Sulfur dioxide (SO 2 ), as the main member of reactive sulfur species (RSS), it is mainly produced in mitochondria and involved in a variety of activities at the cellular level. Excessive inhalation of SO 2 could cause respiratory tract damage, cardiovascular disease and even cancer. The mitochondrial and lysosomal as two important organelles, their interactions (fusion and contact) are important for maintaining eukaryotic homeostasis. Some study indicated that SO 2 is active in the above interaction process. In this work, benzopyranium salt unit was constructed as fluorophore I, where O + was the mitochondrial target site, and naphthalimide was linked to morpholine to construct fluorophore II, where morpholine was the lysosomal target group. Studies have shown that the probe has a good performance in targeting both mitochondria and lysosomes. And after the reaction with SO 2 , FRET was broken, resulting in red quenching, and green emitting, which made it can detect SO 2 with a ratiometric response. Cells cultured with nystatin showed decreased red and green fluorescence increased, indicating that the autophagy of mitochondria produced SO 2 . In addition, synthesized control reagents (targeting lysosomes alone and responding to SO 2 ) from no signal to gradually enhanced blue fluorescence, indicating that SO 2 produced by mitochondria is transferred to lysosomes. What's more, it could monitor the changes of SO 2 concentration under heat stroke. More importantly, it could quantitatively detect sulfite concentration in Yuba and crystal sugar.
The effects of adsorption behavior and assembly mechanism of proteins and lipids at the interface on the formation of yuba films were investigated. The thickness of yuba films increased rapidly from nano to micro scale within minutes according to the scanning electron microscopy (SEM) images. The confocal laser scanning microscope (CLSM), SEM images, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the formation of protein aggregates (40–100 nm) was an essential requirement for the development of yuba. Meanwhile, a relatively loose spatial structure was formed by protein aggregates under the influence of water vapor. This structure served as the foundation for incorporating lipids. Interfacial adsorption kinetics indicated that increasing the concentration (from 3 to 9 mg/mL) of protein aggregates enhanced the rearrangement rate. This finding demonstrated that the variations of interfacial protein aggregate concentration were a crucial factor leading to the non-linear growth of film thickness.
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