Analytical Chemistry Chemical Cytometry Quantitates Superoxide

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simulations, 34,35 which can be helpful in the design of controlling flow channels that punctually provide H2O2 solution to micropumps according to a predetermined schedule. Autonomous Sequential Switching of the Micropumps. We next studied the function of the micropump. After the lower compartment of the pump was filled with H2O2 solution, the diaphragm inflated and the solution in the upper reservoir was ejected and then mobilized in the extending flow channel. During this step, the H2O2 solution moved forward in the controlling flow channel and filled the lower compartment of the next pump. From that point forward, the same step was repeated. Needless to say, the concentration of H2O2 injected into the controlling flow channel affects the flow velocity of the solution in the upper flow channel. Although the flow velocity definitely depends on the H2O2 concentration, significant leakage and destruction of the gel layer was observed over a certain threshold, which also depended on the size of the pump. Considering these dynamics, 1.6 or 3.2 M H2O2 was used in the following experiments, depending on the size of the pump. For the handling of many solutions, several micropumps can be connected to the controlling flow channel and to the upper flow channels for solutions to be transported. To adjust the timing and order of the injection of solutions, the distance between pumps can be adjusted in a network of flow channels. Compartments and constrictions can also be introduced, as was discussed earlier. In the device shown in parts A and B of Figure 4, micropumps are connected with one another by rectangular compartments at their sides and centers, respectively. In the device shown in Figure 4B, the compartments are filled with solution after the compartment of a neighboring micropump in the upper stream is filled with solution. With the small compartments in the crowded layout, however, the extension of the liquid columns from the upper reservoirs was not so significant compared with that of the device shown in Figure 4A. The device shown in Figure 4C has additional small compartments to delay the movement of the solution. Note the difference in the length of the liquid columns, which shows that the actuation of the micropump can be distinctly delayed in the lower stream of the controlling flow channel, unlike the device shown in Figure 4A and 4B. This result demonstrates that additional delaying structures can in fact be used to adjust the timing to trigger the actuation of the micropumps. Coordinated Operation of Micropumps for Chemical Analyses. By properly designing a network of flow channels with micropumps located in appropriate positions, microfluidic devices can be constructed for various purposes, including chemical analyses that require the specific processing of solutions. In the device shown in Figure 5, there are two micropumps to eject solutions and two pumps to apply pressure. Here, H 2O2 was also used as an analyte. A solution containing H2O2 and Amplex Red (5 mM) and another solution containing 50 U/mL HRP, both prepared with a 50 mM Tris-HCl buffer solution (pH 7.4), were used to fill the reservoirs. After another H2O2 solution was injected into the controlling flow channel, it first filled the compartments of the micropumps. Following this, the analyte H2O2 solution in the reservoir was injected into the upper flow (34) Erickson, D.; Li, D.; Park, C. B. J. Colloid Interface Sci. 2002, 250, 422– 430. (35) Young, W.-B. Colloids Surf., A 2004, 234, 123–128. 6874 Analytical Chemistry, Vol. 82, No. 16, August 15, 2010 Figure 4. Arrays of micropumps with controlling flow channels with different structures. Rectangular compartments are connected with the controlling flow channels at the edges (A), at the center (B), and via smaller delaying compartments (C). channels for transport after 9 s (Figure 5B, panels 1 and 2). After a time delay (117 s), the larger pumps that apply pressure were switched on and the solutions in the upper flow channel were pinched off from the rest of the solutions, transported to the center, and merged in the mixing channel (Figure 5B, panels 3 and 4). The average flow velocity in the mixing channel was 94 µm/s. Solutions containing the enzyme and the substrates were transported and mixed in the flow channel. The enzymatic reaction by HRP produced highly fluorescent resorufin, which generated red fluorescence under a fluorescence microscope. Figure 5C shows the dependence of the fluorescence intensity on the concentration. The fluorescence intensity was measured 3 min after mixing. In the graph plotted on the semilog scale, the dependence of the fluorescence intensity on the concentration could be clearly observed.
