biostudies-literatureIyer LKNIGMS NIH HHS4629-39https://www.ebi.ac.uk/biostudies/studies/S-EPMC3913734biostudies-literatureUnknown10(12)Local side-chain interactions in lyophilized protein formulations were mapped using solid-state photolytic labeling-mass spectrometry (ssPL-MS). Photoactive amino acid analogues (PAAs) were used as probes and either added to the lyophilized matrix or incorporated within the amino acid sequence of a peptide. In the first approach, apomyoglobin was lyophilized with sucrose and varying concentrations of photoleucine (L-2-amino-4,4'-azipentanoic acid; pLeu). The lyophilized solid was irradiated at 365 nm to initiate photolabeling. The rate and extent of labeling were measured using electrospray ionization/high-performance liquid chromatography/mass spectrometry (ESI-HPLC-MS), with labeling reaching a plateau at ~30 min, forming up to six labeled populations. Bottom-up MS/MS analysis was able tMolecular pharmaceuticsPhotolytic labeling to probe molecular interactions in lyophilized powders.PMC3913734NIH RO1 GM085293R01 GM085293Iyer LKMoorthy BSTopp EMfalsePhotolytic labeling to probe molecular interactions in lyophilized powders.Local side-chain interactions in lyophilized protein formulations were mapped using solid-state photolytic labeling-mass spectrometry (ssPL-MS). Photoactive amino acid analogues (PAAs) were used as probes and either added to the lyophilized matrix or incorporated within the amino acid sequence of a peptide. In the first approach, apomyoglobin was lyophilized with sucrose and varying concentrations of photoleucine (L-2-amino-4,4'-azipentanoic acid; pLeu). The lyophilized solid was irradiated at 365 nm to initiate photolabeling. The rate and extent of labeling were measured using electrospray ionization/high-performance liquid chromatography/mass spectrometry (ESI-HPLC-MS), with labeling reaching a plateau at ~30 min, forming up to six labeled populations. Bottom-up MS/MS analysis was able t2013-01-01T00:00:00Z2013 Dec2026-05-01T20:19:39.297Z2019-03-27T01:21:16ZS-EPMC39137342412517510.1021/mp4004332