Assessment of process parameters on the production of diglycerides rich in omega-3 fatty acids through the enzymatic glycerolysis of fish oil

The main objective of this work is to present new experimental information concerning the effect of relevant process parameters related to the production of diglycerides by enzymatic glycerolysis of fish oil. Reaction products can be applied as ingredients in food industry, joining the emulsifying properties of partial glycerides along with the nutritional benefits attributed to the omega-3 fatty acids. From preliminary reactions, conversion was higher for a solvent- and surfactant-free system but the long time to reach appreciable amounts of diglycerides may be a drawback for practical purposes. To overcome this problem, the addition of tert-butanol revealed to be relevant, leading to high diglycerides contents in short times. The system containing Tween 65 led to the highest amount of diglycerides. This study described the feasibility of enzymatic synthesis of diglycerides rich in EPA and DHA in short reaction times as well by using a more environmentally friendly process.     

Bond Length of CFRP Composites Attached to Precast Concrete Walls

Carbon fiber composite connections for hollow-core precast concrete wall panels have been investigated with respect to bond behavior. A panel assembly made up of three precast concrete walls was loaded in the in-plane direction using a cyclic quasi-static load, which was transferred to the wall interface as a shear force. The application of the carbon-fiber-reinforced polymer (CFRP) composite was varied in the covered area, number and orientation of plies, and the concrete surface preparation. An expression, which compares well with the experimental findings, is presented for the effective bond length of carbon fiber composite sheets. The effective bond length of the connection depends on the peel-off shear strength of the concrete, the maximum tensile strain in the composite, the modulus of elasticity of the composite, and thickness of the composite plate.     

Growth mode transitions and scaling behaviour at successive stages of molecular beam epitaxy

Recently developed kinetic model for homoepitaxial growth is extended to the case of heteroepitaxy (without lattice mismatch) by introducing different adatom surface mobilities in the first layer (heterodiffusion) and in all the next layers (self-diffusion). With this model the effect of two adatom mobilities as a function of the Schwoebel step-edge barrier is studied with an emphasis on the growth mode transitions. It is shown that the difference between homo- and heteroepitaxy is confined to the first few monolayers and is crucially sensitive to the ratio between the hetero- and self-diffusion coefficients: lower heterodiffusion coefficient with respect to that of self-diffusion improves essentially epitaxial growth and vice-versa. This is important for growing smooth ultrathin layers needed in modern nanotechnology. Island density kinetics in successive growing layers is studied and it is found that in smooth growth regime it acquires eventually (after deposition approx. 10 monolayers) a universal scaling form and corresponding scaling exponents have been determined.     

Serotonin Promotes Serum Albumin Interaction with the Monomeric Amyloid β Peptide

Prevention of amyloid β peptide (Aβ) deposition via facilitation of Aβ binding to its natural depot, human serum albumin (HSA), is a promising approach to preclude Alzheimer’s disease (AD) onset and progression. Previously, we demonstrated the ability of natural HSA ligands, fatty acids, to improve the affinity of this protein to monomeric Aβ by a factor of 3 (BBRC, 510(2), 248–253). Using plasmon resonance spectroscopy, we show here that another HSA ligand related to AD pathogenesis, serotonin (SRO), increases the affinity of the Aβ monomer to HSA by a factor of 7/17 for Aβ₄₀/Aβ₄₂, respectively. Meanwhile, the structurally homologous SRO precursor, tryptophan (TRP), does not affect HSA’s affinity to monomeric Aβ, despite slowdown of the association and dissociation processes. Crosslinking with glutaraldehyde and dynamic light scattering experiments reveal that, compared with the TRP-induced effects, SRO binding causes more marked changes in the quaternary structure of HSA. Furthermore, molecular docking reveals distinct structural differences between SRO/TRP complexes with HSA. The disintegration of the serotonergic system during AD pathogenesis may contribute to Aβ release from HSA in the central nervous system due to impairment of the SRO-mediated Aβ trapping by HSA.     

Fine Splitting of Electron States in Silicon Nanocrystal with a Hydrogen-like Shallow Donor

Electron structure of a silicon quantum dot doped with a shallow hydrogen-like donor has been calculated for the electron states above the optical gap. Within the framework of the envelope-function approach we have calculated the fine splitting of the ground sixfold degenerate electron state as a function of the donor position inside the quantum dot. Also, dependence of the wave functions and energies on the dot size was obtained.     

Synthesis and characterization of novel linear and crosslinked polyelectrolytes derived from the acetoacetic ester and acrylic acid

Summary Novel linear and crosslinked polyelectrolytes based on acetoacetic ester and acrylic acid were synthesized for the first time via Michael addition reaction followed by radical polymerization. The structure and properties of polyelectrolytes were characterized by FTIR, Raman and NMR spectroscopy, TGA, DSC, GPC, viscometry and potentiometric titration. Considerable influence of water content on the swelling rate of hydrogels was established. The swelling-deswelling properties of hydrogels were studied in dependence of pH, ionic strength and in water-organic solvent mixtures.     

PSIC: profile extraction from sequence alignments with position-specific counts of independent observations

Sequence weighting techniques are aimed at balancing redundantobserved information from subsets of similar sequences in multiplealignments. Traditional approaches apply the same weight toall positions of a given sequence, hence equal efficiency ofphylogenetic changes is assumed along the whole sequence. Thisrestrictive assumption is not required for the new method PSIC(position-specific independent counts) described in this paper.The number of independent observations (counts) of an aminoacid type at a given alignment position is calculated from theoverall similarity of the sequences that share the amino acidtype at this position with the help of statistical concepts.This approach allows the fast computation of position-specificsequence weights even for alignments containing hundreds ofsequences. The PSIC approach has been applied to profile extractionand to the fold family assignment of protein sequences withknown structures. Our method was shown to be very productivein finding distantly related sequences and more powerful thanHidden Markov Models or the profile methods in WiseTools andPSI-BLAST in many cases. The profile extraction routine is availableon the WWW (http://www.bork.embl-heidelberg.de/PSIC or http://www.imb.ac.ru/PSIC).     

Coherent anti-Stokes Raman scattering enhancement of thymine adsorbed on graphene oxide

Coherent anti-Stokes Raman scattering (CARS) of carbon nanostructures, namely, highly oriented pyrolytic graphite, graphene nanoplatelets, graphene oxide, and multiwall carbon nanotubes as well CARS spectra of thymine (Thy) molecules adsorbed on graphene oxide were studied. The spectra of the samples were compared with spontaneous Raman scattering (RS) spectra. The CARS spectra of Thy adsorbed on graphene oxide are characterized by shifts of the main bands in comparison with RS. The CARS spectra of the initial nanocarbons are definitely different: for all investigated materials, there is a redistribution of D- and G-mode intensities, significant shift of their frequencies (more than 20 cm^-1), and appearance of new modes about 1,400 and 1,500 cm^-1. The D band in CARS spectra is less changed than the G band; there is an absence of 2D-mode at 2,600 cm^-1 for graphene and appearance of intensive modes of the second order between 2,400 and 3,000 cm^-1. Multiphonon processes in graphene under many photon excitations seem to be responsible for the features of the CARS spectra. We found an enhancement of the CARS signal from thymine adsorbed on graphene oxide with maximum enhancement factor about 10⁵. The probable mechanism of CARS enhancement is discussed.