Analytical Chemistry Chemical Cytometry Quantitates Superoxide

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Figure 4. SEM images of (a-d) Si samples patterned by printing with (a) NBD/1 M H2SO4, (b)1MH2SO4, (c) ABD/0.5 M HCl, and (d) 0.5 M HCl inks; (e, f) Cu samples patterned by printing with (e) NBD/1 MH2SO4 and(f)1MH2SO4 inks. Table 2. Film Thicknesses for NA Layer Coupled to CP Film and Associated Controls surface film thickness/nm a PPF-CP 1.0 ± 0.3 PPF-CP/SOCl2/NA 2.0 ± 0.5 PPF-CP/NA 1.0 ± 0.4 PPF-H2SO4/SOCl2/NA 0.4 ± 0.2 a AFM line profiles are shown in Figure S-4 (Supporting Information). NA + CP on PPF. CP groups were printed on PPF using nonpatterned stamps and CBD/1 M H2SO4 ink. The films were activated by immersion in SOCl2 for 30 min and then transferred to a 20 mM NA/ACN solution at room temperature for 24 h to promote coupling of NA groups to the CP layer via the formation of amide bonds. These samples are denoted PPF-CP/ SOCl2/NA. Controls were also prepared: PPF-CP blanks were obtained by printing CP films onto PPF without subsequent activation or immersion in NA/ACN; for PPF-CP/NA blanks, only the activation step was omitted; and for PPF-H2SO4/ SOCl2/NA, blanks were prepared by printing PPF with blank 1MH2SO4, followed by “activation” and immersion in NA/ ACN. Prior to their analysis, all samples and controls were sonicated for 5 min in ACN. AFM depth profiling results are shown in Table 2, and cyclic voltammograms of the modified surfaces and typical AFM line profiles are shown in Figures S-3 and S-4 (Supporting Information). Activation of the CP film and reaction with NA increased the film thickness from 1.0 ± 0.3 to 2.0 ± 0.5 nm, consistent with the coupling of NA groups to the CP layer. When the activation step 7032 Analytical Chemistry, Vol. 82, No. 16, August 15, 2010 Figure 5. AFM image of VACNTs tethered to a patterned AP layer on PPF. was omitted, there was no change in film thickness, confirming that NA does not physisorb to the CP film. Interestingly, a thin surface layer of NA was detected electrochemically (Figure S-3, Supporting Information) and by AFM measurements on the PPF-H2SO4/SOCl2/NA controls. The measured thickness (0.4 ± 0.2 nm) of this film is less than expected for a monolayer of NA groups (0.8 nm), indicating a submonolayer coverage. We assume that NA couples directly to a low concentration of carboxylate functionalities on the (otherwise) bare PPF surface. SWCNT + AP on PPF. This second example of the utility of printed films as tethers is based on recent work in which we assembled and characterized vertically aligned carbon nanotube (VACNT) forests on AP films electrografted to PPF. 46 To test whether printed AP films could be used similarly, PPF surfaces were patterned using ABD/0.5 M HCl ink and then immersed in a DMSO solution (2 mL) of cut SWCNTs (0.2 mg mL -1 ) and N,N′dicyclohexylcarbodiimide (1 mg mL -1 )for24hat65°C. These conditions promote formation of amide bonds between surfaceimmobilized AP groups and carboxylate groups at the cut ends of the SWCNTs. The resultant surfaces were sonicated in acetone for 10 s and then in isopropyl alcohol for 10 s prior to imaging by AFM. The image shown in Figure 5 (and the SEM image in Figure S-5, Supporting Information) is similar to those previously obtained for VACNTs on electrografted AP tether layers. 46 These examples demonstrate that MCP yields tether layers with their usual reactivity, and hence, the method can be used to prepare patterned substrates which form the basis of more complex structures. Buildup MCP Patterning of Two-Component Surfaces. Two- or multicomponent films in which secondary modifiers are patterned on top of a continuous base film have potential applications in sensing, where (for example) the base film is tailored to reduce nonspecific interactions with the analyte while the patterned secondary modifiers act either as tethers for attachment of recognition species or as the recognition elements themselves. This “buildup” method relies on the ability of the substrate to reduce the secondary modifiers by electron transfer across the base film. Reduction of the printed secondary modifier generates radicals which couple to the base film. Hence, a covalently coupled structure spontaneously forms in a single, simple step requiring no additional reagents. The buildup method (46) Garrett, D. J.; Flavel, B. S.; Shapter, J. G.; Baronian, K. H. R.; Downard, A. J. Langmuir 2010, 26, 1848–1854.
