Erratum: "Sub-terahertz spectroscopy reveals that proteins influence the properties of water at greater distances than previously detected" [J. Chem. Phys. 142, 055101 (2015) The initial purpose of the study is to systematically investigate the solvation properties of different proteins in water solution by terahertz (THz) radiation absorption. Transmission measurements of protein water solutions have been performed using a vector network analyser-driven quasi-optical bench covering the WR-3 waveguide band (0.220-0.325 THz). The following proteins, ranging from low to high molecular weight, were chosen for this study: lysozyme, myoglobin, and bovine serum albumin (BSA). Absorption properties of solutions were studied at different concentrations of proteins ranging from 2 to 100 mg/ml. The concentration-dependent absorption of protein molecules was determined by treating the solution as a two-component model first; then, based on protein absorptivity, the extent of the hydration shell is estimated. Protein molecules are shown to possess a concentration-dependent absorptivity in water solutions. Absorption curves of all three proteins sharply peak towards a dilution-limit that is attributed to the enhanced flexibility of protein and amino acid side chains. An alternative approach to the determination of hydration shell thickness is thereby suggested, based on protein absorptivity. The proposed approach is independent of the absorption of the hydration shell. The derived estimate of hydration shell thickness for each protein supports previous findings that protein-water interaction dynamics extends beyond 2-3 water solvation-layers as predicted by molecular dynamics simulations and other techniques such as NMR, X-ray scattering, and neutron scattering. According to our estimations, the radius of the dynamic hydration shell is 16, 19, and 25 Å, respectively, for lysozyme, myoglobin, and BSA proteins and correlates with the dipole moment of the protein. It is also seen that THz radiation can serve as an initial estimate of the protein hydrophobicity. C 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License. [http://dx
This paper reports a comparative study of sub-THz frequency-selective surface (FSS) filter performance in relation to its method of fabrication. Three techniques are considered: conventional inkjet printing, microprecision inkjet printing, and photolithography. The complete design process is presented highlighting steps from substrate selection through to electromagnetic modeling and finally broadband THz filter characterization. Electromagnetic modeling is performed using the CST full-wave frequency-domain solver. Experimental characterization of substrate material, ink, and final FSS designs is done both by THz timedomain spectrometry and quasi-optically at WR-10 and WR-3 waveguide bands using PNA-X vector network analyzer. The center frequencies for bandpass FSS filters are 100 and 300 GHz, which enables prospective utilization in a quasi-optical multiplier system.
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