氨肽酶N荧光探针的研究进展

氨肽酶N(aminopeptidase N,APN)是一种外肽酶,广泛存在于哺乳动物体内,可从蛋白质多肽链的N末端水解中性或碱性氨基酸,在人体中具有多种重要的生理功能。APN可作为癌症诊断的标志物,尿液中APN也可作为肾小球肾炎的早期生物标志物。本文综述了APN荧光探针的研究进展,主要包括亲和力型APN荧光探针和反应型APN荧光探针,并对它们的优缺点进行了比较;最后对APN荧光探针的发展前景进行了展望。     

Recent progress in Michael addition-based fluorescent probes for sulfur dioxide and its derivatives

In this review, we have summarized the recent progress of Michael addition-based fluorescent probes for SO₂ and its derivatives in the design strategies, sensing performances, detection mechanisms and applications.     

Recent advances in formaldehyde-responsive fluorescent probes

Formaldehyde is one of the simplest reactive carbonyl species. In view of the harmfulness of formaldehyde in nature and humans, it is of great signifi cance to further elucidate roles and functions of formaldehyde by a noninvasive detection approach. Fluorescent probes have become a popular tool to track and detect formaldehyde in vitro and in vivo, which have attracted more and more interest recently. This review focuses on various reaction mechanisms to design the fluorescent probes for detecting formaldehyde.     

Biomarker-targeted fluorescent probes for breast cancer imaging

This review summarized fluorescent probes for breast cancer imaging according to different biomarkers probes recognized.     

Discovery of naphthalimide conjugates as fluorescent probes for α_1-adrenoceptors

α_1-Adrenoceptors(α_1-ARs), including at least three subtypes, α_(1A), α_(1B) and α_(1D), which play essential roles in G protein-coupled receptors(GPCRs), can convey multiple pivotal extracellular signals in varied tissues and organs. In this research, a series of napthalimide-based small-molecule fluorescent probes(1a–1f) for α_1-ARs, including two parts, a pharmacophore(quinazoline and phenylpiperazine) for α_1-AR recognition and a fluorophore(naphthalimide) for visualization, were designed and synthesized successfully. These compounds display excellent fluorescence property and high affinity to receptors,which were used successfully for in vitro visualization of α_1-adrenoceptors.     

Relative sensitization efficiency of fluorescent probes/sensitizers for monitoring and acceleration of cationic photopolymerization of monomers

The performance of a series of 1-amino-2,6-dicyano-3,5-diphenylbenzene derivatives (i.e., meta-terphenyls) as fluorescent molecular probes for monitoring cationic photopolymerization of monomers by the Fluorescence Probe Technique (FPT) was studied. It was found that the m-terphenyls accelerate the cationic photopolymerization initiated with diphenyliodonium photoinitiators at the wavelength where the photoinitiator alone does not work. Consequently, application of the m-terphenyls in a dual role: (a) as fluorescent probes for monitoring the cationic polymerization progress, and (b) as long-wavelength sensitizers for diphenyliodonium photoinitiators is proposed. Next, a precise method for determination of relative sensitization efficiency of the sensitizers has been devised and applied for evaluation of the performance of the m-terphenyl sensitizers in comparison to that of a commercial sensitizer: 2,4-diethyl-9H-thioxanthen-9-one.     

Design and synthesis of squaraine based near infrared fluorescent probes

A novel class of dialkylanthracene containing squaraine dyes (Sq1-3) possessing intense absorption and emission in the NIR region has been synthesized. Structural and electronic features investigated using DFT methods suggest that the significant bathochromic shifts observed on replacing dialkylaniline by dialkylanthracene in this class of molecules can be attributed to a reduction in the HOMO-LUMO gap mainly due to enhanced hydrogen bonding between the carbonyl group of the cyclobutane ring and the neighboring aromatic hydrogen in the dyes containing the anthracene moiety. The absence of fluorescence in aqueous media and high fluorescence when encapsulated into hydrophobic domains make this class of dyes especially useful as probes for mapping such domains in biological systems.     

Recent advances in molecular fluorescent probes for organic phosphate biomolecules recognition

This review provided a systematic overview of the recent researches on the small-molecule fluorescent probes for recognition various organic phosphate biomolecules (OPBs) including nucleotides, NAD(P)H, FAD/FMN and PS. The general strategies and the recognition mechanisms for these OPBs probe designs were described and emphasized to inspire the better design for fluorescent probes in the future.     

