Site Density Functional Theory and Structural Bioinformatics Analysis of the SARS-CoV Spike Protein and hACE2 Complex

The entry of the SARS-CoV-2, a causative agent of COVID-19, into human host cells is mediated by the SARS-CoV-2 spike (S) glycoprotein, which critically depends on the formation of complexes involving the spike protein receptor-binding domain (RBD) and the human cellular membrane receptor angiotensin-converting enzyme 2 (hACE2). Using classical site density functional theory (SDFT) and structural bioinformatics methods, we investigate binding and conformational properties of these complexes and study the overlooked role of water-mediated interactions. Analysis of the three-dimensional reference interaction site model (3DRISM) of SDFT indicates that water mediated interactions in the form of additional water bridges strongly increases the binding between SARS-CoV-2 spike protein and hACE2 compared to SARS-CoV-1-hACE2 complex. By analyzing structures of SARS-CoV-2 and SARS-CoV-1, we find that the homotrimer SARS-CoV-2 S receptor-binding domain (RBD) has expanded in size, indicating large conformational change relative to SARS-CoV-1 S protein. Protomer with the up-conformational form of RBD, which binds with hACE2, exhibits stronger intermolecular interactions at the RBD-ACE2 interface, with differential distributions and the inclusion of specific H-bonds in the CoV-2 complex. Further interface analysis has shown that interfacial water promotes and stabilizes the formation of CoV-2/hACE2 complex. This interaction causes a significant structural rigidification of the spike protein, favoring proteolytic processing of the S protein for the fusion of the viral and cellular membrane. Moreover, conformational dynamics simulations of RBD motions in SARS-CoV-2 and SARS-CoV-1 point to the role in modification of the RBD dynamics and their impact on infectivity.     

DSC-, TG- und TMA-uUntersuchungen an lacken

DSC measurements on lacquers give information on possible uses, curing conditions and curing time. These data allow optimizing the processing of lacquers. TMA measurements of the glass transition and the softening of films of laquers permit making statements as to baking temperatures, elasticity, and degree of cure of the film of lacquer. Thermogravimetric investigations on the film of lacquer allow drawing conclusions as to the curing process that has taken place within the film and the degree of decomposition by heat and/or oxidation.     

Advanced Thermo-Optical Materials for Micro-Optical Applications

Thermo-optical phenomena in absorbing media containing nanosize ferromagnetic or ferroelectric particles in liquid or solid state matrix are investigated. Enhanced thermo-optical properties have been observed in lanthanum doped lead zirconate-titanate (PLZT) ceraMisc, sodium-bismuth titanate single crystals and ferrofluids near phase transitions.