Analytical Chemistry Chemical Cytometry Quantitates Superoxide

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Figure 6. (A) SPR angle-time curves of the separation products obtained after Fe3O4 MNP-antiadenosine aptamer conjugates are reacted with different concentrations of adenosine for 30 min. Inset: The linear relationship between the logarithms of adenosine concentrations and the SPR angle shift resulting from the binding of Fe3O4 MNP-antiadenosine aptamer conjugates. (B) SPR angle-time curves of 1 µM antiadenosine aptamer without adenosine (red line) and after react with 1 mM adenosine for 30 min (black line). 10 nM adenosine because parts of aptamers on Fe3O4 MNPs react with adenosine and form its tertiary structure, which cannot hybridize with its complementary ss-DNA. With the further increase of the concentration of adenosine added to the Fe3O4 MNP-antiadenosine aptamer conjugate solution, the SPR angle shift continuously decreases until most of the antiadenosine aptamer binds with adenosine. By analyzing the change of SPR angle shift with the concentrations of adenosine, a good linear relationship between the logarithms of adenosine concentrations and the SPR angle shift is obtained with a range of 10-1 × 10 4 nM (shown in the insert of Figure 6A). This detection result is comparable with most other aptasensors 44 and is a little lower than that of detection results from SPR aptasensor which utilize Au NPs as an amplification reagent 20,29 but much superior to the detection results obtained by a general SPR sensor based on a molecularly imprinted technique. 45,46 It should be pointed out that the SPR angle shift only decreases to ∼107.33 m° even when the aptamer reacts with 1 mM adenosine. This nonspecific adsorption may come from the stereohindrance effect of aptamer possessing different structures. After adenosine is added to Fe3O4 MNP-aptamer conjugates, most free-coiled aptamers react with adenosine and form its tertiary structure. However, the formation of a tertiary structure of an aptamer may inhibit the further reaction between its adjacent free-coiled aptamer and adenosine. To clearly show the amplification effect of Fe3O4 MNPs, as a comparison, the SPR response resulting from the binding of aptamer without MNP is also studied. The black line in Figure 6B is the SPR angle shift resulting from the binding of 1 µM antiadenosine aptamer after antiadenosine aptamer reactes with 1 mM adenosine for 0.5 h. Only a 24.6 m° SPR angle shift is observed. Although the SPR angle shift resulting from the binding of antiadenosine aptamer could increase to 65.7 m° (Red line in Figure 6B) in the absence of adenosine, this value is still much lower than that of the (44) Wang, Y. L.; Wei, H.; Li, B. L.; Ren, W.; Guo, S. J.; Dong, S. J.; Wang, E. K. Chem. Commun. 2007, 5220–5222. (45) Taniwaki, K.; Hyakutake, A.; Aoki, T.; Yoshikawa, M.; Guiver, M. D.; Robertson, G. P. Anal. Chim. Acta 2003, 489, 191–198. (46) Yoshikawa, M.; Guiver, M. D.; Robertson, G. P. J. Mol. Struct. 2005, 739, 41–46. 6788 Analytical Chemistry, Vol. 82, No. 16, August 15, 2010 Figure 7. SPR angle-time curves of the separation products obtained after Fe3O4 MNP-antiadenosine aptamer conjugates are reacted with different analytes for 30 min. value resulting from the binding of Fe3O4 MNP-antiadenosine aptamer conjugates (1082.94 m°). Besides sensitivity, the specification of aptamer promises the selectivity of the present SPR sensor for adenosine. Figure 7 exhibits SPR angle-time curves of the separation products obtained after Fe3O4 MNP-antiadenosine aptamer conjugates are reacted with different analytes for 30 min. It could be easily seen that the addition of Fe3O4 MNP-antiadenosine aptamer conjugates which are reacted with 1 × 10 6 nM cytidine, guanosine, and uridine result in big SPR angle shifts. However, The SPR angle shift only increases a little after Fe3O4 MNP-antiadenosine aptamer conjugates are reacted with 1 × 10 6 nM adenosine. These results not only demonstrate that Fe3O4 MNPs could greatly enhance the SPR signal but also, more importantly, give us an important indication that SPR spectroscopy could be an excellent candidate for detecting an MNP-based separation product. CONCLUSION In summary, the SPR response of the carboxyl group modified Fe3O4 MNPs of two different sizes onto an amino group modified SPR gold substrate has been studied. The results show the monolayer adsorption of Fe3O4 MNPs could
esult in a big SPR signal change with a low optical loss. To evaluate the practicability of the use of Fe3O4 MNPs in enhancing the SPR signal for biosensing, a novel SPR sensor based on ICIA for the detection of adenosine is constructed using Fe3O4 MNP-antiadenosine aptamer conjugates as the amplification reagents. The experimental results demonstrate that the SPR sensor possesses a good sensitivity and a high selectivity for adenosine. Importantly, by changing the kind of biomolecules labeled by MNPs, the present detection method will be able to explore new applications of SPR spectroscopy for the detection of a large variety of MNPbased separation products. At the same time, the technique demonstrated in this work could also offer a new direction in designing high performance SPR biosensors for sensitive and selective detection of small molecules by the amplification effect of MNPs. ACKNOWLEDGMENT This work is supported by National Science Foundation (EEC- 0823974). Authors thank Prof. Camesano Terri and her graduate student Sena Ada for assistance with AFM characterization. Received for review March 10, 2010. Accepted July 8, 2010. AC100812C Analytical Chemistry, Vol. 82, No. 16, August 15, 2010 6789
