Supporting Information Photocontrol of STAT6 dimerization and translocation Sunanda Lahiri, Ralf Seidel, Martin Engelhard and Christian F. W. Becker Figure S1: Cy5 labeled caged phosphorylated STAT6 prepared by expressed protein ligation of recombinantly produced STAT6(1-634) and synthetic peptides comprising amino acids 635-668. Synthesis of caged phosphotyrosine Figure S2: N-α- Fmoc-phospho(1-nitrophenylethyl-2-cyanoethyl)-L-tyrosine Synthesis of caged phosphotyrosine was carried out as previously described by Rothman et al. 1, 2 Analytical data of the final product: 1 H NMR (500MHz, CDCl 3, Me 4 Si) δ (ppm): 8.4 (br, s, 1 H); 7.8 (d, J HH = 8 Hz, 1 H); 7.6 (m, 3 H); 7.5- 7.4 (m, 3 H); 7.3-7.2 (m, 3 H); 7.17-7.19 (m, 2 H); 6.9 (m, 4 H); 6.1 (m, 1 H); 5.4 (m, 1 H); 4.52 (s, 1 H) ; 4.34 (s, 1 H); 4.25 (s, 2 H); 4.0 (s, 2 H); 3.0 (m, 2 H); 2.50 (m, 2 H); 1.64 (dd, J HH = 2 Hz, 6 Hz, 3 H). 13 C NMR (400 MHz, CDCl 3 ) δ (ppm): 177.8, 156.0, 149.1, 146.9, 143.9, 141.5, 136.8, 134.2, 134.1, 131.1, 129.2, 127.9, 125.2, 124.7, 120.2, 120.15, 120.1, 116.2, 74.3, 67.2, 63.0, 54.9, 47.3, 37.2, 24.3, 20.9. 31 P NMR (400 MHz, CDCl 3 ) δ (ppm): -7.74. ESI-MS: [M+Na] + obs : 708.13, [M+H] + cal : 685.13. Yield: 329 mg (50%) 1 Supplementary Material (ESI) for Molecular BioSystems This journal is (c) The Royal Society of Chemistry, 2010