Figure 5. Device to eject and mix solution plugs. (A) Layout of the controlling flow channels (dashed line, shaded) and the flow channels for transport (solid line). (B) Movement of a H2O2 solution in the controlling flow channels (dashed arrows) and an analyte H2O2 solution in flow channels for the transport of solutions (solid arrows). (1) The reservoirs of the micropumps were filled with solutions. (2) The solutions were injected into the main channel. (3, 4) The solutions were transported by the exertion of pressure from the leftmost and rightmost pumps and were merged at the T-junction. (C) Dependence of the fluorescence intensity on the concentration of H2O2 ejected from a micropump. Five runs were performed, and the averages and standard deviations are shown. The dashed lines show the average +3σ of the background fluorescence. The concentration of the H2O2 solution injected into the controlling flow channel was 1.6 M. The dimensions of the chip were 25 mm × 16 mm. More complicated manipulation of solutions could also be carried out. The device shown in Figure 6 has three injection pumps and three micropumps to exert pressure upon the ejected plugs. Three lines of controlling flow channels were used. In each channel, a pump to eject a necessary solution and a pump to apply pressure were connected. The lower compartment of each injection pump was used to delay the arrival of the H2O2 solution to the pumps to apply pressure located in the lower stream. GOD and LOD were immobilized at the bottom of the reservoirs of pumps A and C. First, we used solutions containing either glucose or lactate. The reservoir of pump A was filled with a phosphate buffer solution containing glucose and Amplex Red (5 mM), and the reservoir of pump C was filled with another phosphate buffer solution containing lactate and Amplex Red (5 mM). The reservoir of pump B was filled with a phosphate buffer solution to wash the reaction chamber. The enzymatic reactions by the oxidases produced H2O2. In view of the volume of the solutions and the activity of the immobilized enzymes, it could be assumed that the enzymatic conversion was virtually completed in the examined ranges of concentration of glucose and lactate during this preparatory period. Three minutes after the filling with solutions, the H2O2 solution was introduced into the controlling flow channel. Following this, a row of plugs was injected into the main flow channel from the reservoirs of the pumps located in the lower stream. In accordance with the flow channel design, pumps A-F were switched on 28, 85, 174, 187, 259, and 336 s after the injection of the H2O2 solution into the controlling flow channel. The velocity of a plug passing through the reaction chamber was 35 µm/s, the same velocity at which the three pumps would apply pressure. When the first plug containing Amplex Red and H2O2 produced by GOD arrived at the reaction chamber, fluorescence was generated in the chamber, as it was in the previously mentioned device, and its intensity was measured 90 s after the solution reached the chamber. After the reaction chamber was rinsed with a rinsing plug that was ejected from pump B, the last plug containing Amplex Red and H2O2 produced by LOD was introduced into the reaction chamber, and the fluorescence intensity was measured as before. The same experiment was carried out using the same solution containing glucose, lactate, and Amplex Red to fill pumps A and C. Figure 7 shows the calibration plots obtained using solutions containing only glucose or lactate and the data points obtained for solutions containing both of them. For the limited ranges of concentration that were employed, the plots were apparently linear. The values obtained for solutions containing both glucose and lactate in different combinations of concentration came close to the calibration plots, which demonstrated that the device can be used for the analysis of different analytes that coexist in the same solution. We note again that no wires or tubes were deployed around the chip to apply electrical signals or pressure. The necessary reagent solutions can be stored in the injection ports beforehand. The only thing that must be done is to introduce a sample solution and initiate the flow of the H2O2 solution in the controlling flow channel. The H2O2 solution can also be stored in a separate reservoir and can then be injected by applying a small degree Analytical Chemistry, Vol. 82, No. 16, August 15, 2010 6875
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Anal. Chem. 2010, 82, 6745-6750 Let
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purchased from Invitrogen-Molecular
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Figure 3. Electropherograms of TPP-
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Anal. Chem. 2010, 82, 6751-6755 Res
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(pH 8.0) with cysteine and cystamin
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Figure 4. Ion mobility mass spectra
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GOx glucose + O298 gluconic acid +
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coater at 2000 rpm for 20 s, and th
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Figure 5. Comparison of cyclic volt
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in channels with either no grooves
