The quantum chemistry polarizable force field program (QuanPol) is implemented to perform combined quantum mechanical and molecular mechanical (QM/MM) calculations with induced dipole polarizable force fields and induced surface charge continuum solvation models. The QM methods include Hartree-Fock method, density functional theory method (DFT), generalized valence bond theory method, multiconfiguration self-consistent field method, Møller-Plesset perturbation theory method, and time-dependent DFT method. The induced dipoles of the MM atoms and the induced surface charges of the continuum solvation model are self-consistently and variationally determined together with the QM wavefunction. The MM force field methods can be user specified, or a standard force field such as MMFF94, Chemistry at Harvard Molecular Mechanics (CHARMM), Assisted Model Building with Energy Refinement (AMBER), and Optimized Potentials for Liquid Simulations-All Atom (OPLS-AA). Analytic gradients for all of these methods are implemented so geometry optimization and molecular dynamics (MD) simulation can be performed. MD free energy perturbation and umbrella sampling methods are also implemented.

ε-poly-lysine (ε-PL) is a naturally-occurring homopolymer produced by the fermentation process. Here, we report a new chemical strategy based on ring opening polymerization to obtain ε-PL from lysine.

An effective shielding of both apical positions of a neutral Ni(II) active site is achieved by dibenzosuberyl groups, both attached via the same donors' N-aryl group in a Cs-type arrangement. The key aniline building block is accessible in a single step from commercially available dibenzosuberol. This shielding approach suppresses chain transfer and branch formation to such an extent that ultrahigh molecular weight polyethylenes (5 × 10 6 g mol-1) are accessible, with a strictly linear microstructure (< 0.1 branches/1000C). Key features of this highly active (4.3 × 10 5 turnovers h-1) catalyst are an exceptionally facile preparation, thermal robustness (up to 90 o C polymerization temperature), ability for living polymerization and compatibility with THF as a polar reaction medium.

Recently, metal–organic framework (MOF)-based electrospun fibers have attracted considerable attention as adsorbents for organic contaminant removal from water. To prepare these fibers, two common strategies including blending electrospinning and surface coating are employed. However, fibers obtained from the two strategies still have some disadvantages, such as adsorption site blockage and unstable loading. Here, we constructed interconnected mesopores in the electrospun zeolitic imidazolate framework-8 (ZIF-8)/polyacrylonitrile (PAN) fibers with the assistance of poly­(vinylpyrrolidone) to expose more adsorption sites of ZIF-8 and make ZIF-8 more stable. Moreover, the mesopores could also enhance the diffusion of contaminant molecules and create MOF–polymer interfaces in the fiber, which improve the adsorption rate and adsorption capacity, respectively. The obtained fibers were used to adsorb antibiotic tetracycline from water. Benefiting from the mesoporous adsorption channels and the MOF–polymer interface, porous ZIF-8/PAN fibers showed faster adsorption kinetics than ZIF-8/PAN blending fibers and larger adsorption capacity than ZIF-8-coated PAN fibers and ZIF-8/PAN blending fibers. The maximum adsorption capacity of porous ZIF-8/PAN fibers was 885.24 mg/g, which is close to that of pure ZIF-8. After 10 adsorption–desorption cycles, the removal efficiency was still above 97%. In addition, porous ZIF-8/PAN fibers could act as the membrane adsorbents to dynamically separate tetracycline with a treated capacity of 9.93 × 103 bed volumes. These results demonstrate that our prepared porous ZIF-8/PAN fibers have great potential in antibiotic drug removal.

Organotin-mediated regioselective protection has been extensively used in organic synthesis for many years. However, the mechanistic origin of the resulting regioselectivity is still not clear. By the comparison of the steric and stereoelectronic effects controlling the geometry of five-membered rings formed from neighboring group participation, from intramolecular acyl group migration, or from orthoester transesterification on pyranoside rings, a theory on the pattern resulting from the reaction with dibutyltin oxide is presented. It is thus suggested that the regioselectivity of organotin-mediated protection is controlled by analogous steric and stereoelectronic effects as in neighboring group participation and acyl group migration, mainly dependent on the stereoelectronic effects of the pyranoside itself, and not related to complex stannylene structures. An organotin protection mechanism is also suggested, emanating from steric and stereoelectronic effects, nucleophilicity, and organotin acyl migration.

