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To become specialized binders, antibodies undergo a process called affinity maturation to maximize their binding affinity. Despite this process, some antibodies retain low-affinity binding to diverse epitopes in a phenomenon called polyreactivity. Here we seek to understand the molecular basis of this polyreactivity in antibodies. Our results highlight that polyreactive antigen-binding fragments (Fabs) bind their targets with low affinities, comparable to T cell receptor recognition of autologous classical major histocompatibility complex. Extensive mutagenic studies find no singular amino acid residue or biochemical property responsible for polyreactive interaction, suggesting that polyreactive antibodies use multiple strategies for engagement. Finally, our crystal structures and all-atom molecular dynamics simulations of polyreactive Fabs show increased rigidity compared to their monoreactive relatives, forming a neutral and accessible platform for diverse antigens to bind. Together, these data support a cooperative strategy of rigid neutrality in establishing the polyreactive status of an antibody molecule. [Display omitted] • Polyreactive antibodies show increased rigidity and neutrality in their binding surfaces • Polyreactive antibodies engage with low affinities akin to autologous TCR-MHC interactions Binding promiscuity is an inherent property of immune recognition, manifested in antibodies as polyreactivity. Borowska et al. dissect this phenomenon at the molecular level and show that the binding surfaces of polyreactive antibodies use increased rigidity and neutrality in ligand engagement. This provides a key mechanism for understanding polyreactivity in antibodies. [ABSTRACT FROM AUTHOR]

Generating monoclonal antibodies from single B cells is a valuable tool for characterizing the specificity and functional properties of humoral responses. We and others developed protocols that have facilitated major advances in our understanding of B cell development, tolerance, and effector responses to HIV and influenza. Here, we demonstrate various refinements and dramatically reduce the time required to produce recombinant antibodies. Further, we present new methods for cloning and isolating antibodies from cells with lower immunoglobulin mRNA levels that may be resistant to traditional techniques. Together, these refinements significantly increase single-cell antibody expression efficiency and are easily integrated into established and novel pipelines. [ABSTRACT FROM AUTHOR]

Abstract: A scalable four-step synthesis of the ornithine transcarbamylase inhibitor N 5-phosphonoacetyl-l-ornithine (PALO) is achieved through boroxazolidinone protection of ornithine. Investigations in the model organism Saccharomyces cerevisiae found that, in contrast to a previous report, PALO did not influence growth rate or expression of genes involved in arginine metabolism. [Copyright &y& Elsevier]