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indicators of atmospheric processin
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Figure 1. GC/MS total ion chromatog
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Table 2. Concentrations and Stable
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on a substrate are preferred. 20-24
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Figure 4. SERS analysis of NAADP co
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Anal. Chem. 2010, 82, 6775-6781 Hig
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tion, 2 µL of proprionaldehyde wer
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Figure 4. Analysis of 2a by HPLC-MS
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eaction of 1a with PBH can be condu
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Numerous references had demonstrate
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Figure 1. TEM images of the prepare
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Figure 4. Schematic representation
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esult in a big SPR signal change wi
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also reduces chemical noise, which
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Table 1. Extraction Yields, Liquid
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scanning of AMPP amides of the anal
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Anal. Chem. 2010, 82, 6797-6806 δ
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Figure 1. Schematic view of the pre
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from the specimen and enclosed in a
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Figure 4. (A) IRMS mass-44 chromato
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Table 3. Ambient Measurement Result
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Anal. Chem. 2010, 82, 6807-6813 Dir
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Polymerase (1 U per sample). Reacti
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of which was constant for all ampli
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analytically useful signals at less
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carbon black and RP-C18 for the ext
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solution in an equal volume, and 1
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Table 2. Concentrations and Ratios
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Anal. Chem. 2010, 82, 6821-6829 Mac
Page 79 and 80: mg/mL protein, followed by separati
Page 81 and 82: Figure 2. Productivity of SEQUST an
Page 83 and 84: Figure 4. High-resolution MS/MS spe
Page 85 and 86: Figure 6. Characterization of PSMs
Page 87 and 88: containing T-T mismatches. 23 Based
Page 89 and 90: Figure 1. Extinction spectra of sol
Page 91 and 92: Figure 3. (A) The value of Ex650 nm
Page 93 and 94: Figure 5. Extinction spectra and co
Page 95 and 96: wished to explore the dehydration o
Page 97 and 98: constant medium for separation; we
Page 99 and 100: Figure 2. Standards of (Pi)n, n ) 1
Page 101 and 102: Figure 5. Quantitative calibration
Page 103 and 104: Anal. Chem. 2010, 82, 6847-6853 Met
Page 105 and 106: Figure 1. 226 Ra spectrum by liquid
Page 107 and 108: Table 1. Counting Properties and De
Page 109 and 110: Table 3. Analysis of 226 Ra in Sedi
Page 111 and 112: mercial microarray scanner and fabr
Page 113 and 114: Figure 2. Optical transmission meas
Page 115 and 116: Figure 5. Volcano plots detailing t
Page 117 and 118: data as well. The 41 genes in Table
Page 119 and 120: corresponding compound if its chemi
Page 121 and 122: Figure 1. Schematic illustration of
Page 123 and 124: Table 1. Absolute Quantification Re
Page 125 and 126: ment. Therefore, the long-time drea
Page 127 and 128: Figure 1. Chemically actuated micro
Page 129: Figure 2. Influence of a surfactant
Page 133 and 134: Anal. Chem. 2010, 82, 6877-6886 Imm
Page 135 and 136: NaCl, phosphate buffer saline (PBS)
Page 137 and 138: Figure 2. Product ion mass spectra
Page 139 and 140: -70 °C resolved the problem, givin
Page 141 and 142: Table 1. Intraday Precision and Acc
Page 143 and 144: Anal. Chem. 2010, 82, 6887-6894 Fer
Page 145 and 146: Figure 1. Infrared spectra of (A) u
Page 147 and 148: Figure 3. Cyclic voltammograms obta
Page 149 and 150: Figure 6. Calculated charge from ch
Page 151 and 152: Anal. Chem. 2010, 82, 6895-6903 Ele
Page 153 and 154: Table 1. Chemical Structure, pKa Va
Page 155 and 156: pH with a tilted baseline (Figure 1
Page 157 and 158: Table 2. Linearity and Detection Li
Page 159 and 160: ascorbic acid (AA), uric acid (UA),
Page 161 and 162: the multielement capabilities, the
Page 163 and 164: RESULTS AND DISCUSSION Sulfur Detec
Page 165 and 166: Table 2. Molecular Properties and C
Page 167 and 168: Anal. Chem. 2010, 82, 6911-6918 Dir
Page 169 and 170: dilution and hybridization buffer.
Page 171 and 172: solution under appropriate incubati
Page 173 and 174: Figure 4. Standardization curve for
Page 175 and 176: Anal. Chem. 2010, 82, 6919-6925 Ele
Page 177 and 178: the ×10 objective, to have a large
Page 179 and 180: 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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