Dansyl Group Research Articles

The Optimization of the One-Pot Synthesis of Au@SiO2Core-Shell Nanostructures: Modification with Dansyl Group and Their Fluorescent Properties.

This work describes the optimization of the one-pot synthesis of fine core-shell nanostructures based on nanogold (Au NPs) and silica (SiO2). The obtained core-shell nanomaterials were characterized by Transmission Electron Microscopy (TEM and by the method of spectroscopes such as UV-Vis Spectroscopy and Fourier Transform Infrared Spectroscopy (FT-IR). In addition, the measurement of the zeta potential and size of the obtained particles helped present a full characterization of Au@SiO2 nanostructures. The results show that the influence of reagents acting as reducers, stabilizers, or precursors of the silica shell affects the morphology of the obtained material. By controlling the effect of the added silica precursor, the thickness of the shell can be manipulated, the reducer has an effect on the shape and variety, and then the stabilizer affects their agglomeration. This work provides also a new approach for Au@SiO2core-shell nanostructure preparation by further modification with dansyl chloride (DNS-Cl). The results show that, by tuning the silica shell thickness, the intensity of the fluorescence spectrum of Au@SiO2-(CH2)3-NH-DNS nanocomposite is about 12 times higher than that of DNS-Cl.

Ratiometric peptide-based fluorescent probe with large Stokes shift for detection of Hg2+ and S2− and its applications in cells imaging and smartphone-assisted recognition

In this work, a new ratiometric fluorescent probe DKA was synthesized based on the double sides of lysine backbone conjugated with alanine and dansyl groups. DKA exhibited fluorescence ratiometric response for Hg2+ with high sensitivity (13.4 nM), specific selectivity (only Hg2+), strong anti-interference ability (no interference), fast recognition (within 60 s) and wide pH range (5–10). The stoichiometry of binding of DKA and Hg2+ was determined to be 1:1 via Job’s plot, ESI-HRMS and 1HNMR titration analysis. Subsequently, the in situ formation of DKA-Hg2+ complex was used for highly selective detection of S2− as a novel fluorescence “on–off” probe, and the lowest detection limit for S2− was 12.9 nM. In addition, DKA possessed excellent cells permeation and low toxicity, and fluorescence imaging of Hg2+ and S2− was performed in living Hacat cells. Most importantly, the digital imaging using a smartphone color recognition APP indicated that DKA could semi-quantitatively and visually detected Hg2+ and S2− without expensive equipment.

Epoxide Ring‐Opening Reactions for Abundant Production of Mugineic Acids and Nicotianamine Probes

AbstractA succinct synthetic approach to mugineic acids and 2’‐hydroxynicotianamine was established. Unlike all other synthetic methods, this approach utilized epoxide ring‐opening reactions to form two C−N bonds and is characterized by the absence of redox reactions. Mugineic acid was synthesized from three readily available fragments on a gram scale in 6 steps. The protected 2’‐hydroxynicotianamine was also synthesized in 4 steps, and the dansyl group, serving as a fluorophore, was introduced through a click reaction after propargylation of the 2’‐hydroxy group. The dansyl‐labeled nicotianamine (NA) iron complexes were internalized by oocytes overexpressing ZmYS1 (from maize) or PAT1 (from human) transporters, indicating successful transport of the synthesized NA‐probe through these transporters.

Epoxide Ring-Opening Reactions for Abundant Production of Mugineic Acids and Nicotianamine Probes.

A succinct synthetic approach to mugineic acids and 2'-hydroxynicotianamine was established. Unlike all other synthetic methods, this approach utilized epoxide ring-opening reactions to form two C-N bonds and is characterized by the absence of redox reactions. Mugineic acid was synthesized from three readily available fragments on a gram scale in 6 steps. The protected 2'-hydroxynicotianamine was also synthesized in 4 steps, and the dansyl group, serving as a fluorophore, was introduced through a click reaction after propargylation of the 2'-hydroxy group. The dansyl-labeled nicotianamine (NA) iron complexes were internalized by oocytes overexpressing ZmYS1 (from maize) or PAT1 (from human) transporters, indicating successful transport of the synthesized NA-probe through these transporters.

