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1.
Surface effects on quantum dot-based energy transfer 总被引:1,自引:0,他引:1
CdSe quantum dot (QD)-phthalocyanine (Pc) conjugates were prepared as energy transfer donor-acceptor pairs, and the efficiency of the energy transfer process in this system was investigated as a function of QD size and under different surface chemistry conditions. The kinetics and efficiency of the energy transfer process were studied by femtosecond time-resolved laser spectroscopy. We observed that the energy transfer efficiency does not follow a linear dependence on spectral overlap integrals as predicted by the F?rster theory for molecules. This observation is found to be due to the involvement of QD surface states in the energy transfer process from the photoexcited QDs to the molecular energy acceptor. 相似文献
2.
A novel strategy for “signal on” and sensitive one-spot simultaneous detection of multiple small molecular analytes based on electrochemically encoded barcode quantum dot (QD) tags is described. The target analytes, adenosine triphosphate (ATP) and cocaine, respectively, are sandwiched between the corresponding set of surface-immobilized primary binding aptamers and the secondary binding aptamer/QD bioconjugates. The captured QDs yield distinct electrochemical signatures after acid dissolution, whose position and size reflect the identity and level, respectively, of the corresponding target analytes. Due to the inherent amplification feature of the QD labels and the “signal on” detection scheme, as well as the sensitive monitoring of the metal ions released upon acid dissolution of the QD labels, low detection limits of 30 nM and 50 nM were obtained for ATP and cocaine, respectively, in our assays. Our multi-analyte sensing system also shows high specificity to target analytes and promising applicability to complex sample matrix, which makes the proposed assay protocol an attractive route for screening of small molecules in clinical diagnosis. 相似文献
3.
We report on a simple strategy for the determination of zinc ion by using surface-modified quantum dots. The probe consists of manganese-doped quantum dots made from zinc sulfide and capped N-acetyl-L-cysteine. The particles exhibit bright yellow-orange emission with a peak at 598?nm which can be attributed to the 4T1→6A1 transition of Mn(II). This bright fluorescence is effectively quenched by modifying the sulfur anion which suppresses the radiative recombination process. The emission of the probe can then be restored by adding Zn(II) which causes the formation of a ZnS passivation layer around the QDs. The fluorescence enhancement caused is linear in the 1.25 to 30?μM zinc concentration range, and the limit of detection is 0.67?μM. Figure
A “turn-on” fluorescent probe based on manganese-doped zinc sulfide quantum dot capped with N-acetyl-L-cysteine (NAC) was obtained and using it to determine the concentration of zinc (II) according to the fluorescent enhancement in aqueous solution. 相似文献
4.
Yu Kyung Tak Won Young Kim Min Jung Kim Eunyoung Han Myun Soo Han Jong Jin Kim Wook Kim Jong Eun Lee Joon Myong Song 《Analytica chimica acta》2012
Forensic DNA samples can degrade easily due to exposure to light and moisture at the crime scene. In addition, the amount of DNA acquired at a criminal site is inherently limited. This limited amount of human DNA has to be quantified accurately after the process of DNA extraction. The accurately quantified extracted genomic DNA is then used as a DNA template in polymerase chain reaction (PCR) amplification for short tandem repeat (STR) human identification. Accordingly, highly sensitive and human-specific quantification of forensic DNA samples is an essential issue in forensic study. In this work, a quantum dot (Qdot)-labeled Alu sequence was developed as a probe to simultaneously satisfy both the high sensitivity and human genome selectivity for quantification of forensic DNA samples. This probe provided PCR-free determination of human genomic DNA and had a 2.5-femtogram detection limit due to the strong emission and photostability of the Qdot. The Qdot-labeled Alu sequence has been used successfully to assess 18 different forensic DNA samples for STR human identification. 相似文献
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The kinetics of peptide-membrane association have been studied previously using stopped-flow tryptophan fluorescence; however, such experiments do not directly report the coil-to-helix transition process, which is a hallmark of peptide-membrane interaction. Herein, we report a new method for directly assessing the kinetics of the helix formation accompanied by the peptide-membrane association. This method is based on the technique of fluorescence resonance energy transfer (FRET) and an amino acid FRET pair, p-cyano-L-phenylalanine and tryptophan. To demonstrate the utility of this method, we have studied the membrane-mediated helix folding dynamics of a mutant of magainin 2, an antibiotic peptide found in the skin of the African clawed frog, Xenopus laevis. Our results indicate that the coil-to-helix transition occurs during the binding of the peptide to the lipid vesicle (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine/1-palmitoyl-2-oleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)], 3:1, wt/wt) but prior to the full insertion of the peptide into the hydrophobic region of the lipid bilayers. 相似文献
7.
