Advances in Colloid and Interface Science (v.131, #1-2)

TSDC spectroscopy of relaxational and interfacial phenomena by V.M. Gun'ko; V.I. Zarko; E.V. Goncharuk; L.S. Andriyko; V.V. Turov; Y.M. Nychiporuk; R. Leboda; J. Skubiszewska-Zięba; A.L. Gabchak; V.D. Osovskii; Y.G. Ptushinskii; G.R. Yurchenko; O.A. Mishchuk; P.P. Gorbik; P. Pissis; J.P. Blitz (1-89).
Applications of thermally stimulated depolarisation current (TSDC) technique to a variety of systems with different dispersion phases such as disperse and porous metal oxides, polymers, liquid crystals, amorphous and crystalline solids, composites, solid solutions, biomacromolecules, cells, tissues, etc. in gaseous or liquid dispersion media are analysed. The effects of dipolar, direct current (dc) and space charge relaxations are linked to the temperature dependent mobility of molecules, their fragments, protons, anions, and electrons and depend on thermal treatment, temperature and field intensity of polarisation, heating rate on depolarisation or cooling rate on polarisation. Features of the relaxation mechanisms are affected not only by the mentioned factors but also by morphological, structural and chemical characteristics of materials. The interfacial phenomena, especially the role of interfacial water, received significant attention on analysis of the TSDC data. Comparison of the data of TSDC and dielectric relaxation spectroscopy (DRS), differential scanning calorimetry (DSC), 1H NMR spectroscopy with layer-by-layer freezing-out of bulk and interfacial water, adsorption/desorption of nitrogen, water and dissolved organics demonstrates high sensitivity and information content of the TSDC technique, allowing a deeper understanding of interfacial phenomena.
Keywords: TSDC; Interfacial water; Fumed silica; Fumed mixed oxides; Silica gel; Amorphous solids; Glasses; Crystalline solids; Liquid crystals; Polymers; Composites; Proteins; Cells; Seeds; Tissues; Relaxation mechanisms; Dipolar relaxation; DC relaxation; Space charge relaxation; Activation energy of relaxation; Relaxation time; DRS; DSC; 1H NMR;

Combination of some newly developed microscopic and spectroscopic techniques with conventional Langmuir monolayer method can provide more quantitative information with the molecular orientation and reorganization process of spread amphiphilic molecules at the air/water interface. These techniques are extended to investigate the hydrolysis process of spreading lipid monolayer catalyzed by different enzymes, phospholipases A2, C and D, respectively. Synchrotron X-ray diffraction and infrared reflection absorption spectroscopy are able directly to give the structural information of the assembled monolayer, interfacial activity of amphiphiles and their components at the interface. Microscopic technique such as Brewster angle microscopy (BAM), fluorescence microscopy (FM) can be used to trace the morphological changes dynamically as the spreading lipid monolayer is hydrolyzed at the air/water interface. We summary here some latest progress in this filed and give a brief review over the hydrolysis features of phospholipid monolayer catalyzed by different enzymes. It is attempted to establish a model of membrane hydrolysis process in order to better understand the mechanism of membrane metabolism and signal transduction in a living system.
Keywords: Enzymes; Phospholipid monolayer; Interfacial reaction; Hydrolysis; Molecular recognition;