Objective The objective of this project is to identify, synthesise, test, improve and make initial studies with a range of task-oriented electron paramagnetic resonance (EPR) spin probes. These spin probes will all be nitroxide free radicals. Most of the range will be derivatives of imidazoline/imidazolidine compounds, although other nitroxides will be examined where their properties are likely to be of use in the proposed research directions. Initial physiological and metabolic studies with these spin probes will both demonstrate their efficacy and lay the ground-work for development of lines of metabolic, physiological and medically-oriented studies employing EPR techniques.The major tasks at which the new spin probes will be aimed relate to the ability of some spin probes to vary the width of their EPR spectrum depending upon the pH of the local environment, e.g. upon whether the spin probe molecule is protonated or unprotonated. Imidazole-based compounds are already known to respond in this way and have been used by several of the Teams involved in this application. A limited range of other nitroxides has the same properties to useful extents. The Teams will work to produce a range of pH-sensitive spin probes with useful properties. These will include probes of different pK, which can be used as molecular pH sensors over a pH range from about 1 to 8. These values will enable the spin probes to be used from tasks ranging from monitoring the pH of the mammalian stomach (typically about pH 2; one of our proposed studies is examination of the efficacy of anti-acid compounds), through studies of the pH inside cells and subcellular organelles (range of pH from 5.5 to 7.0; we wish to use these probes to assist in elucidation of aspects of ATP synthesis in chloroplasts and mitochondria) to blood at pH up to about 7.5 (we wish to look at drug transport and interactions, many of which relate to pH).In addition to pH, other task orientations to be explored will be the abilities of the probes to act as markers for drug delivery systems, especially where slow-release systems are employed (we wish to monitor drug release from liposomes and from slow-degrading solids) and to act as sensors to the oxygen concentration of the local environment (e.g. to be used as part of the interest in energetics).Properties other than pH-sensitivity are also important to the tasks to be performed by the spin probes. A major property is the ability to remain in the water phase of tissue (hydrophilicity), hence to remain in extracellular or intracellular compartments, or to prefer the lipid phase (lipophilicity), hence to embed within the membranes. These properties enable targeting of the spin probe to enable information to be gained about specific cellular environments. The degree of hydro- or lipophilicity can be altered by changing the nature of side-groups attached to the core spin probe molecule. Further changes can be made such as addition of ionic side groups or groups aimed at specific cellular targets. Such modifications will be explored to improve targeting of the probes.The performance of these spin probes, e.g. their EPR sensitivity can also be increased. The major method to do this, in addition to improving targeting and hence local concentration, is to use isotopic substitution. The ideal spin probe has narrow spectral lines, which can be achieved by substitution of the hydrogen of the molecule by deuterium. In addition, increased sensitivity can be achieved by replacement of the nitrogen of the radical centre by a 15-N atom, hence producing a 2-line rather than a 3-line EPR spectrum.The group of Teams, although having a common interest in spin probes and EPR, have very different types of expertise and, together, offer a unique combined approach to this research. The expertise of the Teams in Novosibirsk is in organic and physical chemistry and the efforts of these Teams will be directed towards synthesis, primary testing (stability, lipophilicity, toxicity and sensitivity range) and performance improvement (side group modification and isotopic substitution) of the spin probes. The Nijmegen Team have expertise in advanced spectroscopic techniques and will employ these to provide detailed information about the physico/chemical nature of the new spin probes, including relaxation behaviour and proton coupling which will assist those who are to employ the probes in vivo and in improvement of probe structure. The Moscow Team are experts in cellular energetics and will study the applications of the new spin probes in this area, particularly in areas such as ATP synthesis mechanisms and proton pumping in chloroplasts and mitochondria (pH-sensitive probes), as well as using oxygen-sensitive probes in larger systems to examine problems such as oxidative stress in seeds during drying (which affects viability). The expertise of the Aberdeen Team is directed to in vivo EPR imaging and spectroscopy in medically related animal model systems. They will explore the potential of the new spin probes in a variety of studies aimed at eventual medical application including effectiveness of anti-acids, monitoring of bladder urine pH and kidney function, at drug release mechanisms in vivo and at stress-related oxygen tension variation in muscles.The expected outcomes of this study include both answers to a number of specific questions in metabolism and physiology and, on a broader base, the production of a range of high-sensitivity, task-oriented nitroxide EPR spin probes. These probes will offer a powerful new tool to the research community in general. Programme(s) IC-INTAS - International Association for the promotion of cooperation with scientists from the independent states of the former Soviet Union (INTAS), 1993- Topic(s) 4 - Life Sciences OPEN - OPEN Call Call for proposal Data not available Funding Scheme Data not available Coordinator UNIVERSITY OF ABERDEEN EU contribution No data Address Foresterhill AB25 2ZD ABERDEEN United Kingdom See on map Total cost No data Participants (5) Sort alphabetically Sort by EU Contribution Expand all Collapse all Johann Wolfgang Goethe-Universität Frankfurt am Main Germany EU contribution No data Address Marie-Curie-Stra?e 11 60439 Frankfurt am Main See on map Total cost No data M.V. Lomonosov Moscow State University Russia EU contribution No data Address Vorobjovy gory 119899 Moscow See on map Total cost No data Siberian Branch of Russian Academy of Sciences Russia EU contribution No data Address Institutskaja Street 3 630090 Novosibirsk See on map Total cost No data Siberian branch of Russian Academy of Sciences Russia EU contribution No data Address Lavrentiev prospect, 8 630090 Novosibirsk See on map Total cost No data University of Nijmegen Netherlands EU contribution No data Address Toernooiveld 1 6525 ED Nijmegen See on map Total cost No data
