Non-covalent hydrogen bond interactions between the π cloud of cycloalkenes and three atmospheric common nucleation precursors (H2S, H2O, and MeOH) have been investigated using DFT and CCSD(T). The structures and the energies of the 1:1 and 1:2 adducts were computed with the B3LYP-D3 method. The analysis of the investigated electronic properties and geometric parameters shows that cyclohexene is a stronger hydrogen bond acceptor than cyclopentene, then followed by 1,4-cyclohexadiene and 1,3-cyclohexadiene. Comparable red shifts of the OH-/SH-stretching vibrational frequencies were noticed for the studied clusters. Increasing the ring size enhances the hydrogen bond interaction, and increasing the π delocalization decreases the hydrogen bond interactions. This is further confirmed by Bader’s quantum theory of atoms in molecules. The nonadditivity effects were observed in the trimolecular complexes. All the complexes were analyzed by energy decomposition analysis to divide the interaction energy into individual components. Furthermore, the dipole moments and atmospheric implications were also investigated.
Seven new phloroglucinol derivatives, myrtucommunins A–D (1–4), 6-methylisomyrtucommulone B (5), 4-methylmyrtucommulone B (6), and 2-isobutyryl-4-methylphloroglucinol 1-O-β-d-glucopyranoside (7), and one new chromone derivative, undulatoside A 6′-O-gallate (8), were isolated from the leaves of Myrtus communis (Myrtaceae). Myrtucommunins A–D (1–4) were conjugates of polymethylated acylphloroglucinol and flavonol rhamnoside. The absolute configurations of the rhamnosyl moieties for 1–4 were confirmed to be l in each case by HPLC analyses, while those of the aglycones were assigned by comparisons of the experimental and TDDFT calculated ECD spectra. 6-Methylisomyrtucommulone B (5) and 4-methylmyrtucommulone B (6) were assigned as 6/6/6 tricyclic acylphloroglucinol derivatives with a racemic nature. Antimicrobial activities of 1–8 and related known compounds were evaluated. 相似文献
It is demonstrated that the cyclopentadienyl-free simple lanthanide amides [(Me(3)Si)(2)N](3)Ln(mu-Cl)Li(THF)(3)(Ln = La, Sm, Eu, Y, Yb) and Ln[N(SiMe(3))(2)]3 (Ln = Y, Yb) are highly efficient catalysts for the guanylation of both aromatic and secondary amines with a high activity under mild conditions. It is found that these catalysts are compatible with a wide range of solvents and substrates. 相似文献
The results of an investigation into the influence of sulfolane, a commonly used supercharging agent, on electrospray ionization mass spectrometry (ESI-MS) measurements of protein–ligand affinities are described. Binding measurements carried out on four protein–carbohydrate complexes, lysozyme with β-d-GlcNAc-(1→4)-β-d-GlcNAc-(1→4)-β-d-GlcNAc-(1→4)-d-GlcNAc, a single chain variable fragment and α-d-Gal-(1→2)-[α-d-Abe-(1→3)]-α-d-Man-OCH3, cholera toxin B subunit homopentamer with β-d-Gal-(1→3)-β-d-GalNAc-(1→4)[α-d-Neu5Ac-(2→3)]-β-d-Gal-(1→4)-β-d-Glc, and a fragment of galectin 3 and α-l-Fuc-(1→2)-β-d-Gal-(1→3)-β-d-GlcNAc-(1→3)-β-d-Gal-(1→4)-β-d-Glc, revealed that sulfolane generally reduces the apparent (as measured by ESI-MS) protein–ligand affinities. To establish the origin of this effect, a detailed study was undertaken using the lysozyme–tetrasaccharide interaction as a model system. Measurements carried out using isothermal titration calorimetry (ITC), circular dichroism, and nuclear magnetic resonance spectroscopies reveal that sulfolane reduces the binding affinity in solution but does not cause any significant change in the higher order structure of lysozyme or to the intermolecular interactions. These observations confirm that changes to the structure of lysozyme in bulk solution are not responsible for the supercharging effect induced by sulfolane. Moreover, the agreement between the ESI-MS and ITC-derived affinities indicates that there is no dissociation of the complex during ESI or in the gas phase (i.e., in-source dissociation). This finding suggests that supercharging of lysozyme by sulfolane is not related to protein unfolding during the ESI process. Binding measurements performed using liquid sample desorption ESI-MS revealed that protein supercharging with sulfolane can be achieved without a reduction in affinity.