No abstract

Ca 2þ sparklets are local elevations in intracellular Ca 2þ produced by the opening of a single or a small cluster of sarcolemmal L-type Cav1.2 Ca 2þ channels. At present, however, the spatial organization and mechanisms of modulation of Ca 2þ sparklets in cardiac myocytes is unknown. Here, we tested the hypothesis that Ca 2þ sparklets activity varies within the sarcolemma of neonatal cardiac myocytes and that chemically-induced translocation of PKCa increases the Ca 2þ sparklet activity in these cells. Consistent with this hypothesis we found that application of the PKC activator phorbol 12,13-dibutyrate (PDBu; 500 nM) increased Ca 2þ sparklet activity in neonatal cardiac myocytes. Analysis of the spatial distribution Ca 2þ sparklet activity was not random (i.e. did not have a Poisson distribution). Rather, as in reported in smooth muscle cells, Ca 2þ sparklet activity was higher at specific regions of the cell. Translocation of PKCa to the sarcolemma of neonatal cardiac myocytes resulted in an increase in Ca 2þ sparklet activity in specific regions of the cell. Data will be presented on the relationship between Ca 2þ sparklet activity and Ca 2þ release from the sarcoplasmic reticulum via ryanodine receptors (i.e. Ca 2þ sparks) during excitation-contraction coupling. Our data suggest that Ca 2þ sparklet (i.e. L-type Ca 2þ channels) activity varies within the sarcolemma of neonatal cardiac myocytes and that they are modulated by PKCa, potentially regulating SR Ca 2þ release during EC coupling in heart.

Two 25 base-pair cDNA strands are encapsulated within an optically trapped nanodroplet, and we observe the kinetics of their hybridization in dynamic equilibrium via single-molecule fluorescence resonance energy transfer (FRET) as a function of temperature and of the solution's NaCl concentration. We have observed the duplex unfolding and refolding, and we have observed quasistable partially unfolded states under low salinity conditions. Furthermore, our measurements reveal that, even in conditions under which the duplex is stable, it undergoes conformational fluctuations in solution.