Binding of __SP__ __NODE__ protein in cellular_fraction from 130.0 day old embryonic __SP__ atrium and 260 kd protein in cellular_fraction from 130.0 day old embryonic __SP__ atrium is greater than binding of __SP__ __NODE__ protein in cellular_fraction from 46 day old adult __SP__ heart and 260 kd protein in cellular_fraction from 46 day old adult __SP__ heart .