Ultracentrifugation biases plasma binding assays for peptides above 2000 Da

The wire

1. 01A Journal of Pharmaceutical Sciences study found molecular weight drives vertical concentration gradients after ultracentrifugation, with peptides above roughly 2000 Da showing greater than two-fold differences across the supernatant.
2. 02Unbound fraction values underpin dose and exposure modeling for therapeutic peptides, so biased sampling can distort protein binding data used in development programs.
3. 03The authors recommend collecting aliquots from a strictly defined mid-region of the tube; the work is a laboratory methods study and does not report clinical consequences.

From the source

The effect of sedimentation on the unbound fraction of therapeutic peptides in plasma determined using ultra-centrifugation method

Journal of pharmaceutical sciences · 2026 Oct 6 · Huang J, Yu Q, Ni J et al.