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ABSTRACT: A new fluorescence reagent, N,N-bi[4(1-pyrene)-butyroyl]-lysine (1) was synthesized. The new fluorescence sensor showed high sensitivity (detection limit up to 20.7μgL(-1)) and specific selectivity for Pb(2+) over other metal ions examined in aqueous solutions. It could also be used to remove Pb(2+) from aqueous solutions by filtering the insoluble 1-Pb(2+) complex with sufficient reversibility.
Analytica chimica acta 11/2012; 751:135-9. · 4.31 Impact Factor
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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. · 2.41 Impact Factor
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ABSTRACT: Adenovirus is widely used in gene therapy and vaccination as a viral vector, and its hypervariable regions (HVRs) on hexon are the main antigen recognition sites of adenovirus. The modification of this area by genetic engineering will change the antigenic specificity of the virus. In addition, recent studies have demonstrated the importance of coagulation factor X (FX) in adenovirus serotype 5-mediated liver transduction in vivo. The binding site of adenovirus to FX is the HVRs on hexon. By constructing five proteins containing chimeric HVRs from different adenovirus serotypes, we focused on the antigenic specificity and the affinity for FX of these proteins compared with the corresponding viruses. Our data showed that HVR5 and HVR7 had only a part of hexon activity to neutralizing antibodies (NAbs) compared with the complete activity of HVR1-7. Results also demonstrated a differential high-affinity interaction of the HVRs proteins with FX and indicated that HVRs protein had a similar binding ability with corresponding adenovirus serotype. These results highlighted some properties of chimeric HVRs proteins and revealed the influence on the structure and function of hexon proteins and adenovirus resulting from the HVRs.
Biochemical and Biophysical Research Communications 04/2012; 421(2):170-6. · 2.48 Impact Factor
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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.
Nanoscale 03/2012; 4(7):2251-4. · 5.91 Impact Factor
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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.
ACS Applied Materials & Interfaces 03/2012; 4(3):1267-72. · 4.53 Impact Factor
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ABSTRACT: Here we report the rapid and convenient patterning of proteins on porous polymer film using the inverse microemulsion approach. Following this method, proteins, which were dissolved in water, were transferred into dichloromethane solution of polymers through the formation of inverse microemulsion by mixing the two solutions. The protein-containing microemulsion droplets accumulated automatically into large and stable ones on the surface of organic solution casting on solid substrates, and formed tightly packed microemulsion droplet arrays driven by surface tension. With the evaporation of organic solvent and water, the microemulsion droplet arrays, which act as the template, turn to honeycomb patterned pores bearing proteins in them. The formed protein patterns can be locally applied for the detection of other proteins through specific recognition. The generality and reproducibility for the formation of BSA/PS microporous film and protein patterning by using different polymers and solvents were demonstrated by investigating surfactant addition, polymer and solvent types, and casting volume on the morphology of the microporous films. A preliminary mechanism for the protein patterning is discussed based on the analysis of the experimental results.
Chemistry 12/2011; 18(2):526-31. · 5.93 Impact Factor
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ABSTRACT: A novel homoplastic podand fluorescent sensor based on flexible hydrophilic lysine was prepared. Lysine with two dansyl groups-appended at both ends supplied a possibility for a tridentate binding toward Hg(II) and finally resulted in a unique selectivity to Hg(II) over other transition-metal ions with a hypersensitivity (detection limit 2.0 nM) in neutral buffered aqueous solutions. Notably, the coordination of chloride ion to the complex of sensor-Hg(II) brought forth that the trend in the NMR chemical shift for hydrogen and carbon atoms of the sensor was contrary to the findings in the former reports, which shows upfield shifts for the hydrogens and the alkane carbons but downfield shifts for the dansyl carbons, respectively.
Inorganic Chemistry 09/2011; 50(20):10028-32. · 4.60 Impact Factor
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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. · 6.17 Impact Factor
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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.
Organic & Biomolecular Chemistry 06/2011; 9(11):4032-4. · 3.70 Impact Factor
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ABSTRACT: Survivin exists as a homodimeric conformation to act as a suppressor of apoptosis in organisms. Previously, we found that the deletants with truncations of N-terminal residues up to Arg18 lost the binding ability to Smac/DIABLO but not the binding force of homodimers. In order to establish the relationship between function and structural stability, thermal unfolding of SurF and its deletants in buffer have been studied in the present paper. The fluorescent results indicated that with the removal of the N-terminus, the thermal stability of the tertiary structure dropped vigorously, especially for SurΔN18. However, using circular dichroism (CD) spectroscopy, we observed that the main unfolding of the secondary structures was not affected very much with N-terminus deletion. Fourier transform infrared (FT-IR) spectroscopy and two-dimensional (2D) correlation analysis were further used to provide structural information that occurred in the main transitions, which were associated with conformational changes of several β-components and α-helix, followed by the gain of some aggregations and random coils at high temperature. In addition, more aggregates were found to form for the longer N-terminal deletants during the main unfolding.
