Sandia Labs FY21 LDRD Annual Report


Saliva mimicking medium for use in viral studies. The global outbreak of SARS-CoV-2 has emphasized the need for a deeper understanding of infectivity, spread, and treatment of airborne viruses. With convergently evolved structural similarities to viral pathogens, tailless phages are an ideal surrogate for studying respiratory pathogenic viruses. Phages are highly tractable, allowing investigations to proceed quickly and at the lowest biosafety level. However, the aerosolization of enveloped SARS-CoV-2 surrogate phi6 usually results in a ~3 log 10 reduction in viability, limiting its usefulness as a surrogate for aerosolized coronavirus in “real world” contexts. Recent work has shown that saliva or artificial saliva greatly improves the stability of viruses in aerosols and microdroplets relative to standard dilution/storage buffers, like an SM buffer. The LDRD team investigated whether media could be formulated that preserves the viability of airborne phi6. A supplement has been identified that dose-dependently stabilizes phi6 to nearly zero losses in the aerosol testbed and outperforms commercially formulated artificial saliva. These data suggest that the saliva mimetic media may facilitate a lower-cost alternative to artificial saliva for future airborne virus studies. (PIs: Bryce Ricken and Jesse Cahill) New approach for fundamental mechanism discovery in polymer upcycling. A deep mechanistic understanding of complex multi-phase processes is critical to rational, physics-based co-design of advanced new polymers, catalysts, and depolymerization/repolymerization chemistries. This LDRD project investigated the use of detailed chemical analysis of the gas flow above a reacting catalyst to provide insight into catalytic depolymerization reactions. Gas-phase chemical species were detected by vacuum-ultraviolet (VUV) photoionization mass spectrometry (PIMS)—a high-throughput method that can distinguish among chemical isomers with the same molecular formula and is equally sensitive to stable products and short-lived reactive radicals. In the first of two proof-of-principle demonstrations, the team quantified methyl radical intermediates and observed selective C-C bond activation in small aliphatic hydrocarbons, which are model oligomers of polyethylene plastics. In the second demonstration, researchers revealed the dominance of singly-unsaturated, methylated alkene products in the deconstruction of high-density polyethylene (HDPE). This work, performed in collaboration with Johns Hopkins and UC-Davis researchers, opens the door to detailed mechanistic studies of depolymerization and shows the power of cutting-edge gas-phase analysis tools to investigate complex multi-phase processes. (PI: Leonid Sheps)

Synchrotron-VUV PIMS analysis of gas flow over a solid catalyst/ polymer yields detailed isomer-resolved product distribution in the deconstruction of HDPE.



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