Evan Neidholdt
36 Noyes, x6543 (626-395-6543); 227 BI, x2778 (626-395-2778)
Email: eln@caltech.edu

B.A., 2005, Concordia University Irvine, Chemistry and Mathematics

Ph.D. Candidate, Caltech

Download/view Resume: (Update 10-21-09)
Resume, .pdf

Evan developed the Ambient Pressure Pyroelectric Ion Source for Mass Spectrometry. (Neidholdt, E.L.; Beauchamp, J.L. Anal. Chem. 2007, 79, 3945-3948). Abbreviated APPIS, It is a novel ionization source with promising characteristics. It differs from traditional ion sources in its simplicity and robust design. The source comprises a z-cut pyroelectric crystal (lithium niobate or lithium tantalate) with an attached resistive heating element. Thermally cycling the crystal by as little as 30 K from ambient gives rise to tremendous electrical potentials on the z- faces of the crystal. The source has been shown capable of ionizing acidic and basic species by deprotonation or protonation (respectively). We have determined the ionization mechanism to involve ambient pressure chemical ionization near the crystal surface involving ambient gases near the crystal (Neidholdt, E.L.; Beauchamp, J.L. J. Am. Soc. Mass Spec. Submitted for publication, 2008). The source consumes very little power, and is particularly durable, making it suitable for a number of harsh environments.

Another part of Evan's work involves studies of non-covalently bound gas phase clusters, specifically clusters of benzoic acid with the divalent metals Mg(II), Ca(II), Sr(II), Ba(II), Zn(II), Mn(II), and Pb(II). Through decarbonylation of benzoate anion, phenide anion (C6H5-) is obtained. Of particular interest are reactions of organomagesium complexes such as phenylmagnesium, as similar species have been shown to be reactive in the gas phase.

Lastly, Evan is involved in the continuation of the Free Radical Initiated Peptide Sequencing (FRIPS) project initiated by former group members Heather Cox and Rob Hodyss. This project examines the suitability for use in proteomics of certain commercially available free radical initiators. These radical initiators cleave peptides differently than tryptic digests or Edman degradation, and show the potential for a tunable peptide sequencing tool.  A series of model peptides, with the general formula AARAAAXAA where X is any one of the 20 amino acids, has been investigated using the FRIPS methodology.  Distinct reactivity classes emerge, allowing for the customization of reaction via these free radical reactions. 

Beauchamp Research Group
Noyes Laboratory of Chemical Physics and the Beckman Institute
Pasadena, California 91125