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Sedimentation velocity analytical ultracentrifugation (SV-AUC) has become the "gold standard" for characterization of the empty, partial, and full capsids of gene therapy products (e.g., AAV and Adenovirus vectors). Other techniques, such as SEC-MALS, TEM, and mass photometry, are commonly used for capsid quantitation, however, the resolving power of these techniques is lacking. In this body of work, SV-AUC was implemented in the characterization of a dual-vector AAV system where the difference in packaged genomes was ∼400 nucleotides. The instrument parameters and SV-AUC analysis were optimized to accurately quantitate both AAV vectors with less than 8% error and with highly correlated linearity (R 2 > 0.99) as compared to ddPCR. The results of this work highlight the resolution and accuracy of dual-vector capsid quantitation by SV-AUC and demonstrate the use of the powerful Bayesian analysis implemented in the SEDFIT analysis software., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: All authors are employees or consultants of BioAnalysis, LLC or Decibel Therapeutics, Inc. (now part of Regeneron). This work was funded by BioAnalysis, LLC and Decibel Therapeutics, Inc., (Copyright © 2024 American Pharmacists Association. Published by Elsevier Inc. All rights reserved.)

AMSH plays a critical role in the ESCRT (endosomal sorting complexes required for transport) machinery, which facilitates the down-regulation and degradation of cell-surface receptors. It displays a high level of specificity toward cleavage of Lys63-linked polyubiquitin chains, the structural basis of which has been understood recently through the crystal structure of a highly related, but ESCRT-independent, protein AMSH-LP (AMSH-like protein). We have determined the X-ray structure of two constructs representing the catalytic domain of AMSH: AMSH244, the JAMM (JAB1/MPN/MOV34)-domain-containing polypeptide segment from residues 244 to 424, and AMSH219(E280A), an active-site mutant, Glu280 to Ala, of the segment from 219 to 424. In addition to confirming the expected zinc coordination in the protein, the structures reveal that the catalytic domains of AMSH and AMSH-LP are nearly identical; however, guanidine-hydrochloride-induced unfolding studies show that the catalytic domain of AMSH is thermodynamically less stable than that of AMSH-LP, indicating that the former is perhaps structurally more plastic. Much to our surprise, in the AMSH219(E280A) structure, the catalytic zinc was still held in place, by the compensatory effect of an aspartate from a nearby loop moving into a position where it could coordinate with the zinc, once again suggesting the plasticity of AMSH. Additionally, a model of AMSH244 bound to Lys63-linked diubiquitin reveals a type of interface for the distal ubiquitin significantly different from that seen in AMSH-LP. Altogether, we believe that our data provide important insight into the structural difference between the two proteins that may translate into the difference in their biological function., (Copyright © 2011 Elsevier Ltd. All rights reserved.)