[Show abstract][Hide abstract] ABSTRACT: Through a self-assembly of arginine/lysine-rich peptide from human papillomavirus (HPV) capsid protein and an Eu-containing polyoxometalate (POM), Na9[EuW10O36]•32H2O (EuW10), the formation of well-defined hybrid nanospheres in aqueous solution was presented, in showing large luminescence enhancement of POM and can be used as a potential “turn-on” fluorescence probe in biology. The binding mechanisms between them have been explored at molecular level by using transmission electron microscopy (TEM), scanning electron microscopy (SEM), fluorescence spectra, isothermal titration calorimetry (ITC), zeta-potential and nuclear magnetic resonance (1H NMR) titration spectra. ITC study confirmed the assembly was completely enthalpy driven, zeta-potential proved that the driving force was governed mainly by the electrostatic interaction, 1H NMR spectroscopy indicated changes in hydrogen-bond of EuW10 and the peptide segment, and the binding model were clarified finally. Our design constructed the self-assembly fabrication of well-defined nanoparticles by using inorganic POM and bio-applicable peptide, and especially it combined with strong fluorescence characterization together. The enhanced luminescence and specific targeted-HPV peptide ability would be important and useful in the detection of HPV capsid protein and/or HPV genotypes, and such protocol could be extended to other virus once using the corresponding peptides. Therefore, the present report will be helpful to promote the development of anti-virus agents in future.
The Journal of Physical Chemistry C 04/2015; 119(15):8321-8328. DOI:10.1021/acs.jpcc.5b00032 · 4.77 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Previously, we have explored the mechanism of the response of BSA-protected small gold nanoclusters(Au16NCs@BSA) to silver(I) ions (Ag+) by using XPS, but the role of the ligand BSA in this response was not clear. Therefore, we used FT-IR and circular dichroism (CD) spectra to monitor the changes of the secondary structure of ligand BSA. After adding Ag+ to the AuNCs@BSA, compare with the native BSA, the ligand-BSA showed little differences in the position of main peaks but more differences in the profile of this peak in FT-IR spectra. While in CD spectra it is not only peak shape changed but also peak position. All the results showed silver ions can bind to ligand BSA, and induced their secondary structure changes. But the changes of ligand BSA are not enough to influence the fluorescence emission of AuNCs@BSA, especially for the emission of AuNCs. And BSA-protected different size gold nanoclusters have the similar changes in spatial structure of ligand BSA, but only the Au16NCs@BSA could response to Ag+, which indicated that the ligand BSA was not the key role for the special fluorescent response.
[Show abstract][Hide abstract] ABSTRACT: A continuous fluorometric assay system based on melittin and a pyrene derivative 1 for trypsin and its inhibitor screening is successfully developed by taking advantage of the noncovalent-binding-induced pyrene excimer. The 1 melittin assembly and its disassembly after further addition of trypsin are confirmed by the fluorescence changes at 475 nm. Such a system can be applied to other proteases of melittin, and essentially, the concept based on the noncovalent-binding-induced continuous fluorometric assay can be extended to other biochemical analyses.
[Show abstract][Hide abstract] ABSTRACT: We report the clarification of responsive mechanism of the BSA-protected small gold nanoclusters (Au16NCs@BSA) to silver(I) ions (Ag+). The titration of Au16NCs@BSA solutions with Ag+ produces a blue-shift and enhancement of the fluorescence spectra, but no similar effects can be observed for other metal ions. Meanwhile, an isosbestic point in UV–vis absorbance spectra of Au16NCs@BSA induced by Ag+ is observed, which indicates a stoichiometric conversion of one substance to another. Through X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and MALDI-TOF mass spectrum measurements, the reduction of Ag+ to Ag0 by Au16NCs@BSA have been ascertained, where the Au16NCs act as reductant toward Ag+ in forming hybrid Au@AgNCs adducts. The mechanism revealed provided a facile and mild method to build high luminescent alloy nanoclusters.
The Journal of Physical Chemistry C 07/2013; 117(31):16159–16165. DOI:10.1021/jp403466b · 4.77 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We investigated the pH-induced fluorescence changes of BSA-protected gold nanoclusters, Au16NCs@BSA, and the corresponding conformational changes of ligand protein by fluorescence, circular dichrosim (CD) and IR spectral measurements. The studies presented here demonstrated that BSA in AuNCs@BSA underwent identifiable conformational changes on both the secondary and the tertiary structure levels. The results of CD and IR interpreted the significant change of second structures at extreme acidity and alkaline, where more unordered structures were gained. Of note was that the extreme alkaline (pH = 11.43) induced the changes from exposed to buried α-helices, which was different from the pH-induced structural changes of BSA. In addition, the large fluorescence intensity gap of tryptophan between AuNCs@BSA and native BSA indicated efficient energy transfer took place between BSA and AuNCs, implying that the gold core resided near tryptophan in BSA.
