Analytical Chemistry Chemical Cytometry Quantitates Superoxide

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ion transfer and diffusion processes, which are not the focus of this research. The redox capacity of the system was found to correspond to several nanomolar of oxidizable ferrocene groups in the membrane, which is only a fraction of nominal ferrocene concentration. This suggests that the ferrocene groups are sufficiently dilute and immobile in the membrane and that it is the surface confined functionalities that are predominantly electrochemically accessible. Nonetheless, the redox capacity appears to be adequate for most voltammetric ion transfer applications. The membranes were characterized in contact with aqueous electrolytes, and interrogation with normal pulse voltammetry suggests excellent reproducibility and an anion selectivity pattern that corresponds to the expected Hofmeister selectivity sequence. The cathodic potential window remained featureless, supporting the notion of a membrane containing predominantly ferrocene moieties that can be oxidized by the concomitant extraction of anions from the sample. It is expected that adequate chemical doping of the membrane with cation-exchanger species will make the cationic response region at cathodic potentials analytically 6894 Analytical Chemistry, Vol. 82, No. 16, August 15, 2010 accessible, but this was not yet explored here. Experiments in the presence of potassium hexacyanoferrate(III) showed that possible presence of ferrocene groups at the surface of the ionselective membrane do not cause redox sensitivity of the electrode. Moreover, the high reproducibility of the sampled anion transfer currents (standard deviation below 1%) as well as the high redox capacity of the material (about 520 µC) makes ferrocene bound PVC an attractive material for electrochemical all solid state ionselective electrode fabrication. ACKNOWLEDGMENT The authors wish to thank the Australian Research Council (Grant DP0987851) and the National Institutes of Health (Grant EB002189) for financial support of this research. Received for review April 23, 2010. Accepted July 10, 2010. AC1010662
Anal. Chem. 2010, 82, 6895–6903 Electrophoretic Analysis of Biomarkers using Capillary Modification with Gold Nanoparticles Embedded in a Polycation and Boron Doped Diamond Electrode Lin Zhou, † Jeremy D. Glennon, † and John H. T. Luong* ,†,‡ Innovative Chromatography Group, Irish Separation Science Cluster (ISSC), Department of Chemistry & the ABCRF, University College Cork, Cork, Ireland and Biotechnology Research Institute, National Research Council Canada, Montreal, Quebec, Canada H4P 2R2 Field-amplified sample stacking using a fused silica capillary coated with gold nanoparticles (AuNPs) embedded in poly(diallyl dimethylammonium) chloride (PDDA) has been investigated for the electrophoretic separation of indoxyl sulfate, homovanillic acid (HVA), and vanillylmandelic acid (VMA). AuNPs (27 nm) exhibit ionic and hydrophobic interactions, as well as hydrogen bonding with the PDDA network to form a stable layer on the internal wall of the capillary. This approach reverses electro-osmotic flow allowing for fast migration of the analytes while retarding other endogenous compounds including ascorbic acid, uric acid, catecholamines, and indoleamines. Notably, the two closely related biomarkers of clinical significance, HVA and VMA, displayed differential interaction with PDDA-AuNPs which enabled the separation of this pair. The detection limit of the three analytes obtained by using a boron doped diamond electrode was ∼75 nM, which was significantly below their normal physiological levels in biological fluids. This combined separation and detection scheme was applied to the direct analysis of these analytes and other interfering chemicals including uric and ascorbic acids in urine samples without off-line sample treatment or preconcentration. Indoxyl sulfate (IXS), a metabolite of tryptophan (TRP) and a dietary protein, is derived from intestinal metabolism and liver conjugation 1 and excreted in urine in high concentration. It is also an endogenous compound in mammals, in mouse plasma and brain samples, as detected by liquid chromatography/tandem mass spectrometry. 2 This circulating protein-bound uremic toxin stimulates glomerular sclerosis, interstitial fibrosis, and the progression rate of renal failure. IXS induces endothelial dysfunction by inhibiting endothelial proliferation and migration in vitro * To whom correspondence should be addressed. † Innovative Chromatography Group, Irish Separation Science Cluster (ISSC), Department of Chemistry & the ABCRF, University College Cork. ‡ Biotechnology Research Institute, National Research Council Canada. (1) Dealler, S. F.; Hawkey, P. M.; Millar, M. R. J. Clin. Microbiol. 