The Study of Small Biomolecules using Laser Ablation

The Study of Small Biomolecules using Laser Ablation Fourier Transform Microwave (LAFTMW) Spectrometer in the Gas Phase Ryan G. Bird, David W. Pratt University of Pittsburgh Justin L. Neill, Brooks H. Pate University of Virginia

Motivation • Biology: Structure vs Function • Develop new technique to identify structure of biomolecules • The larger the molecule, the higher the melting point • Develop technique for studying thermally unstable molecules • Previously shown ability to simplify spectra using MODR

Fourier Transform Microwave Spectroscopy MW Pulse MW transition b a FID Spectrum

Narrow Band Spectrometer Arbitrary Waveform Generator MW Synthesizer 240 MHz 2 Gs/s ν 0 - 30 MHz ν 0 30 MHz Flat Mirror 30 MHz Pulse Free Induction Decay Fourier Transform ~30 MHz 500 MHz Digitizer (10 Gs/s)

Laser Ablation Nd: YAG Rotation/Translation Motor

Ablation Nozzle Sample Pellet Solenoid YAG Laser 532 nm Walker, K. A. ; Gerry, M. C. L. Journal of Molecular Spectroscopy 1997, 182, 178. Suenram, R. D. ; Lovas, F. J. ; Fraser, G. T. ; Matsumura, K. The Journal of Chemical Physics 1990, 92, 4724. Lesarri, A. ; Mata, S. ; Lopez, J. C. ; Alonso, J. L. Review of Scientific Instruments 2003, 74, 4799. ~15 mm

Timing Sequence Nozzle Pulse 1000 µs Sample Ablation Laser Pulse ~5 ns Gas Expansion ~500 µs ~ 500 ns Polarization and Detection MW Pulse 1. 75 µs FID Signal Collection 10 µs

1, 3, 5 -Trithiane 30 ← 2 0 100 avg 10 µs FID Lesarri, A. ; Mata, S. ; Blanco, S. ; Lopez, J. C. ; Alonso, J. L. Journal of Chemical Physics 2004, 120, 6191.

Urea 111 ← 000 100 avg 10 µs FID Kretschmer, U. ; Consalvo, D. ; Knaack, A. ; Schade, W. ; Stahl, W. ; Dreizler, H. Molecular Physics 1996, 87, 1159

2 -Hydroxypyridine 303 ← 202 100 avg 10 µs FID Tanjaroon, C. ; Subramanian, R. ; Karunatilaka, C. ; Kukolich, S. G. J. Phys. Chem. A 2004, 108, 9531.

Summary • • Ability to heat molecules using laser ablation Use of laser dye increases ablation efficiency Need to rotate sample to maintain signal Pellet composition has a dramatic effect on signal intensity

Future Work • Continue developing ablation nozzles • Introduce fiber optics for better coupling between laser and pellet • Explore other options for introducing molecules into the gas phase (Electrospray) • Incorporate MODR with ablation nozzle to simplify the spectra of large molecules • Use a chirped-pulse to collect broadband spectra

Future Work (cont) • Work towards larger biomolecules such as nucleic base pairs, peptides, enzyme-substrate complexes • Study base pair mimics such as 2 PY-2 AP dimer

Acknowledgements Pratt Group: Dr. David Pratt Diane Miller Phil Morgan Jessica Thomas Justin Young A. J. Fleisher Casey Clements Pitt Machine Shop: Tom Gasmire Pate Group: Dr. Brooks Pate Justin Neill Dr. Steve Shipman Matt Muckle Tubergen Group: Dr. Michael Tubergen Andrew Conrad