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See when aggregation is a risk

Dynamic light scattering

Dynamic light scattering (DLS) is a highly sensitive technique to check the expected size and polydispersity of proteins or other macromolecules in solution. The polydispersity index (PDI) indicates the level of heterogeneity of particle diameters in the sample. Non-uniform particle sizes in solution give a high PDI, while uniform particle sizes yield a low PDI. When samples get stressed out by the wrong formulation, storage conditions, or a thermal ramp you can watch size and PDI increase as your sample has issues. DLS helps uncover the presence of aggregates or contaminants in your sample that would be missed by UV/Vis detection or other quantification methods alone.

kD, B22, and G22

Weak, nonspecific interactions between protein molecules can have a large impact on colloidal stability and aggregation during the development of protein-based drugs. When you need to take a peek at the protein-protein interactions that may lead to aggregation, kD, B22, and G22 all give rapid insight at how your molecules behave when they get crowded. kD, or the diffusion interaction parameter, is a holistic look at how proteins behave in a formulation when concentration increases and things start to get crowded. B22 is the second virial coefficient and looks at protein-protein interactions without a few of the thermodynamic and hydrodynamic factors included in kD.

At high protein concentrations, short-range intermolecular interactions become more prominent and can increase the risk of protein aggregation. For these conditions, the Kirkwood-Buff Integral (G22) serves as the best measure of colloidal stability because it accounts for protein crowding effects that give rise to strongly attractive or repulsive interactions. G22 pulls back the curtain to show if concentration will create more aggregation problems for your proteins. The more negative your results are, the more repulsive the protein is.


For a hi-def look into aggregation, thermodynamics can show whether aggregation is likely and what path proteins will take when aggregating. ΔG is a quantitative stability measurement that describes the ratio of folded to unfolded protein present in a given sample. A protein’s resistance to chemical denaturation can tell you its ΔG. Measure that over multiple concentrations to see what aggregation pathway is thermodynamically favored. If your ΔG stays constant, breathe easy.


Uncle is the one-stop stability platform for biologics. It combines 3 different measurement modes — fluorescence, SLS and DLS — for a whopping total of 12 stability applications on one system. So you can crank out aggregation data with DLS, then stress out your proteins with a heat ramp to look at conformational stability. All the info you’ll get from Uncle makes picking the best formulation, protein, or viral vector a piece of cake.


Stunner is the only system out there that takes Dynamic Light Scattering (DLS) size measurements and UV/Vis concentration from the same sample at the same time. Get a grip on what storage, agitation or a change to your process or formulation does to your protein. See if there’s any aggregation, measure the hydrodynamic size, grab polydispersity when you need to check uniformity, and get the exact concentration while you’re at it.

UV/Vis and DLS also combine to uniquely measure colloidal stability of your samples with kD or B22 data. Instead of making assumptions, Stunner takes an accurate read on concentration for every data point and combines that with DLS data to show how your protein is interacting with itself in solution.


If DLS is all you need then Punk is your go-to. All it takes is a quick check on 5 µL of sample to see if you’ve got stuff you don’t want — like protein aggregation. The Punk whips out info on sample size distribution and if your protein’s started to aggregate or not in about 30 seconds.



Hunky is the only automated platform for quantifying biologic stability and aggregation pathways with ΔG. Learn, on day one, which protein construct in which formulation has the lowest thermodynamic propensity to aggregate. Quantify your protein’s stability and know if it’s going to aggregate now, not later.