The interaction between Amyloid β (Aβ) peptide and acetylcholine receptor is the key for our understanding of how Aβ fragments block the ion channels within the synapses and thus induce Alzheimer's disease. Here, molecular docking and molecular dynamics (MD) simulations were performed for the structural dynamics of the docking complex consists of Aβ and α7-nAChR (α7 nicotinic acetylcholine receptor), and the inter-molecular interactions between ligand and receptor were revealed. The results show that Aβ25-35 bound to α7-nAChR through hydrogen bonds and complementary shape, and the Aβ25-35 fragments would easily assemble in the ion channel of α7-nAChR, then block the ion transfer process and induce neuronal apoptosis. The simulated amide-I band of Aβ25-35 in the complex is located at 1650.5 cm-1, indicating the backbone of Aβ25-35 tends to present random coil conformation, which is consistent with the result obtained from cluster analysis. Currently existed drugs were used as templates for virtual screening, eight new drugs were designed and semi-flexible docking was performed for their performance. The results show that, the interactions between new drugs and α7-nAChR are strong enough to inhibit the aggregation of Aβ25-35 fragments in the ion channel, and also be of great potential in the treatment of Alzheimer's disease.
The vacuum ultraviolet (VUV) photodissociation of OCS via the F 31Π Rydberg states was investigated in the range of 134–140 nm, by means of the time-sliced velocity map ion imaging technique. The images of S (1D2) products from the CO (X1Σ+) + S (1D2) dissociation channel were acquired at five photolysis wavelengths, corresponding to a series of symmetric stretching vibrational excitations in OCS (F 31Π, v1=0-4). The total translational energy distributions, vibrational populations and angular distributions of CO (X1Σ+, v) coproducts were derived. The analysis of experimental results suggests that the excited OCS molecules dissociate to CO (X1Σ+) and S (1D2) products via non-adiabatic couplings between the upper F 31Π states and the lower-lying states both in the C∞v and Cs symmetry. Furthermore, strong wavelength dependent behavior has been observed: the greatly distinct vibrational populations and angular distributions of CO (X1Σ+, v) products from the lower (v1=0-2) and higher (v1=3,4) vibrational states of the excited OCS (F 31Π, v1) demonstrate that very different mechanisms are involved in the dissociation processes. This study provides evidence for the possible contribution of vibronic coupling and the crucial role of vibronic coupling on the VUV photodissociation dynamics.
Theoretical study was carried out with OX2 (X = Halogen) molecules and calculation results showed that delocalized π36 bonds exists in their electronic structures and O atoms adopt the sp2 type of hybridization, which violated the VSEPR theory’s prediction of sp3 type. Delocalization stabilization energy (DSE) was proposed to measure delocalized π36 bond’s contribution to energy decrease and proved that it brings extra-stability to the molecule. According to our analyses, these phenomena can be summarized as a kind of coordinating effect.
A fundamental study on C?C coupling that is the crucial step in the Fischer-Tropsch synthesis (FTS) process to obtain multi-carbon products is of great importance to tailor catalysts and then guide a more promising pathway. It has been demonstrated that the coupling of CO with the metal carbide can represent the early stage in the FTS process, while the related mechanism is elusive. Herein, the reactions of the CuC3H– and CuC3– cluster anions with CO have been studied by using mass spectrometry and theoretical calculations. The experimental results showed that the coupling of CO with the C3H– moiety of CuC3H– can generate the exclusive ion product COC3H–. The reactivity and selectivity of this reaction are greatly higher than that on the reaction of CuC3– with CO, and this H-assisted C?C coupling process was rationalized by theoretical calculations.