Enzyme mimetic -based

Because of cost and less stabiHty of the biological enzyme, there has been great interest for the use of metalloporphyrins as an alternative for enzymes as a biorecognition element in biosensor applications (Arduini et al., 2009). Recendy, enzyme mimetic-based biosensors have been reported for the determination of various biomarkers with high stabihty and reproducibility that enable researchers to easily fabricate biosensors. First, we briefly provide a general overview of porphyrin and its derivatives as enzyme mimetic. 

Selected examples of such oxidations of straight-chain aliphatic compounds are listed in Table 1. The remarkable monohalogenation and co-1 selectivities in these reactions have been attributed to polar, steric, and conformational effects. The yields of monohalogenated derivatives, based on converted (60-80"/)) substrate, are generally quantitative. Comparison of these selectivities with a number of oxidations using bromine, chlorine or rerf-butoxy radical chain carriers shows that aminium radical-mediated oxidation is far superior to others for synthetic, indeed industrial, applications [28]. The high selectivity and clean monooxidation displayed by the aminium radical chain process has been referred as an enzyme-mimetic reaction ... 

More elaborate enzyme mimetics have used acid-base pairs on the rim and in the center of cyclodextrin matrices with similar results. 

Besides the superoxide dismutation mechanism, the reactivity of metal centers, in particular manganese complexes, toward NO is very much dependent on the possibility for binding a substrate molecule. As it will be shown later, the possibility that MnSOD enzymes and some mimetics can react with NO has been wrongly excluded in the literature, simply based on the known redox potential for the (substrate) free enzymes, mimetics, and NO, respectively. Therefore, the general fact that, upon coordination, redox potentials of both the metal center and a coordinated species are changed should be considered in the case of any inner-sphere electron-transfer process as a possible reaction mechanism. 

In this chapter, a novel interpretation of the membrane transport process elucidated based on a voltammetric concept and method is presented, and the important role of charge transfer reactions at aqueous-membrane interfaces in the membrane transport is emphasized [10,17,18]. Then, three respiration mimetic charge (ion or electron) transfer reactions observed by the present authors at the interface between an aqueous solution and an organic solution in the absence of any enzymes or proteins are introduced, and selective ion transfer reactions coupled with the electron transfer reactions are discussed [19-23]. The reaction processes of the charge transfer reactions and the energetic relations... 

Robl JA, Sun C-Q et al (1997) Dual metalloprotease inhibitors mercaptoacetyl-based fused heterocyclic dipeptide mimetics as inhibitors of angiotensin-converting enzyme and neutral endopeptidase. J Med Chem 40 1570-1577... 

The catalytic properties of Mn enzyme structural models are not limited to the natural substrates of the enzymes they mimic. One could classify this catalysis based upon the substrates as biological mimetic catalysis or biomimetic catalysis [175] and biologically inspired catalysis or bioinspired catalysis [176], Unlike biomimetic catalysis, its bioinspired counterpart capitalizes on nature s findings to change nonnatural substrates chemically and, perhaps, unravel novel chemistry. 

The area between enzymatic and chemical catalyses, associated with simulation of biochemical processes by their basic parameters, is accepted as mimetic catalysis. The key aspect of the mimetic catalyst is diversity of enzyme and biomimetic function processes, which principally distinguishes the mimetic model from traditional full simulation. Based on the analysis of conformities and diversities of enzymatic and chemical catalysis, the general aspects of mimetic catalysis are discussed. An idealized model of the biomimetic catalyst and the exclusive role of the membrane in its structural organization are considered. The most important achievements in the branch of catalysis are shown, in particular, new approaches to synthesis and study of biomimetic catalase, peroxidase and monooxidases reactions. 

JA Robl, C Sun, J Stevenson, DE Ryono, LM Simpkins, MAP Cimarusti, T Dejneka, WA Slusarchyk, S Chao, L Stratton, RN Misra, MS Bednarz, MM Asaad, HS Cheung, BE Aboa-Offei, PL Smith, PD Mathers, M Fox, TR Schaeffer, AA Seymour, NC Trippodo. Dual metalloprotease inhibitors mercaptoacetyl-based fused heterocyclic dipeptide mimetics as inhibitors of angiotensin-converting enzyme and neutral endopeptidase. J Med Chem 40 1570-1577, 1997. 

Referring to a mechanistic classification of organocatalysts (Seayad and List 2005), currently the two most prominent classes are Brpnsted acid catalysts and Lewis base catalysts. Within the latter class chiral secondary amines (enamine, iminium, dienamine activation for a short review please refer to List 2006) play an important role and can be considered as—by now—already widely extended mimetics of type I aldolases, whereas acylation catalysts, for example, refer to hydrolases or peptidases (Spivey and McDaid 2007). Thiamine-dependent enzymes, a versatile class of C-C bond forming and destructing biocatalysts (Pohl et al. 2002) with their common catalytically active coenzyme thiamine (vitamin Bi), are understood to be the biomimetic roots ofcar-bene catalysis, a further class of nucleophilic, Lewis base catalysis with increasing importance in the last 5 years. 

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