Structural and spectroscopic studies of a model for catechol oxidase

A binuclear copper complex, [Cu₂(BPMP)(OAc)₂][ClO₄]·H₂O, has been prepared using the binucleating ligand 2,6-bis[bis(pyridin-2-ylmethylamino)methyl]-4-methylphenol (H-BPMP). The X-ray crystal structure reveals the copper centers to have a five-coordinate square pyramidal geometry, with the acetate ligands bound terminally. The bridging phenolate occupies the apical position of the square-based pyramids and magnetic susceptibility, electron paramagnetic resonance (EPR) and variable-temperature variable-field magnetic circular dichroism (MCD) measurements indicate that the two centers are very weakly antiferromagnetically coupled (J = −0.6 cm⁻¹). Simulation of the dipole–dipole-coupled EPR spectrum showed that in solution the Cu–O–Cu angle was increased from 126° to 160° and that the internuclear distance was larger than that observed crystallographically. The high-resolution spectroscopic information obtained has been correlated with a detailed ligand-field analysis to gain insight into the electronic structure of the complex. Symmetry arguments have been used to demonstrate that the sign of the MCD is characteristic of the tetragonally elongated environment. The complex also displays catecholase activity (k _cat = 15 ± 1.5 min⁻¹, K _M = 6.4 ± 1.8 mM), which is compared with other dicopper catechol oxidase models. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

A phylogenomic tree inferred with an inexpensive PCR-generated probe kit resolves higher-level relationships among Neptis butterflies (Nymphalidae: Limenitidinae)

Recent advances in obtaining reduced representation libraries for next-generation sequencing permit phylogenomic analysis of species-rich, recently diverged taxa. In this study, we performed sequence capture with homemade PCR-generated probes to study diversification among closely related species in a large insect genus to examine the utility of this method. We reconstructed the phylogeny of Neptis Fabricius, a large and poorly studied nymphalid butterfly genus distributed throughout the Old World. We inferred relationships among 108 Neptis samples using 89 loci totaling up to 84 519 bp per specimen. Our taxon sample focused on Palearctic, Oriental and Australasian species, but included 8 African species and outgroups from 5 related genera. Maximum likelihood and Bayesian analyses yielded identical trees with full support for almost all nodes. We confirmed that Neptis is not monophyletic because Lasippa heliodore (Fabricius) and Phaedyma amphion (Linnaeus) are nested within the genus, and we redefine species groups for Neptis found outside of Africa. The statistical support of our results demonstrates that the probe set we employed is useful for inferring phylogenetic relationships among Neptis species and likely has great value for intrageneric phylogenetic reconstruction of Lepidoptera. Based on our results, we revise the following two taxa: Neptis heliodore comb. rev. and Neptis amphion comb. rev.