Latent class analysis (LCA) is a statistical method used to group individuals (cases, units) into classes (categories) of an unobserved (latent) variable on the basis of the responses made on a set of nominal, ordinal, or continuous\ud
observed variables. In this article, we introduce LCA in order to demonstrate its usefulness to early adolescence researchers. We provide an application of LCA to empirical data collected from a national survey carried out in 2010 in Italy to assess mathematics and reading skills of fifth-grade primary school pupils (10 years in age). The data were used to measure pupils’\ud
supplies of cultural capital by specifying a latent class model. This article aims to describe and interpret results of LCA, allowing users to replicate the analysis. All LCA examples included in the text are illustrated using the Latent GOLD package, and command files needed to reproduce all analyses with SAS and R are available as supplemental online appendix files along with\ud
the example data files
Copper amine oxidases utilize 2,4,5-trihydroxyphenylalanine quinone (topaquinone) as a cofactor in enzymatic catalysis. This cofactor is formed from a tyrosine residue through a self-catalytic mechanism with the participation of the copper ion at the active site. Although pathways have been postulated for topaquinone biogenesis, portions of this scheme are still unclear. We utilized 4-tert-butyl-derived models for the putative intermediates of topaquinone generation and studied the effect of Cu(II) and Zn(II) ions on each autoxidative step from dopa-to topaquinone-like compounds at physiological pH (7.4). Several polyvinyl-alcohol-based soluble resins bearing mono-and di-hydroxyphenolic moieties were also prepared, and their tendency to give hydroxyquinonic structures when incubated at alkaline pH values was investigated. Our results confirm (although indirectly) the formation of dopa and dopaquinone during topaquinone biosynthesis. Moreover, we collected evidence that, following the formation of dopa, the role of the active-site copper ion in topaquinone biogenesis would be limited to the catalysis of the two subsequent quinonization steps (i.e. from dopa to dopaquinone and from topa to topaquinone), thus disfavoring the possibility of a direct intervention of the metal ion in the hydroxylation of dopaquinone. In particular, Cu(II) was shown to influence deeply the autoxidation of 1,2,5-trihydroxy-4-tert-butylbenzene, used as model of topa, both increasing the reaction rate and changing its mechanism. The mechanistic implications of these findings for the biogenesis of topaquinone and its analogs at the active site of various amine oxidases are discussed.
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