Characterization of Oligomer Formation of Surfactant Protein-D (SP-D) Using AF4-MALLS

Area of Science:

• Biochemistry
• Protein analysis
• Biophysical characterization

Background:

• Surfactant protein-D (SP-D) is a lung protein with therapeutic potential for pulmonary infections.
• Recombinant SP-D exists in multiple, dynamically interconverting oligomeric states.
• Characterizing these states is challenging with traditional chromatography.

Purpose of the Study:

• To develop and apply an alternative separation technique for characterizing SP-D oligomeric states.
• To investigate the association states of recombinant SP-D in aqueous solution.

Main Methods:

• Asymmetrical flow field-flow fractionation (AF4) coupled with UV and multi-angle laser light scattering (MALLS) detection.
• AF4-MALLS was used to separate and determine the molar mass of SP-D species.
• Analysis covered species from monomer to dodecamer and larger aggregates.

Main Results:

• Consistent separation of four distinct SP-D peaks was achieved.
• The largest species, termed "unstructured multimers," were partially resolved.
• Most peaks showed high molar mass homogeneity, consistent with atomic force microscopy (AFM) findings.

Conclusions:

• AF4-MALLS is a powerful tool for analyzing complex protein oligomeric dynamics.
• This technique enables detailed characterization of SP-D association states in solution.
• Understanding SP-D oligomerization is crucial for its therapeutic applications.