Search results for "solution"

Hybrid methacrylate monolithic columns containing magnetic nanoparticles for capillary electrochromatography

2015

Abstract Vinylized iron oxide magnetic nanoparticles (VMNPs) were incorporated into polymethacrylate monolithic columns to develop novel stationary phases with enhanced separation performance. The VMNPs were dispersed in a polymerization mixture containing gycidyl methacrylate and ethylene glycol dimethacrylate as monomers, cyclohexanol and 1-dodecanol as porogens and azobisisobutyronitrile as initiator. The stability of the VMNPs in the polymerization mixture was investigated at several VMNP contents. Using short UV-polymerization times, polymeric beds with homogenously dispersed VMNPs were obtained. The novel stationary phases were characterized by scanning electron microscopy. The chroma…

The CEC behaviour of several synthetic peptides related to the activin ��A-��D subunits

2008

The resolution of several structurally related synthetic peptides, derived from the loop 3 region of the activin betaA-betaD subunits, has been studied using capillary electrochromatography (CEC) with Hypersil n-octadecylsilica as the sorbent. The results confirm that the CEC migration of these peptides can be varied in a charge-state-specific manner as the properties of the background electrolyte, such as pH, salt concentration and content of organic modifier, or temperature are systematically changed. Acidic peptides followed similar trends in retention behaviour, which was distinctly different to that shown by more basic peptides. The CEC separation of these peptides with the Hypersil n-…

EFFECTS OF SENSITIZED AND UNSENSITIZED LONGWAVE U.V.-IRRADIATION ON THE SOLUTION PROPERTIES OF DNA

1971

— Two types of photoreactions occur in DNA irradiated in aqueous systems with longwave u.v.-light (Λ > 295 nm), namely, (a) thymine dimerization, and (b) single- and double-strand breakage of the sugar phosphate backbone; these two reactions are unrelated. The presence of acetophenone as a photosensitizer caused an increase in dimerization by a factor of 16, and an increase in single-strand breaks by a factor of 4. The number of thymine dimers per single-strand break is about 100 in the sensitized and 25 in the unsensitized reaction. The alteration of the radius of gyration of DNA molecules is that expected by the degradation observed. At the same time the change in hyperchromicity is very …

Speciation of chitosan-phosphate and chitosan-nucleotide systems in an NaCl aqueous solution

2010

AbstractThe speciation of chitosan (310 kDa) with organic (adenosine 5’-monophosphate, AMP, and adenosine 5’-triphosphate, ATP), and inorganic phosphorus containing ligands (phosphate and pyrophosphate) was investigated in NaCl aqueous solutions at I = 0.1mol L−1 and T = 25°C. For all the systems, the investigated results obtained gave evidence for the formation of (chitosan)LHi complex species (L = nucleotides, phosphate and pyrophosphate; i = 1 to 4, but for AMP, i = 1 to 3). The stability data of complex species were used to calculate the sequestering ability of chitosan towards phosphorus compounds considered here, expressed as pL50 i.e., – log(total chitosan concentration) necessary to…

Solid state electrochemical behavior of organosulfur compounds

2017

Abstract The solid-sate electrochemistry of organosulfur compounds existing in petroleum and its derived matrices is described using the voltammetry of immobilized microparticles methodology. Cyclic and square wave voltammogrammetric responses of sulfur compounds responsible of aging of asphalt pavements, namely, thiophenes, disulfides, sulfides, sulfoxides and sulfones were determined at compound-modified graphite electrodes in contact with 0.10 M H2SO4. The electrochemical oxidation/reduction products were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy with energy dispersion x-ray detection (SEM-EDX) couple…

A Co2O2 metallacycle exclusively supported by l-valine

2008

Abstract [Co2(OH)2( l -valine)4]·2.5H2O has been prepared under hydrothermal conditions and constitutes the first example of a [Co2O2] core supported exclusively by aminoacids. This synthetic dimetallic model for redox active metalloenzymes is one of the few binary aminoacid compounds of biologically relevant metal ions that has been structurally characterized, showing the possibilities of this synthetic approach for preparation of models in bioinorganic chemistry.

Electrochemical synthesis of sulfamides.

2021

Herein we demonstrate the first electrochemical synthesis protocol of symmetrical sulfamides directly from anilines and SO2 mediated by iodide. Sulfamides are an emerging functional group in drug design. Highlights are the direct use of SO2 from a stock solution and no necessity of any supporting electrolyte. Overall, the reaction has been demonstrated for 15 examples with yields up to 93%.

Magnetic Disaccommodation in Manganese Ferrites in the Temperature Region IV

1991

The magnetic relaxation in polycrystalline, nonstoichiometric manganese ferrite samples MnxFe3−xO4 is investigated as a function of the Mn content (0 ≦ x ≦ 1). The analysis of the experimental results shows that in the temperature region IV two different relaxation processes at 285 (IV) and 220 K (IVa) can be distinguished. The process IV exhibits orientational relaxation characteristics and is composed by the superposition of two Debye processes with activation energies close to 0.75 and 0.80 eV whereas relaxation IV a could be associated with vacancy migration through the lattice, but future investigations are necessary to probe this. Es wird die magnetische Relaxation in polykristallinen…

Amino Acid Esters as Chiral Auxiliary Groups in Lewis Acid Catalyzed Reactions of Electron-rich Siloxydienes with Imines

1990

Thermodynamics of copolymer solutions: how the pair interactions contribute to the overall effect.

2014

Vapor pressure measurements were performed for solutions of poly(methyl methacrylate-ran-tert-butyl methacrylate) with different weight fractions of tert-butyl methacrylate units, and their parental homopolymers in chloroform at 323 K, over a large domain of concentrations. The Flory–Huggins interaction parameters obtained from these experimental investigations show complex dependences of the Flory–Huggins interaction parameter on concentration and copolymer composition. This behavior can be modeled by taking into account an approach which considers the ability of the polymers to rearrange in a response to changes in their molecular surroundings [Adv. Polym. Sci. 2011, 238, 1–66]. According…