Definition many limiting substrates

Because few plant enzymes have been purified to a homogeneous state, final and definitive conclusions cannot yet be drawn concerning their substrate specificities. Many aminotransferase preparations hitherto studied have not shown absolute specificity for a single amino donor compound or amino acceptor compound. Where an incompletely purified enzyme catalyzes a multiplicity of reactions, it is obviously difficult to be certain whether the reactions are all being catalyzed by the same enzyme or by different enzymes present in the preparation. With this reservation, it is nevertheless possible to draw a number of conclusions from currently available data. The outer limits of specificity can fi-equently be ascertained, even though it may sometimes be found subsequently that purer preparations will exhibit more restricted substrate specificities. 

Capillary burst valves, which are rotationaUy actuated, stop flow by the counterpressure induced at a capillary feature such as a hydrophobic constriction or a sudden expansion in a (hydrophilic) channel (Fig. 4). If the substrate material is hydrophobic, the valve is typically formed by a constriction in the microchannel. These burst valves yield once the spin rate passed a certain threshold governed by the valve geometry, its radial position, the contact angle, and the surface tension of the liquid. Mainly due to minimum feature sizes and manufacturing tolerances, there is a practical limit which, on the one hand, restricts the maximum burst frequency and, on the other hand, smears out the definition of the nominally discrete burst frequencies into bands. In many applications the number of independently controllable burst valves and thus the number and vigorousness of LUOs are significantly capped [4]. 

The above ranges assume that other growth factors are optimal but clearly they will narrow as combinations of stresses are introduced. However, there is a lack of information about such interactions between the various environmental factors and their effects on the growth limits of salmonellae, and this is a research area which merits further quantitative definition. It should then be feasible to design and formulate new food products, within organoleptic constraints, which would not intrinsically support the multiplication of salmonellae . Many conventional foods and raw materials, however, provide ideal substrate conditions for growth of salmonellae and it is not practical or economic to alter their composition without loss of marketable character. In such cases, control can best be achieved by manipulation of extrinsic environmental factors (with emphasis on... 

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