A water soluble luminescent 1D metal organic coordination polymer of Zn(II) [Zn(FDA)(2,2′-bpy)(H2O)]·2H2O (2,2′-bpy = 2,2′-bipyridine and FDA = 2,5-furandicarboxylate), 1 was successfully synthesized by solvothermal method. This crystalline compound 1 showed strong luminescence emission at 325 nm upon excitation at 290 nm in aqueous medium. The luminescence intensity was highly sensitive towards a bio-metabolized purine derivative, uric acid (UA). However, it did not show any considerable response towards structurally similar other purine derivatives like adenine (Adn), guanine (Gua) and theobromine (Tbr). The compound 1 was found to be highly selective and sensitive towards uric acid (UA) with a detection limit of 300 ppb. The sensitivity and selectivity of 1 towards UA was also investigated in the presence of several metal ions, anions and organic bio-molecules which are commonly found in human urine. The results indicated that 1 could be a potential probe for selective detection and estimation of UA in urine. The mechanism of the sensing was explained successfully and it was also supported by DFT calculation.

Trace-level and selective detection of uric acid by a luminescent Zn (II) based 1D coordination polymer in aqueous medium

The standard Michaelis-Menten expression for the rate of an enzyme-catalysed reaction (v) can be extended using the ratio of two polynomials in the substrate concentration (s). Such rational functions are nonlinear and their behaviour can vary considerably. Comparisons of two such functions requires more than a simple consideration of a particular coefficient, especially given the coefficients do not necessarily have any mechanistic significance. A second issue is the identification of particular coefficients that contribute significantly to the overall error of the estimate of v at a given s. As the number of coefficients rises this becomes increasingly difficult. To address the first of these issues we provide a general expression for the estimated confidence band of an arbitrary rational function of this type. We employ sensitivity analysis to address the second issue and provide general expressions for the coefficient elasticities. We apply these in the analysis of the kinetics of chymotrypsin and muscle lactate dehydrogenase.

Confidence bands for rational rate equations

A novel, portable electrochemical sensing gadget has been developed to analyze the level of uric acid in human urine. It uses gold nanoparticles embedded, chemically modified carbon paste electrode. The uric acid level is identified as the main marker in a majority of the diseases, such as urolithiasis, gout, myeloma, and so on. The main objective of the present effort was to study the level of uric acid accurately in minimum time. For this, we developed an instant, real-time monitoring kit to give accurate and fast data on the level of uric acid in a real sample. The initial work focused on developing chemically modified gold nanoparticles embedded carbon paste electrode, while the later part was aimed at converting the effort into a full detecting kit with a real time display unit to display levels of uric acid and to give a suitable indication. Since the detection kit requires neither sophisticated lab nor specific conditions to work, it is portable. This can be used as a uric acid screening device even in rural health centers. This paper can help the medical practitioners as well as the lab technicians to analyze samples quickly and give better support to the patients.

A Portable Detection Kit Using Au Nanoparticles Modified Carbon Paste Electrode for Screening Uricemia Patients

The phototransformation of 2-chloro, 6-chloro and 2,6-dichloropurines under UVC excitation (254 nm) has been studied and the major photoproducts have been identified using absorption spectroscopy, HPLC and mass spectrometry. It was shown that hydroxypurines were formed as the main products for all three investigated compounds both in the presence and absence of oxygen. In the case of 6-chloro- and 2,6-dichloropurine, a photodimer is also formed as a minor photoproduct in the absence of oxygen but is efficiently quenched in the presence of oxygen. Nanosecond photolysis experiments also revealed significant intersystem crossing to the triplet state of the chloropurines which has been characterized (transient absorption spectra, triplet formation quantum yields and rate constants of quenching by oxygen, Mn2+ ions and ground state). Experimental evidence allows to conclude that the triplet state is involved in photodimer formation whereas the hydroxypurine is formed from the reaction of the excited singlet state of chloropurines with the solvent (water addition) through heterolytic C–Cl bond rupture. Mass spectrometry and 1H NMR results allowed to propose a chemical pathway for dimer formation in the case of 2,6-dichloropurine in a two-step process: first a homolytic rupture of C–Cl bond in the triplet state of the molecule with the formation of purinyl radicals, which subsequently react with an excess of ground state molecules and/or hydroxypurine primarily formed.

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UVC induced oxidation of chloropurines: excited singlet and triplet pathways for the photoreaction

Uric acid, the end product of purine degradation, causes hyperuricemia and gout, afflicting hundreds of millions of people. The debilitating effects of gout are exacerbated by dietary purine intake, and thus a potential therapeutic strategy is to enhance purine degradation in the gut microbiome. Aerobic purine degradation involves oxidative dearomatization of uric acid catalyzed by the O2-dependent uricase. The enzymes involved in purine degradation in strictly anaerobic bacteria remain unknown. Here we report the identification and characterization of these enzymes, which include four hydrolases belonging to different enzyme families, and a prenyl-flavin mononucleotide-dependent decarboxylase. Introduction of the first two hydrolases to Escherichia coli Nissle 1917 enabled its anaerobic growth on xanthine as the sole nitrogen source. Oral supplementation of these engineered probiotics ameliorated hyperuricemia in a Drosophila melanogaster model, including the formation of renal uric acid stones and a shortened lifespan, providing a route toward the development of purinolytic probiotics. 

Anaerobic purinolytic enzymes enable dietary purine clearance by engineered gut bacteria.

A new kinetic model is presented for analysis of experimental data of oxidation process catalyzed by milk xanthine oxidase The kinetics for two substrates, xanthine and its analog 2-chloroadenine, in a broad pH range (58–90) are best described by an equation which is a rational function of degree 2:3 and 2:2, respectively

Kinga Banach

Papers

Kinetic model of oxidation catalyzed by xanthine oxidase-the final enzyme in degradation of purine nucleosides and nucleotides.