Theoretical Study on Interactions of β-cyclodextrin with Trans-dichloro(dipyridine) platinum(II)

Physical Characterization of Inclusion Complexes of Triphenyl Phosphate and Cyclodextrins in Solution

The goal of this work is to provide physical insights into the formation and stability of inclusion complexes (ICs) in aqueous solution between cyclodextrins (CDs) and a common flame retardant, triphenyl phosphate (TPP). Quantum chemistry calculations reveal the possible energetically favorable geometries of TPP in their 1:1 IC form with α-, β-, and γ-CDs as well as their associated complexation, conformational, and interaction energies. High-resolution mass spectrometry (MS) and tandem MS were used with electrospray ionization to study the soluble ICs formed between TPP and CDs. Successful formation of TPP ICs with both β- and γ-CD in solution was detected in the ratio of 1:1 using high-resolution MS in the positive ion mode. Collision-induced dissociation confirmed the formation of TPP ICs with β- and γ-CDs by generating two product ions, TPP and β- or γ-CD, in both cases. Although quantum chemistry calculations suggest that IC formation with α-CD is energetically possible, an IC with α-CD is not observed in aqueous solution using MS, which aligns with what we also previously observed in the solid state. Since TPP forms stable ICs with β- and γ-CDs both in the solid state and in solution suggests that complexation could be a safer alternative than applying TPP directly to a substrate. In addition, complexation with CDs in solution also opens up new processing methods to create flame-retardant fabrics and foams with TPP.

Recent Progress in Treating Protein-Ligand Interactions with Quantum-Mechanical Methods

We review the first successes and failures of a “new wave” of quantum chemistry-based approaches to the treatment of protein/ligand interactions. These approaches share the use of “enhanced”, dispersion (D), and/or hydrogen-bond (H) corrected density functional theory (DFT) or semi-empirical quantum mechanical (SQM) methods, in combination with ensemble weighting techniques of some form to capture entropic effects. Benchmark and model system calculations in comparison to high-level theoretical as well as experimental references have shown that both DFT-D (dispersion-corrected density functional theory) and SQM-DH (dispersion and hydrogen bond-corrected semi-empirical quantum mechanical) perform much more accurately than older DFT and SQM approaches and also standard docking methods. In addition, DFT-D might soon become and SQM-DH already is fast enough to compute a large number of binding modes of comparably large protein/ligand complexes, thus allowing for a more accurate assessment of entropic effects.

Enhanced semiempirical QM methods for biomolecular interactions

Recent successes and failures of the application of 'enhanced' semiempirical QM (SQM) methods are reviewed in the light of the benefits and backdraws of adding dispersion (D) and hydrogen-bond (H) correction terms. We find that the accuracy of SQM-DH methods for non-covalent interactions is very often reported to be comparable to dispersion-corrected density functional theory (DFT-D), while computation times are about three orders of magnitude lower. SQM-DH methods thus open up a possibility to simulate realistically large model systems for problems both in life and materials science with comparably high accuracy.