1
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Monge Neria R, Kisley L. Single-Molecule Imaging in Commercial Stationary Phase Particles Using Highly Inclined and Laminated Optical Sheet Microscopy. Anal Chem 2023; 95:2245-2252. [PMID: 36652205 DOI: 10.1021/acs.analchem.2c03753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
We resolve the three-dimensional, nanoscale locations of single-molecule analytes within commercial stationary phase materials using highly inclined and laminated optical sheet (HILO) microscopy. Single-molecule fluorescence microscopy of chromatography can reveal the molecular heterogeneities that lead to peak broadening, but past work has focused on surfaces designed to mimic stationary phases, which have different physical and chemical properties than the three-dimensional materials used in real columns and membranes. To extend single-molecule measurements to commercial stationary phases, we immobilize individual stationary phase particles and modify our microscope for imaging at further depths with HILO, a method which was originally developed to resolve single molecules in cells of comparable size to column packing materials (∼5-10 μm). We describe and characterize how to change the angle of incidence to achieve HILO so that other researchers can easily incorporate this method onto their existing epi- or total internal reflection fluorescence microscopes. We show improvements up to a 32% in signal-to-background ratio and 118% in the number of single molecules detected within stationary phase particles when using HILO compared to epifluorescence. By controlling the objective position relative to the sample, we produce three-dimensional maps of molecule locations throughout entire stationary phase particles at nanoscale lateral and axial resolutions. The number of localized molecules remains constant axially throughout isolated stationary phase particles and between different particles, indicating that heterogeneity in a separation would not be caused by such affinity differences at microscales but instead kinetic differences at nanoscales on identifiable and distinct adsorption sites.
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Affiliation(s)
- Ricardo Monge Neria
- Department of Physics, Case Western Reserve University, Cleveland, Ohio44106-7079, United States
| | - Lydia Kisley
- Department of Physics, Case Western Reserve University, Cleveland, Ohio44106-7079, United States.,Department of Chemistry, Case Western Reserve University, Cleveland, Ohio44106-7079, United States
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2
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Calabrase W, Bishop LDC, Dutta C, Misiura A, Landes CF, Kisley L. Transforming Separation Science with Single-Molecule Methods. Anal Chem 2020; 92:13622-13629. [PMID: 32936608 DOI: 10.1021/acs.analchem.0c02572] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Empirical optimization of the multiscale parameters underlying chromatographic and membrane separations leads to enormous resource waste and production costs. A bottom-up approach to understand the physical phenomena underlying challenges in separations is possible with single-molecule observations of solute-stationary phase interactions. We outline single-molecule fluorescence techniques that can identify key interactions under ambient conditions. Next, we describe how studying increasingly complex samples heightens the relevance of single-molecule results to industrial applications. Finally, we illustrate how separation methods that have not been studied at the single-molecule scale can be advanced, using chiral chromatography as an example case. We hope new research directions based on a molecular approach to separations will emerge based on the ideas, technologies, and open scientific questions presented in this Perspective.
