It is experimentally challenging to directly obtain structural information of the transition state (TS), the high-energy bottleneck en route from reactants to products, for solution-phase reactions. Here, we use single-molecule experiments as well as high-level quantum chemical calculations to probe the TS of disulfide bond reduction, a bimolecular nucleophilic substitution (S N2) reaction. We ...

This special issue is dedicated to the memory of Dr. Ahmed Zewail, the founder of the field and the public-keynote speaker of the Leuchtturm (Tower of Light) Lecture (https:// www.femto12.org/leuchtturm) at FEMTO12. Femtochemistry addresses the very nature of the chemical bond. It aims at unraveling the ultrafast dynamics of bond forming and breaking. Molecules and atoms are the building blocks...

Conspectus The desire to study molecular systems that are much larger than what the current state-of-the-art ab initio or density functional theory methods could handle has naturally led to the development of novel approximate methods, including semiempirical approaches, reduced-scaling methods, and fragmentation methods. The major computational limitation of ab initio methods is the scaling pr...

The bond energy of molecular fragments to metal surfaces is of great fundamental importance, especially for understanding catalytic reactivity. Thus, the energies of adsorbed intermediates are routinely calculated to understand and even predict the activity of catalytic materials. By correlating our recent calorimetry measurements of the adiabatic bond dissociation enthalpies of three oxygen-bo...

Oxymetazoline is a decongestant. It works by constricting (shrinking) blood vessels (veins and arteries) in your body. The nasal formulation acts directly on the blood vessels in your nasal tissues. Constriction of the blood vessels in your nose and sinuses leads to drainage of these areas and a decrease in congestion. Oxymetazoline is an adrenomimetic that nonselectively agonizes α1...

There are 30026 symmetry-distinct ways to arrange 20 water molecules in a dodecahedral cage with nearly optimum hydrogen bond lengths and angles, analogous to the arrangements that give rise to the zero-point entropy in ice-Ih. The energy of hydrogen bond isomers in (H2O)20 , assumed to be similar in the past, differs by up to 70 kcal/mol. The isomers differ widely in their hydrogen bond length...

Classical force fields describe the interaction between atoms that are bonded or nonbonded via simple potential energy expressions. Their parameters are often determined by fitting to ab initio energies and electrostatic potentials. A direct quantum chemical guide to constructing a force field would be the atom-atom partitioning of the energy of molecules and van der Waals complexes relevant to...

Numerous studies have been undertaken to establish the mechanism of dNTP binding and template-directed incorporation by DNA polymerases. It has been established by kinetic experiments that a rate-limiting step, crucial for dNTP selection, occurs before chemical bond formation. Crystallographic studies indicated that this step may be due to a large open-to-closed conformational transition affect...

A facile method for cross-linking organic molecules has been developed by computational modeling, instrumentation design, and experimental research. Briefly, organic molecules are hit by H2 with controllable kinetic energy in our novel apparatus where a high flux of hyperthermal H2 is generated. When a C–H bond of the organic molecule is hit by H2 at about 20 eV, efficient kinematic energy-tran...