Understanding the tertiary structure of peptides is fundamental in the field of biopharmaceuticals, as it directly impacts their functional properties, including binding affinity, stability, and pharmacological activity. For peptide-based drugs like liraglutide, an antidiabetic agent used in the treatment of Type 2 diabetes and obesity, the three-dimensional arrangement of the molecule influences both its interaction with receptors and its overall therapeutic efficacy. Therefore, structural characterization, particularly the tertiary structure, is critical in both drug development and quality control.
Liraglutide is a glucagon-like peptide-1 (GLP-1) analogue, and its tertiary structure allows it to mimic natural human GLP-1 while exhibiting prolonged stability in the bloodstream. Techniques such as Small-Angle X-ray Scattering (SAXS) offer valuable insights into the low-resolution structure of peptides and proteins in solution. SAXS can be used to obtain parameters such as the radius of gyration (Rg), which is indicative of the overall compactness of the peptide, and the Pair Distribution Function (PDDF), which provides a more detailed structural fingerprint of the peptide’s spatial arrangement.
This application note presents SAXS data obtained at room temperature for a liraglutide formulation of 6mg/ml using a laboratory SAXS instrument at DANNALAB.
The Pair Distribution Function (PDDF) was derived from the SAXS intensity profile using indirect Fourier transformation, providing detailed insights into the spatial distribution of atom pairs within the liraglutide molecule. The calculated Rg from this laboratory-based SAXS instrument was found to be approximately 2.09±0.2 nm, a key parameter reflecting the overall size, oligomeric state, and compactness of the peptide structure in solution. Comparison of the DANNALAB SAXS data with the synchrotron data [1] shows a high degree of similarity in the overall shape of the PDDF function and the Rg value.
The determination of tertiary structural parameters, such as the radius of gyration and the spatial distribution of atoms, helps assess how the liraglutide molecule folds and interacts in solution. Since the tertiary structure plays a pivotal role in the peptide's pharmaceutical function, these data are important in guiding the formulation, stability studies, and regulatory approval processes for this type of peptides. This capability of laboratory SAXS instruments provides a cost-effective and accessible means to support biopharmaceutical development, offering crucial insights into the structural properties of peptide-based drugs.
