We studied the dynamic behavior of red shifted mutants of the fluorescence of green fluorescent protein (GFP) like S65T and EGFP by FCS and discovered a fast blinking effect dependent on the pH of the used buffer. This indicates that the protein spends a considerable amount of time in a dark state, with transitions back and forth to the bright state on the 100 ?s time scale. The findings can be related to the overall fluorescence that decreases at low pH. Structural knowledge about this protein suggests that the dark state is actually a protonated form of the chromophore that shifts the absorption to smaller values where no excitation by the FCS laser can occur. FCS thus allows to derive precise kinetic and thermodynamic information of this reversible protonation process.

Agency
National Institute of Health (NIH)
Institute
National Center for Research Resources (NCRR)
Type
Biotechnology Resource Grants (P41)
Project #
2P41RR004224-11
Application #
6121856
Study Section
Project Start
1998-09-30
Project End
1999-08-31
Budget Start
1997-10-01
Budget End
1998-09-30
Support Year
11
Fiscal Year
1998
Total Cost
Indirect Cost
Name
Cornell University
Department
Type
DUNS #
City
Ithaca
State
NY
Country
United States
Zip Code
14850
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