Susumu Arimori 《Tetrahedron letters》2004,45(7):1539-1542
Six modular photoinduced electron transfer (PET) sensors bearing two phenylboronic acid receptors have been evaluated as fluorescent disaccharide sensors. The length of linker separating the two boronic acid moieties was varied and the sensors’ interaction with disaccharides assessed via fluorescence spectroscopy. It was shown that saccharide selectivity was influenced by the choice of linker length. Diboronic acid sensors 3n also displayed significant specificity for the disaccharides linked to the carbon on the 3rd or 6th position (as numbered from the anomeric centre) over those linked at the 4th position. 相似文献
8.
Xiaoshan Zhu Dayue Duan Steen Madsen Nelson G. Publicover 《Analytical and bioanalytical chemistry》2010,396(3):1345-1353
In this work, the compatibility of quantum dots (QDs) with immunobuffers was studied by investigating the fluorescence stability
of QDs in immunobuffers (in this research immunobuffers were defined as buffers for immunoaffinity binding or separation).
Experimentally, the fluorescence signals of QDs with different surface chemistries (amine-terminated, streptavidin-coated,
or antibody-conjugated) in commonly used immunobuffers were monitored versus time. The effect of some buffer composition on
the compatibility of QDs with these buffers was also explored. Based on experimental data, the QD compatibility with these
buffers is summarized, and it is found that a trace amount of bovine serum albumin added to most of these buffers helps QDs
to achieve compatibility with them. Moreover, with QD as fluorescence label and C-reactive protein as a model analyte, a magnetic
bead-based assay was performed using compatible and incompatible QD–immunobuffer systems. It is shown that compatible QD–immunobuffer
systems can be used to achieve a higher assay signal/background ratio.
相似文献
9.
Melzak KA Bender F Tsortos A Gizeli E 《Langmuir : the ACS journal of surfaces and colloids》2008,24(16):9172-9180
Acoustic devices were employed to characterize variations in the mechanical properties (density and viscoelasticity) of liposomes composed of 1-oleoyl-2-palmitoyl- sn-glycero-3-phosphocholine (POPC) and cholesterol. Liposome properties were modified in three ways. In some experiments, the POPC/cholesterol ratio was varied prior to deposition on the device surface. Alternatively, the ratio was changed in situ via either insertion of cholesterol or removal of cholesterol with beta-cyclodextrin. This was done for liposomes adsorbed directly on the device surface and for liposomes attached via a biotin-terminated poly(ethylene glycol) linker. The acoustic measurements make use of two simultaneous time-resolved signals: one signal is related to the velocity of the acoustic wave, while the second is related to dissipation of acoustic energy. Together, they provide information not only about the mass (or density) of the probed medium but also about its viscoelastic properties. The cholesterol-induced increase in the surface density of the lipid bilayer was indeed observed in the acoustic data, but the resulting change in signal was larger than expected from the change in surface density. In addition, increasing the bilayer resistance to stretching was found to lead to a greater dissipation of the acoustic energy. The acoustic response is assessed in terms of the possible distortions of the liposomes and the known effects of cholesterol on the mechanical properties of the lipid bilayer that encloses the aqueous core of the liposome. To aid the interpretation of the acoustic response, it is discussed how the above changes in the lipid bilayer will affect the effective viscoelastic properties of the entire liposome/solvent film on the scale of the acoustic wavelength. It was found that the acoustic device is very sensitive to the mechanical properties of lipid vesicles; the response of the acoustic device is explained, and the basic underlying mechanisms of interaction are identified. 相似文献
10.
Lišková M Voráčová I Klepárník K Hezinová V Přikryl J Foret F 《Analytical and bioanalytical chemistry》2011,400(2):369-379
A number of biologically important molecules, such as DNA, proteins, and antibodies, are routinely conjugated with fluorescent
tags for high-sensitivity analyses. Here, the application of quantum dots in the place of bright and size-tunable luminophores
is studied. Several selected bioconjugation reactions via zero-length cross-linkers, long-chain linkers, and oriented methods
for linking of quantum dots with proteins were tested. Anti-ovalbumin, anti-proliferating cell nuclear antigen, anti-hemagglutinin,
and anti-CD3 membrane protein as model antibodies and annexin V were used as high-specificity selectors. The reaction yield
and efficiency of the prepared immunoluminescent probes were tested by capillary zone electrophoresis with laser-induced fluorescence
detection. 相似文献
11.
“Host” molecules, containing a binding site that is highly specific for an analyte “guest,” are used as sensors to register
analyte binding through a variety of mechanisms such as colorimetric, fluorescent, or electrochemical signals. There is increasing
interest in the host–guest chemistry on the surface of quantum dots (QDs) and in the changes that it produces in the luminescent
properties of QDs. The bulk of this study focuses on those QDs with bound host molecules (crown ether, cyclodextrin, calixarene,
and porphyrin) and the selectivity they display toward metal ions and small organic molecules. 相似文献
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Shi L De Paoli V Rosenzweig N Rosenzweig Z 《Journal of the American Chemical Society》2006,128(32):10378-10379
Preparation of FRET-based quantum dots as protease sensors-RGDC peptide molecules are bound to the surface of CdSe/ZnS quantum dots. The peptide molecules are then labeled with rhodamine dye molecules. The emission color of the quantum dots change from green to orange due to fluorescence resonance energy transfer (FRET) between the quantum dots and the bound rhodamine molecules. Cleavage of the peptide by selective proteases releases the rhodamine molecules from the quantum dots surface, which results in decreasing FRET efficiency between the quantum dots and the rhodamine molecules. The emission color of the quantum dots changes back to green. 相似文献
15.
