One of the challenges
facing single particle imaging with ultrafast
X-ray pulses is the structural heterogeneity of the sample to be imaged.
For the method to succeed with weakly scattering samples, the diffracted
images from a large number of individual proteins need to be averaged.
The more the individual proteins differ in structure, the lower the
achievable resolution in the final reconstructed image. We use molecular
dynamics to simulate two globular proteins in vacuum, fully desolvated
as well as with two different solvation layers, at various temperatures.
We calculate the diffraction patterns based on the simulations and
evaluate the noise in the averaged patterns arising from the structural
differences and the surrounding water. Our simulations show that the
presence of a minimal water coverage with an average 3 Å thickness
will stabilize the protein, reducing the noise associated with structural
heterogeneity, whereas additional water will generate more background
noise.