Hydrodynamics of Diffusion in Lipid Membrane Simulations

By performing molecular dynamics simulations with up to 132 million coarse-grained particles in half-micron sized boxes, we show that hydrodynamics quantitatively explains the finite-size effects on diffusion of lipids, proteins, and carbon nanotubes in membranes. The resulting Oseen correction allows us to extract infinite-system diffusion coefficients and membrane surface viscosities from membrane simulations despite the logarithmic divergence of apparent diffusivities with increasing box width. The hydrodynamic theory of diffusion applies also to membranes with asymmetric leaflets and embedded proteins, and to a complex plasma-membrane mimetic

Simulation of reforms of direct and indirect taxation for France

We study the welfare effects of combining the European Commission's proposal for VAT harmonization with different degrees of weakening of the 'quotient familial' , a feature of the French system of direct taxation which can be interpreted as aiming at taxing 'equivalised' household income. We compare two approaches to the calibration of the baseline situation and to the simulation of reactions to changes in the tax system. One of these takes fixed costs of work into account. For both we find that a tentative implementation of the Commission's proposal, keeping the low rate unchanged, is favourable to a narrow majority (the status quo is preferred on a number of criteria), but that it results in a high VAT rate in excess of the proposal. While a weakening of the quotient familial brings this rate within the desired bracket, the combined reform appears much less desirable than the pure VAT reform. This goes some way against the notion that the quotient familial constitutes a tax relief which is only significant for richer households. --

Simulation of reforms of direct and indirect taxation for France

We study the welfare effects of combining the European Commission's proposal for VAT harmonization with different degrees of weakening of the 'quotient familial' , a feature of the French system of direct taxation which can be interpreted as aiming at taxing 'equivalised' household income. We compare two approaches to the calibration of the baseline situation and to the simulation of reactions to changes in the tax system. One of these takes fixed costs of work into account. For both we find that a tentative implementation of the Commission's proposal, keeping the low rate unchanged, is favourable to a narrow majority (the status quo is preferred on a number of criteria), but that it results in a high VAT rate in excess of the proposal. While a weakening of the quotient familial brings this rate within the desired bracket, the combined reform appears much less desirable than the pure VAT reform. This goes some way against the notion that the quotient familial constitutes a tax relief which is only significant for richer households

Effect of a conventional energy-restricted modified diet with or without meal replacement on weight loss and cardiometabolic risk profile in overweight women

<p>Abstract</p> <p>Background</p> <p>Abdominal obesity, atherogenic dyslipidemia and hypertension are essential risk factors for cardiovascular diseases. Several studies showed favorable effects of weight loss in overweight subjects on cardiometabolic risk profile.</p> <p>Methods</p> <p>This open-label, randomized, controlled study investigated the effect of an energy-restricted modified diet with (MR) or without meal replacements for weight control (C) on weight loss, body composition and cardiometabolic risk profile in overweight women. Of 105 randomized participants, 87 were eligible for per protocol analysis. Anthropometric, clinical, blood, 24 h-urine parameters and dietary intake were assessed at baseline and after 12 weeks.</p> <p>Results</p> <p>Dietary intervention resulted in a significant weight loss in both groups (MR: -5.98 ± 2.82 kg; p < 0.001, C: -4.84 ± 3.54 kg; p < 0.001). However, the rate of responder (weight loss >5%) was higher in MR (77%) versus C group (50%) (p = 0.010). A significant reduction in waist circumference (WC) and body fat mass (BFM) was observed in both groups. Body cell mass (BCM) and lean body mass (LBM) decreased, while percentage of BCM of body weight increased in MR more than in C group. Systolic and diastolic blood pressure (BP) significantly decreased and to a similar extent in both groups. Total cholesterol (TC), LDL-C but also HDL-C declined significantly in both groups, while no change occurred in triglycerides.</p> <p>Conclusions</p> <p>Both dietary intervention strategies had a similar effect on weight loss and body fat distribution, but rate of responder was significantly higher in MR group. Systolic BP decreased to a similar extent in both groups. Cardiometabolic risk profile improved only partly in both groups.</p

Atomistic simulation of PDADMAC/PSS oligoelectrolyte multilayers: overall comparison of tri- and tetra-layer systems

By employing large-scale molecular dynamics simulations of atomistically resolved oligoelectrolytes in aqueous solutions, we study in detail the first four layer-by-layer deposition cycles of an oligoelectrolyte multilayer made of poly(diallyl dimethyl ammonium chloride)/poly(styrene sulfonate sodium salt) (PDADMAC/PSS). The multilayers are grown on a silica substrate in 0.1M {NaCl} electrolyte solutions and the swollen structures are then subsequently exposed to varying added salt concentration. We investigated the microscopic properties of the films, analyzing in detail the differences between three- and four-layers systems. Our simulations provide insights on the early stages of growth of a multilayer, which are particularly challenging for experimental observations. We found a rather strong entanglement of the oligoelectrolytes, with a fuzzy layering of the film structure. The main charge compensation mechanism is for all cases intrinsic, whereas extrinsic compensation is relatively ehanced for the layer of the last deposition cycle. In addition, we quantified other fundamental observables of these systems, as the film thickness, water uptake, and overcharge fractions for each deposition layer

¹H, ¹³C and ¹⁵N and ³¹P chemical shift assignment for stem-loop 4 from the 5′-UTR of SARS-CoV-2

The SARS-CoV-2 virus is the cause of the respiratory disease COVID-19. As of today, therapeutic interventions in severe COVID-19 cases are still not available as no effective therapeutics have been developed so far. Despite the ongoing development of a number of effective vaccines, therapeutics to fight the disease once it has been contracted will still be required. Promising targets for the development of antiviral agents against SARS-CoV-2 can be found in the viral RNA genome. The 5′- and 3′-genomic ends of the 30 kb SCoV-2 genome are highly conserved among Betacoronaviruses and contain structured RNA elements involved in the translation and replication of the viral genome. The 40 nucleotides (nt) long highly conserved stem-loop 4 (5_SL4) is located within the 5′-untranslated region (5′-UTR) important for viral replication. 5_SL4 features an extended stem structure disrupted by several pyrimidine mismatches and is capped by a pentaloop. Here, we report extensive ¹H, ¹³C and ¹⁵N and ³¹P resonance assignments of 5_SL4 as the basis for in-depth structural and ligand screening studies by solution NMR spectroscopy

Finite-size-corrected rotational diffusion coefficients of membrane proteins and carbon nanotubes from molecular dynamics simulations

We investigate system-size effects on the rotational diffusion of membrane proteins and other membrane-embedded molecules in molecular dynamics simulations. We find that the rotational diffusion coefficient slows down relative to the infinite-system value by a factor of one minus the ratio of protein and box areas. This correction factor follows from the hydrodynamics of rotational flows under periodic boundary conditions and is rationalized in terms of Taylor-Couette flow. For membrane proteins like transporters, channels, or receptors in typical simulation setups, the protein-covered area tends to be relatively large, requiring a significant finite-size correction. Molecular dynamics simulations of the protein adenine nucleotide translocase (ANT1) and of a carbon nanotube porin in lipid membranes show that the hydrodynamic finite-size correction for rotational diffusion is accurate in standard-use cases. The dependence of the rotational diffusion on box size can be used to determine the membrane viscosity