Biocatalytic element

Moreover, Eu is placed in the c/x (bidentate) map considerably far off the other REEs except of Sm and Tb, the latter showing toxicological peculiarities also (Emsley 2001), with Eu(II) placed next to Ba, Sr, unlike other REE or Ce(IV). Taking the existence of some contrived area in the c/x plane to be an established precondition for essentiality now (except, perhaps for Ca and Cu), one is caused to ask how the ligand properties of either substrates or products of principal biochemical transformations control the set of possibly or actually biocatalytic elements It was outlined before that... 

While enzymatic biosensors have gained increasing popularity over the past decades, researchers also focused on the development of whole ceU- and tissue-based biosensors. One of the first studies that reported the use of living cells as biocatalytic elements for biosensors was published in 1978 by G.A. Rechnitz... 

Raw materials (substrate or feedstock) costs are usually a significant cost element in most biocatalytic processes. Their importance highlights the importance of good buying policy and skills and, when possible, the effective use of forwards buying and futiues markets to obtain cheap raw materials etc. despite variabilities in their... 

These theoretical frameworks were selected for formal integration and explanation , making no assumptions other than the ability of living beings to reproduce and that some chemical features of (biocatalytically) essential can be pinpointed which distinguish them from non-essential elements. Explanation here means reduction to some theoretical framework in quantitative terms also, that is, constructing a model which can account for the observed effects vs. exclusion of others which are not observed, e.g., non-essentiality of some other elements owing to a semi-empirical description of their chemical properties. 

A multitude of different and closely matching biocatalytic functions which also means that a new function to be established during evolution or ontogeny will not necessarily - not even as a rule -imply integration of yet another heteroelement (cp. the number of functional proteins in some highly organized creature - often many thousands - to that of available elements - less than 40 - and recall the rule of three functions ). Rather the rule of three functions will limit functionalization of heteroelements (cp. Chapter 4). 

It does not matter that essentiality of some other elements (Na, K, Ca, Sr, Si) - if it actually refers to a certain element which cannot be replaced - will be unrelated to biocatalysis e.g., K can be fully replaced by Rb in many organisms (Scott and DeVoe 1954 Lwoff and Ionesco 1947), Ca roles, e.g. in control of cell budding can likewise be fulfilled by Sr and by various REE ions as a rule, while there are specific functions (unknown up to now) for Sr in corals and certain algae and for Ba in desmides, biocatalytic or not. Thus, neither K nor Ca are fundamental as single elements in such organisms. Examples for such different reasons of essentiality include electrolyte balances, changes of membrane permeability or protein shapes... 

Once we acknowledge this, we should proceed to ask whether an npgrade to three- or more-level trophic chains in the Cambrian also might have had an impact on the nnmber of essential elements (usually larger in animals than in plants or bacteria) which is/ was dne to selection criteria from chemistry rather than those derived from pnre SNA. These selection criteria might inclnde the chance to obtain some element by grazing a biomat or catching prey up to an extent which allows for its eventnal biochemical or biocatalytic use. 

Within the c/x plot for bidentate complexation there is a very constrained region containing all the classical (and some exotic or nltratrace) essential metal ions other than Cn, which exert biocatalytic functions in the center. The heavier alkaline earths Ca. Sr (for corals and foraminifers) and Ba (in desmides) are essential elements bnt hardly for pnrposes of biochemical catalysis, that is, substrate binding measured by c and x does not matter for heavy alkaline earth essentiality. 

Table 3.1 Complex formation constants for E (L) = -0.323 V, representing binding into metalloproteins. Data are given for essential (biocatalytic) and some other, both essential and undefined elements...

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