Sequence-Defined Tertiary Amine-Based Oligomer Employing a Scalable, Support-Free, and Protection/Deprotection-Free Iterative Strategy.

Sequence-defined oligomers (SDOs) with their unique monomeric sequence and customizable nature are attracting the attention of researchers globally. The structural and functional diversity attainable in SDOs makes this platform promising, albeit with challenges in the synthesis. Herein, we report the design and synthesis of a novel class of SDO by incorporating tertiary amines into the backbone from commercially available inexpensive materials. Tertiary amines were selected due to their various material and biomedical applications. Even though the synthesis and purification of amine compounds are challenging, their various significant applications, such as pharmaceuticals, catalysts, surfactants, corrosion inhibitors, dye intermediates, polymer additives, rubber accelerators, gas treating agents, agriculture, and analytical chemistry, make them fascinating. The synthetic strategy that is designed here is extremely efficient and economical for the scalable synthesis of the SDO and is support-free, protection-deprotection chemistry-free, and catalyst/template-free. Most importantly, no extra design and synthesis of the monomer is required here. The key reactions employed for the SDO synthesis are (i) transformation of the hydroxy group to a halide and (ii) substitution of the halide by the secondary amine units. Including the purifying processes, the multigram synthesis of 4-mer was completed in 12-14 h. The synthetic strategy was established by synthesizing two different sequences of SDOs. The SDOs are characterized by 1H NMR and LC-MS. The tandem MS (MS/MS) experiment was conducted in order to validate the sequences over the SDO chain. Furthermore, the SDO platform was advanced in two ways: (i) by increasing the chain length via attaching a linker, which provides a rapid method for increasing the tertiary amine over the SDO chain, and (ii) postsynthetic modification of SDO with other functional groups, including guanidine for biological importance and a well-known fluorophore dansyl group for material significance.

5-Alkyloxymethyl Derivatives of 2ʹ-Deoxyuridine Bearing 2,4-Dinitrophenyl and Dansyl Groups: Synthesis and Antibacterial Activity

Condensation of 3ʹ,5ʹ-di-O-acetyl-5-bromomethyl-2ʹ-deoxyuridine with 6-trifluoroacetylaminohexan1-ol yielded 5-(6-trifluoroacetylaminohexyl-1-oxymethyl)-3ʹ,5ʹ-di- O-acetyl-2ʹ-deoxyuridine. Its deblocking with an aqueous alcoholic solution of ammonia gave 5-(6-aminohexyl-1-oxymethyl)-2ʹ-deoxyuridine, and condensation with triazole and 2-chlorophenyl phosphorodichloridate followed by treatment with an aqueous solution of ammonia led to the formation of 5-(6-aminohexyl-1-oxymethyl)-2ʹ-deoxycytidine. The interaction of the obtained compounds with 2,4-dinitrofluorobenzene or N-hydroxysuccinimide esters of N-2,4-dinitrophenylaminohexanoic acid or 5-dimethylaminonaphthalene-1-sulfonyl glycine was used to synthesize DNP- and DNS-derivatives of 2ʹ-deoxyuridine as well as 5-(6-DNP-aminohexanoylaminohexyl-1-oxymethyl)-2ʹ-deoxycytidine. DNP derivatives of 2ʹ-deoxyuridine were shown to inhibit the growth of Micrococcus luteus.

A novel peptide-based fluorescent probe with large Stokes shift for simultaneous detection of zinc (II) and mercury (II): Smartphone, test strips, living cells and real samples applications

A simple and efficient peptide-based fluorescent probe L with large Stokes shift was synthesized, which used dansyl group as fluorophore and tetrapeptide backbone (HisGluPheCys-NH2) as recognition group for the determinations of Zn2+and Hg2+by different fluorescence response modes in 100% aqueous solution. L exhibited a highly efficient and specific selectivity for Zn2+ based on fluorescence enhancement as well as the naked eye recognition of Zn2+ was realized through the solutions color changed. Meanwhile, as a highly selective “turn off” probe, L could rapidly detect Hg2+ based on obvious fluorescence quenching. The limit of detection (LODs) for Zn2+ and Hg2+were 52.6 and 49.7 nM, respectively. Moreover, L has good accuracy, exciting water-solubility and low toxicity, which was successfully applied to determinations of Zn2+ and Hg2+ in real water samples and fluorescence imaging of Zn2+ and Hg2+ in living cells. Test strips of probe L was prepared by immersion and used for visual detection of Zn2+ and Hg2+by naked eye. Finally, the gradient change of fluorescence color of L was captured by smartphone, and then content analysis was carried out by smartphone color recognition APP.

