From the Lab: Measuring Protein Size Just Got Easier
Lysozyme is the "gold standard" reference in spectroscopy—the go-to test protein for any new laboratory method. It is also the go-to-test for our Optical-DOSY.
When it comes to measure the diffusion coefficient (=size) of small proteins like Lysozyme, we often find ourselves caught between various technical hurdles:
The Size Limit: Like many proteins, Lysozyme is too small for a quick DLS measurement, where ambient dust particles can scatter more light than the protein itself, masking the true signal.
The Sensitivity Limit: It is on the “large” side for standard NMR-DOSY, where resolution and sensitivity become major bottlenecks for big biomolecules.
The Buffer Trap: In standard PBS and deuterated solvent, Lysozyme is prone to aggregation or altered diffusion behavior at high concentrations.
Our goal was simple: to measure the size of Lysozyme in its truly native state—in 100% water—at low concentration, leveraging its intrinsic absorbance at 280 nm.
On Friday afternoon, we put our new UV/Vis-DOSY cuvette to the test. Within just two hours of sample preparation, we achieved a preliminary diffusion coefficient of around 9.5 10-7 cm2/s.
This corresponds to a hydrodynamic radius (Rh) of ~2.2 nm—a result that aligns well with the literature.
This measurement represents more than just a successful test experiment; it validates a workflow that removes the traditional "Solvent Tax" and "Preparation Friction" from the lab:
No Need for Expensive Prep: In particular, no need for expensive deuterated solvents or labelling probes.
Dust Immunity: Our optical absorption approach avoids the particulate scatter.
Low Concentration Success: Using the 280 nm Tryptophan/Tyrosine peak allows at low concentration.
We still have a road ahead of us, but we couldn’t start the week in a better way. We are taking significant steps toward a future where measuring diffusion is as simple as using your own UV/Vis spectrometer.