[Show abstract][Hide abstract] ABSTRACT: We have developed a series of azadipeptide nitriles with different P3 groups. A triaryl meta-phenyl derivative, compound , was not only a potent inhibitor for cathepsin K (K(i) = 0.0031 nM), but also highly selective over both cathepsins B and S (∼1000-fold). A protein-ligand docking study performed on the series provided a possible explanation why compound could be significantly more potent than the others, especially compound in the same series.
[Show abstract][Hide abstract] ABSTRACT: We investigated the pressure-induced fluorescence enhancement of BSA-protected gold nanoclusters, AuNCs@BSA, and the corresponding conformational changes of ligand protein by in situ fluorescence and IR spectral measurements. It is documented that the fluorescence enhancement of AuNCs@BSA is essentially attributed to the conformational changes of the ligand, which undergoes substantial secondary and tertiary structural changes. Under compression BSA loses more buried α-helical structure, while it changes oppositely in the AuNCs@BSA as the protein adopts a more flexible conformational state at the boundary surface of gold nanoclusters. The present work will be helpful to understand the fundamental mechanism and to reveal the important factors of ligands in nanoclusters, which are hope to improve the luminescence efficiency of gold nanoclusters in final.
The Journal of Physical Chemistry C 12/2012; 117(1):639–647. DOI:10.1021/jp309175k · 4.77 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this study, we report a histidine-based fluorescence probe for Cu(2+) and Hg(2+), in which the amino group and imino group were modified by two common protective groups, 9-fluorenylmethoxycarbonyl and trityl group, respectively. In a water/methanol mixed solution, the probe displayed a selective fluorescence "turn-off" response to Cu(2+) when the ratio of CH(3)OH/H(2)O was higher than 1:1. Specifically, when the solvent is changed to 1:1 methanol/water, the 304 nm fluorescence peak is enhanced, while the 317 nm peak is weakened, upon addition of either Cu(2+) or Hg(2+) ions. The mechanism for such distinct responses of the probe to Cu(2+) and Hg(2+) was further clarified by using NMR and molecular simulation. The experiment results indicated that the polarity of solvent could influence the coordination mode of 1 with Cu(2+) and Hg(2+), and control the fluorescence response as a "turn-off" or ratiometric probe.
Photochemistry and Photobiology 04/2012; 88(4):824-30. DOI:10.1111/j.1751-1097.2012.01159.x · 2.68 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A one-step microwave-assisted method is used for the synthesis of small gold nanoclusters, Au(16)NCs@BSA, which are used as a fluorescence enhanced sensor for detection of silver(I) ions with high selectivity and sensitivity.
[Show abstract][Hide abstract] ABSTRACT: Due to possessing unique optical properties, semiconductor quantum dots (QDs) have been applied to construct bioconjugates. Using QDs as donors, the Förster resonance energy transfer (FRET) system can be developed and applied to biological imaging and sensing, and various construction strategies have been reported. To provide a new practicable method, we introduce a protocol with two routes to construct a supramolecular FRET system based on the high-affinity interaction between melittin and phosphocholine. Melittin exists with a random coil structure in aqueous environments but will adopt a bent helix when inserted into natural or artificial membranes. Such specific and high affinity protein-membrane interaction makes it possible to construct a QDs-based FRET system. The strategy applying protein-membrane interaction to construct a QDs-based FRET system can be applied to the investigation on the protein-membrane interaction through distance-depended FRET and further proteolysis of trypsin. Because of the existence of various protein-membrane interactions in real life, the system has the potential to be expanded to other related systems.
