Glycerol effects on protein flexibility: a tryptophan phosphorescence study

Area of Science:

• Biophysics
• Protein Dynamics
• Biochemistry

Background:

• Understanding protein dynamics is crucial for function.
• Solvent viscosity's effect on protein fluctuations is not fully understood.
• Tryptophan phosphorescence is sensitive to its local environment.

Purpose of the Study:

• Investigate protein flexibility using tryptophan phosphorescence.
• Determine the impact of glycerol, a viscogenic cosolvent, on protein dynamics.
• Analyze how solvent viscosity and temperature affect protein structural fluctuations.

Main Methods:

• Utilized tryptophan phosphorescence lifetime as an intrinsic probe.
• Studied alcohol dehydrogenase, alkaline phosphatase, apoazurin, and RNase T1.
• Measured phosphorescence lifetime across varying glycerol concentrations and temperatures.

Main Results:

• Glycerol's effect on structural fluctuations deviates from Kramers' law for some proteins.
• Cosolvent-induced structural changes impact even the protein core.
• Frictional coefficients vary significantly between flexible and rigid protein sites, with temperature-dependent anomalies.

Conclusions:

• Protein flexibility is influenced by solvent viscosity in complex ways.
• Cosolvents can alter protein dynamics, affecting internal structures.
• Solvent damping is particularly effective for large-amplitude, low-frequency motions in flexible protein regions.