Biomimetic adsorbent

Another potential application of PHA is as biomimetic adsorbents for wastewater purification. Wei and co-workers [36] prepared a new biomimetic adsorbent using a lipid-derived P(3HB) homopolymer. 

An interesting investigation was made to indicate that PHB can form a new biodegradable adsorption material. Poly-3-hydroxybutyrate (PHB) was used as a new material to prepare a biomimetic adsorbent by a modified double emulsion solvent evaporation technique. The enrichment capacities of the adsorbent for toxic liposoluble organic compounds were evaluated by chlorobenzene (CB) and o-nitrochlorobenzene (u-NCB) with the adsorption isotherms, enrichment factor (EF) and enrichment kinetics. ... 

So far, certain biomimetic catalysts (1 and 2b in Fig. 18.17) have been shown to reduce O2 to H2O under a slow electron flux at physiologically relevant conditions (pH 7,0.2-0.05 V potential vs. NHE) and retain their catalytic activity for >10" turnovers. Probably, only the increased stability of the turning-over catalyst is of relevance to the development of practical ORR catalysts for fuel cells. In addition, biomimetic catalysts of series 1,2,3, and 5, and catalyst 4b are the only metalloporphyrins studied in ORR catalysis with well-defined proximal and distal environments. For series 2, which is by far the most thoroughly studied series of biomimetic ORR catalysts, these well-defined environments result in an effective catalysis that seems to be the least sensitive among all metalloporphyrins to the electrode material (whether the catalyst is adsorbed or in the film) and to chemicals present in the electrolyte or in the O2 stream, including typical catalyst poisons (CO and CN ). 

The prevalence of the heme in O2 metabolism and the discovery in the 1960s that metallophthalocyanines adsorbed on graphite catalyze four-electron reduction of O2 have prompted intense interest in metaUoporphyrins as molecular electrocatalysts for the ORR. The technological motivation behind this work is the desire for a Pt-ffee cathodic catalyst for low temperature fuel cells. To date, three types of metaUoporphyrins have attracted most attention (i) simple porphyrins that are accessible within one or two steps and are typically available commercially (ii) cofacial porphyrins in which two porphyrin macrocycles are confined in an approximately stacked (face-to-face) geometry and (iii) biomimetic catalysts, which are highly elaborate porphyrins designed to reproduce the stereoelectronic properties of the 02-reducing site of cytochrome oxidase. 

Biomimetic sensors, prepared from catalase adsorbed on diasorb and A1203, treated with trypsine and adhered to an aluminum electrode surface using 7.5% polyacrylamide gel of... 

Self-assembled and spontaneously adsorbed monolayers offer a facile means of controlling the chemical composition and physical structure of a surface. As discussed later in Chapter 5, applications of these monolayers include modeling election transfer reactions, biomimetic membranes, nano-scale photonic devices, solar energy conversion, catalysis, chemical sensing and nano-scale lithography. 

The possibility that an electron-transfer path is involved in photo-sensitized oxygenation has been considered on several occasions. This is relevant in several fields of application, from the biomimetic oxygenation of indole and flavin derivatives [106] to pollutant control. With reference to latter, it has been suggested that SET occurs in heterogeneous photosensitized oxidation by solid semiconductors, in which the adsorbed substrate donates an electron to the photogenerated hole and... 

A potentially important development for the future of biomimetic research was published recently. Using a procedure developed by Whitesides, nucleophiles micropattemed on a gold surface were used as initiators to prepare poly(Y-benzyl-L-glutamate). Thus, an array of poly(amino acid) layers covalently attached to the surface was obtained. These would potentially act as mediators of biomimetic reactions. German workers have described the production of protein-DNA double and triple layers adsorbed on smfaces. Adhesion between layers was provided by biotin-streptavadin interactions and binding was detected by a quartz crystal microbalance. These studies may have some relevance to the understanding of protein DNA interactions at interfaces in biological systems. 

Tailored adsorbents are those synthesized for a purification of a specific component. They are made by sophisticated chemistry whereby biospecific or biomimetic ligands are bonded via a linker to a support. Examples of tailored adsorbents are affinity adsorbents and immuno adsorbents. Such materials serve for the isolation of components of high value in milligram amounts. 

H., and Lecomte, S. (2007) Kinetics of the electron transfer reaction of cytochrome c(552) adsorbed on biomimetic electrode studied by time-resolved surface-enhanced resonance Raman spectroscopy and electrochemistry. European Biophysics Journal, 36,1039-1048. 

We have recently investigated whether the BMPs/OPs shown to be present by immunolocalization in the concavities are adsorbed onto the sintered biomimetic... 

Labrou NE, Karagouni A, Clonis YD (1995) Biomimetic-dye affinity adsorbents for enzyme purification application to the one-step purification of Candida boidinii formate dehydrogenase. Biotechnol Bioeng 48(3) 278-288... 

As our intent in this review is to address questions of NO c reductions at heme active sites from a mechanistic inorganic perspective, the use of simple heme model compounds is quite useful and will be thoroughly described. Here similar issues of solubility and reactivity come into play, as biomimetic NO c catalysis requires either water-soluble porphyrins or surface-adsorbed catalysts. As might be expected, questions of intersite reactivity come into play both in the reactivity of transient intermediate species such as nitroxyl-adducts, and in multielectron reactivity required for assimilatory reductase activity. We will begin with brief descriptions of the known families of heme-based NOjc reductases and the all-too-few electrochemical investigations of these native enzymes. 

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