Photis Dais
Photis Dais
Tel: +30-81-393637
Fax: +30-81-210951
E-mail: dais@talos.cc.forth.gr
THE NMR LABORATORY
The NMR laboratory is a part of the Chemistry Department and is supported by the University of Crete and by National and EC grants. It is equipped with three NMR spectrometers, a Bruker AMX500 operating at 500 MHz for liquids, a Bruker MSL300 operating at 300 MHz for liquids and solids, and a Varian FTA operating at 80 MHz for liquids. Theoretical calculations (conformational analysis, dynamic simulations) are performed in personal PCs, and in the computing facilities of the University of Crete. The current personnel of the NMR laboratory involves two undergraduate students, two graduate students, two post-doctoral fellows, and one technician.
UNDERGRADUATE AND GRADUATE COURSES
The following courses are offered to the Chemistry Department:
REREARCH INTERESTS
There are three main research activities in the NMR laboratory related to studies on structure and dynamics of small and large molecules by employing liquid and solid-state NMR spectroscopy.
The first project concerns with studies on structure and conformational dynamics of oligo- and polysaccharides in solution, by employing modern NMR spectroscopy and NMR relaxation measurements. In particular, variable temperature 13C relaxation measurements at different magnetic fields in combination with dynamic modeling give valuable quantitative information about the flexibility of carbohydrate chains in solution as a function of the nature of the monomer residues and the type of glycosidic linkages. The flexibility of carbohydrate chains as a function of their geometry is an important property for their industrial uses, as thickeners, gelling agents and regulators of the rheology of the aqueous phase, etc. In this respect, a systematic study is now in progress to investigate the dynamics of linear and branched homo-, and hetero-polysaccharides of industrial interest. Preliminary results on inulin, amylose, dextran, β-(1® 3)-, and α-(1® 3)-glucans showed different local chain dynamics in dimethylsulfoxide and water solutions.
The examination of the mirostructure, morphology, and chain dynamics of industrial synthetic polymeric systems in the liquid and solid state is the second research activity in the NMR laboratory. Important mechanical and physical properties of synthetic polymeric systems, such as homopolymers, copolymer and polymer blends, depend primarily of molecular structure, bulk morphology, and local chain dynamics. Therefore, the study of these factors in solution and in the solid state should play a decisive role in understanding structure/property relationships for synthetic polymeric materials. Experiments in this laboratory on polymeric systems bearing pendent chromophore groups unravelled the close relationship between microstructure and local chain dynamics with their photophysical properties. Intensive research on industrial polymers with photoconductive properties, is currently in progress.
A third research project carried out in the NMR laboratory deals with the structure determination of natural products. Our current research interest focus on the toxic substances known as mycotoxins, that they are now recognized to be a major agricultural problem. These substances are metabolites, which are produced from certain species of fungi growing on cereals, nuts, soybeans, and several other crops including fruit; they are potential hazards to humans and animals when they are ingested. The Food and Agriculture Organization of the United Nations estimates that 25 % of the world’s food crops are affected by mycotoxins each year. Economic losses caused by fungi and mycotoxin contamination are estimated to be hundrends of billions each year world wide. Reduced yields, reduced nutritive value, increased processing costs, unsafe mycotoxin residues in animal products, higher product prices, loss of foreign and domestic markets, lower foreign exchange earnings, increased import costs, these are only a few of the direct and indirect economic factors in the list that influence dramatically consumer prices and national economies. Our main concern with mycotoxin is twofold: First, a systematic study to elucidate the relationship between their molecular structure and their toxic properties, and second to establish new effective analytical techniques for easy and sensitive mycotoxins monitoring in foods. The first task will be accomplished by employing modern multi-dimensional NMR methods, whereas LC NMR will be used to determine mycotoxins at very low concentrations (μg), on the basis of their unique 1H NMR spectra.
RECENT PUBLICATIONS