Why is phase determination required after protein crystallization?

After successful crystallization and the diffraction pattern is obtained with our protein crystallization services, the next challenge is to get an electron density map from which detailed information about the structure can be deduced. This is only possible if the ‘phase problem’ can be solved. Each reflection on the diffraction pattern corresponds to a wave consisting of an amplitude and a phase. The amplitude of diffraction spots can be simply measured by taking the square root of the intensity that X-ray detector records. However, the information on the phases, which contain critical information for determining the electron density distribution in the unit cell, is lost during data collection. The structure of small molecules may be solved in the absence of phase information, but this is not true for macromolecules such as proteins.

Explanation:

https://www.creative-biostructure.com/phase-determination-87.htm

the correct option is option d