Improvement of a powerful spectroscopic technique will open up opportunities to study the structure of proteins and nucleic acids, according to researchers in Canada. 

Infrared multiple-photon dissociation (IRMPD) is a powerful spectroscopic technique, allowing the study of mass-selected ions. Travis Fridgen at the Memorial University of Newfoundland and colleagues have modified the technique, using high-intensity radiation that is resonant with a strong absorption of the molecule being studied. This increases the rate of photon absorption.

 

   

 

IRMPD is a soft method of dissociating ions and molecules and usually only the lowest-energy dissociation pathways are observed. Fridgen's method allows access to higher-energy dissociation channels, for some species. 

The intermolecular interactions typically probed by IRMPD are important in understanding solvation, ion structures, and the weak interactions which govern the secondary and tertiary structures of molecules such as proteins and nucleic acids.

 Fridgen has used his technique to obtain the spectra of simple methanol, ethanol and propanol proton-bound dimers. This is only a stepping stone to more complex studies, Fridgen admits. 'It is important to understand these relatively simple species before moving on to more complicated systems such as peptides where amino acids from different parts of the chain can be bound by similar interactions,' he said. 

According to Fridgen, more work needs to be done both to explain the spectra theoretically, and to use the theory to predict infrared spectra. He added, 'Much more experimental work needs to be done on heterogeneous proton-bound dimers and that will be part of the focus of future work.' 

Philip Earis