Tunis University

About: Tunis University is a education organization based out in Tunis, Tunisia. It is known for research contribution in the topics: Population & Thin film. The organization has 11745 authors who have published 15400 publications receiving 154900 citations. The organization is also known as: University of Tunis & UT.

Energy-band structure of GaAs and Si: A sps * k.p method

Abstract: A twenty-band $\mathbf{k}\ensuremath{\cdot}\mathbf{p}$ Hamiltonian taking into account the spin-orbit coupling is used to describe the valence band and the first two conduction bands all over the Brillouin zone. The basis functions are ${\mathrm{sp}}^{3}{s}^{*}$-like functions used in linear combination of atomic orbitals. To get the right dispersion up to the Brillouin zone edge, the influence of other bands $(d$ bands) is mimicked via Luttinger-like parameters in the valence band and in the conduction band. The method is applied to GaAs and Si. A satisfying agreement is obtained near the band extrema as well in the direct gap semiconductor (GaAs) as in the indirect gap semiconductor (Si). In particular, while the $\mathbf{k}\ensuremath{\cdot}\mathbf{p}$ Hamiltonian parameters are adjusted to get the longitudinal mass 0.92 of the silicon conduction band, the transverse mass, which results from the calculation without further adjustment, is equal to 0.19 which is the experimental value.

Identification of LukPQ, a novel, equid-adapted leukocidin of Staphylococcus aureus

Abstract: Bicomponent pore-forming leukocidins are a family of potent toxins secreted by Staphylococcus aureus, which target white blood cells preferentially and consist of an S- and an F-component. The S-component recognizes a receptor on the host cell, enabling high-affinity binding to the cell surface, after which the toxins form a pore that penetrates the cell lipid bilayer. Until now, six different leukocidins have been described, some of which are host and cell specific. Here, we identify and characterise a novel S. aureus leukocidin; LukPQ. LukPQ is encoded on a 45 kb prophage (ΦSaeq1) found in six different clonal lineages, almost exclusively in strains cultured from equids. We show that LukPQ is a potent and specific killer of equine neutrophils and identify equine-CXCRA and CXCR2 as its target receptors. Although the S-component (LukP) is highly similar to the S-component of LukED, the species specificity of LukPQ and LukED differs. By forming non-canonical toxin pairs, we identify that the F-component contributes to the observed host tropism of LukPQ, thereby challenging the current paradigm that leukocidin specificity is driven solely by the S-component.