Bioimaging ofglucose analogs labeled at the C-1 or C-2 position with a fluorescent dansylamino group.

Glucose is the most important energy source in all organisms; however, our understanding of the pathways and mechanisms underlying glucose transportation and localization in living cells is incomplete. Here, we prepared two glucose analogs labeled with a dansylamino group at the C-1 (1-Dansyl) or C-2 (2-Dansyl) position; the dansyl group is a highly fluorescent moiety that is characterized by a large Stokes shift between its excitation and emission wavelengths. We then examined the cytotoxicity of the two glucose analogs in mammalian fibroblast cells and in the ciliated protozoan Tetrahymena thermophila. In both cell types, 2-Dansyl had no negative effects on cell growth. The specificity of cellular uptake of glucose analogs was confirmed using an inhibitor of glucose transporter in NIH3T3 cells. In NIH3T3 cells and T. thermophila, fluorescence microscopy revealed that the glucose analogs localized throughout the cytoplasm, but especially at the periphery of the nucleus. In T. thermophila, we also found that swimming speed was comparable in media containing non-labeled glucose or one of the glucose analogs, which provided more evidence not only that the analogs were not cytotoxic in these cells but also that the analogs had no negative effect on the ciliary motion. Together, the present results suggest that the glucose analogs have low toxicity and will be useful for bioimaging of glucose-related systems.

Fluorescent Mechanism of a Highly Selective Probe for Copper(II) Detection: A Theoretical Study.

A highly selective probe for copper(II) detection based on the dansyl group was theoretically studied by means of (time-dependent) density functional theory. The calculated results indicated that the oscillator strength of the fluorescent process for the probe molecule is considerably large, but the counterpart of its copper(II) complex is nearly zero; therefore, the predicted radiative rate kr of the probe is several orders of magnitude larger than that of its complex; however, the predicted internal conversion rate kic of both the probe and its complex is of the same order of magnitude. In addition, the simulated intersystem crossing rate kisc of the complex is much greater than that of the probe due to the effect of heavy atom from the copper atom in the complex. Based on the above information, the calculated fluorescence quantum yield of the probe is 0.16% and that of the complex becomes 10-6%, which implies that the first excited state of the probe is bright state and that of the complex is dark state. For the complex, the hole-electron pair analysis indicates that the process of S0 → S1 belongs to metal-to-ligand charge transfer; its density-of-state diagram visually illustrates that the highest occupied molecular orbital (HOMO) contains the ingredient of the s orbital from the copper atom, which decreases the frontier orbital energy level and the overlap integral of HOMO and LUMO.

Site-Selective Incorporation of a Functional Group into Lys175 in the Vicinity of the Active Site of Chymotrypsin by Using Peptidyl α-Aminoalkylphosphonate Diphenyl Ester-Derivatives.

We previously reported that Lys175 in the region of the active site of chymotrypsin (Csin) could be site-selectively modified by using an N-hydroxy succinimide (NHS) ester of the peptidyl derivative containing 1-amino-2-ethylphenylphosphonate diphenyl ester [NHS-Suc-Ala-Ala-PheP(OPh)2]. In this study, the Lys175-selective modification method was expanded to incorporate functional groups into Lys 175 in Csin. Two types of peptidyl phosphonate derivatives with the dansyl group (Dan) as a functional molecule, Dan-β-Ala-[Asp(NHS) or Glu(NHS)]-Ala-Ala-(R)-PheP(OPh)2 (DanD and DanE, respectively), were synthesized, and their action was evaluated when modifying Lys175 in Csin. Ion-exchange chromatography (IEC), fluorescence spectroscopy, and LC-MS/MS were used to analyze the products from the reaction of Csin with DanD or DanE. By IEC and LC-MS/MS, the results showed that DanE reacted with Csin more effectively than DanD to produce the modified Csin (DanMCsin) bearing Dan at Lys175. DanMCsin exhibited an enzymatic activity corresponding to 1/120 of Csin against Suc-Ala-Ala-Phe-pNA. In addition, an effect of Lys175 modification on the access of the proteinaceous Bowman-Birk inhibitor to the active site of DanMCsin was investigated. In conclusion, by using a peptidyl derivative containing 1-amino-2-ethylphenylphosphonate diphenyl ester, we demonstrated that a functional group could be incorporated into Lys175 in Csin.

