Search results for "solu"
showing 10 items of 7577 documents
Membrane Lipid-Polypeptide Molecular Associations in Non Aqueous Solvent. Effect of Phosphatidylcholine Concentration and Temperature and their Influ…
1986
Abstract The use of an Ultrastyragel 500 A column for the study of interactions between phosphatidylcholine and gramicidin A in tetra-hydrofuran is described. Analysis of vacant peak has allowed to establish the influence that eluent lipid composition, concentration of injected gramicidin and temperature have on the interaction. At 20[ddot] C, for the assayed phospholipid concentration range (0.04 to 0.14 %, w/v), the lipid/polypeptide molar binding ratio, BR, varies from 1.3 to 6.9. An increase in temperature from 20 to 40[ddot] C causes a decrease in BR of about 20 %. On the other hand, the interaction releases some of the water bound to the lipid polar head, suggesting that the binding i…
Energetic analysis of succinic acid in water droplets: insight into the size-dependent solubility of atmospheric nanoparticles
2021
<p>Size-dependent solubility is prevalent in atmospheric nanoparticles, but a molecular level understanding is still insufficient, especially for organic compounds. Here, we performed molecular dynamics simulations to investigate the size dependence of succinic acid solvation on the scale of ~1-4 nm with the potential of mean forces method. Our analyses reveal that the surface preference of succinic acid is stronger for a droplet than the slab of the same size, and the surface propensity is enhanced due to the curvature effect as the droplet becomes smaller. Energetic analyses show that such surface preference is primarily an enthalpic effect in both systems, while the entropi…
Methacrylate ester-based monolithic columns for nano-LC separation of tocopherols in vegetable oils
2010
The separation and determination of tocopherols (Ts) in vegetable oils by nano-LC chromatography with UV-vis detection using lauryl methacrylate ester-based monolithic columns has been developed. The separation of Ts was optimized in terms of mobile phase composition on the basis of the best compromise among efficiency, resolution and analysis time. Using a mobile phase composed of ACN/methanol/water, an excellent resolution between Ts was achieved within 18 min. The LODs were lower than 0.26 μg/mL, being repeatability values of retention time and peak area below 0.15 and 3.1%, respectively. The method was applied to the quantification of Ts and tocotrienols present in several vegetable oil…
Untersuchungen über die emulsionspolymerisation des acroleins. Polymere acroleine. 15. Mitteilung
1959
Die Polymerisation des Acroleins mit verschiedenen Emulgatortypen wird untersucht. Es zeigt sich, das eine Losung von Polyacrolein in wasriger schwefliger Saure ein vorzuglicher Emulgator fur die Emulsionspolymerisation von Acrolein mit Redox-Systemen ist. An diesem System wird der Einflus der Emulgatorkonzentration S, der Initiatorkonzentration ci, der Monomerkonzentration und der Temperatur gepruft. Man findet folgende Beziehungen: VBr ∼ S1/5; VBr ∼ c; und VBr ∼ M. Die experimentellen Ergebnisse werden mit den nach der Theorie von SMITH und EWART zu erwartenden verglichen und diskutiert. The polymerization of acrolein with several types of emulsifiers has been investigated. There is shown…
1977
The solution polymerization of styrene in methylene dichloride catalysed by trifluoromethanesulfonic acid takes place at a high rate even at low catalyst concentration. The S-shaped course of the conversion curves is explained by a reaction mechanism, in which the catalyst rapidly forms an inactive complex with one monomer molecule, and this monomer-acid complex is in equilibrium with the free catalyst molecule from which the propagating species are formed. Therefore, the formation of active initiating species becomes a slow process which depends also on the change of monomer concentration during polymerization. It is assumed that the active initiating species are formed from two or three m…
Polymere 3-acryloyloxyalkyl- und 3-acryloyloxyaryl-4-thiazolidone als strahlenschutzsubstanzen
1977
The syntheses of 3-acryloyloxyalkyl- and 3-acryloyloxyaryl-2-phenyl-4-thiazolidones (3a–c) from the corresponding hydroxyl derivatives 2a–c and acrylic acid chloride are described. These monomers were homopolymerized and copolymerized with N-vinyl-2-pyrrolidone by radical initiation. The resulting water soluble copolymers were tested in animals for radioprotective activity and prolongation of efficiency.
1988
The structure of 1-azabicyclo[4.2.0]octane (1) was evaluated by NMR spectroscopy. It was found that the six-membered ring has a chair conformation with the four membered ring in the N-axial and C-6-equatorial position, and as a consequence, the monomer allows neither a ring inversion nor a nitrogen inversion. It possesses two centers of chirality, one at the nitrogen atom and one at C-6. Homopolymerization was carried out in methanol at 60°C with N-alkyl ammonium salts of 1 affording the polymer in high yield within a few hours. Its NMR spectra reveal that the polymer chain is preferably arranged in the biequatorial position of the six-membered ring. As a polybase the polymer can be titrate…
Structure and properties of zwitterionic polysoaps: functionalization by redox-switchable moieties
2007
Redoxactive monomeric and polymeric surfactants containing viologen and N-alkylated nicotinic acid moieties were synthesized. These systems are potentially able to trigger reversible changes of self-organization by creation or removal of a charge via a redox reaction. Hence, they are investigated with respect to solubility, aggregation behavior, and their electrochemical properties in water. — All monomers, but only the viologen polymers are water-soluble and drastically decrease the surface tension of water. Critical micelle concentrations are observed for the monomers only. — The chemical reversibility of the redox reactions of the compounds in water was investigated using cyclic voltamme…
13C nuclear magnetic resonance spectra of several podocarpane and cassane diterpenoids
1990
The 13C NMR spectra of several diterpenic derivatives having the podocarpane and cassane skeleton were recorded and interpreted. The most significant effects due to substituent orientation, B/C ring junction stereochemistry and conformational changes are briefly discussed.
Ozone absorption in aqueous phenol solutions
1977
Abstract The rate of ozone absorption in aqueous solutions of phenol was measured in a wetted-wall laboratory absorber. The liquid and gas flow rates were fixed as well as the pH and temperature. The phenol concentration was varied in the range 2–300 ppm and the ozone partial pressure over an eight fold range. The gas phase resistance to mass transfer was determined by absorbing SO2 from an SO2N2 mixture in KOH aqueous solutions. The results have been interpreted by means of a simple kinetic assumption.