Conformational Studies of Gram-Negative Bacterial Quorum Sensing 3-oxo N-acyl Homoserine Lactone Molecules

In their 1H NMR spectra in CDCl3 3-oxo-N-acyl homoserine lactones (OHLs) show significant downfield chemical shifts of the amide N-H proton when compared to the parent N-acyl homoserine lactones (AHLs). NMR spectroscopic and DFT calculation studies have shown that this is most likely due to the presence of a stabilising intramolecular H-bond from the N-H to the 3-oxo group. The 1H NMR spectra also show evidence for the enol tautomers and that the amount of enol present for a range of OHLs is 4.1-4.5% in CDCl3 and 6.5-7.2% in CD3CN. In contrast, DFT calculations show that the lowest energy enol tautomer and the keto tautomer are of equal energy in the gas phase, but that the keto tautomer is more stable in chloroform, acetonitrile and water solution. The calculations also show that there is no evidence for any n→p* or C5 H-bonding interactions being present in either the lowest energy keto or enol tautomer of the OHLs in solution or the gas phase, which is in contrast to the reported solid-state structure

Pushing the Limits of Quantum Computing for Simulating PFAS Chemistry

Accurate and scalable methods for computational quantum chemistry can accelerate research and development in many fields, ranging from drug discovery to advanced material design. Solving the electronic Schrodinger equation is the core problem of computational chemistry. However, the combinatorial complexity of this problem makes it intractable to find exact solutions, except for very small systems. The idea of quantum computing originated from this computational challenge in simulating quantum-mechanics. We propose an end-to-end quantum chemistry pipeline based on the variational quantum eigensolver (VQE) algorithm and integrated with both HPC-based simulators and a trapped-ion quantum computer. Our platform orchestrates hundreds of simulation jobs on compute resources to efficiently complete a set of ab initio chemistry experiments with a wide range of parameterization. Per- and poly-fluoroalkyl substances (PFAS) are a large family of human-made chemicals that pose a major environmental and health issue globally. Our simulations includes breaking a Carbon-Fluorine bond in trifluoroacetic acid (TFA), a common PFAS chemical. This is a common pathway towards destruction and removal of PFAS. Molecules are modeled on both a quantum simulator and a trapped-ion quantum computer, specifically IonQ Aria. Using basic error mitigation techniques, the 11-qubit TFA model (56 entangling gates) on IonQ Aria yields near-quantitative results with milli-Hartree accuracy. Our novel results show the current state and future projections for quantum computing in solving the electronic structure problem, push the boundaries for the VQE algorithm and quantum computers, and facilitates development of quantum chemistry workflows

The structure of glibenclamide in the solid state

The structure of glibenclamide, 5-chloro-N-(2-{4-[(cyclohexylamino) carbonyl] aminosulfonyl}phenyl) ethyl)-2-methoxybenzamide, an important antidiabetic drug, has been studied both in solution and in the solid state by a combination of NMR spectroscopy and theoretical calculations. The possibility that glibenclamide suffers a tautomerization under melting to afford a desmotrope was rejected. Copyright © 2012 John Wiley & Sons, Ltd.Peer Reviewe

Size dependence of ionization potentials and dissociation energies for neutral and singly-charged Cn fullerenes (n = 40-70)

Dissociation energies and ionization potentials of neutral and singly-charged fullerenes have been obtained from density functional theory calculations for sizes ranging from 40 to 70 atoms. Good agreement with available experimental data has been obtained. Our results confirm that magic number fullerenes with n = 50, 60 and 70 present the largest ionization potentials and dissociation energies. We have found that the most stable isomer for n = 62 is a non-classical structure with a chain of four adjacent pentagons surrounding a heptagon, and for n = 50 is a structure of D3 symmetry that violates the pentagon adjacency penalty rule. Both unusual structures lead to the best agreement with experiment

Ionization potentials and dissociation energies of neutral, singly and doubly charged Cn fullerenes from n = 20 to 70

Using B3LYP density functional theory, first and second ionization potentials as well as dissociation energies for neutral, singly and doubly charged fullerenes with sizes between 20 and 70 atoms have been evaluated. Comparison with available experimental data is good except for the doubly charged species. The results show that neutral fullerenes with a magic number of atoms, namely C32, C50, C60 and C70, have the largest stability against ionization and C2 evaporation. A similar large stability is observed for the corresponding singly and doubly charged magic fullerenes, except for C32+ and C322+. Neutral and positively charged C62 is found to be rather unstable. Also, C2+ emission is shown to become competitive with C2 emission for sufficiently small doubly charged fullerenes. The origin of these and other properties is discussed in detail