Femtosecond transient absorption of ionised aqueous tyrosine

• Main Author: Lim, Yong Liang
• Other Authors: Loh Zhi Heng
• Format: Final Year Project
• Language: English
• Published: 2018
• Subjects: DRNTU::Science::Chemistry
• Online Access: http://hdl.handle.net/10356/76203
• Institution: Nanyang Technological University

The ionisation process involving tyrosine molecules in this study was performed via photoionisation with freeze-frame capture of the tyrosyl radical dynamics using exquisite time resolution. This allows better appreciation for femtochemistry since few studies have been done to understand the ultrafast dynamics of tyrosine and its radical species on the femtosecond timescale. With this understanding, it could provide for better identification of tyrosine and its intermediate species in other chemical reactions through similar means. Similarly, the methodology applied in this study can be further employed on other similar amino acids like tryptophan and phenylalanine, so as to better understand the vibrational dynamics of such aromatic biomolecules. Coherent ultrafast vibrational wave packets were observed; this was done by ionisation of tyrosine in sodium hydroxide solution (pH 14) via strong-field ionisation and the use of sub- 10 femtoseconds (fs) time-resolved pulses on time-resolved transient-absorption pump-probe spectroscopy. Various vibrational frequencies (19 out of 60) were identified from the Fast Fourier Transformation (FFT) power spectrum; after which 8 out of the 19 frequencies consistently appeared when a second method of data processing in the form of first moment analysis was employed. As an observation, most of them corresponded to vibrations due to the aromatic ring of the side chain based on the vibrational modes identified.