Gas phase infrared spectra of nonaromatic amino acids

We present the first gas phase Fourier transform infrared (FTIR) spectra of the uncapped (natural) amino acids glycine, alanine, threonine, cysteine, methionine and capped methionine by using a fast thermal heating technique up to around 520 K to vaporize them. The experimental spectra taken in the range 700–4000 cm−1 show no sign of decomposition and are in good agreement with ab initio calculated frequencies and intensities of the non-zwitterionic form of the amino acids.