Investigation of Protonated Serine Clusters using Infrared Photodissociation Spectroscopy and Fourier Transform Ion Cyclotron Resonance Spectrometry
Date Issued
2006
Date
2006
Author(s)
Tsai, I.-A.
DOI
en-US
Abstract
This thesis depicts an investigation of infrared photodissociation spectra of protonated serine clusters, H+(Ser)n, n=2-8, using a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer coupled with an OPO infrared laser system. Density functional theory calculations performed at B3LYP/6-311++G* level are also presented to assist interpretation of the spectra for H+(Ser)2. This combined investigation provides information on the structure of these ionic clusters in the gas phase.
The content of this thesis is divided into four chapters. Chapter one introduces the serine octamer including the formation of this magic number cluster and the strong preference for homochirality and the possibility of its importance related to the prebiotic chemistry. Chapter two depicts the methods used for both experiment and calculation. Methods and apparatus used in vibrational predissociation spectroscopy, ESI–FT-ICR mass spectrometry, optical parametric oscillator lasers and ab initio calculations are described. Chapter three illustrates results and related discussion. Two dominant peaks corresponding to the free carboxyl O-H stretching at 3565 cm-1 and the free aliphatic hydroxyl O-H stretching at 3673 cm-1, respectively, are observed over the 3500-3750 cm-1 in the infrared photodissociation spectra. For H+(Ser)2,The spectral fingerprints of the transition are the observed intensity ratio of these two bands is 1.2:1, indicating an equal number of –COOH and –CH2OH groups in this binary complex with a neutral structure. The 3565 cm-1 band, on the other hand, progressively decreases in intensity with increasing n and it disappears completely at n = 8, suggesting that the protonated serine octamer is dominated by zwitterionic structures.
Chapter four gives a conclusion. It is concluded that the infrared photodissociation spectroscopy of protonated serine clusters H+(Ser)n, n = 2 – 8, provides evidence for a size-dependent transition from neutral to zwitterionic network structures.
Subjects
質子化絲胺酸團簇
兩性離子結構
紅外解離光譜
傅立葉轉換離子迴旋共振質譜儀
protonated serine clusters
zwitterionic structure
infrared photodissociation spectroscopy
Fourier transform mass spectrometry
density functional theory calculation
Type
thesis
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