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A new approach for precise complex optical parameter of highly absorptive liquid is proposed for transmission THz time-domain spectroscopy. Due to the nature of liquid, indirect measurement of sample thickness increases inaccuracy in optical parameter. Here, we reduced uncertainty in optical parameter through an algorithm optimizing sample thickness by Kramers-Kronig relations. Less than 2% error...
The water relaxation dynamics is measured for DMPC vesicle solution and LMPC micelle solution from the dielectric spectroscopy. Both lipid have a same headgroup, which is interacting parts with the surrounding water molecules, but the change of the water relaxation time with increasing lipid concentration shows opposite trend. The result suggests that one needs to consider the lipid structure in water...
Salt-induced change in water dynamics inside multi-lamellar vesicles (MLV) is experimentally studied with terahertz (THz) time-domain spectroscopy (TDS). The dielectric constants of lipids dispersed in NaCl solutions with different salt concentrations are measured. We find that the water molecules with fast relaxation time (∼100 fs) significantly increase with NaCl concentrations. Furthermore, by...
Intracelluar water is expected to have different physical properties from those of bulk water. Using polyethylene glycol, we induce model intracellular environment on DMPC lipid solution and we shows the accelerated movement of non-hydrogen bonding (NHB) water molecules interacting with DMPC in polyethylene glycol (PEG) solution from the dielectric response in the terahertz range. With the measurement...
Dynamics and structure of water network around nucleic acid have been subjects of intensive studies due to their contributions to biological process. Here, we identified spatiotemporal features of DNA hydration through examining fully-hydrated DNA solutions by THz spectroscopy. The results suggest the presence of weakly bound water beyond tight-binding hydration layer with the timescale of 11.6ps...
We investigate the ion effect on 1, 2-ditetradecanoyl-sn-glycero-3-phosphocholine lipid hydration with attenuated total reflection terahertz time domain spectroscopy. The absorption difference between lipid solutions and buffers (water and NaCl solution) shows that lipid-ion interaction accelerates the water reorientation motion confined in nanometer scale structure.
Activation energy of phospholipids in aqueous solution was obtained by terahertz (THz) time domain spectroscopy. The THz absorption as a function of temperature, an Arrhenius plot, yields activation energy of water relaxation process. Head group structure and phase dependence of the activation energy is reported.
DNA conformational change is proved in THz frequency range. Distinct difference in absorption of condensed and extended DNA is observed. The result suggests that THz spectroscopy identifies global change in DNA structure sensitively.
Hydration state of lipid bilayer during the gel to fluid phase transition is measured with THz time domain spectroscopy (TDS). Hydration water showed bulk-water-like behavior at gel phase, but showed non-bulk-like behavior at fluid phase.
Interaction of DNA and hydration water affects both structure and function of DNA. Here, we find out the relaxation time of DNA hydration water probed by THz-TDS under biological condition. Double Debye relaxation model is applied for figuring out relaxation time of hydration water. We observed 14.9ps for 50mM of DNA solution. This is much slower compared to bulk water, 8.15ps. The results indicate...
We study the refractive index and the absorption coefficient of liquid water with collimated beam and focused beam. Optical parameters with focused beam are inaccurate explained by the Gouy shift. This inaccuracy is theoretically calculated and will be compared with the experimental results with THz-TDS.
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