Table 3. Film Thickness Measurements on PPF Substrates Modified with CP Films with and without Overprinting of a NP Layer a film thickness/nm b sonication solvent and time CP region CP/NP region H2O (5 min) 1.6 ± 0.3 2.2 ± 0.3 H2O (5 min) 1.4 ± 0.3 2.1 ± 0.2 H2O (5 min) + ACN (30 min) 1.7 ± 0.6 2.1 ± 0.3 H2O (5 min) + ACN (30 min) 1.5 ± 0.4 2.0 ± 0.2 a Samples were prepared in duplicate. b AFM line profiles are shown in Figure S-7 (Supporting Information). Figure 6. SEM images of surfaces that were immersed in 10 mM CBD/0.1 H2SO4 for 30 min and subsequently printed with (a) ABD/ 0.5 M HCl and (b) 0.5 M HCl inks. After printing, the surfaces were immersed in Au nanoparticle solution for 40 min. was demonstrated by printing the secondary modifiers NP and AP. CP + NP on PPF. NP groups were printed onto a base CP film grafted spontaneously to PPF at OCP. Two ∼3.0 × 1.5 mm 2 PPF samples were immersed in 10 mM CBD/0.1 M H2SO4 solution for 30 min to form the base films. One half of each sample was then printed with a nonpatterned stamp using NBD/1 M H2SO4 ink. Cyclic voltammetry (Figure S-6, Supporting Information) confirmed that NBD had reacted in the expected manner giving an NP layer. AFM depth profiling measurements of printed and unprinted sections (Table 3) show that printing increases the film thickness, consistent with attachment of NP to the CP layer. The magnitude of the increase (∼0.4-0.7 nm) corresponds to the addition of a submonolayer of NP groups on top of the CP film. However, NP is also expected to couple within the CP film, and hence, the concentration of printed NP groups may be higher than indicated by film thickness data. To test the stability of the printed layers, the samples were sonicated in ACN for 30 min and the AFM measurements were repeated. The data in the lower part of Table 3 indicate that the film thicknesses did not change significantly, consistent with covalent attachment both to the substrate surface and between the base and printed layers. CP + AP on PPF. In the second example of the buildup printing approach, AP groups were patterned onto a spontaneously grafted layer of CP groups using a patterned stamp with ABD/ 0.5 M HCl ink. A blank was also prepared on a CP layer by printing with blank 0.5 M HCl ink. The printed surfaces were immersed for 40 min in a solution of Au nanoparticles and then sonicated in H 2O for 30 s prior to analysis by SEM. Figure 6 shows the SEM images where the assembled Au nanoparticles clearly reveal the patterned immobilization of AP (Figure 6a) in comparison with the control (Figure 6b). The buildup approach for preparing patterned two- or multicomponent surfaces should be applicable to all substrates at which grafting from aryldiazonium salt solutions proceeds spontaneously at OCP. However, the requirement that the second aryldiazonium cation be reduced by the substrate places some limitations on the nature and thickness of the base film and also on the aryldiazonium cation derivative. For strongly reducing substrates (such as zinc), it should be possible to print even relatively difficultto-reduce aryldiazonium cations onto thick base films. On the other hand, printing on less-reducing substrates (such as Au) is likely to be successful only with easily reduced aryldiazonium salt derivatives on thin base films. In the examples above, the base films were formed by spontaneous grafting from a aryldiazonium salt solution. There is no reason why MCP, electrografting, and/ or other classes of modifiers cannot be used. Methods such as electro-oxidation of primary amines 47 or arylhydrazines; 48 electroreduction of iodonium, 49,50 sulfonium 51 salts, or vinylic compounds; 52 photolytic or thermal grafting of alkenes and alkynes; 53-56 or photografting of arylazides 57 would greatly widen the range of functionalities that could be added to the surface. CONCLUSION Microcontact printing using aryldiazonium salt