Development Of Novel Fluorescence Probes For Hydrogen Persulfide And Thiophenol And Their Applications

Hydrogen sulfide has attracted research workers attention in biochemical research because these molecules show a variety of physiological functions.However,recent studies suggested that H2Sn may be the real signaling in some biological mechanisms.Hydrogen polysulfides(H2Sn,n>1)are the direct redox forms of endogenous H2S.H2Sn may compensate for some physiological functions that H2S cannot fulfill.The redox couple of H2S and H2Sn is very likely to coexist in biological systems and they work together to regulate suifur balance.Unfortunately,there are very few reports on fluorescent probes for H2Sn detection,so far.Therefore,it is very important to understand the mechanism and the physiological function of hydrogen sulfide in the formation process of the living body and it is very important to design a new fluorescent probe for the detection of H2Sn.Thiophenols are widely used in organic synthesis,pharmaceuticals and various industrial products.Thiophenols are a class of highly toxic and pollutant compounds.Prolonged exposure to thiophenols in water or soil can cause a series of serious endanger in ecological environment and health problems.Therefore,the design of high sensitivity,high selectivity for the detection of thiophenol in the chemical,biological and environmental fields is of great significance.Based on the above experimental basis,this paper designed a new fluorescence reaction mechanism to detect H2Sn and thiophenol.The thesis consists of four chapters as following:Chapter 1:This paper mainly introduces the basic structure and identification mechanism of fluorescent probe molecules,and the research progress on the fluorescent probe for fluorescence analysis method for the detection of polysulfide and thiophenol.On this basis,the progress of this dissertation was proposed.In chapter 2,we have developed a ratiometric fluorescent probe 1 for H2Sn by using aziridine as the recognition unit.So taking the advantage of two nucleophilic reactions can be occurred in H2Sn(n>1)with compounds containing bis-electrophilic groups.Upon introducing H2Sn in neutral solution,first the aziridine ring was attacked to afford an ring-opening reaction to form an intermediate containing an amide group,after the 9-position carbon atom in oxyanthene derivatives arracked by the nitrogen-atom in amide group to form the corresponding apirolactam compound.The fonrm of cyclization in the molecule causes the 3-position of the oxanthracene to be converted from the quinone to the phenolic.At this time,under the excitation conditions of the light,between the phenolic hydroxyl protons and the nitrogen atom on the benzothiazole ring,the ESIPT process occurs,so the reaction system exhibits 2-(2'-hydroxyphenyl)benzothiazole fluorescence,the maximum emission wavelength at 450nm.Thus a ratiometric fluorescent probe for H2Sn was developed.Therefore,the fluorescence intensity at 598 nm and 450 nm gave a significant change and the ratios of the fluorescence intensity at 450 nm and 598 nm(1450/598)with the H2Sn concentration increased.The probe 1 showed a high selectivity towards H2Sn and the probe did not give any fluorescence responsed to these active sulfur,reactive oxygen and nitrogen.Moreover,the probe proves to be able to assessing H2Sn levels in live cells.In chapter 3,we have developed a fluorescent probe 2 for thiophenols by using aziridine as the recognition unit.In the design of probe 2,we expected the aziridine moiety and dansyl group to be the recognition unit and signaling unit,respectively.The fluorescence of probe 2 dansyl group should be effectively quenched or weakened via the twisted in tramolecular charge transfer(TICT)effect.Upon introducing thiophenols in neutral solution,the aziridine ring of the sensor could be opened upon reacting with thiophenols,to form the corresponding amide compound.Since the amide compound produced in the above reaction process has poor solubility in the aqueous solution,the product can be aggregated in the aqueous solution,the TICT process controlled,resulting in a significant increase in the fluorescence signal of the reaction system.The fluorescence intensity at 505 nm gave a significant change and we noted that the fluorescence intensity increased linearly with the concentrations of thiophenols in the range of 4-15 ?M,the detection limit was calculated to be 0.05 pM.The probe 2 showed a high selectivity towards thiophenols.The probe proves to be able to assessing thiophenols levels in live cells.In chapter 4,we have developed the coumarin derivative as the parenta new fluorescent probe 3 for HSA.The probe showed very weak fluorescence in the reaction system.In the prescence HSA,the fluorescence intensity gave a significant change at 601 nm.The probe 3 dispiayed a quick response,high selectivity for Ovalbumin over various amino acids.We noted that the fluorescence intensity at 601 nm were linearly related to the concentrations of HSA in the range of 0-12 ?M and the detection limit for HSA was calculated to be 5.8 nM.