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The behaviour of the synthetic polynucleotide polyAT entrapped in the inner core of a quaternary cationic microemulsion has been investigated by means of CD and UV spectroscopies in the presence of KCl (variable temperature at constant) and NaCl (variable P 0 at constant W 0 and temperature). While the presence of KCl gives rise to effects which are not substantially different from those already reported for NaCl (absence of thermal melting and formation of compact c(À) structures), the peculiar results obtained as a consequence of the progressive addition of cosurfactant (denaturation of the polymer at low [NaCl] and W 0 ; transition from B-to A-form at intermediate [NaCl],formation of c(À) aggregates at high [NaCl]) can be attributed to the characteristics of the microemulsive system (restricted volume), of the micellar water (low dielectric constant and reduced activity) and of the interface (progressively higher cosurfactant concentration).

The three Gaussian components of the IR stretching band of OH for reverse micelles of egg yolk L-α-phosphatidylcholine in benzene have been characterized in frequency, bandwidth, and extinction coefficient. The different types of water identified inside the micelles correspond to hydration layers around the phospholipid polar heads, the first containing up to ∼11 water molecules per polar head, the second with a maximum of 10–12 water molecules per polar head.

In vivo 31P NMR spectroscopy was used to determine the ratios of creatine phosphate (PCr) to adenosine triphosphate (ATP) and inorganic phosphate (Pi) in leg and arm muscles of four sprinters, one marathon runner, and two sedentary subjects. Both ratios were definitely higher in the sprinters indicating that, since muscle ATP and Pi concentrations are constant, the PCr muscle content of these athletes is higher than usual. Sprinters are known to have higher percentages of fast-twitch fibers, which are richer in PCr than slow-twitch fibers. It is concluded that measurements of muscle ATP, PCr, and Pi through in vivo NMR spectroscopy could be used to determine muscle fiber composition.