The protein for crystallization should be homogeneous and >90% purity. The purity of protein shall be checked by HPLC or MS before crystallization. The DLS (dynamic light scattering) result is helpful but not required. The minimum amount is 10ug/ul * 300ul.
You could check the Protein Services of GenScript here: https://www.genscript.com/recombinant-protein-services.html?src=mc