THz Spectra for Some Bio-molecules
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THz Spectra for Some Bio-molecules S. C. Shen & L. Santo & L. Genzel
Received: 29 December 2006 / Accepted: 27 April 2007 / Published online: 24 May 2007 # Springer Science + Business Media, LLC 2007
Abstract THz spectra for some amino acids, peptide and protein have been measured by use of commercial and optically compensated FTS spectrometers. A lot of sharp spectral lines have been observed below 7 THz and attributed, tentatively and in general, to hydrogen bonds and weak intermolecular interactions for the amino-acids and simple peptides, but the detailed explanation is still lack and leaving a big room for further investigation.
1 Introduction The spectroscopic techniques in Terahertz (THz) or as called a decade ago, in far infrared (FIR) wavelength region have been developed rapidly in last two decades. Many kinds of spectrometers in both frequency and time domains, based on coherent THz wave sources, such as THz wave parametric oscillators, quantum cascade lasers, THz-TDS ( time domain spectroscopy) or photo-mixer (optical heterodyne downward conversion) with a photoconductive (PC) antenna, nonlinear optical and crystal, electro-optic Cherenkov radiation etc. are becoming available now for the measurement and investigation of spectroscopic phenomena of all kinds of matters, including bio-molecules and cells [1–13]. It should be mentioned especially that the powerful THz free electron laser are also available or in built very recently [14–19]. All these techniques make the spectroscopic measurements and investigation in this wavelength region much easier than two decades ago, and open new era for this frontier field. It is well known that the normal vibration modes of the bio-molecules in the THz wavelength region are related with the intermolecular interaction and hydrogen bonds, For memory of Prof. Ludwig Genzel S. C. Shen (*) Shanghai Institute of Technical Physics, Chinese Academy of Sciences; and Physical Deparment of Fudan University, Shanghai 200083, China e-mail: [email protected] L. Santo : L. Genzel MPI für Festkörperforschung, Stuttgart, Germany
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Int J Infrared Milli Waves (2007) 28:595–610
which are much weaker than intra-molecular interaction and chemical bonding. In addition the lattice modes, especially the acoustic modes can be extended into very low frequency of this region. These interactions and vibrations are related with the process of proton transferring, which play an essential role in many biochemical and biological phenomena. The spectroscopic investigation, including THz absorption, Raman Scattering, of the vibration modes of bio-molecules has attracted much attention for a few decades [20–30] for both fundamental interesting and possible application in spectroscopic diagnostics of biological and biomedical matters. The facts remind me our hard job in late 1970s and early 1980s on the measurements of FIR spectra for some bio-molecules, including amino-acid, such as α-L-alanine, glycine, leucine, valine, tyrocine, peptide, such as di-L-alanine and poly-glycine, proteins
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