Fig. 3

Average long-axis radius of β-Amylase estimated from their distribution in AFM images. Particles were identified using the threshold or the Otsu’s method when β-Amylase was deposited on bare mica (a) or Nickel pre-treated mica (b). Control represents β-Amylase that was not exposed to X-ray. Standard exposure is about 10 s whereas over-exposed corresponds to a 30 min exposure to X-ray. Long-axis radii were determined with standard parameters of the Grain distribution section of Gwyddion. Upon increase exposure time in X-ray beam, a slight increase in the long-axis radius of β-Amylase is observed which could be interpreted as aggregation of β-Amylase monomers or consolidation of β-Amylase tetramer after radiation damage (see text). The number of identified particles on bare mica was 139, 122, 457 and 230 for over-exposed, exposed 5 min, standard exposure and control, respectively; whereas on nickel pre-treated mica the number of particles was 1877, 136, 1453 and 277 for over-exposed, exposed 5 min, standard exposure and control, respectively