Terahertz Biomolecular Spectroscopy and Medical Imaging
- Terahertz Biomolecular Spectroscopy and Medical Imaging
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- The development of Terahertz (THz) technology has opened the new way for useful applications in physics, chemistry, biology, and medicine. Interestingly, given the theoretical predictions, collective vibrational and torsional motions of biomolecules occur in the THz region. This has attracted much attention in characterization of biologically relevant materials at THz frequencies. THz time domain spectroscopy (TDS) can give good information of materials and is a powerful tool for probing the low frequency collective dynamics of biomolecules leading to conformational change and biomolecular function. Here, we report THz research in biology and medicine, including label-free DNA sensing, THz pulse imaging of human cartilage tissue and cervical cancer lymph node, and THz spectroscopy of crystalline α-lactose monohydrate and aqueous solution. Firstly, large contrasts in the complex refractive index between denatured and hybridized DNA were obtained, indicating that DNA samples of single and double strands can be readily distinguished. Secondly, we observed that each THz image exhibits the distinct structural organization of cartilage and clearly distinguishes between the abnormal and normal cartilage tissues. The water distribution in human osteoarthritic articular cartilage has been quantitatively characterized using THz TDS. We measured the refractive index and absorption coefficient of cartilage tissue in the THz frequency range. Based on our measurements, the estimated water content was observed to decrease with increasing depth cartilage tissue, showing good agreement with a previous report based on destructive biochemical methods. Thirdly, THz absorption spectra of crystalline α-lactose monohydrate showed strong absorption peaks at 0.1 - 2.0 THz. We examined β-amyloid peptide and amyloid fibril by using THz TDS. Collective vibrational modes in THz frequency region are affected by conformational change of biomolecules. Distinct spectral difference between β-amyloid peptide and amyloid fibril was observed in 0.1 ~ 2.0 THz. Finally, hydration dynamics in aqueous solution has been characterized. We precisely measured the dielectric constants of aqueous solution using THz TDS. As the solute concentration increased, THz absorption coefficients of aqueous solutions decreased due to the decrement of bulk water. It indicates that the biomolecule, bulk water, and hydration water in the hydration shell are closely correlated. The dielectric relaxation of sucrose solution was different from those in pure water.
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