Probing electrostatic interactions and structural changes in highly charged protein polyanions by conformer-selective photoelectron spectroscopy

We have recorded the first conformer-selective photoelectron spectra of a protein polyanion in the gas-phase. Bovine cytochrome c protein was studied in 8 different negative charge states ranging from 5- to 12-. Electron binding energies were extracted for all charge states and used as a direct probe of intramolecular Coulomb repulsion. Comparison of experimental results with simulations shows that the experimental outcome can be reproduced with a simple electrostatic model. Energetics are consistent with a structural transition from a folded to an unfolded conformational state of the protein as the number of charges increases. Furthermore, the additional ion-mobility data show that the onset of unfolding can be assigned to charge state 6- where three conformers can be distinguished.     

Biotechnological Approaches on Two High CBD and CBG Cannabis sativa L. (Cannabaceae) Varieties: In Vitro Regeneration and Phytochemical Consistency Evaluation of Micropropagated Plants Using Quantitative 1H-NMR

High cannabidiol (CBD) and cannabigerol (CBG) varieties of Cannabis sativa L., a species with medicinal properties, were regenerated in vitro. Explants of nodal segments including healthy axillary bud, after sterilization, were placed in Murashige-Skoog (MS) culture medium. The shoots formed after 30 days were subcultured in full- or half-strength MS medium supplemented with several concentrations of 6-benzyl-amino-purine (BA) or thidiazuron (TDZ). The highest average number and length of shoots was achieved when both full and half-strength MS media were supplemented with 4.0 μM BA. The presence of 4.0 μM TDZ showed also comparable results. BA and TDZ at concentrations of 4.0, 8.0 μM and 2.0, 4.0 μM respectively, displayed the maximum shooting frequency. The new shoots were transferred on the same media and were either self-rooted or after being enhanced with different concentrations of indole-3-butyric acid (IBA) or α-naphthalene acetic acid (NAA). Presence of 2.0 or 4.0 μM IBA or 4.0 μM NAA resulted to the optimum rooting rates. The maximum average number and length of roots per shoot was observed when the culture media was supplemented with 4.0 μM IBA or NAA. Approximately 92% of the plantlets were successfully established and acclimatized in field. The consistency of the chemical profile of the acclimatized in vitro propagated clones was assessed using quantitative ¹H-NMR high throughput screening. In each variety, analysis of the micropropagated plant in comparison with the mother plant showed no statistically significant differences (p ≤ 0.05) in CBD+ cannabidiolic acid (CBDA) and CBG+ cannabigerolic acid (CBGA) content respectively, thus indicating stability of their chemical profile.     

Theoretical Efficiency Limits of Photoelectrochemical CO2 Reduction: A Route-Dependent Thermodynamic Analysis

Solar-fuel formation via photoelectrochemical (PEC) routes using water and CO₂ as feedstock has attracted much attention. Most PEC CO₂ reduction studies have been focused on the development of novel photoactive materials; however, there is still a lack of understanding of the key limiting factors of this process. In this study, the theoretical limits of Solar-to-Fuel (STF) efficiencies of single- and dual-junction photo-absorbing materials are illustrated for single-step multi-electron CO₂ reduction into fuels including HCOO⁻, CO, CH₃OH and C₂H₅OH. It is also highlighted that STF efficiency depends on the route of two-step PEC CO₂ reduction process using CH₃OH as a model fuel. Finally, it is illustrated the beneficial role of alternative strategies such as dual-junction photo-absorbing electrodes, externally applied bias and subsequent reactor chambers on the maximum theoretical efficiencies of PEC CO₂ reduction.     

Poly(vinyl pyrrolidone)–poloxamer-188 solid dispersions prepared by hot melt extrusion

Poly(vinyl pyrrolidone) (PVP)/poloxamer-188 blends were used as appropriate carriers for the preparation of solid dispersions by hot melt extrusion using aripiprazole (ARIP) as a poor water-soluble model drug. The physical state of ARIP in solid dispersions and its dissolution characteristics were tested for different drug contents and various PVP-to-poloxamer ratios. From TG analysis it was found that all materials were stable at the tested extrusion temperature conditions (110–120 °C) while amorphous drug dispersions were prepared in all cases, due to the miscibility of the polymer matrix with ARIP drug. Furthermore, hydrogen bonds were identified between ARIP (>N–H) and PVP (>C=O) using FT-IR analysis. Finally, ARIP dissolution rate from SDs was pH dependant and increased as the drug content decreased.     

