Objetivo Size, dimensionality, and structure of individual J-aggregate nanoparticles on charged surfaces, explored by time- and space-resolved excitonic superradiance and absorption: quantitative determination of membrane potential in living cellsThe main goal of the project is to develop reliable diagnostics for size, dimensionality, structure, and excitonic state (free or self-trapped) of ordered molecule aggregates (J-aggregates), formed in bulk and on charged surfaces under various conditions, in order to explore the living state of cells, as revealed by its membrane potential.The planned investigations lie on the intersection of two research fields:(1) Investigation of the living state of cells via fluorescence imaging and spectroscopy of J-aggregates, formed on the charged surface of the living cell membrane and;(2) Investigation of excitonic superradiance and absorbance as probes for the microscopic structure of J-aggregates.A traditional tool for monitoring the membrane potential of mitochondria in living cells utilises the stationary absorption and luminescence spectra of J-aggregates formed on the membrane surface, as evidenced by a colour change from monomeric green to the typical red of the aggregates. The membrane potential, existing only in a living cell, causes the formation of J-aggregates and the appearance of the corresponding narrow lines in absorption and luminescence. Such stationary spectroscopy can only give rather general qualitative information on the living state, since it provides no information on the size of the formed J-aggregates that is indicative of the potential magnitude. To derive quantitative data on the membrane potential and its topography, it is necessary to know the J-aggregate size (small compared to that of the membrane) versus coordinates on the membrane surface.The size, N, of a J-aggregate can be derived from the superradiance decay time that is proportional (for small enough aggregates) to 1/N. Within the present project, time-resolved superradiance in combination with absorbance and other spectroscopic characteristics will be used as a probe for the size and structure of J-aggregates, formed on the membrane surface, and, in the end, for the cell membrane potential.Near room temperature, where the biological cell is to be examined, superradiance is suppressed to a great extent and masked by various mechanisms, and it is one of the goals to unmask and separate the contributions. The main focus will be the aggregation of molecules on charged surfaces, depending on its potential. The equilibrium distribution of J-aggregates over types (linear or ring-like, 2-dimensional, 3-dimensional such as spheres and nanotubes) and sizes will be reconstructed via the minimization of free energy with the use of the kinetic and spectroscopic data on excitonic superradiance and absorption.In particular, the membrane potential will be derived as one of the parameters of this equilibrium distribution. A reconstruction of the membrane-potential topology will be attempted.The distribution of membrane potential along the membrane surface in living cells will be explored by an improved version of a novel, ultra-sensitive time- and space-correlated single photon counting (TSCSPC) detector that had been developed during recent INTAS-94-4461 and EC BIO4-CT97-2177 projects, by some of the partners.The feasibility of the project is provided by participation of leading experts from various fields, such as cell biology, picosecond spectroscopy, exciton dynamics, and instrument development. The applicants are highly experienced in the investigation of the kinetic, spectral and structural properties of J-aggregates and other low-dimensional systems. Within the past INTAS 96-626, new insights had been obtained, concerning the structure of J-aggregates and nontrivial exciton dynamics in quasi-one-dimensional systems. In particular, the suppression of superradiance due to exciton self-trapping in J-aggregates has been observed and theoretically described. This knowledge will now be applied to biological systems.The expected information gained on the formation of J-aggregates and the temperature behavior of superradiance, however, is not confined to above biological application, since J-aggregates are also promising topical objects in pure and applied physics. Programa(s) IC-INTAS - International Association for the promotion of cooperation with scientists from the independent states of the former Soviet Union (INTAS), 1993- Tema(s) 1B - Condensed Matter, Optics and Plasma Physics OPEN - OPEN Call Convocatoria de propuestas Data not available Régimen de financiación Data not available Coordinador EuroPhoton GmbH Aportación de la UE Sin datos Dirección Mozartstr. 27 12247 Berlin Alemania Ver en el mapa Coste total Sin datos Participantes (4) Ordenar alfabéticamente Ordenar por aportación de la UE Ampliar todo Contraer todo CNRS, Universités Paris 6 et 7 Francia Aportación de la UE Sin datos Dirección Place Jussieu 2 75251 Paris Ver en el mapa Coste total Sin datos Eldy. Ltd Rusia Aportación de la UE Sin datos Dirección M. Toreza prospect 68 194223 St. Petersburg Ver en el mapa Coste total Sin datos National Academy of Sciences of Ukraine Ucrania Aportación de la UE Sin datos Dirección Lenin Ave. 60 61001 Kharkov Ver en el mapa Coste total Sin datos National Academy of Sciences of Ukraine Ucrania Aportación de la UE Sin datos Dirección Lenin Ave. 47 310164 Kharkov Ver en el mapa Coste total Sin datos
