biostudies-literatureKarasawa ANational Institutes of Health, National Institute of General Medical SciencesNIGMS NIH HHS768-777https://www.ebi.ac.uk/biostudies/studies/S-EPMC9634608biostudies-literatureUnknown9(Pt 6)<i>De novo</i> structure determination from single-wavelength anomalous diffraction using native sulfur or phospho-rus in biomolecules (native-SAD) is an appealing method to mitigate the labor-intensive production of heavy-atom derivatives and seleno-methio-nyl substitutions. The native-SAD method is particularly attractive for membrane proteins, which are difficult to produce and often recalcitrant to grow into decent-sized crystals. Native-SAD uses lower-energy X-rays to enhance anomalous signals from sulfur or phospho-rus. However, at lower energies, the scattering and absorption of air contribute to the background noise, reduce the signals and are thus adverse to native-SAD phasing. We have previously demonstrated native-SAD phasing at an energy of 5 keV in air at the NSLS-II FMX beamlIUCrJMulti-crystal native-SAD phasing at 5 keV with a helium environment.PMC9634608107462P30 GM133893116799R01 GM107462P41 GM116799McSweeney SHendrickson WAShi WLiu QAndi BKarasawa AFuchs MRfalseMulti-crystal native-SAD phasing at 5 keV with a helium environment.<i>De novo</i> structure determination from single-wavelength anomalous diffraction using native sulfur or phospho-rus in biomolecules (native-SAD) is an appealing method to mitigate the labor-intensive production of heavy-atom derivatives and seleno-methio-nyl substitutions. The native-SAD method is particularly attractive for membrane proteins, which are difficult to produce and often recalcitrant to grow into decent-sized crystals. Native-SAD uses lower-energy X-rays to enhance anomalous signals from sulfur or phospho-rus. However, at lower energies, the scattering and absorption of air contribute to the background noise, reduce the signals and are thus adverse to native-SAD phasing. We have previously demonstrated native-SAD phasing at an energy of 5 keV in air at the NSLS-II FMX beaml2022-01-01T00:00:00Z2022 Nov2026-05-27T11:16:45.591Z2025-04-05T19:13:23.236ZS-EPMC96346083638114710.1107/S205225252200971X