A Multiresponsive Calix[6]arene Pseudorotaxane Empowered by Fluorophoric Dansyl Groups

We report the synthesis and characterization, by means of NMR and UV-visible spectroscopy and electrochemical techniques, of a dansyl calix[6]arene derivative and of its pseudorotaxane complex with a bipyridinium-based axle. This novel macrocycle shows remarkable complexation ability, in analogy with parent compounds, while the dansyl moieties impart valuable features to the system. Indeed, these units: i) signal the state of the system by fluorescence; ii) can be reversibly protonated, enabling the modulation of the complexation abilities of the macrocycle; iii) participate in photoinduced electron transfer processes, which may be exploited to tune the stability of the supramolecular complex. Therefore, in this multiresponsive pseudorotaxane, the threading and de-threading motions of the molecular components can be modulated either by protonation of the calixarene host or by reduction of the bipyridinium guest, which can be accomplished both by electrochemical reduction and via photoinduced electron transfer. Overall, three orthogonal and reversible stimuli can be used to induce molecular movements of the pseudorotaxane components.

Fluorescence spectral detection of copper(II), mercury(II) and zinc(II) based on a multifunctional peptide-based sensor

A fluorescence peptide-based sensor (Dansyl-His-Thr-Glu-His-Trp-NH2, D-P5) was synthesized by Fmoc solid phase peptide synthesis, using dansyl group as the fluorophore. The sensor exhibited different fluorescence responses and sensitive detections for copper(II), mercury(II) and zinc(II) ions as a multifunctional sensor. The detailed investigation suggested that the limits of detection were 37.6 nmol⋅L−1, 37.8 nmol⋅L−1 and 59.4 nmol⋅L−1 for copper(II), mercury(II) and zinc(II) ions, respectively, and the highly sensitive sensor was not influenced by other species. The sensor exhibited a strong binding ability to copper(II), mercury(II) and zinc(II) ions with the binding constants of 3.23 × 105 L⋅mol−1, 6.37 × 105 L⋅mol−1 and 6.0 × 104 L⋅mol−1, respectively. The binding stoichiometries of the sensor to copper(II), mercury(II) and zinc(II) ions measured by Job's plot were all 1:1. Furthermore, The sensor has been successfully used for the detections of copper(II), mercury(II) and zinc(II) in actual water samples.

Photoinduced electron transfer in host-guest interactions of a viologen derivative with a didansyl-pillar[5]arene

With the goal of understanding the electron transfer mechanism of fluorophore-functionalized pillararenes, a pillar[5]arene bearing two dansyl fluorophore moieties at the opposite rims of its cavity has been synthesized, and the behavior of such a new host molecule has been thoroughly investigated in the presence of an N,N′-di-(6-bromohexyl)-viologen derivative. 1H NMR, NOESY and DOSY experiments demonstrated that the pillar[5]arene recognizes the viologen derivative, forming a 1:1 host-guest complex by including one of the two bromoalkyl chains within its π-rich cavity. Photophysical and electrochemical studies revealed that, upon guest addition to the host, the fluorescence intensity of the complex is progressively quenched by a photoinduced electron transfer process (PET) from one of the dansyl groups of the host to the viologen moiety of the guest.