[Show abstract][Hide abstract] ABSTRACT: As the second most abundant transition-metal ion in the human body, Zn2+ plays crucial roles in many important biological processes; while in the environment, an excessive concentration of Zn2+ may reduce the soil microbial activity resulting in phytotoxic effects. Therefore, developing effective and sensitive detection method for Zn2+ has become crucially important and necessary both in life and environment science. Two new fluorescence probes, 2-((2-hydroxynaphthalen-1-yl)methyleneamino)-3-(1H-imidazol-5-yl) propanoic acid (2) and 2-hydroxy-2-((2-hydroxynaphthalen-1-yl) methyleneamino) acetic acid (3), were easily prepared by a one step reaction between 2-hydroxy-1-naphthaldehyde with histidine and serine, respectively, in ethanol. The optical properties of them were investigated by fluorescence spectra, which displayed specific and sensitive recognition to Zn2+ and especially avoided the interference of Cd2+ when they were tested against a range of physiological and environmentally relevant metal ions in aqueous solution. The responsive mechanism of the two probes to Zn2+ were involved both the CN isomerization and ICT, which were clarified by NBO charge analysis and the HOMO–LUMO energy gap calculation by using B3LYP/6-31G density functional theory.
Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 09/2011; 79(5):1688-1692. DOI:10.1016/j.saa.2011.05.036 · 2.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: An efficient, rapid, and fluorescence visual method for column separation of BSA-protected gold-nanoclusters was proposed based on the dansylation of BSA. After optimization, this procedure can be extended to the separation of any other macromolecule-protected noble metal bioconjugates.
Chemical Communications 08/2011; 47(35):9852-4. DOI:10.1039/c1cc12588e · 6.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A new probe/Cu(2+) complex for the detection of his-tagged protein has been developed, based on an improved probe, Dansyl-Gly-Py (1), by closely mimicing the structure of a peptide, ATCUN. In aqueous solution, 1/Cu(2+) has good selectivity to histidine and cysteine, and further can detect histidine-rich protein by releasing the quenched fluorescence of 1.
[Show abstract][Hide abstract] ABSTRACT: We synthesized a tetra-functional fluorescence probe based on dansyl and peptide motif, dansyl-Gly-Trp (DGT, 1), that efficiently bound several metal ions and showed distinguishing optical properties. The probe 1 could respond to Hg(2+) with enhanced and blue-shifted fluorescence emission but to Cu(2+) with obvious fluorescence quenching. In addition, 1 was sensitive to pH ranging from 2.0 to 5.0 and precipitated in the presence of Pb(2+) at neutral conditions. The combination of these intrinsic properties with the selective responses to different chemical inputs allows this system to be implemented as an ionic switch. Furthermore, 1 could penetrate the cell membrane and accumulated well in intracellular region. The underlying mechanisms of the probe to different kind of metal ion were explored successfully by using either (1)H NMR, NOESY, electron paramagnetic resonance (EPR) or FT-IR spectra. In addition, to investigate the binding model of 1/Hg(2+) and 1/Cu(2+), simulations were also performed by using density functional theory (DFT) and reasonable binding configurations were achieved for these two complexes.
Journal of Fluorescence 05/2011; 21(5):1921-31. DOI:10.1007/s10895-011-0891-6 · 1.67 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A highly selective fluorescent probe, dansyl-l-glutamic methyl diester (1), was easily prepared for Hg2+ detection, which is aggregated by target with a blue-shift and turn-on fluorescence response. The compound also can remove the Hg2+ in aqueous solution by filtering. The involved mechanism was clarified by FTIR in the solid of crystal complex 1/Hg2+ and 1H NMR spectra in aqueous solution.
Sensors and Actuators B Chemical 06/2010; 148(1-148):49-53. DOI:10.1016/j.snb.2010.03.060 · 4.29 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We report a unique protein labeling system based on melittin and a pyrene derivative (1). The specific region of the C-terminal in melittin efficiently induced the formation of the pyrene eximer, which can be used as a tag to target proteins and for further detection.
Chemical Communications 06/2010; 46(21):3768-70. DOI:10.1039/b925401c · 6.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A chemosensor 1, based on the Schiff base, is easily prepared by reacting tryptophan and 2-hydroxy-1-naphthaldehyde in methanol. The optical properties of 1 are investigated in buffered aqueous solution, which displays specific recognition to Zn2+, and especially avoids the interference of Cd2+ when 1 is tested against a range of physiological and environmentally relevant metal ions. Such a novel fluorescent probe can also be used to detect Zn2+ in live cells.
[Show abstract][Hide abstract] ABSTRACT: A hypersensitive water-soluble fluorescent probe, dansyl-L-tryptophan methyl ester (1), was easily prepared for the detection of Hg(2+) with a significantly improved detection limit (5 nM vs. 500 nM) in buffered aqueous solution.
Chemical Communications 09/2009; 29(29):4453-5. DOI:10.1039/b907386h · 6.83 Impact Factor