Average and extreme multi-atom Van der Waals interactions: Strong coupling of multi-atom Van der Waals interactions with covalent bonding

<p>Abstract</p> <p>Background</p> <p>The prediction of ligand binding or protein structure requires very accurate force field potentials – even small errors in force field potentials can make a 'wrong' structure (from the billions possible) more stable than the single, 'correct' one. However, despite huge efforts to optimize them, currently-used all-atom force fields are still not able, in a vast majority of cases, even to keep a protein molecule in its native conformation in the course of molecular dynamics simulations or to bring an approximate, homology-based model of protein structure closer to its native conformation.</p> <p>Results</p> <p>A strict analysis shows that a specific coupling of multi-atom Van der Waals interactions with covalent bonding can, in extreme cases, increase (or decrease) the interaction energy by about 20–40% at certain angles between the direction of interaction and the covalent bond. It is also shown that on average multi-body effects decrease the total Van der Waals energy in proportion to the square root of the electronic component of dielectric permittivity corresponding to dipole-dipole interactions at small distances, where Van der Waals interactions take place.</p> <p>Conclusion</p> <p>The study shows that currently-ignored multi-atom Van der Waals interactions can, in certain instances, lead to significant energy effects, comparable to those caused by the replacement of atoms (for instance, C by N) in conventional pairwise Van der Waals interactions.</p

Sporadic fatal insomnia in a young woman: A diagnostic challenge: Case Report

<p>Abstract</p> <p>Background</p> <p>Sporadic fatal insomnia (sFI) and fatal familial insomnia (FFI) are rare human prion diseases.</p> <p>Case Presentation</p> <p>We report a case of a 33-year-old female who died of a prion disease for whom the diagnosis of sFI or FFI was not considered clinically. Following death of this patient, an interview with a close family member indicated the patient's illness included a major change in her sleep pattern, corroborating the reported autopsy diagnosis of sFI. Genetic tests identified no prion protein (PrP) gene mutation, but neuropathological examination and molecular study showed protease-resistant PrP (PrP^res) in several brain regions and severe atrophy of the anterior-ventral and medial-dorsal thalamic nuclei similar to that described in FFI.</p> <p>Conclusions</p> <p>In patients with suspected prion disease, a characteristic change in sleep pattern can be an important clinical clue for identifying sFI or FFI; polysomnography (PSG), genetic analysis, and nuclear imaging may aid in diagnosis.</p

Magnetic Response in the Holographic Insulator/Superconductor Transition

We study the magnetic response of holographic superconductors exhibiting an insulating "normal" phase. These materials can be realized as a CFT compactified on a circle, which is dual to the AdS Soliton geometry. We study the response under i) magnetic fields and ii) a Wilson line on the circle. Magnetic fields lead to formation of vortices and allows one to infer that the superconductor is of type II. The response to a Wilson line is in the form of Aharonov-Bohm-like effects. These are suppressed in the holographic conductor/superconductor transition but, instead, they are unsuppressed for the insulator case. Holography, thus, predicts that generically insulators display stronger Aharonov-Bohm effects than conductors. In the fluid-mechanical limit the AdS Soliton is interpreted as a supersolid. Our results imply that supersolids display unsuppressed Aharonov-Bohm (or "Sagnac") effects - stronger than in superfluids.Comment: 31 pages, 24 figures; discussion on vortex lattice, few comments and references added; article published in JHE