title: Conformation dependence of pKa's of the chromophores from the purple asFP595 and yellow zFP538 fluorescent proteins.
abstract: Two members of the green fluorescent protein family, the purple asFP595 and yellow zFP538 proteins, are perspective fluorescent markers for use in multicolor imaging and resonance energy-transfer applications. We report the results of quantum based calculations of the solution pKa values for selected protonation sites of the denatured asFP595 and zFP538 chromophores in the trans- and cis-conformations in order to add in the interpretation of photophysical properties of these proteins. The pKa values were determined from the theromodynamic cycle based on B3LYP/6-311++G(2df,2p) calculations of the gas phase free energies of the molecules and the B3LYP/6-311++G(d,p) calculations of solvation energies. The results show that the pKa's of the protonation sites of the chromophore from asFP595 noticeably depend on the isomer conformation (cis- or trans-), while those of zFP538 are much less sensitive to isomerization.
authors.affiliation: Department of Chemistry, M.V. Lomonosov Moscow State University, Leninskie Gory, 1/3, Moscow, 119991, Russian Federation.
authors.forename: A V
authors.initials: AV
authors.lastname: Nemukhin
authors.forename: I A
authors.initials: IA
authors.lastname: Topol
authors.forename: B L
authors.initials: BL
authors.lastname: Grigorenko
authors.forename: A P
authors.initials: AP
authors.lastname: Savitsky
authors.forename: J R
authors.initials: JR
authors.lastname: Collins