inks has been applied to carbon, metal, and semiconductor substrates to give stable, covalently attached, thin films. The thickness and the morphology of the printed film appear to depend on the potential driving force for reduction of the aryldiazonium cation by the substrate. Aminophenyl and carboxyphenyl groups in printed layers retain the ability to form amide bonds with solution species and, consequently, provide useful tethers for more complex surface structures. Microcontact printing using aryldiazonium salts is applicable to all substrate-diazonium salt combinations for which surface modification proceeds spontaneously at open circuit potential in solution. The variable film thickness and roughness, which is substrate- and film-dependent, may be a limitation for some potential applications; however, compared with other methods for patterning layers using aryldiazonium salts, microcontact is low cost and simple to implement with no requirement for electrochemical capability. Tightly defined patterns with feature sizes tens of micrometers upward can be routinely prepared, and (47) Barbier, B.; Pinson, J.; Desarmot, G.; Sanchez, M. J. Electrochem. Soc. 1990, 137, 1757–1764. (48) Malmos, K.; Iruthayaraj, J.; Pedersen, S. U.; Daasbjerg, K. J. Am. Chem. Soc. 2009, 131, 13926–13927. (49) Vase, K. H.; Holm, A. H.; Norrman, K.; Pedersen, S. U.; Daasbjerg, K. Langmuir 2007, 23, 3786–3793. (50) Vase, K. H. j.; Holm, A. H. k.; Pedersen, S. U.; Daasbjerg, K. Langmuir 2005, 21, 8085–8089. (51) Vase, K. H.; Holm, A. H.; Norrman, K.; Pedersen, S. U.; Daasbjerg, K. Langmuir 2008, 24, 182–188. (52) Palacin, S.; Bureau, C.; Charlier, J.; Deniau, G.; Mouanda, B.; Viel, P. ChemPhysChem 2004, 5, 1469–1481. (53) Lasseter, T. L.; Cai, W.; Hamers, R. J. Analyst 2004, 129, 3–8. (54) Ssenyange, S.; Anariba, F.; Bocian, D. F.; McCreery, R. L. Langmuir 2005, 21, 11105–11112. (55) Sun, B.; Colavita, P. E.; Kim, H.; Lockett, M.; Marcus, M. S.; Smith, L. M.; Hamers, R. J. Langmuir 2006, 22, 9598–9605. (56) Yu, S. S. C.; Downard, A. J. Langmuir 2007, 23, 4662–4668. (57) Gross, A. J.; Yu, S. S. C.; Downard, A. J. Langmuir 2010, 26, 7285–7292. Analytical Chemistry, Vol. 82, No. 16, August 15, 2010 7033
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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
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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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Page 241 and 242: Figure 2. Configuration editor wind
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Page 249 and 250: Figure 1. Representation of the Car
Page 251 and 252: Table 2. Capillary Electrophoresis
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Page 257 and 258: Another approach to handle this lim
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Page 263 and 264: CONCLUSIONS In this paper we have i
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Page 271 and 272: Anal. Chem. 2010, 82, 7015-7020 Sel
Page 273 and 274: Table 1. Effect of 1 D-LC Condition
Page 275 and 276: Figure 3. Peak-production rate vers
Page 277 and 278: Anal. Chem. 2010, 82, 7021-7026 Cel
Page 279 and 280: luciferase (T7 control vector) was
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Page 283 and 284: Anal. Chem. 2010, 82, 7027-7034 Pat
Page 285 and 286: Electrochemistry. Electrochemical m
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Page 293 and 294: Figure 1. (A) FL spectra of BSPOTPE
Page 295 and 296: Figure 4. (A) Variation in the FL i
Page 297 and 298: Figure 6. (A) FL spectra of BSPOTPE
Page 299 and 300: Scheme 1. Proposed Mechanism for Fl
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Page 303 and 304: Figure 2. Free fluorophores do not
Page 305 and 306: Anal. Chem. 2010, 82, 7049-7052 Dev
Page 307 and 308: Figure 2. Comparative analysis of d
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