INTRODUCTION: In DNA double helices, hydrogen bonds connect the base pairs across the two strands, and stacking bonds act along the helical axis between neighboring base pairs. Our understanding of DNA and the way it is processed in biology would profit from improved knowledge about the elementary bonds in DNA. Detailed knowledge of the time scales for breaking and forming individual base pairs and base-pair stacks would also help to make more informed decisions in the design of dynamic DNA-based nanoscale devices.