Search for: All records

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series of studies of structurally related heptapeptides where one or two of the potential His or Cys binding sites have been replaced by Gly, or the C‐terminus has been blocked by amidation.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.

 

Chemical dynamics simulations are performed to study the collision induced gas phase unimolecular fragmentation of a model peptide with the sequence acetyl-His 1 -Cys 2 -Gly 3 -Pro 4 -Tyr 5 -His 6 -Cys 7 (analogue methanobactin peptide-5, amb 5 ) and in particular to explore the role of zinc binding in reactivity. Fragmentation pathways, their mechanisms, and collision energy transfer are discussed. The probability distributions of the pathways are compared with the results of the experimental IM-MS, MS/MS spectrum and previous thermal simulations. Collisional activation gives both statistical and non-statistical fragmentation pathways with non-statistical shattering mechanisms accounting for a relevant percentage of reactive trajectories, becoming dominant at higher energies. The tetra-coordination of zinc changes qualitative and quantitative fragmentation, in particular the shattering. The collision energy threshold for the shattering mechanism was found to be 118.9 kcal mol −1 which is substantially higher than the statistical Arrhenius activation barrier of 35.8 kcal mol −1 identified previously during thermal simulations. This difference can be attributed to the tetra-coordinated zinc complex that hinders the availability of the sidechains to undergo direct collision with the Ar projectile.