Browsing by Subject "CRYSTAL-STRUCTURE"
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Item Open Access Initiation of HIV neutralizing B cell lineages with sequential envelope immunizations.(Nature communications, 2017-11-23) Williams, Wilton B; Zhang, Jinsong; Jiang, Chuancang; Nicely, Nathan I; Fera, Daniela; Luo, Kan; Moody, M Anthony; Liao, Hua-Xin; Alam, S Munir; Kepler, Thomas B; Ramesh, Akshaya; Wiehe, Kevin; Holland, James A; Bradley, Todd; Vandergrift, Nathan; Saunders, Kevin O; Parks, Robert; Foulger, Andrew; Xia, Shi-Mao; Bonsignori, Mattia; Montefiori, David C; Louder, Mark; Eaton, Amanda; Santra, Sampa; Scearce, Richard; Sutherland, Laura; Newman, Amanda; Bouton-Verville, Hilary; Bowman, Cindy; Bomze, Howard; Gao, Feng; Marshall, Dawn J; Whitesides, John F; Nie, Xiaoyan; Kelsoe, Garnett; Reed, Steven G; Fox, Christopher B; Clary, Kim; Koutsoukos, Marguerite; Franco, David; Mascola, John R; Harrison, Stephen C; Haynes, Barton F; Verkoczy, LaurentA strategy for HIV-1 vaccine development is to define envelope (Env) evolution of broadly neutralizing antibodies (bnAbs) in infection and to recreate those events by vaccination. Here, we report host tolerance mechanisms that limit the development of CD4-binding site (CD4bs), HCDR3-binder bnAbs via sequential HIV-1 Env vaccination. Vaccine-induced macaque CD4bs antibodies neutralize 7% of HIV-1 strains, recognize open Env trimers, and accumulate relatively modest somatic mutations. In naive CD4bs, unmutated common ancestor knock-in mice Env+B cell clones develop anergy and partial deletion at the transitional to mature B cell stage, but become Env- upon receptor editing. In comparison with repetitive Env immunizations, sequential Env administration rescue anergic Env+ (non-edited) precursor B cells. Thus, stepwise immunization initiates CD4bs-bnAb responses, but immune tolerance mechanisms restrict their development, suggesting that sequential immunogen-based vaccine regimens will likely need to incorporate strategies to expand bnAb precursor pools.Item Open Access Structural Tolerance Factor Approach to Defect-Resistant I2-II-IV-X4 Semiconductor Design(Chemistry of Materials, 2020-02-25) Sun, JP; McKeown Wessler, GC; Wang, T; Zhu, T; Blum, V; Mitzi, DBCopyright © 2020 American Chemical Society. Recent work on quaternary semiconductors Cu2BaSn(S,Se)4 and Ag2BaSnSe4 for photovoltaic and thermoelectric applications, respectively, has shown the promise of exploring the broader family of defect-resistant I2-II-IV-X4 materials (where I, II, and IV refer to the formal oxidation state of the metal cations and X is a chalcogen anion) with tetrahedrally coordinated I/IV cations and larger II cations (i.e., Sr, Ba, Pb, and Eu) for optoelectronic and energy-related applications. Chemical dissimilarity among the II and I/IV atoms represents an important design motivation because it presents a barrier to antisite formation, which otherwise may act as electronically harmful defects. We herein show how all 31 experimentally reported I2-II-IV-X4 examples (with large II cations and tetrahedrally coordinated smaller I/IV cations), which form within five crystal structure types, are structurally linked. Based on these structural similarities, we derive a set of tolerance factors that serve as descriptors for phase stability within this family. Despite common usage in the well-studied perovskite system, Shannon ionic radii are found to be insufficient for predicting metal-chalcogen bond lengths, pointing to the need for experimentally derived correction factors as part of an empirically driven learning approach to structure prediction. We use the tolerance factors as a predictive tool and demonstrate that four new I2-II-IV-X4 compounds, Ag2BaSiS4, Ag2PbSiS4, Cu2PbGeS4, and Cu2SrSiS4, can be synthesized in correctly predicted phases. One of these compounds, Ag2PbSiS4, shows potentially promising optoelectronic properties for photovoltaic applications.