Handbook of Aggregation-Induced Emission, Volume 2. Группа авторов
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Название: Handbook of Aggregation-Induced Emission, Volume 2
Автор: Группа авторов
Издательство: John Wiley & Sons Limited
Жанр: Химия
isbn: 9781119642961
isbn:
Source: Reprinted from Ref. [31] (Copyright 2016 Elsevier B.V.).
Figure 3.13 (a) Design rationale of the fluorescence turn‐on detection of UO22+ based on AIE characteristics of 25. (b) Fluorescence spectra (λex = 370 nm) of 25 (30 mM at pH 10.3) in the presence of different amounts of UO22+. (c) Linear relationship of 25 with the addition of different amounts of UO22+.
Source: Adapted with permission from Ref. [32] (Copyright 2014 Elsevier B.V.).
Figure 3.14 (a) Schematic illustration of the PPi detection mechanism of 26 copper(II) complex. (b) Fluorescent intensity response at 570 nm of 26 copper(II) complex with different anions in a 20% DMSO aqueous solution.
Source: Reprinted from Ref. [39] (Copyright 2015 Royal Society of Chemistry).
Cysteine (Cys) as one of the abundantly existing amino acids plays an indispensable role in physiological activities such as metabolism in complex biological organisms. However, how to improve the selectivity of the probe for cysteine and effectively distinguish it from homocysteine and glutathione in actual detection is a challenge for the fluorescence detection of Cys. Tong et al. reported an SSB‐based fluorescence turn‐on probe 27 for the detection of cysteine over homocysteine and glutathione [40]. As represented in Figure 3.15a, the cyclization reaction between Cys and the acryloyl ester on 27 results in the following hydrolyzation of 27 to produce SSB fluorophore with both AIE and ESIPT. Due to the selectivity of the cyclization reaction efficiency, this method is more selective for cysteine than for homocysteine and glutathione. The linear range of cysteine detection in the buffer is 0.5–30 μM, and the detection limit is 0.46 μM. This method was also applied for the effective quantitation of Cys in FBS.
Figure 3.15 (a) Cyclization reaction of 27 with Cys followed by hydrolysis to give the final SSB fluorophore. (b) Fluorescence spectra of 27 in the presence of different amounts of Cys in PBS buffer. Inset: photographs of 27 before and after the addition of Cys under a 365‐nm UV lamp and the fluorescence intensity at 558 nm as a function of Cys concentration. (c) Fluorescence intensity of 27 in the presence of Cys, Hcy, GSH, and other amino acids.
Source: Reprinted from Ref. [40] (Copyright 2015 Royal Society of Chemistry).
The detection and quantification of biological macromolecules including proteins, enzymes, and polysaccharides are of crucial importance to life science, biotechnology, as well as health care of human beings such as clinical diagnostic examinations and treatment monitoring. Taking advantage of the AIE and ESIPT effects, diverse sensing systems based on SSB fluorophores were facilely set up. Tong's group has established fluorescent SSB probes for the detection of proteins and enzymes with large Stokes shift in the past decade. For instance, Figure 3.16a demonstrates a noncovalently labeled fluorescence turn‐on detection method specifically to a highly cationic protein, protamine [42]. When the pH of the solution was at 9.16, probe 28 dissolved well in water due to the dissociation of the carboxyl group and thus exhibited extreme weak fluorescence. Adding protamine to the solution formed 28‐protamine aggregates based on electrostatic interactions, and the protamine concentration was measured by detecting the fluorescence enhancement signal of the aggregates (Figure 3.16b, c). The detection limit was as low as 43 ng/ml. The probe was also employed to study the electrostatic association between protamine and heparin.
Figure 3.16 (a) Design principle of the fluorescence turn‐on detection of protamine based on AIE characteristics of 28 and its application in detecting the interaction between protamine and heparin. (b) Fluorescence spectra of 28 in the presence of different amounts of protamine (from 0 to 30 mM). The inset shows the photographs of the solution of 28 in the absence (a) and presence (b) of protamine under a 365‐nm UV light. (c) Kinetic behavior of the fluorescence intensity (peaks in fluorescence spectra) of 28 with the addition of different amounts of protamine.
Source: Adapted with permission from Ref. [42] (Copyright 2010 Royal Society of Chemistry).
Another type of a series of SSB probe is to detect hydrophobic proteins such as BSA and human serum albumin (HSA) in aqueous solution. Figure 3.17a shows a ratiometric fluorescent probe 29 for the detection of hydrophobic proteins (casein) or proteins with hydrophobic pockets (BSA, HSA) through hydrophobic interaction [44]. Probe 29 emits a blue fluorescence at 436 nm due to the deprotonation of the hydroxyl group when it dissolves in water at pH 7.4. When binding to the hydrophobic pocket of a protein such as BSA, the OH group recovers generating a new red‐shifted emission enhancement at 518 nm, resulting in an obvious fluorescent color distinction that can be easily distinguished by naked eye (Figure 3.17b, c). The fluorescence intensity ratio, I518/I436, was linearly related to the concentrations of a series of hydrophobic proteins. The detection limits for BSA, HSA, and casein based on IUPAC (CDL = 3 Sb/m) were 16.2, 10.5, and 5.7 mg/ml, respectively.
Enzymes are biomacromolecules that accelerate or catalyze biological or chemical reactions, and most enzymes belong to an important class of proteins in essence. There is no doubt that enzymes play a critical part in nearly all metabolic processes so that the evaluation of enzyme activity is of great significance. A mostly general and direct idea for the enzyme activity detection probe design is to modify the functional group with a substrate of the enzyme to block the probe fluorescence. As shown in Figure 3.18a and d, substituting ortho‐hydroxyl groups of salicylaldehyde to destroy the ESIPT process and quench fluorescence is a very simple and effective way to design fluorescence light‐up enzyme probes. Probes 30 СКАЧАТЬ