Ma Liling Sun Shan Wang Yuhui Jiang Kai Zhu Jiali Li Jun Lin Hengwei 《Mikrochimica acta》2017,184(10):3833-3840
Microchimica Acta - The authors describe a fluorometric nanoprobe for hypochlorite ion. It was prepared by covalently linking o-phenylenediamine to graphene quantum dots (GQDs). The probe displays... 相似文献
16.
Liu TC Zhang HL Wang JH Wang HQ Zhang ZH Hua XF Cao YC Luo QM Zhao YD 《Analytical and bioanalytical chemistry》2008,391(8):2819-2824
Mouse anti-human CD71 monoclonal antibody (anti-CD71) was conjugated with red quantum dots (QDs; 5.3 nm, emission wavelength
λ
em = 614 nm) and used to label HeLa cells successfully. Then green QD-labeled goat anti-mouse immunoglobulin G (IgG; the size
of the green QDs was 2.2 nm; λ
em = 544 nm) was added to bind the red-QD-conjugated anti-CD71 on the cell surface by immunoreactions. Such interaction between
anti-CD71 and IgG lasted 4 min and was observed from the fluorescence spectra: the fluorescence intensity of the “red” peak
at 614 nm increased by 32%; meanwhile that of the “green” one at 544 nm decreased by 55%. The ratio of the fluorescence intensities
(I
544 nm/I
614 nm) decreased from 0.5 to 0.2. The fluorescence spectra as well as cell imaging showed that fluorescence resonance energy transfer
took place between these two kinds of QDs on the HeLa cells through interactions between the primary antibody and the secondary
antibody. 相似文献
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Goswami D 《The Journal of chemical physics》2007,127(12):124305
Quantum interference between multiple excitation pathways can be used to cancel the couplings to the unwanted, nonradiative channels resulting in robustly controlling decoherence through adiabatic coherent control approaches. We propose a useful quantification of the two-level character in a multilevel system by considering the evolution of the coherent character in the quantum system as represented by the off-diagonal density matrix elements, which switches from real to imaginary as the excitation process changes from being resonant to completely adiabatic. Such counterintuitive results can be explained in terms of continuous population exchange in comparison to no population exchange under the adiabatic condition. 相似文献
19.
Jianhao Wang Jingyan Li Jinchen Li Feifei Liu Xiang Zhou Yi Yao Cheli Wang Lin Qiu Pengju Jiang 《Analytica chimica acta》2015
A new method using fluorescence coupled capillary electrophoresis (CE-FL) for monitoring self-assembly and proteolytic cleavage of hexahistidine peptide capped quantum dots (QDs) inside a capillary has been developed in this report. QDs and the ATTO 590-labeled hexahistidine peptide (H6-ATTO) were injected into a capillary, sequentially. Their self-assembly inside the capillary was driven by a metal-affinity force which yielded a new fluorescence signal due to Förster resonance energy transfer (FRET). The highly efficient separation of fluorescent complexes and the FRET process were analyzed using CE-FL. The self-assembly of QDs and biomolecules was found to effectively take place inside the capillary. The kinetics of the assembly was monitored by CE-FL, and the approach was extended to the study of proteolytic cleavage of surface conjugated peptides. Being the first in-depth analysis of in-capillary nanoparticle–biomolecule assembly, the novel approach reported here provides inspiration to the development of QD-based FRET probes for biomedical applications. 相似文献
20.
Luminescent sensors incorporating two luminophores, an indicator and a reference, offer many advantages over intensity measurements from sensors made with one indicator dye. Quantum dots have yet to be widely employed as insensitive reference luminophores in such systems. This work describes the use of near-infrared emitting quantum dots in conjunction with a long-lifetime platinum(II) porphyrin phosphor in a microsphere-based, ratiometric oxygen sensor. The process for self-assembly of the nanocomposite system was developed, and the response and photostability of the prototypes were investigated. Results indicate the sensors possess excellent sensitivity (K(SV) = 0.00826 μM(-1)) at oxygen concentrations below 300 μM and were resistant to photobleaching. The sensor luminophores displayed minimal spectral overlap and little interference from excitation light, preventing the need for optical filters. A reversible photoenhancement of the quantum dot signal was also observed when exposed for extended periods of time. This work demonstrates the advantages of incorporating long-wavelength quantum dots into ratiometric intensity sensing schemes and highlights some key limitations that must be considered in their use. 相似文献