(color online) Extension time trace of a DNA hairpin from the magnetic tweezers experiment. The force increases from 8.26 pN to 13.13 pN with loading rate of 0.09 pN/s, then decreases to 8.26 pN with loading rate of −0.09 pN/s (low panel). Two cycles of stretching are shown. Extension of the DNA hairpin is recorded with sampling rate (black curve, upper panel). The red curve shows the smoothed curve averaged in 0.1 second time window.