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 (T//c), the total diffraction intensities of both hydrated and dehydrated bilayers decreased at similar exponential rates, starting at a cumulative does of 2 multiplied by 10** minus **4 C/cm**2. The intensity anisotropy along diffraction rings was not noticeably altered by radiation. At temperatures less than 6 degree from T//c, 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 T//c ruptured at a cumulative dose of 10** minus **3 C/cm**2, whereas those near or above T//c were more resistant to radiation-induced rupture. The results are discussed in terms of molecular damage, bilayer movement and annealing.