1988, 26 (10), 2152–2156. (2) Wang, G.-F.; Korfmacher, W. A. Rapid Commun. Mass Spectrom. 2008, 23 (13), 2061–2069. and its role in oxidative stress is implicated. 3 Homovanillic acid (HVA) is a major catecholamine metabolite, associated with the brain dopamine level. As a biomarker of metabolic stress of 2-deoxy-D-glucose, the HVA level in the brain and the cerebrospinal fluid is indicative of pheochromocytoma and neuoroblastoma. 4 Metanephrine, one of the hormones produced by the adrenal glands, breaks down to normetanephrine and vanillylmandelic acid (VMA) via the intermediate 4-hydroxy-3-methoxy-phenylglycol. Thus, VMA is always detected in the urine together with HVA and other catecholamine metabolites from pheochromocytoma or catecholamine-secreting chromaffin tumor cells. 5,6 Catecholamine levels can be found in blood samples; however, the urine test reflects the production rate of the catecholamines over the collection period. Even at abnormal levels, the elevated quantities of these catecholamines are still very low, i.e., highly selective and sensitive analytical methods are needed for such important biomarkers. The urinary VMA and HVA values are most useful and can be correlated with the stage of disease, management, any maturation of tumor, and prognosis from children with neuroblastoma. 4 The urine HVA/VMA ratio could be a screening tool to support earlier detection of Menkes disease, a disorder that affects copper levels in the body, leading to copper deficiency. 7a The mechanism that removes HVA from the brain is still poorly understood, however, the efflux transport of HVA from the brain plays an important role in controlling the HVA level in the brain. This HVA efflux transport system is inhibited by several organic anions including IXS, and metabolites of monoamine neurotransmitters but not neurotransmitters per se. 7b Thus, it is of clinical importance to develop a rapid and sensitive method for simultaneous analysis of HVA, VMA, and IXS in urine and other biological samples. (3) Tumur, Z.; Niwa, T. Am. J. Nephrol. 2009, 29, 551–557. (4) Liebner, E. J.; Rosenthal, I. M. Cancer 2006, 32 (3), 623–633. (5) Eisenhofer, G.; Lenders, J. W. M.; Linehan, W. M.; Walther, M. M.; Goldstein, D. S.; Keiser, H. R. New Engl. J. Med. 1999, 340, 1872–1879. (6) Lenders, J. W. M.; Keiser, H. R.; Goldstein, D. S.; Willemsen, J. J.; Friberg, P.; Jacobs, M.-C.; Kloppenborg, P. W. C.; Thien, T.; Eisenhofer, G. Ann. Intern. Med. 1995, 123, 101–109. (7) (a) Menkes, J. H.; Alter, M.; Steigleder, G. K.; Weakley, D. R.; Sung, J. H. Pediatrics 1962, 29, 764–779. (b) Mori, S.; Takanaga, H.; Ohtsuki, S.; Deguchi, T.; Kang, Y.-S.; Hosoya, K.-I.; Terasaki, T. J. Cereb. Blood Flow Metab. 2003, 23, 432–440. (8) (a) Issaq, H. J.; Delviks, K.; Janini, G. M.; Muschik, G. M. J. Liquid Chromatogr. Relat. Technol. 1992, 15/18, 3193–3201. 10.1021/ac101105q © 2010 American Chemical Society 6895 Analytical Chemistry, Vol. 82, No. 16, August 15, 2010 Published on Web 07/16/2010
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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
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mg/mL protein, followed by separati
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Figure 2. Productivity of SEQUST an
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Figure 4. High-resolution MS/MS spe
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Figure 6. Characterization of PSMs
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containing T-T mismatches. 23 Based
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Figure 1. Extinction spectra of sol
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Figure 3. (A) The value of Ex650 nm
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Figure 5. Extinction spectra and co
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wished to explore the dehydration o
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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 and 130: Figure 2. Influence of a surfactant
Page 131 and 132: Figure 5. Device to eject and mix s
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: Figure 6. Calculated charge from ch
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
Page 181 and 182: the NB signal in a much better foot
Page 183 and 184: Scheme 1. Reactions of Selenium Rea
Page 185 and 186: Figure 2. (a) ESI-MS spectrum showi
Page 187 and 188: Figure 4. (a) ESI-MS spectrum showi
Page 189 and 190: Anal. Chem. 2010, 82, 6933-6939 Dif
Page 191 and 192: trode 28 by a finite element using
Page 193 and 194: Figure 4. Comparison between simula
Page 195 and 196: Figure 6. Comparison between simula
Page 197 and 198: educed in the vicinity of double bo
Page 199 and 200: 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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