SAXS for Biopharmaceuticals & Biosimilars
Small‑angle X‑ray scattering for biosimilar comparability studies and biologic structural characterization — higher-order structure analysis in native solution without crystallization.
If you need solution‑state structural characterization of a biologic — for biosimilar comparability, lot release, or regulatory dossier support — DANNALAB provides analytical data and reports to support your submissions, with cGMP documentation available for validated methods. One of very few labs offering SAXS under GMP for biopharmaceuticals.
SAXS for Biologics Characterization
SAXS (and NMR) are the only laboratory methods capable of probing proteins, peptides and biopolymers in native solution environments — making them uniquely suited to study biologics in conditions that closely mimic their natural biological state.
Most of the useful information identified by SAXS is related to:
- Higher‑order structure of biologics in solution
- Oligomeric state and molecular mass determination
- Aggregation pathways and stability assessment
- Conformational space of flexible systems
An advantage of this method is that it permits the observation of objects that have not been stained or fixed, showing them in their native aqueous environment — in contrast to X‑ray crystallography, which generally requires placing samples in non‑physiological environments.
Reconstruction of Higher‑Order Structure
The atomic structure of biopolymers in a crystalline state is traditionally determined using monocrystal X‑ray diffraction. While this is a powerful and well‑established approach, a drawback is the necessity of a crystallization step. This can be a very challenging task for some pharmaceutically‑important substances, such as membrane proteins.
The structural properties of a biopolymer in a natural biological environment, such as its higher‑order structure, may be investigated using SAXS and often becomes the subject of independent interest. The reason for this is related to the fact that the actual structure of a biopolymer in solution may differ from its crystalline structure due to its conformational flexibility and tendency to form oligomers or aggregates.
SAXS is recognized as the tool of choice for determining the tertiary and quaternary structure of a biopolymer in a close‑to‑natural aqueous environment. Alongside solution NMR and cryo‑microscopy, SAXS is one of the only available methods for visualizing the actual higher‑order structure of a biopolymer in its native environment.
The ab‑initio or model‑based reconstruction of a low‑resolution envelope structure using SAXS may be possible with as little as a 0.25 wt% formulation of the biopolymer in the appropriate buffer.
Example: Immunoglobulin IgG1
Envelope structure reconstructed from solution scattering experiments at 0.25% wt in buffer, validated against high‑resolution crystallographic structure from the Protein Data Bank.
Low Concentration Requirements
Structural determination possible with minimal sample quantities in native buffer conditions.
Native Environment
Observation in physiological conditions without crystallization, staining, or fixation artifacts.
Investigation of Peptides & Flexible Systems
For peptides with a defined 3D structure in dispersion, the methods of ab‑initio reconstruction may be useful for accessing dimensions, oligomeric states and approximate molecular masses.
Together with the envelope structure, useful structural invariants such as radius of gyration (Rg) and excluded volume are also determined.
Peptide Characterization
Example: HIV fusion inhibitor — trimeric structure reconstruction validated against high‑resolution crystallographic data (1AIK entry in PDB).
Flexible Systems & Conformational Analysis
For naturally unfolded proteins, ensemble modeling approaches present the system as a collection of the most probable conformations matching experimental data.
SAXS for Stability Studies
Biological pharmaceutical products are known to be particularly sensitive to environmental factors such as temperature change, oxidation, light and shear. Periodic monitoring of the physico‑chemical properties of an intermediate or finished drug substance is required to prove it meets shelf‑life specifications.
Information about the structural parameters obtained from SAXS measurements, such as envelope shape and invariants (mass and radius of gyration), serve as important markers that are correlated with biological activity.
If changes are identified over time, it is an indication of the potential degradation of the biological drug product.
Structural Monitoring
Track changes in Rg, molecular mass, and envelope shape over time and under stress conditions.
Aggregation Detection
Early detection of aggregation and conformational changes that may affect biological activity.
Environmental Stress Testing
Assessment of sensitivity to temperature, pH, oxidation, and mechanical stress.
DANNALAB SAXS Capabilities for Biologics
Structural Characterization
- Ab‑initio envelope reconstruction
- Oligomerization state determination
- Molecular mass estimation
- Analysis possible with 0.25 wt% concentration
Industrial SAXS with GMP Capability
- cGMP available for selected validated methods
- 21 CFR Part 11 compliant data
- QA‑approved deliverables
- Fast turnaround, committed timelines
Flexible Systems
Ensemble modeling for disordered proteins
Method Development
Fit‑for‑purpose SAXS methods
Temperature Control
In‑situ −10°C to +90°C studies
Native Conditions
No crystallization required
Biosimilar Comparability & Biologic Applications
SAXS provides solution-state structural evidence essential for demonstrating biosimilarity — a key component of the "totality of evidence" required by FDA and EMA for biosimilar approval.
As major biologics lose patent protection, SAXS comparability studies help establish structural equivalence between biosimilar candidates and reference products.
Reference Product Comparison
Side-by-side SAXS analysis of biosimilar candidates against originator products, demonstrating higher-order structural similarity in native solution conditions.
Higher-Order Structure (HOS)
Envelope shape, radius of gyration (Rg), and molecular dimensions as structural fingerprints for biosimilar characterization.
Monoclonal Antibodies
Structural characterization, aggregation monitoring, and stability assessment. Biosimilar categories include adalimumab, trastuzumab, rituximab.
Protein Therapeutics & Enzymes
Higher‑order structure determination for enzymes, hormones, growth factors, and replacement enzymes for rare diseases.
Fusion Proteins
Domain orientation and flexibility analysis for engineered fusion constructs (etanercept, Fc‑fusion biosimilars).
Out-of-Patent Biologics
Structural characterization supporting reformulation and novel delivery approaches for biologics with expired patent protection.
LNP-Based Biologic Delivery
Lipid nanoparticles offer solutions for challenging biologic delivery — protecting proteins and peptides from degradation while enabling targeted delivery and sustained release. DANNALAB provides SAXS characterization of LNP-encapsulated proteins, peptides, and antibody conjugates.
Regulatory Pathway Support
DANNALAB provides SAXS analytical data and reports to support your biopharmaceutical regulatory submissions. We supply characterization results for inclusion in your regulatory packages; cGMP-compliant documentation is available for validated methods — please enquire about your specific application.
FDA Pathways
Structural comparability data supporting your 351(k) biosimilar applications. Higher-order structure characterization results for inclusion in BLA dossiers, lot release, and stability-indicating specifications.
EMA & Post-Approval
Analytical data for biosimilar quality comparability exercises meeting European regulatory expectations. Characterization results supporting comparability protocols for manufacturing site transfers and process changes.
cGMP documentation, 21 CFR Part 11 compliance, and QA-approved certificates are available for selected validated SAXS methods. View accreditations →
Related Services
SAXS Method Information
Detailed technical information about our SAXS methods and capabilities.
Drug Delivery Systems
SAXS characterization of liposomes, LNPs, and other nanoparticulate delivery systems.
cGMP Compliance
Full details on our quality system, certifications, and regulatory compliance.
Discuss Your Biologics Project
Contact our technical team to discuss your biopharmaceutical characterization needs, request a quote, or get expert advice on SAXS method development.