Table I.

Apparent dissociation constants (K_d(app)) for Cu(II) binding to α-synuclein variants

	Kd(app) (μM)a
pHb	F4W	F4W/H50S	Syn1-10
5.0	17 ± 4	17 ± 5	19 ± 2
5.5	2.0 ± 0.1	3.4 ± 0.8	2.4 ± 0.1
5.8	0.8 ± 0.1	0.9 ± 0.2	0.7 ± 0.1
6.0	0.5 ± 0.2	0.9 ± 0.2	0.4 ± 0.1
7.0c	0.2 ± 0.2	0.2 ± 0.2	0.2 ± 0.2

^aThe K_d(app) values are obtained from fits of tryptophan fluorescence data shown for the full-length variants (Figure S2) using a two state binding model Syn-Cu ⇆ Syn + Cu.

^bAll buffers were filtered through a 0.22 μm membrane. 20 mM MES and MOPS buffers containing 100 mM NaCl were used for pH 5 to 6 and pH 7, respectively.

^cReliable K_d(app) values cannot be extracted because protein/peptide concentration used in these experiments (1 μM) are 10 fold greater than K_d(app).