Terahertz Spectra Of Catecholamine And Its Interaction With Metal Ions

Catecholamine(CA)as an essential neurotransmitter and hormone in the nervous system,mainly includes dopamine(DA),norepinephrine(NE),and adrenaline(Ad),which is closely associated with neurodegenerative psychiatric diseases.The low frequency vibration response of terahertz electromagnetic waves and biomolecules can reveal the internal mechanism of material structure.It is expected to reveal the correspondence between the molecular structure and the spectral characteristic frequency from the perspective of weak interaction(hydrogen bonds,van der Waals forces,etc.),providing a reference for label-free recognition.At the same time,the dispersion of these biomolecules in an aqueous solution is of great significance,which provides a new perspective for drug preparation.The concrete research contents are as follows:(1)The unique terahertz absorption fingerprints of CA were obtained using a broadband air-plasma terahertz time-domain spectroscopy system.Based on the density functional theory(DFT),we analyzed the molecular vibration modes corresponding to the experimental characteristic peaks.The result shows that the molecular vibration modes are specific and the low frequency region tends to collective vibration,while the high frequency band has collective vibration and local vibration.Analyzing from the structural,the vibration of the flexible side chain skeleton and the functional group will directly lead to the diversification of molecular conformation.Then the temperature response shows that the resonance absorption peak becomes sharper as the temperature decreases.Due to the anharmonic vibration,the thermal expansion and contraction of the crystal lattice,the resonance absorption peaks generally move towards the high frequency(blue shift).However,a few peaks have an abnormal red shift for weak interaction.The research results help to deepen the understanding of the relationship between the molecular structure of catecholamines and biological effects,which provide a reference for the realization of unlabeled terahertz detection.(2)Based on the molecular dynamics theory,we explored the specific recognition of DA with D2 receptor,the weak interaction between DA-D2 R and DA-D3 R systems,and calculated the terahertz theoretical spectra.The results show that DA is stably linked to the amino acid residues SER 197,VAL 115,ASP 114,and TYR 416belonging to the D2 receptor with four hydrogen bonds.The terahertz characteristic spectra of DA-D2 R and-D3 R systems show that the vibration of the DA in the receptor is closely related to the conformation of the ligand-receptor.It is also found that the amino group at the tail of DA does not respond at 8.47 THz in the DA-D2 R system,but responses strongly at 11.83 THz.Terahertz electromagnetic waves and biomolecules can have high-efficiency resonance coupling,which affects the interaction between ligands and protein receptors.It could be the guidance for the experimental detection of ligand-receptor interactions.(3)Based on the experimental detection and theoretical analysis,the cation-π interaction between NE,Ad(containing hydrophobic aromatic ring structure)and Cu2+,Zn2+ was investigated.It is found that the cation-π interaction induced the NE and Ad molecules to dissolve in Cu2+ and Zn2+ solutions.Experimental characterization was carried out by different methods,such as ultraviolet,fluorescence spectroscopy.And molecular dynamics simulation shows that the cation-π interaction between phenolic hydroxyl group on benzene ring and metal ions improved the adsorption energy between molecules and water.The research results reveal that the micro-physical mechanism of cation-π mediates the interaction of NE,Ad,and water,which can give a reference for exploring the diffusion behavior of aromatic biomolecules in electrolyte solutions and the mechanism of substance transport,and also provides new insights for drug design.