Size distributions of polyP preparations used in this study. PolyP was resolved by electrophoresis on 5% polyacrylamide gels with 7M urea (A-B) or on 15% polyacrylamide gels with 7M urea (C) and detected by DAPI-negative staining, or resolved on 15% polyacrylamide gels with 7M urea and detected by toluidine blue staining (D). Lanes containing size-fractionated polyP preparations are labeled by estimated polymer length, while the heterodisperse polyP preparations are labeled polyP type 25, type 45, type 65, type 75⁺, polyP₄₀₀₊, polyP₁₀₀₀₊, “Platelet” (human platelet-derived polyP), “Bact” (S typhimurium polyP), and “Start” (the solubilized “insoluble” polyP preparation that was used as the starting material for obtaining very long-chain polyP). Note that polyP types 25, 45, 65, and 75⁺ refer to the nominal mean polymer lengths (given by the supplier), while the rest of the polyP sizes indicated in this figure were determined either by NMR analyses or were estimated from the sample's migration on analytical PAGE using polyP standards whose mean polymer lengths were determined by NMR (analyses not shown).