to the incoherent scattering function for jump motion between two sites separated by 1.5 A...

We expect wide site separation (2-3 Al/U.C.) to increase cracking versus hydrogen transfer if hydrogen transfer is a two-center reaction like coke formation... 

First doubts about these approaches came from experimental findings where a correlation between the O - H - 0 bond length 2R and the H(D) site separation S with Tc were reported [14-16]. These observations have been... 

The above results also explain the pressure dependence of Tc, which has been observed by neutron diffraction experiments [14-16]. With increasing pressure the proton-proton site separation decreases, which implies a decrease of C and a decrease in Tc in agreement with experiments. 

Kogan A, Spiegler E, Wolfshtein M (2000) Direct solar thermal splitting of water and on-site separation of the products. III. Improvement of reactor efficiency by steam entrainment. Int J Hydrogen Energy 25 739-745... 

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