Abstract
This work represents the development of a three-band (Debye relaxation, intermolecular bending, and stretching vibrational bands) approach to the terahertz time-domain spectroscopy (THz-TDS) for the analysis of aqueous solutions of lactose saturated with highly diluted (HD) antibodies to interferon-gamma. Since THz-TDS is sensitive to a very slight changes in water properties, we aimed to assess its applicability for the analysis of HD antibodies. To evaluate water features in tested samples we also used Fourier transform infrared spectroscopy, considering the first overtone of intramolecular stretching vibrations of water molecules. We showed a broadening of the energy distribution of intermolecular bonds in the solution of HD substances in comparison to the control solution. This broadening corresponded to the presence of an active component even in HD samples. The results of both methods were similar; however, with the THz-TDS it was possible to analyze the changes in energy distribution of intermolecular (hydrogen) bonds in the solutions. Therefore, our approach to THz-TDS method is applicable for analyzing structural properties of the solutions containing HD antibodies and for the indirect investigation of altered aqueous properties in water solutions when direct measurements of a substance concentration are not available.
Highlights
Terahertz spectroscopy is a modern and rapidly developing method capable of analyzing the structure of matter
As terahertz time-domain spectroscopy (THz-TDS) method is highly sensitive to the intermolecular interactions of the water molecules, such a procedure could be the assay of choice for the testing of highly diluted samples
We demonstrate that the THz-TDS method has advantages over the IR spectroscopy method traditionally used to analyze structural properties of water solutions [59,60]
Summary
Terahertz spectroscopy is a modern and rapidly developing method capable of analyzing the structure of matter. The terahertz region corresponds to intermolecular vibrations of molecules in terms of energy (meV) and frequency (THz) values which allows investigating the intermolecular structure and dynamics. In most of these works the studied objects were substances with low quantity of water, whereas this method has been rarely used to study aqueous solutions, for example in [13,14]. This is due to a strong absorption of the water itself which masks the absorption of dissolved substances. Of particular interest are some areas of research exploiting terahertz spectroscopy which have made it possible to obtain previously unknown and fundamentally new data on aqueous
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