Low dose electron diffraction of wet protein crystals
High resolution electron diffraction patterns from wet unstained protein-crystals have been successfully obtained by using very low electron dose (∽10-2 e/Å2, much smaller dose than used by Unwin and Henderson (1975) for electron diffraction of their crystals). This enabled us to follow the radiation damage of the protein crystal due to increasing dosage by recording successive diffraction patterns given by the same crystal. Changes in intensities of both the high and the low order reflections can be studied. Another important consequence is that very low dose electron diffraction can be obtained from the same crystal and iterative procedures such as Gerchberg and Saxton's technique can be applied.The electron diffraction work with very low dose was performed at 200 kV using the environmental chamber in the Jeolco 200. To achieve best electron diffraction conditions with the specimen in the hydration chamber, the objective and intermediate lens currents have been changed.