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Smart Cities Governance: The Need for a Holistic Approach to Assessing Urban Participatory Policy Making
Full text linkMost of the definitions of a ‘‘smart city’’ make a direct or indirect reference to improving performance as one of the main objectives of initiatives to make cities ‘‘smarter’’. Several evaluation approaches and models have been put forward in literature and practice to measure smart cities. However, they are often normative or limited to certain aspects of cities’ ‘‘smartness’’, and a more comprehensive and holistic approach seems to be lacking. Thus, building on a review of the
literature and practice in the field, this paper aims to discuss the importance of adopting a holistic approach to the assessment of smart city governance and policy decision making. It also proposes a performance assessment framework that overcomes the limitations of existing approaches and contributes to filling the current gap in the knowledge base in this domain. One of the innovative elements of the proposed framework is its holistic approach to policy evaluation. It is designed to
address a smart city’s specificities and can benefit from the active participation of citizens in assessing the public value of policy decisions and their sustainability over time. We focus our attention on the performance measurement of codesign and coproduction by stakeholders and social innovation processes related to public value generation. More specifically, we are interested in the assessment of both the citizen centricity of smart city decision making and the processes by which public decisions are implemented, monitored, and evaluated as regards their capability to develop truly ‘‘blended’’ value services—that is, simultaneously socially inclusive, environmentally friendly, and economically sustainable
Effect of metal ions on the kinetics of tyrosine oxidation catalyzed by tyrosinase
No full textThe conversion of tyrosine into dopa is the rate-limiting step in the biosynthesis of melanins catalyzed by tyrosinase. This hydroxylation reaction is characterized by a lag period, the extent of which depends on various parameters, notably the presence of a suitable H donor, such as dopa or tetrahydropterin. Here, it is reported that catalytic amts. of Fe2+ have the same effect as dopa in stimulating the tyrosine hydroxylase activity of the enzyme. Kinetic expts. showed that the redn. of the induction time depended on the concn. of the added metal and the nature of the buffer system used and was not suppressed by superoxide dismutase, catalase, formate, or mannitol. Notably, Fe3+ had only a small delaying effect on tyrosinase activity. Among the other metal ions tested, Zn2+, Co2+, Cd2+, and Ni2+ had no detectable influence, whereas Cu2+ and Mn2+ exhibited a marked inhibitory effect on the kinetics of tyrosine oxidn. These findings are discussed in the light of the commonly accepted mechanism of action of tyrosinase
Mechanism of inhibition of melanogenesis by hydroquinone
No full textHydroquinone (HQ) is one of the most effective inhibitors of melanogenesis in vitro and in vivo, and is widely used for the treatment of melanosis and other hyperpigmentary disorders. In an attempt to get some insight into the mol. mechanism of the depigmenting action, which is still very poorly understood, the effect of HQ on the tyrosinase catalyzed conversion of tyrosine to melanin was examd. Incubation of 0.5 mM tyrosine with 0.07 U/mL tyrosinase in phosphate buffer at pH 6.8 in the presence of 0.5 mM HQ led to no detectable melanin formation, due to the preferential oxidn. of HQ with respect to tyrosine (HPLC evidence). Kinetic investigations showed that HQ is a poorer substrate of tyrosinase than tyrosine; yet, it may be effectively oxidized in the presence of tyrosine owing to the generation of catalytic amts. of dopa acting as cofactor of tyrosinase. Product anal. of HQ oxidn. with tyrosinase in the presence of dopa showed the predominant formation in the early stages of hydroxybenzoquinone (HBQ), arising from enzymic hydroxylation and subsequent oxidn. of HQ, along with lower amts. of benzoquinone (BQ). These results suggest that the depigmenting activity of HQ may partly be related to the ability of the compd. to act as an alternate substrate of tyrosinase, thereby competing for tyrosine oxidn. in active melanocytes
A new look at the rearrangement of adrenochrome under biomimetic conditions
No full textAt physiol. pH values, the rearrangement of adrenochrome leads, besides adrenolutin, to a major dimeric compd. consisting of an adrenolutin moiety covalently linked to the angular 9-position of adrenochrome. When the reaction is carried out in air, the initially generated adrenolutin undergoes autoxidn. to give 5,6-dihydroy-1-methylisatin (DHMIs), which smoothly oxidized to the 4,4'-dimer. Under an O2-depleted atm., formation of these latter compds. is prevented, and the rearrangement of adrenochrome leads mainly to the adrenochrome dimer (∼50% yield) along with adrenolutin and 5,6-dihydroxy-1-methylindole (DHMI) in ∼10% yield each. The product distribution is markedly dependent on the concn. of the aminochrome undergoing rearrangement, the nature of the buffer system used, and the pH of the medium. Heavy metal ions of common occurrence in biol. systems, such as Cu2+, Zn2+, or Co2+, significantly direct the reaction course toward the formation of adrenolutin, whereas Fe2+ and other cations with low redox potentials induce the almost exclusive formation of DHMI
5,6-Dihydroxyindole-2-carboxylic acid, a diffusible melanin precursor, is a potent stimulator of lipopolysaccharide-induced production of nitric oxide by J774 macrophages
No full textPre-incubation of J774 murine macrophages with 5,6-dihydroxyindole-2-carboxylic acid (DHICA), a diffusible intermediate in the biosynthesis of eumelanins, leads to a marked increase in the levels of nitric oxide (NO) produced by lipopolysaccharide (LPS)-induced NO-synthase (iNOS). The effect varies with DHICA concn., being max. at a concn. of 1 × 10-6M, and is suppressed by the NOS inhibitor NG-monomethyl-L-arginine (L-NMMA). No stimulation is obsd. when macrophages are exposed to DHICA after activation with LPS, indicating that the indole does not affect the catalytic activity of iNOS. These results point to a hitherto unrecognized role of DHICA as a chem. messenger mediating interaction between active melanocytes and macrophages in epidermal inflammatory and immune responses
Skin depigmentation by hydroquinone: a chemical and biochemical insight
No full textThe skin depigmenting agent hydroquinone (HQ) is shown to inhibit melanogenesis in vitro by acting as an alternate substrate of tyrosinase and preventing conversion of tyrosine to melanin. Upon the action of tyrosinase, and in the presence of catalytic dopa, HQ is oxidatively metabolized to give eventually highly colored quinonoid materials, by way of HBQ, the hydroxylation-dehydrogenation product of HQ, and p-benzoquinone (BQ). Overall, the chem. depicted in this study is compatible with, and would lend support to most of the currently accepted theories on the mol. mechanism of action of HQ. The ability of the compd. to compete with tyrosine for tyrosinase oxidn., without inducing significant inactivation of the enzyme, is consistent with both the selectivity and reversibility of HQ to undergo hydroxylation and dehydrogenation to yield highly reactive quinones, such as HBQ, BQ and their dimerization products, provides for the first time a convincing chem. basis to the postulated generation within melanocytes of cytotoxic species disrupting fundamental cell processes. Such species may be involved in redox-exchange, radical generating reactions as well as covalent modifications interfering with the melanization pathway and causing a focal degrdn. of melanosomes
Occurrence of two new mycosporine-like aminoacids, mytilins A and B in the edible mussel, Mytilus galloprovincialis
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