Recent advances in molecular fluorescent probes for organic phosphate biomolecules recognition

Organic phosphate biomolecules (OPBs) are indispensable components of eukaryotes and prokaryotes, such as acting as the fundamental components of cell membranes and important substrates for nucleic acids. They play pivotal roles in various biological processes, such as energy conservation, metabolism, and signal modulation. Due to the difficulty of detection caused by variety OPBs, investigation of their respective physiological effects in organisms has been restrained by the lack of efficient tools. Many small fluorescent probes have been employed for selective detection and monitoring of OPBs in vitro or in vivo due to the advantages of tailored properties, biodegradability and in situ high temporal and spatial resolution imaging. In this review, we summarize the recent advances in fluorescent probes for OPBs, such as nucleotides, NAD(P)H, FAD/FMN and PS. Importantly, we describe their identification mechanisms in detail and discuss the general strategies for these OPBs probe designs, which provide new insights and ideas for the future probe designs.     

Unnatural benz-X-azolyl asparagine derivatives as novel fluorescent amino acids: synthesis and photophysical characterization

A family of new asparagine derivatives bearing benzothiazole and benzimidazole units, functionalised with electron donor or acceptor groups, were synthesized in good to excellent yields. The photophysical characterization of these new heterocyclic amino acids was performed by UV-visible absorption and fluorescence emission studies and revealed that the compounds displayed remarkably high fluorescence quantum yields and Stokes' shifts, making them good candidates for application as fluorescent probes by incorporation into peptidic frameworks.     

Synthesis of 3-hydroxyflavone fluorescent probes and study of their fluorescence properties

<正>Direct measurement of dipole potential in biological membranes has been impossible and 3-hydroxyflavones(3HFs) have allowed detection of changes in dipole potential in biological systems.In the present study,sixteen derivatives of 3HF with aliphatic hydrocarbon chains of different lengths at 4′-position and 6-position were synthesized.The basic fluorescence properties of 3HFs are maintained in all the probes in terms of strong blue shift in maximum fluorescence emission wavelength and100 fold increase in quantum yield in organic solvents and in dioleoylphosphatidylcholine(DOPC) small unilamellar vesicles(SUV) in comparison to in aqueous Hepes buffer(15 mmol/L,pH 7.4).More importantly,the ability of the new compounds to report dipole potential changes in biological systems are also maintained,since all the new probes showed spectrum properties that are similar to yet different from that of F4N1,which potentially may allow more sensitive measurement of the dipole potential change in membranes.     

Synthesis of novel Tröger's bases analogues. The first ones fluorescent by excited state intramolecular proton transfer (ESIPT)

Three new Tröger's bases, fluorescent by an ESIPT mechanism and with large Stokes shift has been synthesized from 2-(4^′-amine-2^′-hydroxyphenyl)benzazoles using urotropine and trifluoroacetic acid.     

Synthesis and photophysical characterization of new fluorescent bis-amino acids bearing a heterocyclic bridge containing benzoxazole and thiophene

A series of new bis-alanine derivatives bearing (oligo)thiophene and benzoxazole units as the heteroaromatic bridge were synthesized in moderate to good yields. The photophysical characterization of these bis-amino acids was performed by UV-vis absorption and fluorescence emission studies and revealed that the compounds displayed exceptionally high fluorescence quantum yields, making them good candidates for application as fluorescent probes when incorporated into peptides, as well as peptide conformation-restricting and cross-linking elements.     

Bifunctionalised long-wavelength fluorescent probes for biological applications

The synthesis of benzo[a]phenoxazinium chlorides which are bifunctionalised in position 2 with 4-ethoxy-4-oxobutoxyl, 3-hydroxypropoxyl or 3-chloropropoxyl groups, and in position 9 with the (aminopropyl)amino group, was efficiently performed. The covalent labelling of valine was carried out by using one of the new fluorophores obtained. Photophysical studies in the homogeneous media of ethanol, distilled water and simulated physiological conditions revealed that all the compounds absorbed and emitted from 610 to 651 nm.     

