We observed a pH-dependent shift of the Tt for KI8 from ~20 °C in water (pH = 6.5) to 6 °C in 0.1 F NaOH (pH = 12.9) (Figure ). Furthermore, in buffered solution without NaCl (10 mM HEPES pH 7.4 vs 10 mM CAPS pH 11.2), we also observed a pH-dependent ∆Tt for KI8 of ~8 °C (Figure ). Based on its theoretical pKa, the Lys residues of KI8 are expected to be mostly (82%) but not fully deprotonated at pH = 11.2, while at pH 12.9 they are expected to be almost completely (99.5%) deprotonated. The large decrease in Tt over this relatively small pH change may be due to an outsize contribution of a small amount of charge to the solubility of KI8, or it may be due to other solution differences irrespective of the extent of Lys protonation such as the presence of co-solute buffer molecules or Na + ions. We also consider in our interpretations that the pKa of Lys residues in KI8 may be decreased by the hydrophobicity of their environment within the ELP, and that the degree of hydrophobicity experienced by the Lys residues depends on the phase state. As a control for the contribution of Lys residues, we also investigated the LCST behavior of an ELP the same length as KI8 but consisting only of VPGIG repeats ("I90", Figure , bottom). At a concentration of 0.4 mg/mL in filtered, deionized water, the same concentration as the previous experiments performed with KI8, I90 was observed as monomer-size (15-20 nm) at 4 °C (Figure ). With increasing temperature, I90 particles gradually increased in size to ~500 nm, then jumped to ~1200 nm at 14 °C and continued to grow to over 2 µm in hydrodynamic size.