#### # of People per State

To help you get a better idea of how to measure Intrinsic Viscosity, picture the United States. Let's say that the west coast has four times the population as the east coast. This would be referencing the number of people per state. (Grace, double check to make sure the analogy is correct - this seems a bit weak).

#### # of Proteins Per Volume

Similar to the explanation of the population in the United States, you can apply the same idea to a protein formulation. Intrinsic Viscosity would be measuring the number of proteins per volume.

## How Do You Calculate Intrinsic Viscosity?

Taking absolute viscosity values, we can use the Huggins and Kraemer equations:

ηr = Relative Viscosity
C = Concentration
KH = Huggins Constant (Interaction between molecules)

Also calculated:

The benefit of using Intrinsic Viscosity values includes the Kraemer equation. This equation is often paired with the Huggins equation and combined, they are known as the 'Huggins and Kraemer Equation.'

When calculating Intrinsic Viscosity, you will be able to use the Kraemer equation to confirm that your intrinsic viscosity values are correct.

## What is the Benefit of Intrinsic Viscosity?

Using Intrinsic Viscosity has been proven to be more reliable in comparison to alternative methods where potential particulate impurities, inaccurate measurements can appear minor initially, but can lead to long term drastic harm to drug formulations.

In an industry where optimizing formulations while greatly reducing the timeline (edit this to include the text of how it will shorten the drug cycle), accuracy and precision is imperative in all Upstream and Downstream processes.

## Same Size Proteins Can Display Varied Viscosity

There are proteins that have a similar molecular (?) size. But the change in viscosity as concentration increases can be a different story. For example, Monoclonal Antibodies (mAb) and Gamma Globulin have been known to have similar size. However when increasing in concentration, the viscosity of each display a huge difference.

 Monoclonal Antibodies Gamma Globulin [η], mL/mg 0.00594 0.00629 kH 5.144 1.725 Rh, nm ~ 5.3 5.4

As the graph displays, the viscosity of therapeutic Monoclonal Antibodies (mAb) increase much faster with concentration. The kis much larger which suggests that protein to protein interaction is stronger.

 PBS 30 mg/mL BSA in PBS 4 wt% Sucrose in PBS [η], mL/mg 0.00633 0.00668 0.00579 Rh, nm 5.41 5.51 5.26 kH 1.76 2.02 2.43

As the graph displays, gamma globulin molecules interact more differently depending on media, PBS, and 30 mg/mL BSA/PBS. The size and inter-molecular interactions are larger in 30 mg/mL BSA  in PBS Solution. 4% Sucrose in PBS provides compacter size of proteins.

All data above has been collected by VROC initium, RheoSense's fully automated, high throuput viscometer. Fully automatic – 40 vial rack or 96 well plate

• 18 μL for Measurements
• Sample Retrieval - Rate sweep and Temp Sweeps
• High Repeatability ~ 0.5% of Reading