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Proton Affinities and Photoelectron Spectra of Phenylalanine and N-Methyl- and N,N-Dimethylphenylalanine. Correlation of Lone Pair Ionization Energies with Proton Affinities and Implications for N-Methylation as a Method to Effect Site Specific Protonation of Peptides

Campbell, Sherrie and Marzluff, Elaine M. and Rodgers, M. T. and Beauchamp, J. L. and Rempe, Margaret E. and Schwinck, Kimberly F. and Lichtenberger, D. L. (1994) Proton Affinities and Photoelectron Spectra of Phenylalanine and N-Methyl- and N,N-Dimethylphenylalanine. Correlation of Lone Pair Ionization Energies with Proton Affinities and Implications for N-Methylation as a Method to Effect Site Specific Protonation of Peptides. Journal of the American Chemical Society, 116 (12). pp. 5257-5264. ISSN 0002-7863. https://resolver.caltech.edu/CaltechAUTHORS:20180530-140924277

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Abstract

A Fourier transform ion cyclotron resonance (FT-ICR) technique for measuring gas-phase proton affinities is presented which utilizes collisional dissociation of proton-bound clusters by off-resonance translational excitation. A simplified RRKM analysis relates unimolecular dissociation rates to proton affinities. This technique is used to measure values for the proton affinities of phenylalanine and N-methyl- and N,N-dimethylphenylalanine of 220.3, 223.6, and 224.5 kcal/mol, respectively (relative to the proton affinity of NH_3 = 204.0 kcal/mol). The proton affinity measured for phenylalanine is in excellent agreement with reported literature values. The photoelectron spectra of these three molecules are also presented and analyzed. Assignments of bands to specific ionization processes are aided by comparison with model compounds such as methyl-substituted amines and 2-phenylethylamines. These data are employed to examine the correlation of adiabatic nitrogen lone pair ionization energies with gas-phase proton affinities for phenylalanine, N-methylphenylalanine, and N,N-dimethylphenylalanine in comparison to correlations for other amino acids and selected aliphatic amines. Although amine nitrogen methylation increases the potential for localizing charge at the amine terminus of protonated peptides by increasing the gas-phase proton affinity, the present study establishes that the increase is not sufficient to compete with protonation of some of the more basic side chains in peptides.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://dx.doi.org/10.1021/ja00091a033DOIArticle
ORCID:
AuthorORCID
Beauchamp, J. L.0000-0001-8839-4822
Lichtenberger, D. L.0000-0002-9271-0311
Additional Information:© 1994 American Chemical Society. Received October 25, 1993. Revised Manuscript Received March 31, 1994. J.L.B. gratefully acknowledges the Beckman Foundation and Institute for the initial funding and continuing support of the research facilities, and the National Science Foundation for their funding (CHE-9108318). We acknowledge the financial support of S.C. from a NIH-NRSA traineeship in Biotechnology, E.M.M. from a NIH-NRSA Human Genome traineeship and Rainin Fellowship, and M.T.R. from a California Institute of Technology Consortium grant. D.L.L. acknowledges support of the Department of Energy (Division of Chemical Sciences, Office of Basic Energy Sciences, Office of Energy Research; Contract No. DE-FG02-86ER13501), the National Science Foundation for assistance in support for instrumentation (CHE-9300841) and for support of K.F.S. under the REU program (CHE-376800), and the Materials Characterization Program (Arizona).
Funders:
Funding AgencyGrant Number
Arnold and Mabel Beckman FoundationUNSPECIFIED
NSFCHE-9108318
NIH Predoctoral FellowshipUNSPECIFIED
NIH Postdoctoral FellowshipUNSPECIFIED
Caltech Consortium in Chemistry and Chemical EngineeringUNSPECIFIED
Department of Energy (DOE)DE-FG02-86ER13501
NSFCHE-9300841
NSFCHE-376800
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Arthur Amos Noyes Laboratory of Chemical Physics8878
Issue or Number:12
Record Number:CaltechAUTHORS:20180530-140924277
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180530-140924277
Official Citation:Proton Affinities and Photoelectron Spectra of Phenylalanine and N-Methyl- and N,N-Dimethylphenylalanine. Correlation of Lone Pair Ionization Energies with Proton Affinities and Implications for N-Methylation as a Method to Effect Site Specific Protonation of Peptides Sherrie Campbell, Elaine M. Marzluff, M. T. Rodgers, J. L. Beauchamp, Margaret E. Rempe, Kimberly F. Schwinck, and D. L. Lichtenberger Journal of the American Chemical Society 1994 116 (12), 5257-5264 DOI: 10.1021/ja00091a033
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86723
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:01 Jun 2018 21:53
Last Modified:03 Oct 2019 19:47

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