Long- and Short-Range Electrostatic Fields in GFP Mutants: Implications for Spectral Tuning.
The majority of protein functions are governed by their internal local electrostatics. Quantitative information about these interactions can shed light on how proteins work and allow for improving/altering their performance. Green fluorescent protein (GFP) and its mutation variants provide unique optical windows for interrogation of internal electric fields, thanks to the intrinsic fluorophore group formed inside them. Here we use an all-optical method, based on the independent measurements of transition frequency and one- and two-photon absorption cross sections in a number of GFP mutants to evaluate these internal electric fields. Two physical models based on the quadratic Stark effect, either with or without taking into account structural (bond-length) changes of the chromophore in varying field, allow us to separately evaluate the long-range and the total effective (short- and long-range) fields. Both types of the field quantitatively agree with the results of independent molecular dynamic simulations, justifying our method of measurement.
Department of Physics, Montana State University, Bozeman MT 59717.
M
M
Drobizhev
Department of Chemistry and Biochemistry, Montana State University, Bozeman MT 59717.
P R
PR
Callis
NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore, I-56127 Pisa, Italy.
R
R
Nifosì
Department of Physics, Montana State University, Bozeman MT 59717.
G
G
Wicks
Department of Physics, Montana State University, Bozeman MT 59717.
C
C
Stoltzfus
Department of Cell Biology and Neuroscience, Montana State University, Bozeman MT 59717.
L
L
Barnett
Department of Cell Biology and Neuroscience, Montana State University, Bozeman MT 59717.
T E
TE
Hughes
Department of Chemistry and Biochemistry, Montana State University, Bozeman MT 59717.
P
P
Sullivan
1] Department of Physics, Montana State University, Bozeman MT 59717 [2] National Insitute of Chemical Physics and Biophysics, Tallinn 12618, Estonia.
A
A
Rebane
D000838:Anions; D004583:Electrons; D049452:Green Fluorescent Proteins / Q000378:metabolism*; D006860:Hydrogen Bonding; D008962:Models, Theoretical; D056004:Molecular Dynamics Simulation; D009154:Mutation; D012997:Solvents; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013057:Spectrum Analysis; D055672:Static Electricity; D014867:Water
D000838:Anions; D012997:Solvents; D014867:Water; D049452:Green Fluorescent Proteins