Search

Cys is a common and important sulfur-containing amino acid in living organisms, whose intracellular level changes are associated with a variety of diseases. To specifically detect Cys without interference from other thiol species has considerable significance. However, only selective fluorescent probes are available for cysteine detection; other thiol species can also have certain interference in the sensing process. Herein, we report an irreversible fluorescent probe for the specific detection of cysteine without interference from other thiol species both in living cells and zebrafish. The FR-NIR-Cys probe exhibits a large emission wavelength shift (up to 84 nm) and a significant ratio fluorescence enhancement (up to 41-fold) in the far-red and near-infrared region. Furthermore, we demonstrate that FR-NIR-Cys with good cell permeability can be employed in the far-red to near-infrared imaging of Cys in living cells and zebrafish.

Sulfur dioxide (SO2) derivatives play critical roles in various biological processes. Therefore, effective methods for monitoring SO2 are of vital importance in bisulfite/sulfite biology. In this study, a two-photon (TP) imaging probe (CQ-SO2) for detecting SO2 derivatives was designed and constructed, based on the chromenoquinoline (CQ) fluorophore and a β-chlorovinyl aldehyde sensing moiety. The TP properties of the CQ derivatives were revealed for the first time in this study. This study enriched the biological application range of CQ derivatives and also provided a new choice for the development of TP dyes. In particular, the CQ-SO2 probe exhibited a fast response time (about 5 s), low detection limit (16 nM) and ultrahigh specificity towards SO2 derivatives. Furthermore, the probe was successfully applied to the highly specific TP bioimaging of SO2 derivatives in living cells and zebrafish.

Fermented soy whey (FSW) is a traditional tofu coagulant used extensively in China. In this study, 112 Lactobacillus spp., 18 Streptococcus spp. and 33 yeasts were isolated and identified from naturally fermented soy whey (NFSW). Lactic acid bacteria were found as the major effective strains, and 7 lactic acid bacterial strains could produce enough acid to coagulate soy milk. The pH values and acid production were also monitored during fermentation. The JMC-1 strain showing Gram-positive and rod-shaped was determined to have a high acid-producing activity among the 7 strains. API 50 CHL strip and phylogenetic analysis of 16S rDNA gene sequence demonstrated that the JMC-1 strain was identified as Lactobacillus plantarum. Lactic acid and acetic acid were the major organic acids in fermented soy whey, which increased during the fermentation. High-performance liquid chromatography revealed that the concentrations of these acids increased significantly as fermentation time was prolonged. Compared with CaSO4 tofu and MgCl2 tofu, the tofu prepared by L. plantarum JMC-1 was of better quality in terms of sensory evaluation, texture, yield, and retention capacity.