Evaluation of a Raman Chemometric Method for Detecting Protein Structural Conformational Changes in Solution.

Area of Science:

• Biophysical Chemistry
• Protein Science
• Spectroscopy

Background:

• Protein structural changes, particularly tertiary and secondary structures, precede aggregation.
• Monitoring these changes is crucial for understanding protein stability and formulation.
• Raman scattering offers potential for routine structural analysis.

Purpose of the Study:

• To develop and optimize a Raman spectroscopy method using principal component analysis (PCA) for detecting pH-induced tertiary structural changes in proteins.
• To assess the method's efficacy in monitoring protein conformation and aggregation.
• To evaluate the impact of formulation excipients, such as sucrose, on spectral analysis.

Main Methods:

• Utilized principal component analysis (PCA) on Raman spectra of α-lactalbumin solutions.
• Optimized sample preparation and spectral parameters for a bulk Raman probe.
• Analyzed spectral regions (600-1850 cm⁻¹ and 1530-1780 cm⁻¹) and compared with circular dichroism (CD) data.

Main Results:

• PCA of Raman spectra effectively detected pH-induced tertiary structural changes in protein conformation.
• Analysis of a limited spectral region (1530-1780 cm⁻¹) improved discrimination of protein states, especially in the presence of sucrose.
• The method accurately distinguished structural differences in concentrated protein solutions.

Conclusions:

• Raman spectroscopy coupled with PCA is a promising tool for monitoring protein structural stability.
• The method can detect subtle conformational changes relevant to aggregation.
• Further exploration for routine monitoring in solution and solid states is warranted.