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Affiliation(s)
- William Calabrase
- Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Logan D C Bishop
- Department of Chemistry, Rice University, Houston, Texas 77251, United States
| | - Chayan Dutta
- Department of Chemistry, Rice University, Houston, Texas 77251, United States
| | - Anastasiia Misiura
- Department of Chemistry, Rice University, Houston, Texas 77251, United States
| | - Christy F Landes
- Department of Chemistry, Rice University, Houston, Texas 77251, United States.,Department of Electrical and Computer Engineering, Rice University, Houston, Texas 77251, United States.,Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77251, United States.,Smalley-Curl Institute, Rice University, Houston, Texas 77251, United States
| | - Lydia Kisley
- Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106, United States.,Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, United States
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3
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Bishop LDC, Landes CF. From a Protein's Perspective: Elution at the Single-Molecule Level. Acc Chem Res 2018; 51:2247-2254. [PMID: 30132321 DOI: 10.1021/acs.accounts.8b00211] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Column chromatography is a widely used analytical technique capable of identifying and isolating a desired chemical species from a more complicated mixture. Despite the method's prevalence, theoretical descriptions have not advanced to accommodate today's common analyte, proteins. Proteins are increasingly used as biologics, a term that refers to biological pharmaceuticals, and present new complexities for chromatographic separation. Large variations in surface charge, chemistry, and structure among protein analytes expose the limits in the current theoretical framework's ability to predict the efficiency of a column without empirical data. The bottleneck created by empirical optimization is a strong motivation for a renewed effort to achieve an in-depth understanding of the range of interactions that occur between a protein analyte and the stationary phase that together enable its selective separation from other constituents of a mixture. The physical and chemical processes that dictate the amount of time an analyte spends in the column are often abstracted by theory and treated as statistical distributions. Until recently, these distributions could not be mapped experimentally as traditional experimental techniques could not reveal underlying heterogeneity in structure, charge, and dynamics. Aligning the latest experimental and theoretical advances is thus a hurdle to be overcome so that significant progress can be made toward a predictive chromatographic theory. In this Account, we detail the work of the Landes Lab in developing single-molecule techniques that refine the stochastic theory of chromatography as a first step toward predictive chromatographic column design. We provide a brief review of the development of stochastic theory and establish a mathematical framework to put the discussed physical chemistry in context. We describe our investigations of three pertinent phenomena: mobile/stationary phase exchange, adsorption/desorption kinetics, and hindered diffusion. We highlight experimental evidence that points to nonuniform behavior. Then, we describe our work in developing single-molecule techniques that can evaluate these effects on a protein-by-protein basis. We highlight two developments: fast imaging via super temporal-resolved microscopy (STReM) and visualizing diffusion within pores via a combination of fluorescence correlation spectroscopy and super-resolution optical fluctuation imaging (fcsSOFI). Both methods offer new ways to study chromatographic elution at the single-protein level. Such methods can identify the rare heterogeneities that prevent efficient separations and advance the field closer to predictively optimized protein separations.
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4
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Shen H, Tauzin LJ, Baiyasi R, Wang W, Moringo N, Shuang B, Landes CF. Single Particle Tracking: From Theory to Biophysical Applications. Chem Rev 2017; 117:7331-7376. [PMID: 28520419 DOI: 10.1021/acs.chemrev.6b00815] [Citation(s) in RCA: 273] [Impact Index Per Article: 39.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
After three decades of developments, single particle tracking (SPT) has become a powerful tool to interrogate dynamics in a range of materials including live cells and novel catalytic supports because of its ability to reveal dynamics in the structure-function relationships underlying the heterogeneous nature of such systems. In this review, we summarize the algorithms behind, and practical applications of, SPT. We first cover the theoretical background including particle identification, localization, and trajectory reconstruction. General instrumentation and recent developments to achieve two- and three-dimensional subdiffraction localization and SPT are discussed. We then highlight some applications of SPT to study various biological and synthetic materials systems. Finally, we provide our perspective regarding several directions for future advancements in the theory and application of SPT.
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Affiliation(s)
- Hao Shen
- Department of Chemistry and ‡Department of Electrical and Computer Engineering, §Smalley-Curl Institute, Rice University , Houston, Texas 77251, United States
| | - Lawrence J Tauzin
- Department of Chemistry and ‡Department of Electrical and Computer Engineering, §Smalley-Curl Institute, Rice University , Houston, Texas 77251, United States
| | - Rashad Baiyasi
