| Nucleotides are important components of DNA and RNA in biological body,and they can participate in life activities by combining with metal ions.There are few studies on the coordination modes of nucleotides with metal ions and the properties of their complexes,which restricts the development of complexes.So it’s important to study theoretical researches in these areas.The studies of nucleotide-metal complexes will help to understand the biological significance of nucleotides,to lay a theoretical foundation for fluorescent sensors design,to provide guidance for the application of complexes in the fields of supramolecular chemistry,biology and medicine.In this paper,four 5’-nucleotides were used as raw materials,the effects of different conditions on the synthesis of zinc coordination complexes of 5’-monophosphate nucleotide(NMP-Zn)and copper coordination complexes of 5’-monophosphate nucleotide(NMP-Cu)were studied,the conditions were optimized by orthogonal experiments,and the properties of complexes were studied.Firstly,the influences of substrate concentration,pH,temperature and reaction time on the synthesis of NMP-Zn and NMP-Cu were investigated,and the conditions were optimized by orthogonal experiments,as target of the yield of NMP-Zn and NMP-Cu.The results showed:The yield of NMP-Zn and NMP-Cu increased and then decreased with the increasing of temperature or pH,while the yield increased and then unchanged with the increasing of substrate concentration or reaction time.The optimal conditions for zinc coordination complex of guanosine 5’-monophosphate(GMP-Zn)and copper coordination complex of guanosine 5’-monophosphate(GMP-Cu)were 40 mmol/L,pH 3.5,80℃and 45 min.Secondly,the coordination informations of NMP-Zn and NMP-Cu were analyzed by infrared spectroscopy and Raman spectroscopy,and the structural differences between nucleotides and complexes were analyzed by X-ray diffractometer.On the one hand,compared with corresponding nucleotides,the stretching vibration peak of phosphate group moved to high frequency in the infrared spectra of NMP-Zn and NMP-Cu.The ring vibration peaks and the stretching vibration peaks of C=N or C=O at nucleobases appeared frequency shift or splitting.On the other hand,in the Raman spectra of NMP-Zn and NMP-Cu compared with the corresponding nucleotides,the peaks shape or intensity of C-N,C=N or C=O had some changes.The results indicated that the phosphate group coordinated to the zinc or copper ions,and the interaction existed between zinc or copper ions and nucleobases.Furthermore,the X-ray diffraction data showed that there were significant differences of peak position between complexes and corresponding nucleotides.The disappeared and newly diffraction peaks of complexes indicated the differences of structure between complexes and nucleotides.Finally,the chiral characteristics of NMP-Zn and NMP-Cu in aqueous solution and in solid-state were determined by circular dichroism spectroscopy,and the fluorescence properties were studied by fluorescence spectromer.The positive or negative of Cutton effect didn’t change in the circular dichroism(CD)spectra of complexes,indicating the chiral characteristics were retained.There were no significant changes in the CD spectra of complexes between adenine 5’-monophosphate,cytidine 5’-monophosphate,uridine5’-monophosphate and zinc or copper ions in aqueous solution.But in the CD spectra of GMP-Zn and GMP-Cu in aqueous solution,the positive band at 215 nm became weaker significantly,which meant that the n-π~*trasition was inhibited by the interaction between nucleobases and zinc or copper ions.And the positive or negative Cotton effect had no change in the CD spectra of NMP-Zn and NMP-Cu in the solid-state,which indicated the unchanged of their chiral characteristics.Furthermore,the results of fluorescence spectra revealed that the fluorescence intensity became weaker significantly after nucleotides combined with zinc or copper ions.And the emission wavelength of the maximum peak shifted slightly of adenine5’-monophosphate-zinc/copper and uridine 5’-monophosphate-zinc/copper complexes. |