In vitro magnetic hyperthermia response of iron oxide MNP’s incorporated in DA3, MCF-7 and HeLa cancer cell lines

In the current work, iron oxide magnetic nanoparticles (MNP’s) were synthesized by thermal decomposition of Fe(acac)₃-(iron acetylacetonate) compounds in high-boiling organic solvents containing stabilizing surfactants and examined as possible agents for magnetic hyperthermia treatment, according to their structural, magnetic and heating properties. Three different cancer cell lines (DA3, MCF-7 and HeLa cell lines) were used to assess the suitability of the MNP’s. The experimental results proved that the synthesized MNPs are non-toxic and the uptake efficiency was extremely good. Further, from in vitro hyperthermia results, very fast thermal response was observed (reaching hyperthermia levels in less than 200 s), which minimize the duration of the cell and human body exposure in a high frequency AC external magnetic field.      

A new method for M–H and λ–H determination using the magnetostrictive delay line technique

In this paper, a new technique for the determination of M–H loop and λ–H loop is proposed, based on the magnetostrictive delay line (MDL) technique and used for long magnetostrictive ribbons, wires and rods of uniform cross-section. The principle of the M–H loop determination is based on the biasing field effect at the MDL search coil, while the principle of the λ–H loop is based on the biasing and pulsed field effects at the MDL excitation point.     

Modeling of contaminant transport resulting from dissolution of nonaqueous phase liquid pools in saturated porous media

A mathematical model for transient contaminant transport resulting from the dissolution of a single component nonaqueous phase liquid (NAPL) pool in two-dimensional, saturated, homogeneous porous media was developed. An analytical solution was derived for a semi-infinite medium under local equilibrium conditions accounting for solvent decay. The solution was obtained by taking Laplace transforms to the equations with respect to time and Fourier transforms with respect to the longitudinal spatial coordinate. The analytical solution is given in terms of a single integral which is easily determined by numerical integration techniques. The model is applicable to both denser and lighter than water NAPL pools. The model successfully simulated responses of a 1,1,2-trichloroethane (TCA) pool at the bottom of a two-dimensional porous medium under controlled laboratory conditions.Notation a,a ₁ defined in (45a) and (45b), respectively - b defined in (45c) - b vector of true model parameters (n×1) - vector of estimated model parameters (n×1) - c liquid phase solute concentration (solute mass/liquid volume), M/L³ - c _s aqueous saturation concentration (solubility), M/L³ - C dimensionless liquid phase solute concentration, equal toc/c _s - molecular diffusion coefficient, L²/t - ^e effective molecular diffusion coefficient, equal to / ^*, L²/t - D _x longitudinal hydrodynamic dispersion coefficient, L²/t - D _z hydrodynamic dispersion coefficient in the vertical direction, L²/t - e random vector with zero mean (m×1) - erf[x] error function, equal to (2/ ^1/2) - f vector of fitting errors or residuals (m×1) - Fourier operator - _-1 Fourier inverse operator - g vector of model simulated data (m×1) - k mass transfer coefficient, L/t - average mass transfer coefficient, L/t - K _d partition or distribution coefficient (liquid volume/solids mass), L³/M - pool length, L - _o distance between the pool and the origin of the specified Cartesian coordinate system, L - Laplace operator - _-1 Laplace inverse operator - m number of observations - M Laplace/Fourier function defined in (38) - n number of model parameters - N Laplace/Fourier function defined in (39) - p defined in (46) - Pe _x Péclet number, equal toU _x /D _x - Pe _z Péclet number, equal toU _x /D _z - q defined in (47) - R retardation factor - s Laplace transform variable - S objective function - Sh local Sherwood number, equal tok/ _e - Sh _o overall Sherwood number, equal to l/ _e - t time,t - T dimensionless time, equal toU _x t/ - u dummy integration variable - u vector of independent variables - U _x average interstitial velocity, L/t - x spatial coordinate in the longitudinal direction, L - X dimensionless longitudinal length, equal to (x–)/ - y vector of observed data (m×1) - z spatial coordinate in the vertical direction, L - Z dimensionless vertical length, equal toz/ - Fourier transform variable - defined in (37) - defined in (50) - porosity (liquid volume/aquifer volume), L³/L³ - defined in (52a) and (52b), respectively - decay coefficient, t^–1 - dimensionless decay coefficient, equal to /U _x - bulk density of the solid matrix (solids mass/aquifer volume), M/L³ - dummy integration variable - ^* tortuosity