Structure-fluorescence Relationship Of Naphthalimide Fluorophore And Applications In Biology

As one of the traditional environment sensitive dyes,naphthalimide has been widely used in fluorescence sensing and imaging with the convenient chemical modification and fluorescent tuning.However,due to impact of TICT and hydrogen bond,the brightness and photo stability of naphthalimide appear insufficient.Especially,when facing the single molecule and super resolution imaging,the fluorescence property is in urgent need to be improved by a large margin.Nowadays,with the combination of bioortho gonal reaction and emerging biological labeling technique,such as protein tag and unnatural amide acid,the accurate location and sensing of small organic molecule probes are realized.Nevertheless,the systematic research based on naphthalimide in the burgeoning field appears deficient.Besides,in order to obtain accurate and generalduty response signal,the emergence of signal transformation strategies need to be discovered.For the expansion of fluorophores and biological applications,two following work are carried out based on the fluorescence structure-function relationship of naphthalimide:enhancing the fluorescence intensity and photostablity of naphthalimide;On this basis,novel fluorescence probes were established for labeling and sensing target proteins(1)The fluorescence quantum yield of multiple fluorophores was remarkably improved through the effectively inhibiting twist intramolecular charge transfer(TICT)by aziridine.The aziridinly fluorophores were synthesized based on 1,8-naphthalimide which showed high fluorescence quantum yield(?=0.43,water)along with excellent photo stability and large stokes shift(??=151 nm).Meanwhile,inhibition mechanism that the energy level of TICT state is higher than LE state,was elaborated in detail with theoretical calculation.Besides,fluorescence quantum yield of different fluorophores were also enhanced in water with the assistance of aziridine.(2)A series of SNAP-tag probes based on naphthalimide were designed and sythesized according the kill mechanism of TICT,which could specifically imaging target protein without washing.Due to the fluorescence quenching caused by aggregation,BGAN-Aze realized a large fluorescence enhancement(?39 fold)after labeled with SNAP-tag which made wash-free imaging come ture.In addition,BGAN-Aze was successfully applied in super-resolution imaging with the increased photostability and brightness through the effectively inhibiting TICT by azetidine.BGAN-Amino could tag SNAP-tag rapidly which exhibited the fast record labeling rate(t1/2= 11 s,k = 14436±1189 M-1 s-1)among fluorogenic probes.(3)Novel ratiometric fluorescence probes(BuAN-AceN,SML-AceN)based on excited-state proton transfer(ESPT)were designed and synthesized which could response to microenvironment and target protein BuAN-AceN showed short emission wavelength(?470 nm)in water and long emission wavelengh(?550 nm)in other solvents.Rational occurrence mechanism of proton-transfer via environmental changes was proposed through the analysis of NMR titration,transient spectra and model compound.Ratiometric measurement for hCA was realized through SML-AceN which carried sulfanilamide analogue.The emission wavelength realized bathochromic-shift from 463 nm to 535 nm.Furthermore,various fluorophores with the introduction of characteristic functional group,showed the new luminous mechanism was universal in different fluorophores.