Investigation of the Optical Properties for Quaternary Se60-xGe35Ga5Sbx (x = 0, 5, and 10) Chalcogenide Glass

A quenching technique was used to prepare the chalcogenide system of the Se60−xGe35Ga5Sbx (x = 0, 5, and 10 at. %), which was deposited as thin films onto glass substrates using a thermal evaporation technique. X-ray diffraction patterns were used for structure examination of the fabricated compositions, which exposes the amorphous nature of the deposited samples. Meanwhile, the chemical compositions of the prepared samples were evaluated and calculated via the energy-dispersive X-ray spectroscopy (EDX), which was in agreement with the measured compositional element percentages of the prepared samples. Based on the optical reflectance R and transmittance T spectra from the recorded spectrophotometric data ranging from 350 to 2500 nm, the influence of the Sb element on the Se60−xGe35Ga5Sbx thin films’ optical properties was studied. The film thickness and the refractive index were calculated via Swanepoel’s technique from optical transmittance data. It has been observed that the films’ refractive index increases with increasing x value over the spectral range. The refractive index data were used to evaluate the dielectric constants and estimate dispersion parameters Eo and Ed using the Wemple−DiDomenico model. The optical energy gap Egopt was calculated for the tested compositions. The result of the optical absorption analysis shows the presence of allowed direct and indirect transitions.

Validation of Reactivity Descriptors to Assess the Aromatic Stacking within the Tyrosine Gate of FimH

Antagonists of the FimH adhesin, a protein almost universally present at the extremity of type-1 fimbriae expressed by Escherichia coli, have been abundantly in the spotlight as alternative treatments of urinary tract infections. The antagonists function as bacterial antiadhesives through highly specific α-d-mannose binding in a charged and polar pocket at the tip of the FimH lectin domain and by the stacking of alkyl or aromatic moieties substituted on the mannose with two tyrosine residues (Tyr48 and Tyr137) at the entrance of the mannose-binding pocket. Using high-resolution crystal data, interaction energies are calculated for the different observed aromatic stacking modes between the tyrosines and the antagonist. The dispersion component of the interaction energy correlates with the observed electron density. The quantum chemical reactivity descriptors local hardness and polarizability were successfully validated as prediction tools for ligand affinity in the tyrosine gate of FimH and therefore have potential for rapid drug screening.