Shedding Light on History
Research in the de Vries Group involves a powerful combination of Laser Spectroscopy and Mass Spectrometry by employing laser induced desorption of molecules from surfaces, photo-ionization, multiphoton spectroscopy, nanosecond/picosecond/femtosecond spectroscopy and mass spectrometry on a wide variety of projects.
Gas phase techniques enable the study of isolated molecules, free of interactions. A major thrust is the laser spectroscopy of isolated biomolecular building blocks, and more specifically the excite state dynamics of DNA. These include single DNA bases and amino acids, as well as their clusters with each other and with water molecules. We investigate the general hypothesis that photostability to UV radiation was a primary mechanism in the prebiotic selection of life's building blocks. Notice how the canonical bases all have excited state lifetimes on the picosecond timescale and less, while alternative bases have lifetimes in excess of nanoseconds!
The de Vries lab has helped develop the use of an atomic force microscope (AFM) to sample material at submicron resolution, well below the optical diffraction limit. The sampled material is later analyzed by a combination of high resolution laser spectroscopy and mass spectrometry. Other analytical methods are currently being explored.
Atomic force microscopy enables much higher spatial resolution but lacks the chemical information that light based techniques can provide. Our new combination of laser MS with the AFM-TD sampling now makes it possible to perform spectroscopic analysis with submicron spatial resolution. We have shown that this approach allows R2PI analysis on small samples such as painting cross-sections typically found in cultural heritage.
In collaboration with the Getty Conservation Institute, we identify organic paint pigments within microscopic layers of artwork. The Microscope Laser Mass Spectrometer allows for unparalleled identification of organic molecules with high spatial resolution.
Additionally, we partner with the Department of Anthropology as well as the MesoAmerican Research Facility to investigate archaeological artifacts in order to identify trace “marker” compounds. These marker compounds include molecules from a variety of sources, including beer, wine and coffee.
IR-R2PI spectroscopy together with quantum calculations identifies shapes of small peptides, isolated in the gas phase.