Okay, I'm going to talk about the molecular basis for hydrodynamic properties of peggulated

proteins.

And so I may not need to say the following, but usually I want to start with why peggulation

or polyethylene glycolic conjugation.

The main answer is therapeutics.

The effect of peggulation on pharmaceuticals has been known for over 20 years, in the fact

that it improves the efficacy of many therapeutic molecules.

Two of the main reasons that it improves the efficacy is decreased serum half-life and

decreased immunogenicity.

But there's another aspect to this peggulation that we're also interested in, and that's

formulation.

So for proteins like monoclonal antibodies, typically those are formulated at 150 milligrams

per mil to minimize the injection volume.

And many proteins do not like to be in solution at this high concentration, they'll precipitate

or aggregate.

And peggulation helps this.

It decreases the aggregation of many proteins, and this is monitored by decreases in viscosity

and decreases in opalescence for formulation.

So we'd like to understand how peggulation will help prevent aggregation in these high

concentrations.

And in general, we'd like to learn more about peggulated proteins because they probably

will become more prevalent in the future.

But it's difficult to study proteins at 150 milligrams per mil.

So a more accessible biophysical question we can ask is, what are the concentration-dependent

properties of proteins in semi-dilute solution, i.e. 1 to 10 milligrams per mil?

And we make the assumption that the properties we discover in semi-dilute concentrations

will predict the properties of the more concentrated solutions.

The properties I'm talking about are those of diffusion and transport that depend on

concentration-dependent nonspecific interaction.

So these are attraction, repulsion, all separations and orientations.

This is a colloidal type interaction.

It's not a biophysical site-specific binding, which I probably don't have to say to this

audience, but I'm a biophysicist and when we think of binding, we think of locking key

So we did a collaborative study on this question that has two arms, an experimental arm and

a theoretical arm.

The experimental arm used analytical ultracentrifugation and dynamic light scattering of peggulated

human serum albumin, which I will call PEG-HSA.

And the people who did the experimental arm are listed here and you will know many or

recognize many of these names.

And they measured the solution properties, solution hydrodynamic properties of a series

of PEG-laden human serum albumins.

Human serum albumin was chosen because it's relatively easily obtained and it's a well-behaved

in solution, so it's a good biophysical protein to study.

On the theoretical side, we did molecular dynamics of PEG-HSA models that were the same

species studied in the experimental side.

We took the trajectories of these simulations and generated conformational ensembles and

then we used each member of the ensemble to calculate solution hydrodynamic properties

using a program called HORAD.

And then by comparing ensembles that gave the same solution properties as the experimental

side, we could interpret the molecular basis for those properties.