Title

Ion Mobility – Mass Spectrometry Study of the Redox Activity of Methanobactin Analog Peptides

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemistry

Date of Award

Spring 2016

Abstract

The methanobactin (mb-OB3b) produced by Methylosinus trichosporium OB3b is currently the best characterized example of a chalkophore, a class of low molecular weight copper-binding oligopeptides similar to iron-binding siderophores, and are hypothesized to mediate copper acquisition from the external environment of the methanotrophs. The redox activity and Cu(I) binding of a series of analog methanobactin (amb) peptides with the sequences acetyl-His1-Cys2-Gly3-Pro4-His5-Cys6 (Mw=694.81Da, amb1), acetyl-His1-Cys2-Tyr3-Pro4-His5- Cys6 (Mw=800.93 Da, amb2), acetyl-His1-Cys2-Gly3-Tyr4-Pro5-His6-Cys7 (Mw=857.99 Da, amb3), acetyl-His1-Cys2-Gly3-Ser4-Pro5-His6-Cys7-Ser8 (Mw=1032.15 Da, amb4) and acetylHis1-Cys2-Gly3- Pro4-Tyr5-His6-Cys7 (Mw=858 Da, amb5), were investigated using ion mobility - mass spectrometry (IM-MS). These peptides were studied in binary mixtures to compare their activity. For determining the relation between oxidation of peptide and reduction of metal ion, amb2 was further investigated by pretreating it with H2O2. A time course experiment of 1:1 molar ratio mixture of amb2:Cu(II) each at 25 μM, was performed using 1mM pentaglycine as an internal standard over a time period of 210 min in order to determine whether the redox activity of ambs is time dependent or not. Apart from Cu(II), amb2 was also titrated with Fe(II) to find out if there is a disulfide bond formation upon adding Fe(II) molar eq instead of Cu(II) molar eq. The Cu(II) titration of amb4 from pH 3.0 to 11.0 was studied using IM-MS for further determination of redox activity and Cu(I) binding and later the collision cross sections were measured at pH 4.0, pH 9.0 and pH 10.50.

Advisor

Laurence A. Angel

Subject Categories

Chemistry | Physical Sciences and Mathematics

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