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                  International Journal of Terahertz Science and Technology
Vol.3, No.4, December 2010. PP.149-200 (5) -- Special Issue on THz-Bio
date£º2010-12-31 00:38:39 Click No.£º9543

TST, Vol. 3, No. 4, PP. 149-162

(Invited Paper) Why is THz Sensitive to Protein Functional States?
Oxidation State of Cytochrome C

Yunfen He1, J.-Y. Chen2, J. R. Knab3, Wenjun Zheng1 and A. G. Markelz1*
Physics Department, University at Buffalo, SUNY, Buffalo, NY 14260
2Washington State University, Pullman, WA
3Technical Univeristy of Delft, Delft, Netherlands

£¨Received July 02, 2010 £©

Abstract: We investigate the presence of structural collective motions on a picosecond time scale for the heme protein, cytochrome c, as a function of oxidation and hydration, using terahertz (THz) time-domain spectroscopy and molecular dynamics simulations. Structural collective mode frequencies have been calculated to lie in this frequency range, and the density of states can be considered a measure of flexibility. A dramatic increase in the THz response occurs with oxidation, with the largest increase for lowest hydrations and highest frequencies.  For both oxidation states the measured THz response rapidly increases with hydration saturating above ~25% (g H2O/g protein), in contrast to the rapid turn-on in dynamics observed at this hydration level for other proteins. Quasi-harmonic collective vibrational modes and dipole-dipole correlation functions are calculated from the molecular dynamics trajectories. The collective mode density of states alone reproduces the measured hydration dependence providing strong evidence of the existence of these collective motions. The large oxidation dependence is reproduced only by the dipole-dipole correlation function, indicating the contrast arises from diffusive motions consistent with structural changes occurring in the vicinity of a buried internal water molecule.

Keywords: Structural collective motions, Terahertz, Molecular dynamics, Heme protein, Cytochrome c

doi: 10.11906/TST.149-162.2010.12.15

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TST, Vol. 3, No. 4, PP. 163-171

(Invited Paper) Practical Considerations for in Vivo THz Imaging

Emma Pickwell-MacPherson
Electronic and Computer Engineering, The Hong Kong University of Science and Technology,
Clearwater Bay, Hong Kong

£¨Received June 28, 2010 £©

Abstract: Terahertz imaging systems have advanced significantly over recent years and now in vivo terahertz imaging is plausible. In this paper we discuss the constraints that need to be considered in designing and implementing a terahertz system for in vivo imaging. We describe the requirements and limitations of system geometry, data acquisition rate, image resolution and penetration depth. Furthermore we explain how various factors are dependent on each other. We show how some of the physical limitations can be overcome using novel data processing.

Keywords:  In vivo, Biomedical imaging, Spectroscopy

doi: 10.11906/TST.163-171.2010.12.16

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TST, Vol. 3, No. 4, PP. 172-182

(Invited Paper) Quantitative Water Content Measurements in Food Wafers Using Terahertz Radiation

P Parasoglou1, E P J Parrott1,2, J A Zeitler1*, J Rasburn3 and H Powell3, L F Gladden1 and M L Johns1
Department of Chemical Engineering and Biotechnology, University of Cambridge, New Museums Site Pembroke Street, Cambridge, CB2 3RA, UK
2Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE
3Nestec York Ltd., Nestl¨¦ Product Technology Centre, Haxby Road, PO Box 204, York. YO91 1XY, UK

£¨Received August 24, 2010 £©

Abstract: A quantitative, non-invasive method of measuring the moisture content (< 25 wt %) of solid food wafers is presented. The method utilizes terahertz (THz) radiation and exploits its high sensitivity to small amounts of water. A linear relationship between transmitted THz signal intensity and moisture content is observed in the range 0.2-0.6 THz. Higher frequencies are affected by scattering due to the size of the pores in the food wafer. A robust quantitative measurement protocol, which requires simple calibration, is implemented based on a direct interpretation of the THz time domain signal.

Keywords: Spectroscopy, THz, Moisture determination, Food wafers

doi: 10.11906/TST.172-182.2010.12.17

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TST, Vol. 3, No. 4, PP. 183-191

(Invited Paper) The Hydrogen Bonding Signature of Peptides and Proteins in the Far Infrared

Youssef El Khoury, Aur¨¦lien Trivella and Petra Hellwig*
Laboratoire de Spectroscopie Vibrationnelle et Electrochimie des Biomol¨¦cules Institut de Chimie, UMR 7177, Universit¨¦ de Strasbourg 1 rue Blaise Pascal, 67008 Strasbourg Cedex (France)

£¨Received November 22, 2010 £©

Abstract: Spectroscopic techniques that use the low frequency region are strongly emerging for the study of biological molecules. Far infrared and far Raman spectroscopies, THz time domain approaches and inelastic neutron scattering reveal the presence of vibrational modes involving inter- and intramolecular hydrogen bonding. Due to their collective nature, such modes are highly sensitive to the conformational state of the molecule. Here the influence of the secondary structure on these vibrational features in the far infrared for model compounds and proteins of well known structure are described. Since temperature has a large effect on hydrogen bonding, the development of the signature of poly-L-lysine between 14 and 294 K is presented. The data does not only reveal the increase of the number of hydrogen bonds with temperature, but also the reorganizations within the structures.

Keywords: Far infrared, Hydrogen bonding, Proteins, Polyamino acids, Temperature dependence

doi: 10.11906/TST.183-191.2010.12.18

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TST, Vol. 3, No. 4, PP. 192-200

(Invited Paper) Recent Progress of Terahertz Spectroscopy
on Medicine and Biology in China

Biaobin Jin1, Cunlin Zhang2, Peiheng Wu1, Shenggang Liu3
School of Electronic Science & Engineering, Nanjing University, China
2Department of Physics, Capital Normal University, China
3Terahertz S &T Research Center, University of Electronic Science and Technonlgy of China, China

£¨Received November 29, 2010 £©

Abstract: Terahertz (THz) spectroscopy provides a powerful tool for characterization of a great many biomolecules and tissues. Here, the fruitful work by Chinese researchers in recent years is presented, covering the THz spectroscopy on biomolecules, identification of illicit drugs and medical imaging. There are numerous challenges and problems toward the application of THz spectroscopy technique.

Keywords: Terahertz Spectroscopy, Biomolecules, Identification of illicit drugs, Medical imaging

doi: 10.11906/TST.192-200.2010.12.19

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