In the last reporting period we have continued a long-standing collaboration with Dr. David Margulies on the characterization of interactions of proteins constituting the peptide loading complex, specifically the TAPBPR protein and its interactions with MHC class I molecules in the presence of different peptides. Further, we have applied sedimentation velocity analytical ultracentrifugation to characterize TCR/MHC interactions in the context of NMR structural studies of conformational changes upon binding. We have also continued our collaboration with Dr. Patrizia Farci applying surface plasmon resonance biosensing to examine the interaction of anti-core antibodies isolated and cloned from livers of patients HBV-associated acute liver failure with their HBV core antigens, with Dr. Lawrence Samelson on the study of multi-protein interactions in signaling particles after T-cell activation, and with Dr. Dan Sackett on the dissociation of tubulin dimer at low concentration. We have embarked on a new collaboration with the laboratory of Dr. Alan Rein to dissect the early oligomerization stages of HIV-1 Gag protein, and cooperativity induced by binding nucleic acid ligands, with the aim to better understand the energetics and structural changes involved in capsid assembly. The interactions of Gag are highly complex and will provide a stringent test for AUC at different concentration and size ranges. Other new collaborative applications of AUC include studies of coated gold nanoparticles and their interactions with different serum proteins with Dr. Alioscka Souza, the oligomeric state of RS1 protein with Dr. Vijay Camasamudram, and the study of chaperone interactions with the laboratory of Dr. Sue Wickner.