Mechanism of coupling

Mechanisms of Coupling. Because the active coupling species is the ioni2ed coupler (35,52), the rate of the coupling reaction and hence its abihty to compete for oxidi2ed developer is dependent on the pH of the process, the piC or acidity of the coupler or less frequentiy the rate of coupler ioni2ation, and the reactivity of the resulting coupler anion with the QDI (40). 

The resulting PL intensity depends on the absorption of the incident light and the mechanism of coupling between the initial excited states and the relaxed excited states that take part in emission. The spectrum is similar to an absorption spectrum and is useful because it includes higher excited levels that normally do not appear in the thermalized PL emission spectra. Some transitions are apparent in PLE spectra from thin layers that would only be seen in absorption data if the sample thickness were orders of magnitude greater. 

The general mechanism of coupling reactions of aryl-alkenyl halides with organometallic reagents and nucleophiles is shown in Fig. 9.4. It contains (a) oxidative addition of aryl-alkenyl halides to zero-valent transition metal catalysts such as Pd(0), (b) transmetallation of organometallic reagents to transition metal complexes, and (c) reductive elimination of coupled product with the regeneration of the zero-valent transition metal catalyst. 

If the reaction shown in Figure 10-1 is to go from left to right, then the overall process must be accompanied by loss of free energy as heat. One possible mechanism of coupling could be envisaged if a common obligatory intermediate (I) took part in both reactions, ie,... 

MO) with the protons in the nodal plane. The mechanism of coupling (discussed below) requires contact between the unpaired electron and the proton, an apparent impossibility for n electrons that have a nodal plane at the position of an attached proton. A third, pleasant, surprise was the ratio of the magnitudes of the two couplings, 5.01 G/1.79 G = 2.80. This ratio is remarkably close to the ratio of spin densities at the a and (3 positions, 2.62, predicted by simple Hiickel MO theory for an electron placed in the lowest unoccupied MO (LUMO) of naphthalene (see Table 2.1). This result led to Hiickel MO theory being used extensively in the semi-quantitative interpretation of ESR spectra of aromatic hydrocarbon anion and cation radicals. 

Davidson, A. L. (2002). Mechanism of coupling of transport to hydrolysis in bacterial ATP-binding cassette transporters, J. Bacteriol., 184, 1225-1233. 

Voth, G. A. (1986), On the Relationship of Classical Resonances to the Quantum Mechanics of Coupled Oscillator Systems, J. Phys. Chem. 90, 3624. 

Liberman EA, Topaly VP, Tsofina LM, Jasaitis AA, Skulachev VP. Mechanism of coupling of oxidative phosphorylation and the membrane potential of mitochondria. Nature 1969 222(198) 1076-1078. 

The composition of the two-component pathway is very variable. The nature of the external signal and the reactions triggered in the cell may be very diverse. The sensor kinase may be a part of the receptor that registers the signal, or it may be on a polypeptide chain separate from the receptor. Furthermore, there are different mechanisms of coupling of the main functions of the two-component pathway. The sensor and reaction regulator may be on a single polypeptide or they may be on separate proteins. In addition, the proteins involved may be membrane proteins. 

Diamond, J. M., Bossert, W. H. Stamding gradient osmotic flow. A mechanism of coupling of water and solute transport in epithelia. J. gen. Physiol. 50, 2061 (1967)... 

The mechanism of coupling of allyltin and allylpalladium can be altered by the addition of maleic anhydride to the reaction mixture (vide infra).m In this modified procedure, reaction of the allylpalladium chloride dimer with allyl-Bun3Sn now gives coupling without allyl inversion of the allyltin reagent. 

Electromagnetic interference (EMI) refers to the interaction between electric and magnetic helds and sensitive electronic circuits and devices. EMI is predominantly a high-frequency phenomenon. The mechanism of coupling EMI to sensitive devices is different from that for power frequency disturbances and electrical transients. The mitigation of the effects of EMI requires special techniques, as will be seen later. Radio frequency interference (RFT) is the interaction between conducted or radiated radio frequency helds and sensitive data and communication equipment. It is convenient to include RFI in the category of EMI, but the two phenomena are distinct. 

To evaluate the collective coupling effects, we make the assumption that the only efficient mechanism of coupling is that introduced by Jk of Section II.B.l.c. Thus, we neglect the terms discarded in order to pass from (2.87) to (2.88), which result from the interactions with the other electronic states (in particular S2), and which may introduce differential stabilization of the vibronic levels. 

Likhtenshtein, G.I. and Shilov, A.E. (1976) On the chemical mechanism of coupling of ATP hydrolysis reactions, Dokl. Acad. Nauk. SSSR229, 1127-1130. 

A substantial number of observations have demonstrated that the stress-70 proteins bind denatured proteins, as well as some short peptides, and that ATP hydrolysis (possibly with concomitant release of Pj or ADP) results in the release of bound peptides (de Silva et ai, 1990 Hendershot, 1990 Hurtley 1989 Kassenbrock 1988 Palleros etai, 1991). Conversely, bindingof peptides to stress-70 proteins induces ATPase activity above basal levels peptide-induced ATPase activity is often used as a facile in vitro assay for stress-70 protein activity. Schematically, this activity can be subdivided into (1) ATP binding and hydrolysis, followed by product release (P and ADP), (2) peptide binding and release, and (3) a mechanism of coupling peptide binding/release and nucleotide hydrolysis/product release. 

Figure 34.32. Proton Transport-Coupled Rotation of the Flagellum. (A) MotA-MotB may form a structure having two half-channels. (B) One model for the mechanism of coupling rotation to a proton gradient requires protons to be taken up into the outer half-channel and transferred to the MS ring. The MS ring rotates in a counterclockwise direction, and the protons are released into the inner half-channel. The flagellum is linked to the MS ring and so the flagellum rotates as well.

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