Only one matching reference was found.
Campbell, S.; Marzluff, E.M.; Rodgers, M.T.; Beauchamp, J.L.; Rempe, M.E.; Schwinck, K.F.; Lichtenberger, D.L., 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, J. Am. Chem. Soc., 1994, 116, 5257. [all data]