Abstract-Terahertz identification and quantification of neurotransmitter and neurotrophy mixture

Yan Peng, Xiaorong Yuan, Xiang Zou, Wanqing Chen, Hui Huang, Hongwei Zhao, Bo Song, Liang Chen, and Yiming Zhu

https://www.osapublishing.org/boe/abstract.cfm?uri=boe-7-11-4472

Terahertz spectroscopy has been widely used for investigating the fingerprint spectrum of different substances. For cancerous tissues, the greatest difficulty is the absorption peaks of various substances contained in tissues overlap with each other, which are hard to identify and quantitative analyze. As a result, it is very hard to measure the presence of cancer cell and then to diagnose accurately. In this paper, we select three typical neurotransmitters (γ-aminobutyric acid, L-glutamic acid, dopamine hydrochloride) and two typical metabolites (inositol and creatine) in neurons to measure their terahertz spectra with different mixture ratios. By choosing characteristic absorption peaks, removing baseline and using the least square method, we can identify the components and proportions of each mixture, where the goodness of fit to practical situation is up to 94%. These results provide important evidences for identifying nerve substances and obtaining exact quantitative analysis.

© 2016 Optical Society of America

Full Article  |  PDF Article

Abstract-Molecular Recognition and Interaction between Uracil and Urea in Solid-State Studied by Terahertz Time-Domain Spectroscopy

Jingqi Yang , Shaoxian Li , Hongwei Zhao , Bo Song , Guoxin Zhang , Jianbing Zhang , Yiming Zhu , and Jiaguang Han

J. Phys. Chem. A, Just Accepted Manuscript

DOI: 10.1021/jp506045q

Publication Date (Web): October 28, 2014

Copyright © 2014 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/jp506045q?journalCode=jpcafh

Using terahertz time-domain spectroscopy characterization, we observe that urea is able to recognize and interact with uracil efficiently even in solid phase without involving water or solvents. A cocrystal configuration linked by a pair of hydrogen bonds between uracil and urea was formed. Terahertz absorption spectrum of the cocrystal shows a distinct new absorption at 0.8 THz (26.7 cm-1) which originates from the intermolecular hydrogen bonding. Both mechanical milling and heating can accelerate the reaction efficiently. Density functional theory was adopted to simulate the vibrational modes of the cocrystal and the results agree well with the experimental observation. Multi-techniques, including powder X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy were performed to investigate the reaction process and presented supportive evidences. This work enables in-depth understanding of recognition and interaction of urea with nucleobases, and comprehending the denaturation related to RNA. We also demonstrate that terahertz spectroscopy is an effective and alternative tool for online measurement and quality control in pharmaceutical and chemical industry.

Abstract-Anisotropic Dielectric Relaxation of the Water Confined in Nanotubes for Terahertz Spectroscopy Studied by Molecular Dynamics Simulations

Wenpeng Qi , Jige Chen , Junwei Yang , Xiaoling Lei, Bo Song , and Haiping Fang

J. Phys. Chem. B, Just Accepted Manuscript

DOI: 10.1021/jp3120435

Publication Date (Web): June 10, 2013

Copyright © 2013 American Chemical Society

http://pubs.acs.org/doi/pdfplus/10.1021/jp3120435

The dynamics and structure of hydrogen-bond network in confined water are of importance in understanding biological and chemical processes. Recently, the terahertz (THz) time domain spectroscopy is widely applied for studying the kinetics of molecules and hydrogen-bond network in water. However, the characteristics of the THz spectroscopy varying with respect to the confinement and the mechanism underlying the variation are still unclear. Here, based on molecular dynamics simulations, the relationship between the anisotropic dielectric relaxation and the structure of the water confined in a carbon nanotube (CNT) was investigated. The results show that there are two preferred hydrogen-bond orientations of the confined water in the nanotube: 1) parallel to the CNT axis and 2) perpendicular to the CNT axis, which are clearly different. Moreover, the response of the orientations to the increment of the CNT diameters is opposite, leading to the opposite variations of the dielectric relaxation times along the two directions. The anisotropy in the relaxation time can be presented by the anisotropic dielectric permittivity which is able to be observed through THz spectroscopy. The anormal behaviors above are attributed to the special structure of the water close to the nanotube wall due to the confinement and hydrophobicity of CNT. These studies contribute an important step in understanding the THz experiments of water in nano scales, and designing a chamber for specific chemical and biological reactions by controlling the diameters and materials of the nanotube.