SCN as a local probe of protein structural dynamics

Area of Science:

• Biophysics
• Protein dynamics
• Spectroscopy

Background:

• Understanding protein dynamics is crucial for comprehending biological function.
• Vibrational spectroscopy offers a sensitive method for probing molecular environments.

Purpose of the Study:

• To explore the utility of thiocyanate (-SCN) as a vibrational probe for lysozyme dynamics.
• To investigate how -SCN labeling affects protein structure and local hydration.

Main Methods:

• Attachment of -SCN labels to alanine residues in lysozyme.
• Analysis of one-dimensional infrared (IR) and far-infrared spectra.
• Isotopic substitution (12C to 13C) for spectral analysis.

Main Results:

• IR spectra showed frequency shifts indicating moderate interactions between the -SCN probe and its environment.
• Isotopic substitution confirmed quantitative agreement with known spectral behavior.
• Far-infrared spectra revealed label-specific information and local structural changes, such as α-helix disruption at Ala129.
• Label reorientation correlated with changes in local hydration over time.

Conclusions:

• The -SCN group is a versatile probe for studying protein dynamics.
• -SCN provides valuable information in both high-frequency (CN-stretch) and far-infrared spectral regions.
• This labeling strategy can reveal local structural alterations and hydration dynamics within proteins.