Title

An Ion-Mobility Mass Spectrometry Study of Leucine-Enkephalin (Yggfl) and Ubiquitin Associated with Selected Metal Ions

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemistry

Date of Award

Fall 2011

Abstract

Leucine-enkephalin (YGGFL) is a biologically active neuropeptide in the nociceptive pathway. Its ability to bind to various transition metal ions is determined and compared relatively for two different concentrations of 0.10 mM and 0.010 mM with a metal to peptide concentration ratio of 1:1. It is observed that the different transition metal ions, Cobalt (II), Copper (II), Iron (II), Manganese (II), Nickel (II), and Zinc (II) possess different binding affinities to leucine-enkephalin relatively. But at 90% confidence intervals they were determined to be distinguishable groups with Ni2+ and Mn2+ to be the group with highest relative binding affinity and Cu2+ and Fe2+ to be the group with least binding affinity to YGGFL and Co and Zn2+ were in the middle. The order for K1 and K3 was observed to be Ni2+=Mn2+>Zn2+=Co2+ >Cu2+>Fe2+. Ubiquitin (Ub) is a small 76 residue biological protein with a molecular weight of 8564.47 Da, which plays a key role in regulation of proteins, in the post transitional conjugation of target proteins by ubiquitin proteolysis cycle. Palladium complexes are useful reagents because they bind to the side groups of histidine and methionine and reproducibly cleave the peptide bond. Various charge states of the Pd(II)-Ubiquitin complex spectra were examined for their conformational changes. By Ion mobility-mass spectrometry, it is observed that the Pd(II)-Ub complexes exhibited two distinct conformational forms, in the gas-phase, and these conformations were further investigated using collisional activation to study their relative stability, unfolding and dissociation pathways. All the species exhibited elongated and compact conformations at gentle voltage conditions and elongated conformations at higher voltage conditions. Various species [UbPd2en+5H], [Ub-Pd2en+5H], [Ub-Pden+7H] upon collisional activation, tend to unravel from their compact to elongated conformations and then lose the en (ethylenediamine) ligand, followed by dissociating into product ions.

Advisor

Laurence Angel

Subject Categories

Chemistry | Physical Sciences and Mathematics

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