Having tested his techniques by studying proteins, this 'first look' indicates that there are a wealth of fascinating spectra waiting to be revealed by Dr Paul Donaldson's new methods, opening up more possibilities for analysing the inner workings and processes of many important applications from catalysts and batteries, to biomolecular structure and dynamics, to nanoscience. Paul's new techniques aim to help the vibrational spectroscopy community advance their research.
Illuminating a sample of molecules with visible or infrared light can reveal the vibrational frequencies of the different chemical bonds in the sample. From such "vibrational spectra," an abundance of useful molecular information about the molecules in the sample can be obtained. For example, you can find out what they are, whether they are in a "crowd", how the "crowd" is arranged, and how much the crowd is jostling each other. Molecules are complex little things, and interpreting vibrational spectra is not always straightforward. Measuring "multidimensional" vibrational spectra can help – this is achieved by focussing multiple pulses of light one-thousandth of a nanosecond or less into the sample.
In his paper published in the Royal Society of Chemistry journal Chemical Science, Paul has applied new 2D-IR-Raman spectroscopy approaches to study the amide I band - a molecular vibration unique to proteins; the molecular machines of life. The vibrational frequencies of the amide I band vary depending on whether the protein is coiled or arranged in sheets. Using CLF-Ultra's comprehensive mid-IR ultrafast laser capabilities; femtosecond lasers, picosecond lasers and mid-IR pulse shaping, Paul collected 2D-IR-Raman spectra of the amide I band for proteins in sheet and coil form. The results were remarkably distinct, which alludes to the previously mentioned notion that there are many more fascinating spectra waiting to be revealed by the new techniques.
Paul stated that the Ultra lab at the Central Laser Facility has been instrumental in helping him develop his new spectroscopic techniques: “When I first arrived at the CLF as a staff scientist, I realised that state-of-the-art CLF lasers at CLF-Ultra could provide the chance to bring my daydream to life and some more!"
When recalling the development of his new approaches to measure multidimensional spectra Paul said,
"By last summer I probably had a thousand spectra, but the whole project still felt like a house of cards. The more I looked at the spectra I was collecting, the less I understood. I tore up 5 versions of manuscripts over the last two years, each time starting again. By 2019 I had actually collected enough data to finally figure out how to explain what was going on. I finally realized the correct way of looking at the complex 5 dimensional datasets. I was then in the situation that instead of being confused by all the weird patterns, they started to make sense, which brings me to my Chemical Science paper - where the methods give fantastic spectra of the vibration of proteins - the molecules of life, and show beautifully the basic structures they comprise."
Read the paper here: https://doi.org/10.1039/D0SC02978E.