Application Of Terahertz Spectroscopy On Hydrates And Solid-state Molecular Recognition Reaction

Terahertz(THz)spectroscopy is sensitive to the molecular structures and weak interactions of hydrates.So THz spectroscopy can provide a new perspective to study the molecular structures and understand the relationship between the molecular structures and functions by analyzing the THz spectra.Taking ninhydrin and cytosine as object,we measure the THz spectra of the hydrates and its anhydrous forms of ninhydrin and cytosine and find that the characteristic absorption peaks exist in THz region.The crystal water can induce the molecules to form supramolecular structures by self-assembly according to the results of SEM.The dehydration process of ninhydrin also is monitored on-line using THz spectroscopy.The results exhibit that THz spectrum is dependent on the temperature.We present firstly the sweeping gas is necessary to study the dehydration process using THz spectroscopy.Water molecules can be used as an agile and effective probe.The quantum chemical calculations are performed to study the THz spectra.The geometry optimization and energy calculations base on Density Functional Theory(DFT)are performed.The corresponding vibrational modes of the characteristic absorption peaks are assigned according to the calculations.The results indicate the THz absorption peaks originate from the vibrational modes and intermolecular interactions.The water molecules form hydrogen bonding network which is important for lattice stability.In order to study the mechanism of the mutagenic agents interact with deoxyribonucleic acid(DNA),solid-state reactions between cytosine and oxalic acid are investigated using THz spectroscopy.The results show that co-crystal is formed by molecular recognition when the crystal waters exist in cytosine and oxalic acid.And co-crystal has the characteristic absorption peaks in THz region.Solid-state reactions are monitored on-line using THz spectroscopy.The results indicate that the roles of crystal waters in cytosine and oxalic acid are different.Then the geometry optimization and energy calculations are performed based on the the crystal structure of co-crystal using DFT.The corresponding vibrational modes of the characteristic absorption peaks of co-crystal are assigned.And the reaction conditions and mechanism of the crystal waters interact with cytosine and oxalic acid are obtained.Our research is instructive and meaningful to study the mechanism of the mutagenic agents induce denaturation of DNA structures.