Detection by fluorescence microscopy of N-aminopeptidases in bacteria using an ICT sensor with multiphoton excitation: Usefulness for super-resolution microscopy

New ICT-based Ratiometric Two-Photon Near Infrared Probe for Imaging Tyrosinase in Living Cells, Tissues and Whole Organisms

“…All starting materials (reagents and solvents) were purchased from Sigma-Aldrich, including the enzymes TYR, dipeptidyl peptidase IV (DPP IV), acetylcholinesterase (AChE), lipase (PNLIP), and the enzyme inhibitor quercetin, with the highest degree of purity. Alanine aminopeptidase (ANEP) was produced and purified as previously described [25].…”

“…The overall design strategy of the probe DCM-HBU was founded on the attachment of an enzyme active moiety 4-hydroxybenzylamine (very similar to tyrosine) to a signal reporter NIR TP chromophore dicyanomethylene-4H-pyran (DCM), perturbing the ICT effect that controls the spectral properties of DCM [24]. By treatment with TYR, its catalytic action restores the ICT process and concomitantly the fluorescence of the DCM-NH2 [25], providing a ratiometric signal between the emission maxima from the dye and the probe. Due to the enzymatic reaction, color change from yellow to red, allowing colorimetric detection of TYR with the naked eye.…”

Two-Photon Fluorescent Probes for Detecting Enzyme Activities in Live Tissues

“…Proteolytic enzymes, also termed proteases, peptidases, and proteinases, are a subgroup of hydrolases that catalyze peptide bonds which belong to enzyme classification 3 (EC 3). Proteolytic enzymes are essential for all living organisms and are involved in various biological processes, such as cell growth, signal transduction, metabolism, and immune response. − Therefore, several TP enzymatic probes have been devised for detection of specific proteases in living systems. − Aminopeptidase (EC 3.4.11) is an important subclass of proteases that catalyze the hydrolysis of N-terminal peptide bonds in proteins or peptides . Aminopeptidases can be further categorized based on the enzyme that cleaves the first peptide bond or second peptide bond (dipeptidyl-peptidases).…”

Novel A–D–A structural imidazole derivatives with charge transfer excited states: importance of molecular structure design in obtaining a “turn-on” type fluorescence probe

“…[8][9][10][11][12] The common sensing mechanisms of the organic fluorescence sensor include photoinduced electron transfer (PET), 13,14 fluorescence resonance energy transfer (FRET), 15,16 and intramolecular charge transfer (ICT). 17,18 Among them, ICT fluorescence sensors are mainly prepared by organic small molecules with a D-A structure. [19][20][21][22] When metal ions bind with the donor or acceptor groups in the D-A molecule, the charge distribution and conjugation degree of the molecule are affected, which can not only lead to the enhancement or weakening of the molecular emission intensity but also often cause the deviation of the emission peak, sometimes even evident color changes.…”

“…23 Therefore, the ICT fluorescence sensor based on the D-A structured molecule has stronger anti-interference ability in a complex environment than the general fluorescent probe, which only changes the fluorescence intensity. 17,23 However, the recognition of metal ions by most existing ICT fluorescence sensors is still in the quenching response stage. [24][25][26][27] Thus, it is still necessary to further develop novel D-A structure organic fluorescence probes to obtain ICT fluorescence sensors with a fluorescence turn-on response or fluorescence color change response.…”