biostudies-literatureChao HCNational Institute of General Medical SciencesNIGMS NIH HHS704-713https://www.ebi.ac.uk/biostudies/studies/S-EPMC9648535biostudies-literatureUnknown33(4)A hallmark of electrospray ionization (ESI) of large polymeric molecules is its tendency to generate charge state distributions. When a distribution of polymers is subjected to ESI, the charge state distribution of each component can lead to a mass spectrum composed of a highly congested mixture of ions with overlapping mass-to-charge (<i>m</i>/<i>z</i>) ratios. When the polymers are composed of a common monomeric unit (i.e., a homopolymer), the overlap of the charge state distributions of the polymer components can give rise to striking spectral patterns with a dense central cluster of peaks having similar <i>m</i>/<i>z</i> values and wing-like patterns on either side. We refer to the central cluster of peaks as an "Emerald City," with a nod to the Wizard of Oz, combining the wings as an Journal of the American Society for Mass SpectrometryCharacterization of Homopolymer Distributions via Direct Infusion ESI-MS/MS using Wide Mass-to-Charge Windows and Gas-Phase Ion/Ion Reactions.PMC9648535R37 GM045372R37-GM45372McLuckey SAChao HCShih MLee KWfalseCharacterization of Homopolymer Distributions via Direct Infusion ESI-MS/MS using Wide Mass-to-Charge Windows and Gas-Phase Ion/Ion Reactions.A hallmark of electrospray ionization (ESI) of large polymeric molecules is its tendency to generate charge state distributions. When a distribution of polymers is subjected to ESI, the charge state distribution of each component can lead to a mass spectrum composed of a highly congested mixture of ions with overlapping mass-to-charge (<i>m</i>/<i>z</i>) ratios. When the polymers are composed of a common monomeric unit (i.e., a homopolymer), the overlap of the charge state distributions of the polymer components can give rise to striking spectral patterns with a dense central cluster of peaks having similar <i>m</i>/<i>z</i> values and wing-like patterns on either side. We refer to the central cluster of peaks as an "Emerald City," with a nod to the Wizard of Oz, combining the wings as an 2022-01-01T00:00:00Z2022 Apr2025-04-05T11:27:37.272Z2025-04-05T11:27:37.272ZS-EPMC96485353520177010.1021/jasms.2c00001