The switchable catalysis using a commercial salenMn catalyst was firstly developed and applied in the one‐pot selective copolymerization from anhydrides, epoxides, CO2 and ϵ‐caprolactone (ϵ‐CL) mixtures for the precise synthesis of AB, ABA and novel ABC block copolymers. The observed unique double switch process comprising three different polymerization cycles was rationalized by theoretical calculations. Surprisingly, the first block turned out to be an efficient macromolecular initiator for the consecutive introduction of carbonate linkages into copolymers, albeit with dominant cyclization with the catalyst alone. Further, through the selective reaction on different epoxides, the switchable copolymerization of up to five monomers was achieved yielding well‐defined multi‐block copolymers with structural diversity and functionality.

To explore the inhibitory mechanism of catechins for digestive enzymes, we investigated the binding mode of catechins to a typical digestive enzyme-trypsin and analyzed the structure-activity relationship of catechins, using an integration of molecular docking, molecular dynamics simulation and binding free energy calculation. We found that catechins with different structures bound to a conservative pocket S1 of trypsin, which is comprised of residues 189–195, 214–220 and 225–228. In the trypsin-catechin complexes, Asp189 by forming strong hydrogen bonding, and Gln192, Trp215 and Gly216 through hydrophobic interactions, all significantly contribute to the binding of catechins. The number and the position of hydroxyl and aromatic groups, the structure of stereoisomers, and the orientation of catechins in the binding pocket S1 of trypsin all affect the binding affinity. The binding affinity is in the order of Epigallocatechin gallate (EGCG) > Epicatechin gallate (ECG) > Epicatechin (EC) > Epigallocatechin (EGC), and 2R-3R EGCG shows the strongest binding affinity out of other stereoisomers. Meanwhile, the synergic conformational changes of residues and catechins were also analyzed. These findings will be helpful in understanding the knowledge of interactions between catechins and trypsin and referable for the design of novel polyphenol based functional food and nutriceutical formulas.

The opioid inactive isomer (+)-naltrexone is one of the rare Toll-like receptor 4 (TLR4) antagonists with good blood-brain barrier (BBB) permeability, which is a lead with promising potential for treating neuropathic pain and drug addiction. (+)-Naltrexone targets the lipopolysaccharides (LPS) binding pocket of myeloid differentiation protein 2 (MD-2) and blocks innate immune TLR4 signaling. However, the details of the molecular interactions of (+)-naltrexone and its derivatives with MD-2 are not fully understood, which hinders the ligand-based drug discovery. Herein, in silico and in vitro assays were performed to elucidate the innate immune recognition of the opioid inactive (+)-isomers. The results showed that the conserved LPS binding pocket of MD-2 accommodated these opioid inactive (+)-isomers. The calculated binding free energies of (+)-naltrexone and its derivatives in complex with MD-2 correlated well with their experimental binding affinities and TLR4 antagonistic activities. Hydrophobic residues in the MD-2 cavity interacted directly with these (+)-naltrexone based TLR4 antagonists and principally participated in ligand binding. Increasing the hydrophobicity of substituted group at N-17 improved its TLR4 antagonistic activity, while charged groups disfavored the binding with MD-2. Molecular dynamics (MD) simulations showed the binding of (+)-naltrexone or its derivatives to MD-2 stabilized the "collapsed" conformation of MD-2, consequently blocking the binding and signaling of TLR4. Thermodynamics and dynamic analysis showed the topology of substituted group at N-17 of (+)-naltrexone affected the binding with MD-2 and TLR4 antagonistic activity. This study provides a molecular insight into the innate immune recognition of opioid inactive (+)-isomers, which would be of great help for the development of next-generation of (+)-opioid based TLR4 antagonists.