Rotational Spectrum Of Tryptophan

Abstract

The rotational spectrum of the natural amino acid tryptophan has been observed using a recently constructed LA-MB-FTMW spectrometer, specifically designed to optimize the detection of heavier molecules at a lower frequency range. Independent analyses of the rotational spectra of individual conformers have conducted to a definitive identification of two different conformers of tryptophan, with one of the observed conformers never reported before. The experimental values of the $^{14}$N nuclear quadrupole coupling constants have been found capital in the discrimination of the conformers. Both observed conformers are stabilized by a O-H$\cdots$N hydrogen bond in the side chain and a N–H$\cdots$$\pi$ interaction forming a chain that reinforces the strength of hydrogen bonds through cooperative effects.