Active dominance

Brusick and Matheson (1976) reported that 1,1-dimethylhydrazine failed to increase reversions in Salmonella typhimurium or Saccharomyces cerevisiae gene mutation assays with or without metabolic activation. A concentration-related response was observed in the mouse lymphoma assay (with activation). Dominant lethal tests were negative. 

It has always been of some interest to examine the extent to which associative activation dominates the mechanism of substitution of four-coordinate planar cP metal complexes. The coordination unsaturation of these formally 16-electron valence shell complexes predicts that a substitution pathway with increased coordination number (18-electron valence shell) will be favoured over one with a reduced coordination number (14 electrons). This was well understood by workers in the field438 long before Tolman94 published his rules. The first attempt to force a dissociative mechanism was made by Basolo and Baddley513>514 who reasoned that since the steric requirements of associative substitution (rates reduced by steric hindrance from the cis position) were opposite to those of a dissociative mechanism (rates increased or unchanged by increased steric hindrance), sufficient congestion in the substrate should reduce the rate of the associative process to the point where dissociative activation took over. If this did not produce a change in mechanism it could at least indicate a lower limit to the difference of the two modes of activation. 

Most of the activity reaching western Europe was carried on particles of diameter less than 2 jum (Jost et al., 1986 Winkelmann et al., 1987) but larger particles reached Scandinavia (Devell et al., 1986 Persson et al., 1987) and these carried a higher proportion of refractory elements. Spherical particles, condensed from the vapour state, were found with activity dominated by individual elements, for example Ce, Ru, Ba or Mo (U.S.S.R. State Committee, 1986 Persson et al., 1987). With longer distances of travel, the larger particles, and most of the refractory elements, were lost from the plume. Activity reaching Tennessee was found to be in particles with median diameter about 0.4//m, similar to that of cosmogenic 7Be (Bondietti Brantley, 1986). 

Seburn, K. L., Nangle, L. A., Cox, G. A., Schimmel, P. and Burgess, R. W. (2006) An active dominant mutation of glycyl-tRNA synthetase causes neuropathy in a Charcot-Marie-Tooth 2D mouse model. Neuron 51, 715-726. 

In Figure 4 we have designated the RFCC operation where activity dominates the unit (bottoms) conversion as the Activity Regime and the operation where CTO dominates the unit (bottoms) conversion as the Cat-to-Oil (CTO) Regime. 

The second-order term in the rate laws for reactions of low-spin iron(II) diimine complexes with such nucleophiles as hydroxide and cyanide ions has been established as arising from a bimolecular reaction between complex and nucleophile.182 Activation volumes that were obtained for reactions of CN and OH with Fc(phcn)2 1 and Fe(bpy)3 + were in the range of +19.7 to +21.5cm3mol-1.183 Because these observations were not readily accounted for by an associative mechanism, a mechanism analogous to the Eigen-Wilkins mechanism of complex formation was introduced in which dissociative activation dominates in determining the observed activation volumes. However, subsequently it was shown that solvation... 

The word Strychnos was first coined by the Greeks to term toxic Solanaceae species, then used by the Swedish botanist Linne to name dangerous and toxic plants with reference to two typical species, S. nux-vomica and S. colubrina. [1, 2], This toxic property originally stimulated intensive research on Strychnos species, leading to the successful isolation of strychnine (1) from Asian Strychnos and curare alkaloids from South-American Strychnos. For a long time, the tetanising or the curarizing activities dominated the research devoted to Strychnos. 

Oxygen consumption measurements [56-58] suggest distinct oxidation reactions for ferritin ferroxidase and mineralization processes. For the recombinant human and frog H ferritins, ferroxidase activity dominates with low iron loading (less than 50 Fe/ferritin 24-mer) and a Fe/Oa ratio of 2 is observed with H2O2 being the principle reduction product. The catalytic reaction was suggested to follow Eq. (16.3). 

Beliefs about classroom organization -2 Strongly teacher-centered The teacher is at the center of any activity, dominates any activity, lectures, and uses media to focus students attention... 

Fig. 9. Sequential pattern of allosteric control over biosynthesis of aromatic amino acids in the plastid compartment. In the presence of excess aromatic amino acids, L-tyrosine (TYR) inhibits arogenate dehydrogenase, L-phenylalanine (PHE) inhibits arogenate dehydratase and L-tryptophan (TRP) inhibits anthranilate synthase. The three aromatic amino acids exert allosteric inhibition (-) or activation (+) effects upon chorismate mutase-1 as symbolized. However, activation dominates over inhibition. The outcome of these events is to trap L-arogenate (AGN) between the various foci of control in the pathway. As shown symbolically, -arogenate (AGN) then acts to feedback inhibit DAHP synthase-Mn.

Merely changing to the P(p-tolyl)3 complex is enough to make C-H activation dominant for benzene although not for alkane [14b]. Presumably the higher electron density in this case particularly favors addition of the Ph-H system addition of an alkyl C-H with its less electronegative carbon would be expected to be less oxidizing and therefore less favored by modifying the phosphine. 

In a survey of different cereals, the lipase activity of oats was found to be much greater than that from wheat or barley varieties. However, incubation of flour preparations with [ C]triacyl glycerols revealed that transacylation reactions were quite active relative to lipase action in wheat, whereas the lipase activity dominated in oat flour preparations. Comparable activities were measured with triolein and tricaprylin substrates. Moreover, analysis of the removal of endogenous and exogenous triacyl glycerols by lipase activity did not reveal a preference for any specific molecular species. 

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