Activity

Ring conformations of 3,4-dihydro-2H-pyran (34DHP) have attracted considerable interest owing to their structural similarity to cyclohexene, an important molecule in stereochemistry. In this study, we investigated the conformational interconversion of 34DHP in both the neutral (S0) and the cationic (D0) ground states. High-resolution vacuum ultraviolet mass-analyzed threshold ionization (VUV-MATI) spectroscopy was utilized to obtain information regarding the adiabatic ionic transition between the S0 and the D0 states. FHD-609 Based on the 0-0 band in the VUV-MATI spectrum supported by the VUV-photoionization efficiency curve, the adiabatic ionization energy of 34DHP was accurately determined to be 8.3355 ± 0.0005 eV (67 230 ± 4 cm-1). To identify the conformer corresponding to this measured value, two-dimensional potential energy surfaces (2D PESs) associated with conformational interconversion in the S0 and the D0 states were constructed at the B3LYP/aug-cc-pVTZ level. It was revealed that in the S0 state, the twisted conformers undergo interconversion through the asymmetric bent conformation on the pseudorotational pathway, whereas in the D0 state, the half-bent conformers directly undergo interconversion via the planar conformation at the saddle point of 2D PES. The change in the conformational interconversion pathway upon ionization is attributed to electron removal from the highest occupied molecular orbital, which consists of a π orbital in the 2C-3C double bond interacting with a nonbonding orbital in the oxygen atom of 34DHP. Then, vibrational assignment of the observed spectrum could be achieved through Franck-Condon fitting for ionic transitions between the neutral twisted and the cationic half-bent conformers. The strong promotion of the ring bending and the 1O-2C-3C asymmetric stretching modes in the adiabatic ionic transitions confirmed the determined cationic structure of 34DHP.Polo-like kinase 1 (PLK1) is a key regulator and coordinator for mitotic signaling that contains two major functional units of a kinase domain (KD) and a polo-box domain (PBD). While individual domain structures of the KD and the PBD are known, how they interact and assemble into a functional complex remains an open question. The structural model from the KD-PBD-Map205PBM heterotrimeric crystal structure of zebrafish PLK1 represents a major step in understanding the KD and the PBD interactions. However, how these two domains interact when connected by a linker in the full length PLK1 needs further investigation. By integrating different sources of structural data from small-angle X-ray scattering, hydroxyl radical protein footprinting, and computational sampling, here we report an overall architecture for PLK1 multidomain assembly between the KD and the PBD. Our model revealed that the KD uses its C-lobe to interact with the PBD via the site near the phosphopeptide binding site in its auto-inhibitory state in solution. Disruption of this auto-inhibition via site-directed mutagenesis at the KD-PBD interface increases its kinase activity, supporting the functional role of KD-PBD interactions predicted for regulating the PLK1 kinase function. Our results indicate that the full length human PLK1 takes dynamic structures with a variety of domain-domain interfaces in solution.Deprotonation of the terminal phosphido complex (PN)2La(PHMes) (1) results in the C-H-activation of one of the PN ligands, formally retaining the PHMes group. The reaction mechanism and the possible involvement of the transient phosphinidene complex 2 are investigated by theoretical and chemical means including a deuteration experiment employing (PN)2La(PDMes) (1-d). Furthermore, the thermal stability of product [K(2.2.2-cryptand)][(PN)(PNcyclo)La(PHMes)] (3b) is examined, giving the diphosphido complex [K(2.2.2-cryptand)][(PN)2La(P2Mes2)] (6).The two isomers of the propylperoxy radical 1-C3H7O2 and 2-C3H7O2, together with their individual rotamers, are identified and assigned by threshold photoelectron spectroscopy with the aid of high-level theoretical computations, from which their accurate adiabatic ionization energies are derived. This study paves the way to probing elusive peroxy radicals and their isomers in advanced mass spectrometry analysis of combustion and atmospheric reactions.The assessment of the penetration depth of conservation treatments applied to cultural heritage stone materials is a burning issue in conservation science. Several analytical approaches have been proposed but, at present, many of them are not fully exhaustive to define in a direct way the composition and location of the conservation products formed after inorganic mineral treatments. Here, we explored, for the first time, the analytical capability of synchrotron radiation μ X-ray diffraction in transmission geometry (SR-μTXRD) for the study of the crystal chemistry and penetration depth of the consolidating phases formed after the application of diammonium hydrogen phosphate (DAP) treatments on a porous carbonatic stone (Noto limestone). The SR-μTXRD approach provided unambiguous information on the nature of the newly formed calcium phosphates (hydroxyapatite, HAP, and octacalcium phosphate, OCP) with depth, supplying important indications of the diffusion mechanism and the reactivity of the substrate. Qualitative and semi-quantitative data were obtained at the microscale with a non-destructive protocol and an outstanding signal-to-noise ratio. The SR-μTXRD approach opens a new analytical scenario for the investigation of a wide range of cultural heritage materials, including natural and artificial stone materials, painted stratigraphies, metals, glasses and their decay products. Furthermore, it can potentially be used to characterize the penetration depth of a phase “A” (or more crystalline phases) in a matrix “B” also beyond the cultural heritage field, demonstrating the potential wide impact of the study.The complete caloric and thermal equations of state for pentaerythritol tetranitrate (PETN) and its decomposition products are developed. The equation for the crystalline state is obtained with quasiharmonic approximation for the vibrational energy, with the force constants being calculated using density functional theory. The equation of state for the products is derived from equilibrium ReaxFF molecular dynamics simulations. Two equations are coupled through the heat of thermal decomposition calculated using ReaxFF at high temperature. Our hydrodynamic code utilizing the developed EOSs reproduces well the detonation velocity and Chapman-Jouguet pressure obtained in the molecular dynamics simulations.