Page 1 and 2: Anal. Chem. 2010, 82, 6745-6750 Let
Page 3 and 4: purchased from Invitrogen-Molecular
Page 5 and 6: Figure 3. Electropherograms of TPP-
Page 7 and 8: Anal. Chem. 2010, 82, 6751-6755 Res
Page 9 and 10: (pH 8.0) with cysteine and cystamin
Page 11 and 12: Figure 4. Ion mobility mass spectra
Page 13 and 14: GOx glucose + O298 gluconic acid +
Page 15 and 16: coater at 2000 rpm for 20 s, and th
Page 17 and 18: Figure 5. Comparison of cyclic volt
Page 19 and 20: in channels with either no grooves
Page 21 and 22: indicators of atmospheric processin
Page 23 and 24: Figure 1. GC/MS total ion chromatog
Page 25 and 26: Table 2. Concentrations and Stable
Page 27 and 28: on a substrate are preferred. 20-24
Page 29 and 30: Figure 4. SERS analysis of NAADP co
Page 31 and 32: Anal. Chem. 2010, 82, 6775-6781 Hig
Page 33 and 34: tion, 2 µL of proprionaldehyde wer
Page 35 and 36: Figure 4. Analysis of 2a by HPLC-MS
Page 37 and 38: eaction of 1a with PBH can be condu
Page 39 and 40: Numerous references had demonstrate
Page 41 and 42: Figure 1. TEM images of the prepare
Page 43: Figure 4. Schematic representation
Page 47 and 48: also reduces chemical noise, which
Page 49 and 50: Table 1. Extraction Yields, Liquid
Page 51 and 52: scanning of AMPP amides of the anal
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Page 55 and 56: Figure 1. Schematic view of the pre
Page 57 and 58: from the specimen and enclosed in a
Page 59 and 60: Figure 4. (A) IRMS mass-44 chromato
Page 61 and 62: Table 3. Ambient Measurement Result
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Page 65 and 66: Polymerase (1 U per sample). Reacti
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Page 75 and 76: Table 2. Concentrations and Ratios
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Page 87 and 88: containing T-T mismatches. 23 Based
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wished to explore the dehydration o
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constant medium for separation; we
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Figure 2. Standards of (Pi)n, n ) 1
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Figure 5. Quantitative calibration
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Anal. Chem. 2010, 82, 6847-6853 Met
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Figure 1. 226 Ra spectrum by liquid
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Table 1. Counting Properties and De
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Table 3. Analysis of 226 Ra in Sedi
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mercial microarray scanner and fabr
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Figure 2. Optical transmission meas
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Figure 5. Volcano plots detailing t
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data as well. The 41 genes in Table
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corresponding compound if its chemi
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Figure 1. Schematic illustration of
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Table 1. Absolute Quantification Re
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ment. Therefore, the long-time drea
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Figure 1. Chemically actuated micro
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Figure 2. Influence of a surfactant
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Figure 5. Device to eject and mix s
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Anal. Chem. 2010, 82, 6877-6886 Imm
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NaCl, phosphate buffer saline (PBS)
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Figure 2. Product ion mass spectra
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-70 °C resolved the problem, givin
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Table 1. Intraday Precision and Acc
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Anal. Chem. 2010, 82, 6887-6894 Fer
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Figure 1. Infrared spectra of (A) u
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Figure 3. Cyclic voltammograms obta
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Figure 6. Calculated charge from ch
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Anal. Chem. 2010, 82, 6895-6903 Ele
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Table 1. Chemical Structure, pKa Va
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pH with a tilted baseline (Figure 1
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Table 2. Linearity and Detection Li
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ascorbic acid (AA), uric acid (UA),
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the multielement capabilities, the
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RESULTS AND DISCUSSION Sulfur Detec
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Table 2. Molecular Properties and C
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Anal. Chem. 2010, 82, 6911-6918 Dir
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dilution and hybridization buffer.