A bifunctional peptide-based fluorescent probe for ratiometric and “turn-on” detection of Zn(II) ions and its application in living cells

In this work, a bifunctional peptide-based fluorescent probe L containing a tetrapeptide scaffold (Pro-Gly-His-Trp-NH2) and a dansyl group was synthesized using solid phase peptide synthesis (SPPS) technology. As designed, L, based on a FRET mechanism, exhibited high selectivity, excellent ratiometric signals, and fast response to Zn2+ in aqueous solutions at an excitation wavelength of 280 nm. In addition, when excited at 320 nm, L exhibited a fluorescent “turn-on” response towards Zn2+ based on PET mechanism. More importantly, the stoichiometry of L and Zn2+ was determined to be 2:1 by fluorescent titration, Job’s plot method, and ESI-MS spectrometry. The association constant for Zn2+ ions was determined to be 6.26 × 108 M−2, while the limit of detection (LOD) of L was estimated as 5.43 nM, which is a much lower value than WHO and EPA guidelines for drinking water. Moreover, L was successfully applied to detect both Zn2+ and Cu2+ in living cells due to good biocompatibility and excellent low toxicity.

A highly selective and sensitive Zn2+ fluorescent sensor based on zinc finger-like peptide and its application in cell imaging

Developing new chemosensors for detection of Zn2+ has attracted great attentions because of the important roles of Zn2+ in biological systems, and it will produce toxic effects with an excessive intake of zinc ion. Metalloproteins are often used as an effective template for the design and development of peptide-based fluorescent sensors. In this study, we designed a new and simple ratiometric fluorescent sensor for Zn2+, which was based on a zinc finger-like peptide and labeled with a dansyl group, i.e., Dansyl-His-Gln-Arg-Thr-His-Trp-NH2 (D-P6), by using solid phase peptide synthesis (SPPS). The dimeric peptide has a high affinity for Zn2+ overothermetalions, as indicated by spectroscopic studies, as well as molecular modeling. Remarkably, the sensor exhibited a highly selective and sensitive ratiometric fluorescent response to Zn2+ by fluorescent resonance energy transfer effect between tryptophan residue and fluorophore dansyl group, with a very low detection limit of 33 nM in aqueous solution. Furthermore, the sensor displayed a very low biotoxicity, which allows successful detection of Zn2+ in living HeLa cells. We believe that the new sensor may have potential applications in biological science.

Quantitative analysis of tryptophan and its metabolites in urine by ultra performance liquid chromatography-tandem mass spectrometry

基于超高效液相色谱-串联质谱(UPLC-MS/MS)建立定量分析色氨酸(Trp)及代谢产物3-OH-犬尿氨酸(3-OH-Kyn)、3-OH-邻氨基苯甲酸(3-OH-AA)、黄尿酸(XA)、犬尿氨酸(Kyn)、5-羟基吲哚乙酸(5-HIAA)、犬尿喹啉酸(KA)和5-羟色胺(5-HT)的方法,应用该方法分析其在尿样中的含量,探讨排泄规律。将尿样稀释、离心后,加入丹磺酰氯(DNS-Cl)衍生,经Thermo C18色谱柱(50 mm×3 mm, 2.7 μm)分离和0.1%甲酸和甲醇梯度洗脱后,采用电喷雾电离(ESI)源,在正离子扫描和多反应监测(MRM)模式下检测。以咖啡酸(CA)为内标,定量分析。结果显示,8种目标化合物的线性关系良好,相关系数(R 2)≥0.9740,检测灵敏(LOD为0.005~0.5 ng/mL),回收率高(93.24%~107.65%)。采用本方法检测分析了健康志愿者70个尿液样本,在尿样中检测到Trp原型及其7种代谢产物。结果表明,体内的Trp是通过原型和代谢两种方式排泄:Trp原型的含量为5.22~20.88 μg/mL;尿液中经代谢后排泄的Trp量是原型的124%~268%,即体内的Trp主要经代谢后排出体外。方法主要研究了Trp-5-HT和Trp-Kyn两条途径的代谢产物含量,Trp经Kyn降解生成的3-OH-AA和3-OH-Kyn含量较多,即Trp-Kyn是体内Trp的主要代谢途径。方法通过UPLC-MS/MS实现了尿液中Trp及其代谢产物含量的检测,能为临床检查提供技术和理论支持。

Fast and Sensitive Bacteria Detection by Boronic Acid Modified Fluorescent Dendrimer.