The Journal of Physical Chemistry B 06/2011; 115(21):7038-44. · 3.70 Impact Factor
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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. · 2.11 Impact Factor
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ABSTRACT: The effects of elevated hydrostatic pressure on four representative proteins, lysozyme, human serum albumin, ubiquitin and RNase A, were investigated by using Fourier transform infrared (FTIR) spectroscopy, by principal component analysis (PCA) and by moving-window two-dimensional (MW2D) correlation analysis. In addition, we revealed the pressure-induced changes of secondary structure elements using curve fitting. With pressure increase, the amide I band shifted to lower wavenumbers, with a transition at 200 MPa, which was indicative of hydration enhancement. Moreover, the pressure-induced behavior of pure water was studied, similar transition pressure was observed with protein in aqueous solution, suggesting that structure change of water around 200 MPa caused a hydration enhancement of protein. Under pressure higher than 200 MPa, the structural changes of the four proteins were obviously different except for the common features shifting to lower wavenumbers with pressure, basically due to the distinct structural differences among them.
Analytical Sciences 01/2011; 27(11):1139-42. · 1.25 Impact Factor
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ABSTRACT: Time-resolved extinction spectra assisted with two-dimensional correlation spectroscopy (2DCOS) analysis and principal component analysis (PCA) were employed to investigate the interaction between bovine serum albumin (BSA) and metal nanoparticles (NPs). A series of localized surface plasmon resonance (LSPR) spectra of metal NPs were measured just after a small amount of BSA was added into metal colloids. Through 2DCOS analysis, remarkable changes in the intensities of the LSPR were observed. The interaction process was totally divided into three periods according to the PCA. Transmission electron microscopy, dynamic light scattering, and ζ-potential measurements were also employed to characterize the interaction between BSA and metal NPs. The addition of BSA brings silver NPs to aggregate through the electrostatic interaction between them, but it has less effect on gold NPs. In a gold and silver mixed system, gold NPs can affect the interaction of silver NPs and BSA, leading it to weaken. The combination of 2DCOS analysis and LSPR spectroscopy is powerful for exploring the LSPR spectra of the metal NP involved systems. This combined technique holds great potential in LSPR sensing through analysis of slight, slim spectral changes of metal colloids.
11/2010;
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ABSTRACT: Survivin, as an apoptosis suppressor, exists as a homodimer interfacing at the N-terminal portion (residues 6-13) of its baculovirus IAP repeat (BIR) domain and a linker segment (residues 89-102). Here we expressed full-length human Survivin (SurF) and a series of its mutants, SurΔN7, SurΔN13, and SurΔN18 with significant truncations of the N-terminus, all of which could still dimerize in solution. Single-molecule force spectroscopy (SMFS) was used to quantitate the unbinding forces of full-length and the mutant homodimers and revealed that the N-terminal residues up to Arg18 were not essential for dimerization. Meanwhile, the binding of SurΔN7 to Smac/DIABLO determined by ELISA was as efficient as the wild-type, but that of SurΔN13 was significantly reduced, and that of SurΔN18 was completely lost. Together, these findings provide direct evidence that the N-terminal sequence of Survivin is not critical for dimer formation but may contribute to correct folding and function of BIR.
The Journal of Physical Chemistry B 11/2010; 114(47):15656-62. · 3.70 Impact Factor
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ABSTRACT: A novel route to the preparation of luminescent silica nanoparticles and coloration for living cells was demonstrated in this article. A europium-substituted polyoxometalate was encapsulated by a hydroxyl-group-terminated double-chain quaternary ammonium cation through an ion replacement process, yielding an organic-inorganic complex with core-shell structure bearing hydroxyl groups located at the periphery. The introduction of -OH groups not only increased the solubility of the complex in polar solvents but also caused it to embed into the inner matrix of silica nanoparticles covalently and be well-dispersed through an in situ sol-gel reaction with tetraethyl orthosilicate. Elemental analysis and spectral characterization confirmed the formation of prepared complexes with the anticipated chemical composition. Scanning and transmission electron microscopy images illustrated the size change of luminescent nanoparticles with smooth surfaces and well-dispersed polyoxometalate complexes inside of the silica matrix. X-ray photonic spectra and ζ-potential measurements revealed the chemical association between the silica matrix and the complex. Luminescent spectral characterization indicated the well-retained photophysical property of Eu-substituted polyoxometalate in silica nanoparticles. The surface amino-modified silica nanoparticles were applied to cell coloration, and the dyed Hela cells were observed through laser confocal fluorescence microscopy.
