Spin probes in micellar and polymer self-associating systems

The results of studies of micellar and self-associating polymer systems by spin probe ESR spectroscopy are summarized. The local dynamics and structures of low-molecular-weight micelles built of cationic surfactants bearing long alkyl chains (from C₁₆ to C₂₂), gels of hydrophobically modified polymers, polymer micelles, micellar complexes of nonionic surfactant (Brij58) with hydrogels based on polyacrylic acid, and associates formed in aqueous solutions of poly(diphenylenesulfophthalide) are discussed. Interest in these systems is caused by prospects of their practical use as carriers in drug delivery, in biotechnology, for the enhancement of oil production, and in other purposes.     

Adsorption and molecular dynamics of low-molecular substances on modified montmorillonite nanoparticles

The effect of the structure of stable nitroxyl radicals on their adsorption from organic solvents on montmorillonite modified with cationic surfactants is examined. The influence of the nature and content of the modifier and solvent, as well as additional modification with cationic dyes, on the adsorption is considered. The kinetic parameters of the adsorption of decane, toluene, and ethanol from the gas phase are determined. The spin probe method is used to determine the phase state and distribution of adsorbed additives, as well as the influence of an additional adsorption of hydrocarbons on the molecular dynamics at the surface of nanoparticles of montmorillonite and nanopigments based on cationic dyes.     

Polypropylene track membranes as a promising material for targets with polarized protons

Polypropylene track membranes made by irradiation of polypropylene films with a beam of high-energy heavy ions followed by chemical etching of latent ion tracks are proposed for being used as a polarized target material. To give membranes paramagnetic properties needed for allowing dynamic polarization of nuclei, the nitroxyl radical 2,2,6,6-tetramethylpiperidine-1-oxyl was introduced in the samples by the thermal diffusion technique. Using the electron paramagnetic resonance method, we obtained information on paramagnetic centers in the polymer matrix of the membranes and determined the nitroxyl radical concentration and rotational mobility of the spin probe in them.     

Molecular mobility in micellar complexes of a nonionic surfactant and the poly(acrylic acid)-based hydrogel

The interaction between the polyelectrolyte gel of crosslinked poly(acrylic acid) (PAA) and nonionic surfactant Brij 58 based on poly(ethylene glycol) (C₁₆H₃₃(CH₂CH₂O)₂₀OH) is studied. It is established that poly(acrylic acid)-surfactant complexes are formed. Nondissociated carboxyl groups of poly(acrylic acid) and oxygen atoms of the surfactant are involved in the complexation. Surfactant micelles are a kind of bridge that connects polymer chains. The presence of the surfactant decreases the equilibrium swelling of the hydrogel. The spin probe method is employed to determine the local mobility of the hydrocarbon core of a micelle in the complex. It was shown that the local mobility is independent of the hydrogel crosslink density and is much lower in acidic than in alkaline media. In acidic media, much more surfactant molecules of micelles are involved in the complexation than in alkaline media. However, even in alkaline media, surfactant micelles cannot leave the hydrogel, while the spin probes located in micelles are at equilibrium with the spin probes present in the external aqueous medium. The prospects for applying the considered systems as carriers for controlled release drugs are discussed.     

Exploring Peptaibol’s Profile,Antifungal, and Antitumor Activity of Emericellipsin A of Emericellopsis Species from Soda and Saline Soils

Features of the biochemical adaptations of alkaliphilic fungi to exist in extreme environments could promote the production of active antibiotic compounds with the potential to control microorganisms, causing infections associated with health care. Thirty-eight alkaliphilic and alkalitolerant Emericellopsis strains (E. alkalina, E. cf. maritima, E. cf. terricola, Emericellopsis sp.) isolated from different saline soda soils and belonging to marine, terrestrial, and soda soil ecological clades were investigated for emericellipsin A (EmiA) biosynthesis, an antifungal peptaibol previously described for Emericellopsis alkalina. The analysis of the Emericellopsis sp. strains belonging to marine and terrestrial clades from chloride soils revealed another novel form with a mass of 1032.7 Da, defined by MALDI-TOF Ms/Ms spectrometers, as the EmiA lacked a hydroxyl (dEmiA). EmiA displayed strong inhibitory effects on cell proliferation and viability of HCT 116 cells in a dose- and time-dependent manners and induced apoptosis.