This study reports a novel, fast, easy, and sensitive detection method for bacteria which is urgently needed to diagnose infections in their early stages. Our work presents a complex of poly(amidoamine) dendrimer modified by phenylboronic acid and labeled by a fluorescent dansyl group (Dan-B8.5-PAMAM). Our system detects bacteria in 20 min with a sensitivity of approximately 104 colony-forming units (CFU)·mL−1. Moreover, it does not require any peculiar technical skills or expensive materials. The driving force for bacteria recognition is the binding between terminal phenylboronic acids on the probe and bacteria’s surface glycolipids, rather than electrostatic interactions. The aggregation caused by such binding reduces fluorescence. Even though our recognition method does not distinguish between live or dead bacteria, it shows selective antibacterial activity towards Gram-negative bacteria. This study may potentially contribute a new method for the convenient detection and killing of bacteria.

A dansyl-derivatized phytic acid analogue as a fluorescent substrate for phytases: experimental and computational approach

A new myo-inositol pentakisphosphate was synthesized, which featured a dansyl group at position C-5. The fluorescent tag was removed from the inositol by a 6-atom spacer to prevent detrimental steric interactions in the catalytic site of phytases. The PEG linker was used in order to enhance hydrophilicity and biocompatibility of the new artificial substrate. Computational studies showed a favorable positioning in the catalytic site of phytases. Enzymatic assays demonstrated that the tethered myo-inositol was processed by two recombinant phytases Phy-A and Phy-C, classified respectively as acid and alkaline phytases, with similar rates of phosphate release compared to their natural substrate.

Dansyl-Labelled Ag@SiO2 Core-Shell Nanostructures—Synthesis, Characterization, and Metal-Enhanced Fluorescence

The present work describes synthesis, characterization, and use of a new dansyl-labelled Ag@SiO2 nanocomposite as an element of a new plasmonic platform to enhance the fluorescence intensity. Keeping in mind that typical surface plasmon resonance (SPR) characteristics of silver nanoparticles coincide well enough with the absorption of dansyl molecules, we used them to build the core of the nanocomposite. Moreover, we utilized 10 nm amino-functionalized silica shell as a separator between silver nanoparticles and the dansyl dye to prevent the dye-to-metal energy transfer. The dansyl group was incorporated into Ag@SiO2 core-shell nanostructures by the reaction of aminopropyltrimethoxysilane with dansyl chloride and we characterized the new dansyl-labelled Ag@SiO2 nanocomposite using transmission electron microscopy (TEM) and Fourier-transform infrared spectroscopy (FTIR). Additionally, water wettability measurements (WWM) were carried out to assess the hydrophobicity and hydrophilicity of the studied surface. We found that the nanocomposite deposited on a semitransparent silver mirror strongly increased the fluorescence intensity of dansyl dye (about 87-fold) compared with the control sample on the glass, proving that the system is a perfect candidate for a sensitive plasmonic platform.

Design and synthesis of dansyl-labeled inhibitors of steroid sulfatase for optical imaging

Steroid sulfatase (STS) is an important enzyme regulating the conversion of sulfated steroids into their active hydroxylated forms. Notably, the inhibition of STS has been shown to decrease the levels of active estrogens and was translated into clinical trials for the treatment of breast cancer. Based on quantitative structure–activity relationship (QSAR) and molecular modeling studies, we herein report the design of fluorescent inhibitors of STS by adding a dansyl group on an estrane scaffold. Synthesis of 17α-dansylaminomethyl-estradiol (7) and its sulfamoylated analog 8 were achieved from estrone in 5 and 6 steps, respectively. Inhibition assays on HEK-293 cells expressing exogenous STS revealed a high level of inhibition for compound 7 (IC50 = 69 nM), a value close to the QSAR model prediction (IC50 = 46 nM). As an irreversible inhibitor, sulfamate 8 led to an even more potent inhibition in the low nanomolar value (IC50 = 2.1 nM). In addition, we show that the potent STS inhibitor 8 can be employed as an optical imaging tool to investigate intracellular enzyme sub-localization as well as inhibitory behavior. As a result, confocal microscopy analysis confirmed good penetration of the STS fluorescent inhibitor 8 in cells and its localization in the endoplasmic reticulum where STS is localized.