Radiation damage of phosphatidylcholine bilayers effects of temperature and hydration

Structural damage by 100 kV electron irradiation in hydrated and dehydrated lecithin bilayers of different acyl chain lengths were measured by the alteration of electron diffraction patterns. At temperatures below the transition temperatures (Tc), the total diffraction intensities of both hydrated and dehydrated bilayers decreased at similar exponential rates, starting at a cumulative dose of 2 x 10(-4) C/cm2. The intensity anisotropy along diffraction rings was not noticeably altered by radiation. At temperatures less than 6 degrees from Tc, the total diffraction intensity of hydrated bilayers increased initially with radiation, while the intensity anisotropy along diffraction rings was also changed by radiation. Unsupported and hydrated bilayers at temperatures well below Tc ruptured at a cumulative dose of 10(-3) C/cm2, whereas those near or above Tc were more resistant to radiation-induced rupture. The results are discussed in terms of molecular damage, bilayer movement and annealing.