However, the curve at pH 6.5 shows an upturn at low q from attractive inter-particle interactions (aggregation) and Bragg reflections indicating colloidal crystals. To further analyze the potential electrostatic nature of this pH-triggered AP205 VLP aggregation process, pHdependent zeta potential analysis was performed at pH 3.0, 4.0, 5.0, 6.0, 6.3, 6.5, 7.0, and 8.0.