Flavin metal complexes

Numerous biomimetic reactions catalyzed by CDs carrying catalytic or reactive functional groups, such as nucleophiles (imidazole, oxime, and amine), enzyme cofactors (pyridoxamine, thiazolium. nicotinamide, cobal-ainine, flavin), metal complexes, etc., were reported. " Typically, enzyme-like kinetics and improved performance of a catalytic group, as compared to a simple analog lacking CD. are observed. 

Electrochemistry of transition metal complexes with flavins, nucleosides and their constituent bases. M. J. Clarke, Rev. Inorg. Chem., 1980, 2, 27-51 (56). 

Flavin-containing Baeyer-Villiger monooxygenases (BVMOs) represent nature s equivalent of conventional peracids or de novo designed metal complexes... 

The addition of cofactors to antibodies is a sure means to confer a catalytic activity to them insofar as this cofactor is responsible for the activity. Indeed for many enzymes, the interaction with cofactors such as thiamins, flavins, pyridoxal phosphate, and ions or metal complexes is absolutely essential for the catalysis. It is thus a question there of building a new biocatalyst with two partners the cofactor responsible for the catalytic activity, and the antibody which binds not only the cofactor but also the substrate that it positions in a specific way one with respect to the other, and can possibly take part in the catalysis thanks to some of its amino acids. 

The stability constant for the lumiflavin semiquinone Zn chelate in aqueous solution was found to be 2xlfr M , with the Cd chelate having about equal stability Aprotic solvents such as DMF serve to increase the stability constants relative to H2O about 10-fold. In all systems tested, the stoichiometry of the flavin semiquinone-metal complex is 1 1. 

The metal complexes of riboflavin-5 -phosphate (flavin mononucleotide, FMN) have been studied. Zn(FMN)-2H20 shows some perturbation of the IR bands of the phosphate group, suggesting that metal binding occurs at the phosphate group.579 Reviews are available.9-15 468c h 1470... 

This chapter focuses on the progress and challenges in the field of photocatalysis as applied towards the water splitting reaction (Eq. 1.). More specifically, homogeneous molecule based systems that mimic the natural photosynthetic system are examined for their potential to drive reaction 1. A number of molecules, including porphyrins, metalloporphyrins and phthalocyanines,17 transition metal complexes of Ru, Os, Re, Rh, Pt, Cu,811 and acridine and flavin derivatives,1214 have been examined as the chormophores and sensitizers for light driven processes. 

Other light-absorbing trace organic compounds such as flavins, as well as inorganic compounds such as nitrate, nitrite, and metal complexes, do not contribute significantly to the total water column absorption. However, many of these compounds are quite photoreactive and will undergo rapid transformation under appropriate light fields. 

A large number of catalysts have been reported in the literature for the H2O2 oxidation of sulfides to sulfoxides. These include various metal complexes (of transition metals and lanthanides), flavins, and henzdhiazoles. 

The flavin is an efficient electron-transfer mediator, but rather unstable. Several transition metal complexes, for instance vanadyl acetylacetonate, can also activate hydrogen peroxide and are capable of replacing the flavin in the dihydroxylation reaction [18]. 

Chemiluminescence has been observed during the oxidation of these compounds by molecular oxygen in the presence of heavy metal catalysts. Copper-II-compounds ([Cu (NH3)4] + and a Cu- flavin mononucleotide complex) were found to be especially efficient. The emitting species seems to be singlet oxygen in both cases. The emission is accompanied by FMN fluorescence [52]. 

---