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Abstract Gold nanoparticles (AuNPs) synthesized in the 1–3 nm range have a specific number of gold core atoms and outer protecting ligands. They have become one of the “hot topics” in recent decades because of their interesting physical and chemical properties. The characterization of their structures is usually achieved by crystal X‐ray diffraction although the structures of some AuNPs remain unknown because they have not been successfully crystallized. An alternative method for studying the structure of AuNPs is electrospray ionization–ion mobility–tandem mass spectrometry (ESI‐IM‐MSMS). This research evaluated how effectively ESI‐IM‐MSMS using the commercially available Waters Synapt XS instrument yielded useful structural information from two AuNPs; Au₂₃(S‐tBu)₁₆and Au₃₀(S‐tBu)₁₈. The study used the maximum range of available collision energies along with ion mobility separation to measure the energy‐dependence of the product ions and their drift times which is a measure of their spatial size. For Au₂₃(S‐tBu)₁₆, the dissociation gave the masses of the outer protecting monomeric [RS–Au–SR] and trimeric [SR–Au–SR–Au–SR–Au–SR] staples where R = tBu, and complete dissociation of the outer layer Au andtBu groups to reveal the Au₁₅S₈core. For Au₃₀(S‐tBu)₁₈, the dissociation products was primarily through the loss of the partial ligands S‐tBu andtBu from the outer protecting layer and the loss of single Au₄(S‐tBu)₄unit. These results showed the that ESI‐IM‐MSMS analysis of the smaller Au₂₃(S‐tBu)₁₆gave information on all it major structural components whereas for Au₃₀(S‐tBu)₁₈, the overall structural information was limited to the ligands of the outer layer. 

Abstract The analog methanobactin (amb) peptide with the sequence ac‐His₁‐Cys₂‐Gly₃‐Pro₄‐Tyr₅‐His₆‐Cys₇(amb_5A) will bind the metal ions of zinc, nickel, and copper. To further understand how amb_5Abinds these metals, we have undertaken a series of studies of structurally related heptapeptides where one or two of the potential His or Cys binding sites have been replaced by Gly, or the C‐terminus has been blocked by amidation. The studies were designed to compare how these metals bind to these sequences in different pH solutions of pH 4.2 to 10 and utilized native electrospray ionization (ESI) with ion mobility‐mass spectrometry (IM‐MS) which allows for the quantitative analysis of the charged species produced during the reactions. The native ESI conditions were chosen to conserve as much of the solution‐phase behavior of the amb peptides as possible and an analysis of how the IM‐MS results compare with the expected solution‐phase behavior is discussed. The oligopeptides studied here have applications for tag‐based protein purification methods, as therapeutics for diseases caused by elevated metal ion levels or as inhibitors for metal‐protein enzymes such as matrix metalloproteinases.