Fluorescent probes for the stabilization and detection of G-quadruplexes and their prospective applications

This review article discusses the non-covalent interaction of various probe molecules of different structural diversity with G-quadruplex forming Guanine rich DNA sequences, revealing remarkable stimuli responsive fluorescence changes which are appropriate for sensing and other technological applications. Tailor-made probes having quadruplex inducing/stabilizing attachments of well-known dye molecules and its derivatives such as, coumarins, cyanines, thiazole orange, pyrazines, thioflavin T, triphenylmethane, tetraphenylethene, dimethylindole red etc have been employed. These probes express their modulations due to the binding to the topologically distinct G-quadruplexes through structural rigidization, aggregation propensity, binding strengths, tunability and other competitive interactions and are viewed as remarkable changes particularly in their fluorescence features. Based on this concept, several studies have reported the development of label free fluorescence sensor for the selective detection of topology specific G-quadruplexes, therapeutic, early diagnostic of cancer, cation-sensing, trace level detection of an anti-cancer drugs etc. have been accomplished. In vivo imaging is also achieved using a cholesterol attached G-quadruplex forming oligonucleotide probe labelled with specific dyes. Since the fine details of the topological information and control mechanisms of G-quadruplex forming sequences are very much essential for targeting and tuning several important biological processes relevant to cancer proliferation and developing stimuli responsive sensors, it is sure that many more contributions in this field will emerge in the coming years.     

Triphenylmethane dyes as fluorescent probes for G-quadruplex recognition

Triphenylmethane (TPM) dyes normally render rather weak fluorescence due to easy vibrational deexcitation. However, when they stack onto the two external G-quartets of a G-quadruplex (especially intramolecular G-quadruplex), such vibrations will be restricted, resulting in greatly enhanced fluorescence intensities. Thus, TPM dyes may be developed as sensitive G-quadruplex fluorescent probes. Here, fluorescence spectra and energy transfer spectra of five TPM dyes in the presence of G-quadruplexes, single- or double-stranded DNAs were compared. The results show that the fluorescence spectra of four TPM dyes can be used to discriminate intramolecular G-quadruplexes from intermolecular G-quadruplexes, single- and double-stranded DNAs. The energy transfer fluorescence spectra and energy transfer fluorescence titration can be used to distinguish G-quadruplexes (including intramolecular and intermolecular G-quadruplexes) from single- and double-stranded DNAs. Positive charges and substituent size in TPM dyes may be two important factors in influencing the binding stability of the dyes and G-quadruplexes.     

Visualizing tributyltin (TBT) in bacterial aggregates by specific rhodamine-based fluorescent probes

Here we present the first examples of fluorescent and colorimetric probes for microscopic TBT imaging. The fluorescent probes are highly selective and sensitive to TBT and have successfully been applied for imaging of TBT in bacterial Rhodobacter ferrooxidans sp. strain SW2 cell-EPS-mineral aggregates and in cell suspensions of the marine cyanobacterium Synechococcus PCC 7002 by using confocal laser scanning microscopy.     

Development of FRET-based dual-excitation ratiometric fluorescent pH probes and their photocaged derivatives

Dual-excitation ratiometric fluorescent probes allow the measurement of fluorescence intensities at two excitation wavelengths, which should provide a built-in correction for environmental effects. However, most of the small-molecule dual-excitation ratiometric probes that have been reported thus far have shown rather limited separation between the excitation wavelengths (20-70 nm) and/or a very small molar absorption coefficient at one of the excitation wavelengths. These shortcomings can lead to cross-excitation and thus to errors in the measurement of fluorescence intensities and ratios. Herein, we report a FRET-based molecular strategy for the construction of small-molecule dual-excitation ratiometric probes in which the donor and acceptor excitation bands exhibit large separations between the excitation wavelengths and comparable excitation intensities, which is highly desirable for determining the fluorescence intensities and signal ratios with high accuracy. Based on this strategy, we created a coumarin-rhodamine FRET platform that was then employed to develop the first class of FRET-based dual-excitation ratiometric pH probes that have two well-resolved excitation bands (excitation separations>160 nm) and comparable excitation intensities. In addition, these pH probes may be considered as in a kind of "secured ratioing mode". As a further application of these pH probes, the dual-excitation ratiometric pH probes were transformed into the first examples of photocaged dual-excitation ratiometric pH probes to improve the spatiotemporal resolution. It is expected that the modular nature of our FRET-based molecular strategy should render it applicable to other small-molecule dual-dye energy-transfer systems based on diverse fluorescent dyes for the development of a wide range of dual-excitation ratiometric probes with outstanding spectral features, including large separations between the excitation wavelengths and comparable excitation intensities.     

Functionalised benzo[a]phenoxazine dyes as long-wavelength fluorescent probes for amino acids

A series of monoreactive functional benzo[a]phenoxazinium chlorides with a carboxyl, hydroxyl, amine or chloromethyl group were used as labels in the preparation of long-wavelength fluorescent amino acid bioconjugates. UV-visible and fluorescence studies of all compounds were carried out in ethanol and water at physiological pH. The absorption and emission of all compounds synthesised were in the range 555-640 nm and 632-681 nm, respectively.