Langmuir 11/2010; 26(23):18430-6. · 4.19 Impact Factor
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ABSTRACT: Capsid proteins binding cell surface proteoglycans is a key early event in human papillomavirus (HPV) infection. The positively charged sequences at the C-terminus of the L1 protein and the N- and C-termini of the L2 protein of HPV-16 can efficiently bind to heparin receptors, which were characterized in the present study by quantitative isothermal titration calorimetry experiments primarily, fluorescence spectroscopy, and static right-angle light scattering. The binding constant, K, was at an order of magnitude of 10(7) M(-1) for the two peptides at the N- and C-termini of HPV-16 L2 and segment b at the C-terminus of HPV-16 L1, while that for other L1 analogues were of a smaller order, illustrating that the heparin binding is a typical sequence-specific and -dependent phenomenon. These results suggest that, in addition to L1, the L2 protein may participate in cell surface attachment during HPV infection. Furthermore, the calorimetry results demonstrated that hydrophobic interactions and hydrogen bonding are involved in peptide binding to heparin in addition to the essential electrostatic interactions. Meanwhile, circular dichroism spectroscopy revealed that binding to heparin does not induce obvious secondary structural changes in the peptides.
The Journal of Physical Chemistry B 08/2010; 114(30):9854-61. · 3.70 Impact Factor
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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. · 6.17 Impact Factor
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ABSTRACT: The effects of sinomenine (SIN, an alkaloid extracted from the Chinese medicinal plant Sinomenium acutum used for centuries to treat rheumatic disease, including rheumatoid arthritis) on apatitic nucleation and matrix vesicle (MV)-induced mineral formation were compared with those of cysteine, levamisole, and theophylline. We found that SIN was not an inhibitor of tissue non-specific alkaline phosphatase (TNAP), a marker of biological mineralization, but confirmed that cysteine, levamisole, and theophylline were. Further, none of these four molecules directly affected the nucleation of hydroxyapatite (HA) formation, in contrast to pyrophosphate (PP(i)) which did. Incubation of 0.25-1.0mM cysteine, theophylline, or levamisole with MVs in synthetic cartilage lymph (SCL) containing AMP and Ca(2+), but not inorganic phosphate (P(i)), prolonged the induction time of mineral formation, apparently by inhibiting TNAP activity. SIN at the same levels neither inhibited TNAP activity nor affected the induction time of MV mineral formation. However, SIN did markedly delay MV-induced mineral formation in SCL containing P(i) (instead of AMP) in a manner similar to theophylline, but to a lesser extent than levamisole. Cysteine did not delay, in fact it slightly accelerated MV-induced mineral formation in Pi-containing SCL. These findings suggest that levamisole, SIN and theophylline may directly affect Ca(2+) and/or P(i) accretion during mineral formation; however, TNAP was not directly involved. The possible roles of annexins and other ion transporters, such as proteins of the solute carrier family implicated in Ca(2+) and P(i) influx are discussed.
Journal of inorganic biochemistry 04/2010; 104(4):446-54. · 3.25 Impact Factor
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ABSTRACT: We propose a new application of generalized two-dimensional (2D) correlation spectroscopy called "concatenated" 2D correlation analysis, which is useful in identifying the presence of strict similarity or very subtle difference between two spectral data sets having a similar origin. This approach is very efficient and can offer many potential applications. In this study, the detailed examination of process reversibility is explored. Two forms of concatenation, horizontal and vertical concatenation of data matrices, are introduced and the latter is discussed in detail. Concatenated 2D correlation analysis allows one to investigate directly the correlation between two independent but related spectral data sets. It can extract more detailed information, such as the comparison of effects of two different perturbations or different systems. We describe the principle of the "mirror-image concatenation" in 2D correlation analysis, which is applied to demonstrate its reliability and efficiency on three spectral models: a synthetic simulation data set; experimental Fourier transform infrared (FT-IR) spectra of the thermally induced unfolding-refolding transition of bovine pancreatic ribonuclease A (RNase A) in aqueous solution; and a set of FT-IR spectra of traditional Chinese medicines (TCM) of similar origin. The concatenated 2D correlation analysis shows its power in revealing the irreversibility of the thermally induced conformation transition of RNase A as well as the comparison of different species of TCM.
Applied Spectroscopy 03/2010; 64(3):343-50. · 1.66 Impact Factor
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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; · 6.17 Impact Factor
