Long- and Short-Range Electrostatic Fields in GFP Mutants: Implications for Spectral Tuning.

Area of Science:

• Biophysics
• Spectroscopy
• Protein Science

Background:

• Protein function is largely determined by internal electrostatics.
• Understanding these interactions is key to protein engineering and function elucidation.
• Green Fluorescent Protein (GFP) offers optical insights into internal electric fields due to its fluorophore.

Purpose of the Study:

• To quantitatively evaluate internal electric fields within GFP mutants.
• To correlate optical measurements with protein electrostatic properties.
• To validate a novel all-optical measurement technique.

Main Methods:

• Utilized an all-optical approach measuring transition frequency and absorption cross-sections.
• Employed two physical models based on the quadratic Stark effect.
• Analyzed various GFP mutants to probe internal electric fields.

Main Results:

• Successfully evaluated both long-range and total effective electric fields.
• Demonstrated quantitative agreement between optical measurements and molecular dynamics simulations.
• Validated the all-optical method for probing protein electrostatics.

Conclusions:

• The all-optical method provides a reliable way to measure internal electric fields in proteins.
• Internal electrostatics of GFP mutants can be accurately quantified.
• This technique advances the study of protein function and engineering.