Sites stoichiometry

Reynafarje, B., and A. L. Lehninger, The K+/site and H+/site stoichiometry of mitochondrial electron transport. J. Biol. Chem. 254 6331, 1978. Valinomycin is used to allow K+ to move inward across the inner membrane in response to the electric potential difference created by H+ efflux. The number of protons pumped out is found to be larger than previously estimated. 

Half-site stoichiometry of acylation is induced by bound coenzyme blocking acylation at the i2-axis-related subunit. 

In an extension of these studies to the natural substrate, Stallcup and Koshland (172) showed further that acylation of the first two sites with DPGA decreases the rate of acylation of the third site, and that DPGA (or other acylating agents) attached to the first two sites increases the rate of deacylation of the third site through subunit interactions. These additional observations provide further support for the concept of negative cooperativity as a cause for half-site reactivity. They could also explain many of the results that have been obtained with muscle enzyme where apparent half-site stoichiometry might have resulted from rapid hydrolysis of the acyl enzyme (53). 

K inches of surface chemical reactions are governed by the elementary reactions llial constitute the reaction mechanism. In accordance with the principle of mass in lion, rates are proportional to surface concentrations (or surface densities) of piulicipating species surface sites, specifically adsorbed solutes, and non-npiTilically adsorbed solutes. The site stoichiometry model presented above is nih il used to express rate equations for surface chemical reactions. 

Results expressed as jUM of complexed metal per litre, assuming a 1 1 metal-binding site stoichiometry the range and average (bracketed) values are reported. 

Defect exarriDles V Iron vacancy in e.g. FejO Vp Oxygen vacancy in a metal oxide Zn" Zinc interstitial in e.g. ZnO Al( Al substitutional dopant in e.g. SrTIOj Defect reaction reouirements 1. Conservation of mass 2. Conservation of lattice site stoichiometry 3. Conservation of charge... 

Note that this is an irreversible reaction, since spontaneous demixing will not occur. This means that one cannot define an equilibrium constant for a dissolution reaction. Closer inspection shows that reaction (2.13) indeed fulfills the required conservation of mass, charge, and lattice site stoichiometry. 

One may try to get rid of the oxygen vacancy in reaction (2.13) by performing the s5mthesis in an oxygen-rich atmosphere. In this case, both mass and lattice site stoichiometry are conserved when adding the oxygen gas, which means that the charge has to be balanced by the addition of a hole ... 

According to (2.28a), W-doping actually decreases the conductivity of n-type BiV04, which is a rather unexpected (and tuidesired) result. It is also possible to write an alternative reaction in which lattice site stoichiometry is preserved by the segregation of vanadium out of the BiV04 in the form of V2O5 ... 

Jiang SP, Love JG, Zhang JP, Hoang M, Ramprakash Y, Hughes AE, Badwal SPS (1999) The electrochtan-ical performance of LSM/zirconia-yttria interface as a function of a-site stoichiometry and cathodic current treatment Sofid State Ionics 121 1-10... 

Bromopyruvate has proved to be an exceedin y versatile affinity label some of the more successful examples of its use as an active-site probe are listed in Table I. Especially interesting are recent studies by Chang and Hsu in which the reagent is shown to be both an inactivator and substrate for pigeon liver malic enzyme, and half-of-sites stoichiometry is observed. 

For the following derivation, six possible trivalent cation—surface site complexes will be considered (1) a single cation plus surface site, SOM (2) amono-hydroxylated cation plus surface site, SOMOH" (3) a dihydroxylated cation plus surface site, SOM(OH)°2 (4) a single cation plus double surface site, (SO)2M (5) a monohydroxylated cation plus double surface site, (SO)2 MOH and (6) a single cation plus triple sinface site, (80)3 M . The disposition of flnee of these cation— sinface site stoichiometries for trivalent cation adsorption at die S— MO interface is shown in Fig. 15. 

A solid is known as stoichiometric if the ratio of the amounts of the two elements that corrstitute it remains corrstant and eqttal to its value in the ideal solid. In the opposite case, the sohd is referred to as non-stoichiometric. Note that the ratios of sites represent the site stoichiometry in an ideal solid as in a real solid. For instance, if we cortsider a birraty solid B2A, the real solid will be stoichiometric if the ratio of the amormts of B and A is 2, but, whether it is stoichiometric or not, in all the cases, the ratio of the B sites to the A sites remains 2 and characterizes the structrrre of the sohd. 

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