Size-selected 2, 5, and 10 nm gold nanoparticles for laser desorption/ionization mass spectrometry

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Title: Size-selected 2, 5, and 10 nm gold nanoparticles for laser desorption/ionization mass spectrometry
Author: Stumpo, Katherine Anne
Abstract: The analytical utility of gold nanoparticles (AuNPs ) for laser desorption /ionization mass spectrometry (LDI -MS ) is examined here . An evaluation of the parameters that affect desorption /ionization show that careful treatments of AuNPs is needed , as subtle changes in the solution environment can result in subsequent changes in the mass spectra . A thorough evaluation of the parameters that affect desorption /ionization of peptides is presented here , and these parameters include : (i ) AuNP -to -analyte ratio , (ii ) AuNP size , (iii ) solvent , (iv ) AuNP surface composition , (v ) pH and buffer effects , (vi ) amino acid sequence , and (vii ) additives such as fructose or glycerol . Specifically , controlling the AuNP -to -analyte ratio , pH , peptide composition , and AuNP size are important parameters for ionization . Additionally , effects of passivating the AuNP surface with halides or oxyanions was investigated . The presence of NaF , NaCl , NaBr , and NH4X (X = F , Cl , Br , I ) were shown to not significantly affect analyte ion abundances , whereas addition of NaI strongly suppressed analyte ion yields . Further physical characterization of the NPs showed that etching had occurred , which suggests that the surface chemistry of the NPs is important for desorption /ionization . Throughout these investigations , questions remain as to what the internal energies of peptides are after the desorption /ionization event , and how energy is deposited . Peptide ion fragmentation is examined under different solution conditions to evaluate the relative internal energies of peptides , and the fragmentation pattern examined for insight into fragmentation mechanisms . The data suggest that radical species are important for fragmentation of peptides when using AuNPs . However , it is likely that multiple processes are actually directing the fragmentation . Finally , based on the data presented in this dissertation , a thermal desorption mechanism of pre -formed ions is proposed . This fundamental research is intended to lay foundations for optimizing the use of nanoparticles in routine LDI -MS analysis as well as giving insight into nanoparticle ionization mechanisms . Since very little work has been done in this area , this dissertation investigates , in detail , many of the subtle characteristics that affect desorption /ionization of biomolecules when using NPs .
URI: http : / /hdl .handle .net /1969 .1 /ETD -TAMU -3127
Date: 2009-05-15

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Size-selected 2, 5, and 10 nm gold nanoparticles for laser desorption/ionization mass spectrometry. Available electronically from http : / /hdl .handle .net /1969 .1 /ETD -TAMU -3127 .

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