Rotational spectrum of tryptophan

Abstract

The rotational spectrum of the natural amino acid tryptophan has been observed for the first time using a combination of laser ablation, molecular beams, and Fourier transform microwave spectroscopy. Independent analysis of the rotational spectra of individual conformers has conducted to a definitive identification of two different conformers of tryptophan, with one of the observed conformers never reported before. The analysis of the 14 N nuclear quadrupole coupling constants is of particular significance since it allows discrimination between structures, thus providing structural information on the orientation of the amino group. Both observed conformers are stabilized by an O-H · · · N hydrogen bond in the side chain and a N-H · · · π interaction forming a chain that reinforce the strength of hydrogen bonds through cooperative effects.

The Structure of the Elusive Simplest Dipeptide Gly‐Gly

“…Advances in laser ablation techniques have made possible the transfer of bare biomolecules into the gas phase to probe their most stable conformers in the isolated environment of a supersonic expansion by laser ablation molecular beam Fourier transform microwave (LA‐MB‐FTMW) spectroscopy . Although the excellent results achieved in natural amino acids and capped dipeptides have boosted the investigation of Gly‐Gly, the numerous attempts to acquire its rotational spectrum failed owing to the photofragmentation problems inherent to the laser ablation process . In the present investigation, the latest improvements of our laser ablation system were used to minimize photofragmentation effects and have finally led to the first rotational study of the Gly‐Gly dipeptide.…”

“…This nuclear quadrupole coupling interaction couples the nuclear spin and the rotation angular momentum, which makes each rotational line split into a complex pattern. The spectroscopic parameters extracted from this interaction can be used as a structural diagnostic reporters on the hydrogen bonding architecture of the conformations . Several sets of μ a ‐type and μ b ‐type R‐branch rotational transitions were ascribed to three different rotamers of Gly‐Gly, labeled as X, Y, and Z. Rotamer X only showed b ‐type rotational spectrum, while the rotamers Y and Z exhibited both a ‐ and b ‐type spectra.…”

Generation and structural characterization of aluminum cyanoacetylide

“…It has been recently employed in the studies of large biomolecules. 18,19 In this investigation, our conventional ablation nozzle holder 17 has been modified by addition of a home-made heatable reservoir extension, placed between the valve and the laser ablation nozzle. The reservoir can hold liquid and/or solid compounds that can be used as precursors of metal bearing species.…”

Rotational spectrum of phenylglycinol

“…Nowadays, broadband microwave spectroscopic techniques (chirped pulsed Fourier transform microwave spectroscopy -CP-FTMW) [2], coupled with laser ablation, are being used to rapidly acquire the rotational spectra of solid compounds [2][3][4][5] in wide frequency ranges, making the search of different coexisting species in the supersonic jet more effective. On other hand, narrowband LA-MB-FTMW [6], provides the sub-Doppler resolution necessary to analyze the nuclear quadrupole coupling hyperfine structure of the observed species, which is a unique tool for the definitive ascription of the low-energy conformers [7][8][9].…”