Liyi Ma,Lixuan Mu,Lushan Huang,Guangwei She,Wensheng Shi
An outstanding fluorescent probe for adenosine 5′-triphosphate (ATP) in the millimolar range will shed deep light on the physiological role of ATP. Many fluorescent probes based on rhodamine spirolactam derivatives have been developed for this purpose and claimed to detect millimolar ATP excellently, where ATP or adenosine 5′-triphosphate disodium salt (ATP-2Na) dissolved in a buffer solution is employed to examine their response to ATP. However, in this work, it was found that both millimolar ATP and ATP-2Na could significantly decrease the pH of the common buffer solution even for several units. Considering the dependence of the rhodamine spirolactam fluorescence on pH, a series of rhodamine spirolactam-based probes was synthesized to investigate their fluorescence response to pH and ATP-2Na. The results demonstrated that the fluorescence response of the probes to millimolar ATP-2Na indeed resulted from both ATP-2Na itself and the pH decrease induced by ATP-2Na. Furthermore, it was evidenced that acidic pH was crucial for the probes to produce fluorescence response to millimolar ATP-2Na itself, and the rhodamine spirolactam-based probes would show poor sensitivity to millimolar ATP-2Na at near-natural pH. Accordingly, the previous conclusion that the rhodamine spirolactam-based probes could detect millimolar ATP excellently was almost erroneous, and might mislead the design and practice of intracellular ATP probe in the future. This work notes that attention should be paid to the physiochemical properties of the analyte and the environmental changes produced by the target analyte.
This study investigated the expediated transformation of halophenols in the presence of nitrite (NO 2 − ) under slightly acidic conditions in ice, whereas such transformation was negligible in liquid water at 4 °C. We proposed that this phenomenon was attributed to the freeze-concentration effect, incurring a pH drop and the aggregation of NO 2 − and halophenols within the liquid-like grain boundary layer amid ice crystals. Within this micro-environment, NO 2 − underwent protonation to generate reactive nitrous acid (HNO 2 ) and nitrosonium ions (NO + ) that facilitate the nitration and oxidation of halophenols. When 10 μМ halophenol was treated by freezing in the presence of 5 μМ NO 2 − , the total yields of nitrated products reached 2.4 μМ and 1.4 μМ within 12 h for 2-chlorophenol (2CP) and 2-bromophenol (2BP), respectively. NO + drove oxidative coupling reactions, generating hydroxyl polyhalogenated diphenyl ethers (OH-PBDEs) and hydroxyl polyhalogenated diphenyls via C-O or C-C coupling. These two pathways were intricately intertwined. The presence of natural organic matter (NOM) mitigated the formation of nitrated products and completely suppressed the coupling products. This study offers valuable insights into the fate of halophenols in ice and suggests potential pathways for the formation of nitrophenolic compounds and OH-PBDEs in natural cold environments. These findings also open up a new avenue in environmental chemistry research.
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