On the Maximal Excess Charge of the Chandrasekhar-Coulomb Hamiltonian in Two Dimensions

We show that for the straightforward quantized relativistic Coulomb Hamiltonian of a two-dimensional atom -- or the corresponding magnetic quantum dot -- the maximal number of electrons does not exceed twice the nuclear charge. It result is then generalized to the presence of external magnetic fields and atomic Hamiltonians. This is based on the positivity of |\bx| T(\bp) + T(\bp) |\bx| which -- in two dimensions -- is false for the non-relativistic case T(\bp) = \bp^2, but is proven in this paper for T(\bp) = |\bp|, i.e., the ultra-relativistic kinetic energy

Crystallization and preliminary characterization of chloromuconolactone dehalogenase from Rhodococcus opacus 1CP

Chloroaromatic compounds are often very persistent environmental pollutants. Nevertheless, numerous bacteria are able to metabolize these compounds and to utilize them as sole energy and carbon sources. ıt Rhodococcus opacus} 1CP is able to degrade several chloroaromatic compounds, some of them {ıt via} a variation of the 3-chlorocatechol branch of the modified {ıt ortho}-cleavage pathway. This branch in {ıt R. opacus} differs from that in {ıt Proteobacteria} in the inability of the chloromuconate cycloisomerase to dehalogenate. Instead, a unique enzyme designated as chloromuconolactone dehalogenase (ClcF) is recruited. ClcF dehalogenates 5-chloromuconolactone to {ıt cis}-dienelactone and shows a high similarity to muconolactone isomerases (EC 5.3.3.4). However, unlike the latter enzymes, it is unable to catalyse the isomerization of muconolactone to 3-⁻oxoadipate enollactone. In order to characterize the catalytic mechanism of this unusual dehalogenase, the enzyme was crystallized and subjected to X-ray structural analysis. Data sets to up to 1.65Å resolution were collected from two different crystal forms using synchrotron radiation. Crystal form I (space group {ıt P}2{\sb 1}) contained 40 subunits in the asymmetric unit, whereas ten subunits were present in crystal form II (space group {ıt P}2{\sb 1}2{\sb 1}2{\sb 1). The self-rotation function revealed the orientations of the molecular symmetry axes of the homodecamer of 52 symmetry