Glassy Dynamics of Protein Folding

A coarse grained model of a random polypeptide chain, with only discrete torsional degrees of freedom and Hookean springs connecting pairs of hydrophobic residues is shown to display stretched exponential relaxation under Metropolis dynamics at low temperatures with the exponent $\beta\simeq 1/4$, in agreement with the best experimental results. The time dependent correlation functions for fluctuations about the native state, computed in the Gaussian approximation for real proteins, have also been found to have the same functional form. Our results indicate that the energy landscape exhibits universal features over a very large range of energies and is relatively independent of the specific dynamics.Comment: RevTeX, 4 pages, multicolumn, including 5 figures; larger computations performed, error bars improve

SAXS studies of the thermally-induced fusion of diblock copolymer spheres : formation of hybrid nanoparticles of intermediate size and shape

Dilute dispersions of poly(lauryl methacrylate)–poly(benzyl methacrylate) (PLMA–PBzMA) diblock copolymer spheres (a.k.a. micelles) of differing mean particle diameter were mixed and thermally annealed at 150 °C to produce spherical nanoparticles of intermediate size. The two initial dispersions were prepared via reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization of benzyl methacrylate in n-dodecane at 90 °C. Systematic variation of the mean degree of polymerization of the core-forming PBzMA block enabled control over the mean particle diameter: small-angle X-ray scattering (SAXS) analysis indicated that PLMA39–PBzMA97 and PLMA39–PBzMA294 formed well-defined, non-interacting spheres at 25 °C with core diameters of 21 ± 2 nm and 48 ± 5 nm, respectively. When heated separately, both types of nanoparticles regained their original dimensions during a 25–150–25 °C thermal cycle. However, the cores of the smaller nanoparticles became appreciably solvated when annealed at 150 °C, whereas the larger nanoparticles remained virtually non-solvated at this temperature. Moreover, heating caused a significant reduction in mean aggregation number for the PLMA39–PBzMA97 nanoparticles, suggesting their partial dissociation at 150 °C. Binary mixtures of PLMA39–PBzMA97 and PLMA39–PBzMA294 nanoparticles were then studied over a wide range of compositions. For example, annealing a 1.0% w/w equivolume binary mixture led to the formation of a single population of spheres of intermediate mean diameter (36 ± 4 nm). Thus we hypothesize that the individual PLMA39–PBzMA97 chains interact with the larger PLMA39–PBzMA294 nanoparticles to form the hybrid nanoparticles. Time-resolved SAXS studies confirm that the evolution in copolymer morphology occurs on relatively short time scales (within 20 min at 150 °C) and involves weakly anisotropic intermediate species. Moreover, weakly anisotropic nanoparticles can be obtained as a final copolymer morphology over a restricted range of compositions (e.g. for PLMA39–PBzMA97 volume fractions of 0.20–0.35) when heating dilute dispersions of such binary nanoparticle mixtures up to 150 °C. A mechanism involving both chain expulsion/insertion and micelle fusion/fission is proposed to account for these unexpected observations

Products based on omega-3 polyunsaturated fatty acids and health effects

The potential role of ?-3 polyunsaturated fatty acids (PUFAs) in preventing cardiovascular (CV) disease has been studied for decades. Docosaexaenoic acid (DHA), eicosapentaenoic acid (EPA), and alpha-linolenic acid (ALA) are known to be most important ?-3 PUFAs for their beneficial roles in human health. The American Heart Association has recommended a comparatively higher daily dosage of 500 mg of ?-3 PUFA for healthy adults. Therefore, demand for ?-3 PUFA enriched fish oil has shown a steady increase during the recent year. Thus, the extraction of ?-3 enriched oils from fish and fish by-products gained tremendous importance. In this chapter, sources and benefits of ?-3 PUFAs on human health and the extraction methods of omega-3 fatty acids are discussed. © 2019 Elsevier Inc

Developmental parameters and physical fitness in preschool children with minor neurological dysfunction

Background. The preschool years constitute a critical period during which significant changes are experienced in the acquisition of locomotor skills due to maturation of the nervous system. Our aim was to investigate the developmental parameters and physical fitness in preschool children with Minor Neurological Dysfunction (MND). Methods. The study was carried out in 212 preschool children without any known health problems. Sociodemographic characteristics of children were recorded. Denver Developmental Screening Test (DDST) II, Touwen Neurological Examination, and Preschool Physical Fitness (PREFIT) test battery were used to assess developmental parameters, neurological status, and physical fitness, respectively. Results. There was a statistical difference in the physical fitness and developmental parameters in preschool children with MND compared with healthy peers (p<0.05). There was also a relationship between physical fitness and developmental parameters (p<0.05). Conclusions. Early identification of problems in developmental parameters and physical fitness in preschool children with MND might help to implement early supportive physiotherapy and rehabilitation. © 2021, Turkish National Pediatric Society. All rights reserved