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solution under appropriate incubati
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Figure 4. Standardization curve for
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Anal. Chem. 2010, 82, 6919-6925 Ele
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the ×10 objective, to have a large
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Figure 2. With a suitable removal o
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the NB signal in a much better foot
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Scheme 1. Reactions of Selenium Rea
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Figure 2. (a) ESI-MS spectrum showi
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Figure 4. (a) ESI-MS spectrum showi
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Anal. Chem. 2010, 82, 6933-6939 Dif
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trode 28 by a finite element using
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Figure 4. Comparison between simula
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Figure 6. Comparison between simula
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educed in the vicinity of double bo
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Figure 2. Normalized product ion ab
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Figure 4. EID (a) and IRMPD (b) of
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Anal. Chem. 2010, 82, 6947-6957 Ide
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Figure 1. Schematic flowchart showi
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difference, ppm compound Table 1. I
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isoforms, its successful use, in th
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Figure 5. Extracted ion current ESI
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m/z 1172.935 was observed for Ser14
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linked products via affinity tags.
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Scheme 2. Fragmentation Mechanism o
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Figure 1. (A) ESI-LTQ-CID-MS 2 prod
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Figure 3. (A) ESI-LTQ-CID-MS 2 prod
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Figure 5. (A) MALDI-TOF/TOF product
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Anal. Chem. 2010, 82, 6969-6975 Ana
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Figure 3. Equilibrium response as a
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Figure 6. The average measured resp
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for the fill time, and we find that
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nucleotide tails. 3-5 Thus, the amo
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allow the use of higher aptamer con
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quent ligation of the aptamers afte
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Anal. Chem. 2010, 82, 6983-6990 Imp
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Figure 2. Configuration editor wind
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Figure 4. Dependencies between volu
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Since the time for liquid expulsion
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Anal. Chem. 2010, 82, 6991-6999 Int
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Figure 1. Representation of the Car
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Table 2. Capillary Electrophoresis
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Figure 4. (A) Typical raw electroph
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field. DNA profiles were delivered
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Another approach to handle this lim
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(principal components, PCs) in whic
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Figure 5. Relevant score plots and
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CONCLUSIONS In this paper we have i
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electroactive-species loaded liposo
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Figure 2. Qdot-based FLFTS response
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Figure 6. Fluorescence imaging of Q
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Anal. Chem. 2010, 82, 7015-7020 Sel
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Table 1. Effect of 1 D-LC Condition
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Figure 3. Peak-production rate vers
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Anal. Chem. 2010, 82, 7021-7026 Cel
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luciferase (T7 control vector) was
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Figure 3. Inhibitory effects of luc
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Anal. Chem. 2010, 82, 7027-7034 Pat
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Electrochemistry. Electrochemical m
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Figure 2. SEM images of Au substrat
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Table 3. Film Thickness Measurement
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Anal. Chem. 2010, 82, 7035-7043 Qua
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Figure 1. (A) FL spectra of BSPOTPE
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Figure 4. (A) Variation in the FL i
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Figure 6. (A) FL spectra of BSPOTPE
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Scheme 1. Proposed Mechanism for Fl
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one or more drawbacks including poo
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Figure 2. Free fluorophores do not
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Anal. Chem. 2010, 82, 7049-7052 Dev
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Figure 2. Comparative analysis of d
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