The mechanism behind the 1H nuclear magnetic resonance (NMR) frequency dependence of T1 and the viscosity dependence of T2 for polydisperse polymers and bitumen remains elusive. https://www.selleckchem.com/products/sn-001.html We elucidate the matter through NMR relaxation measurements of polydisperse polymers over an extended range of frequencies (f0 = 0.01-400 MHz) and viscosities (η = 385-102 000 cP) using T1 and T2 in static fields, T1 field-cycling relaxometry, and T1ρ in the rotating frame. We account for the anomalous behavior of the log-mean relaxation times T1LM ∝ f0 and T2LM ∝ (η/T)-1/2 with a phenomenological model of 1H-1H dipole-dipole relaxation, which includes a distribution in molecular correlation times and internal motions of the nonrigid polymer branches. We show that the model also accounts for the anomalous T1LM and T2LM in previously reported bitumen measurements. We find that molecular dynamics (MD) simulations of the T1 ∝ f0 dispersion and T2 of similar polymers simulated over a range of viscosities (η = 1-1000 cP) are in good agreement with measurements and the model. The T1 ∝ f0 dispersion at high viscosities agrees with previously reported MD simulations of heptane confined in a polymer matrix, which suggests a common NMR relaxation mechanism between viscous polydisperse fluids and fluids under nanoconfinement, without the need to invoke paramagnetism.The acetylglucosaminyltransferase-like protein LARGE1 is an enzyme that is responsible for the final steps of the post-translational modifications of dystroglycan (DG), a membrane receptor that links the cytoskeleton with the extracellular matrix in the skeletal muscle and in a variety of other tissues. LARGE1 acts by adding the repeating disaccharide unit [-3Xyl-α1,3GlcAβ1-] to the extracellular portion of the DG complex (α-DG); defects in the LARGE1 gene result in an aberrant glycosylation of α-DG and consequent impairment of its binding to laminin, eventually affecting the connection between the cell and the extracellular environment. In the skeletal muscle, this leads to degeneration of the muscular tissue and muscular dystrophy. So far, a few missense mutations have been identified within the LARGE1 protein and linked to congenital muscular dystrophy, and because no structural information is available on this enzyme, our understanding of the molecular mechanisms underlying these pathologies is still very limited. Here, we generated a 3D model structure of the two catalytic domains of LARGE1, combining different molecular modeling approaches. Furthermore, by using molecular dynamics simulations, we analyzed the effect on the structure and stability of the first catalytic domain of the pathological missense mutation S331F that gives rise to a severe form of muscle-eye-brain disease.Locally mobile bond-vectors contribute to the conformational entropy of the protein, given by Sk ≡ S/k = -∫(Peq ln Peq)dΩ - ln∫dΩ. The quantity Peq = exp(-u)/Z is the orientational probability density, where Z is the partition function and u is the spatially restricting potential exerted by the immediate internal protein surroundings at the site of the motion of the bond-vector. It is appropriate to expand the potential, u, which restricts local rotational reorientation, in the basis set of the real combinations of the Wigner rotation matrix elements, D0KL. For small molecules dissolved in anisotropic media, one typically keeps the lowest even L, L = 2, nonpolar potential in axial or rhombic form. For bond-vectors anchored at the protein, the lowest odd L, L = 1, polar potential is to be used in axial or rhombic form. Here, we investigate the effect of the symmetry and polarity of these potentials on Sk. For L = 1 (L = 2), Sk is the same (differs) for parallel and perpendicular ordering. The plots of Sk as a function of the coefficients of the rhombic L = 1 (L = 2) potential exhibit high-symmetry (specific low-symmetry) patterns with parameter-range-dependent sensitivity. Similar statements apply to analogous plots of the potential minima. Sk is also examined as a function of the order parameters defined in terms of u. Graphs displaying these correlations, and applications illustrating their usage, are provided. The features delineated above are generally useful for devising orienting potentials that best suit given physical circumstances. They are particularly useful for bond-vectors acting as NMR relaxation probes in proteins, when their restricted local motion is analyzed with stochastic models featuring Wigner-function-made potentials. The relaxation probes could also be molecules adsorbed at surfaces, inserted into membranes, or interlocked within metal-organic frameworks.Indoor formaldehyde from substandard furniture and decorative materials seriously endangers human health. How to remove effectively indoor formaldehyde with low concentration at room temperature is a challenging problem. Using a MnO2/AlOOH composite by the MnO2 modification as a catalyst provides an effective approach to solve this challenge. Here, a new type of MnO2/AlOOH composite catalyst with high ability to remove indoor low-concentration formaldehyde was prepared by redox reaction at room temperature. A MnO2/AlOOH composite with a homogeneous dispersion of MnO2 has high specific surface area and a large amount of surface hydroxyl (-OH) which plays a major role in the adsorption of formaldehyde. A partially crystalline structure was observed in the composite, which contains multivalent Mn ions and a large number of vacancy defects. The surface -OH of composite shows strong oxidation activity through the charge exchange of multivalent Mn ions and vacancy defects. The composite has a higher ability to remove indoor low-concentration formaldehyde compared to the birnessite MnO2 at room temperature. This study proposes a new idea for the improvement of catalytic performance in the structure and composition of the catalyst.Geogenic ammonium in groundwater owing to mineralization of natural organic matter (NOM) has been reported in different geologic settings, but detailed mechanisms responsible for high ammonium concentration levels are poorly understood. To this end, we chose Quaternary high ammonium aquifer systems in central Yangtze River basins and used carbon isotopes in both dissolved organic carbon and inorganic carbon together with characterization of dissolved organic matter (DOM) and groundwater chemistry to reveal mechanisms related to the genesis of ammonium. The results indicate that high levels of geogenic ammonium (up to 33.50 mg/L as N) occur due to long-term water-rock interactions in a relatively sluggish hydrogeological environment with abundant organic matter that is rich in both C and N. The stable carbon isotope data suggest that ammonium in the groundwater is released from intensive degradation of organic matter with higher contents of ammonium associated with methanogenesis. The optical signatures of DOM indicate ammonium in the groundwater is mostly associated with terrestrial humic-like components rather than protein-like components.