- Department of Chemistry and ‡Department of Electrical and Computer Engineering, §Smalley-Curl Institute, Rice University , Houston, Texas 77251, United States
| | - Wenxiao Wang
- Department of Chemistry and ‡Department of Electrical and Computer Engineering, §Smalley-Curl Institute, Rice University , Houston, Texas 77251, United States
| | - Nicholas Moringo
- Department of Chemistry and ‡Department of Electrical and Computer Engineering, §Smalley-Curl Institute, Rice University , Houston, Texas 77251, United States
| | - Bo Shuang
- Department of Chemistry and ‡Department of Electrical and Computer Engineering, §Smalley-Curl Institute, Rice University , Houston, Texas 77251, United States
| | - Christy F Landes
- Department of Chemistry and ‡Department of Electrical and Computer Engineering, §Smalley-Curl Institute, Rice University , Houston, Texas 77251, United States
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5
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Polymer electrolyte and liquid electrolyte based on sulfolane in full cell LiFePO 4 │Li 4 Ti 5 O 12. Electrochim Acta 2016. [DOI: 10.1016/j.electacta.2016.01.086] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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6
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Chen F, Neupane B, Li P, Su W, Wang G. Investigating axial diffusion in cylindrical pores using confocal single-particle fluorescence correlation spectroscopy. Electrophoresis 2016; 37:2129-38. [PMID: 27196052 DOI: 10.1002/elps.201600158] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Revised: 04/17/2016] [Accepted: 05/02/2016] [Indexed: 02/05/2023]
Abstract
We explored the feasibility of using confocal fluorescence correlation spectroscopy to study small nanoparticle diffusion in hundred-nanometer-sized cylindrical pores. By modeling single particle diffusion in tube-like confined three-dimensional space aligned parallel to the confocal optical axis, we showed that two diffusion dynamics can be observed in both original intensity traces and the autocorrelation functions (ACFs): the confined two-dimensional lateral diffusion and the unconfined one-dimensional (1D) axial diffusion. The separation of the axial and confined lateral diffusion dynamics provides an opportunity to study diffusions in different dimensions separately. We further experimentally studied 45 nm carboxylated polystyrene particles diffusing in 300 nm alumina pores. The experimental data showed consistency with the simulation. To extract the accurate axial diffusion coefficient, we found that a 1D diffusion model with a Lorentzian axial collection profile needs to be used to analyze the experimental ACFs. The diffusion of the 45 nm nanoparticles in polyethyleneglycol-passivated 300 nm pores slowed down by a factor of ∼2, which can be satisfactorily explained by hydrodynamic frictions.
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Affiliation(s)
- Fang Chen
- Chemistry Department, North Carolina State University, Raleigh, NC, USA
| | - Bhanu Neupane
- Chemistry Department, North Carolina State University, Raleigh, NC, USA
| | - Peiyuan Li
- Chemistry Department, North Carolina State University, Raleigh, NC, USA
| | - Wei Su
- Chemistry Department, North Carolina State University, Raleigh, NC, USA
| | - Gufeng Wang
- Chemistry Department, North Carolina State University, Raleigh, NC, USA
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7
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Cooper JT, Harris JM. Spatially Multiplexed Imaging: Fluorescence Correlation Spectroscopy for Efficient Measurement of Molecular Diffusion at Solid-Liquid Interfaces. APPLIED SPECTROSCOPY 2016; 70:695-701. [PMID: 26887989 DOI: 10.1177/0003702816631312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Accepted: 08/02/2015] [Indexed: 06/05/2023]
Abstract
Fluorescence correlation spectroscopy (FCS) has become an important technique for the characterization of molecular dynamics, especially at interfaces. Fluorescence correlation spectroscopy provides both temporal and spatial resolution for measuring fast processes at equilibrium through analysis of noise in fluorescence intensities from the statistical fluctuations in a small number of molecules. The small molecular populations produce very low-level fluorescence signals, where time-averaging the fluorescence autocorrelation function is needed to generate reasonable signal-to-noise (S/N) ratios. Recently imaging cameras have been adapted to FCS measurements of molecular dynamics at interfaces (membranes and surfaces) through the use of electron-multiplying charge-coupled device (EM-CCD) detectors for acquisition of fluorescence from addressable areas on the detector. This approach provides a major advantage over traditional focused-spot FCS by allowing electronic control over the location and area of the acquired region on the sample surface. Imaging-FCS can also provide a spatial multiplexing advantage through its ability to measure intensity data from larger areas in parallel with no loss of time resolution. In this work, this multiplexing advantage is exploited to determine molecular diffusion rates from the simultaneous measurement of multiple areas on a surface, the autocorrelation traces from which are averaged to improve the S/N ratio. As proof of concept, the diffusion of 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate (DiI) on a C18-modified interface was measured using this multiplexed method and compared to autocorrelation data acquired from a single spot. Due to the slow thermal recovery of the EM-CCD that inhibits fast time-averaging, spatial multiplexing in imaging-FCS provides an eightyfold time savings to reach the same S/N ratio as multiple (time-averaged) measurements from a single spot.
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Affiliation(s)
- Justin T Cooper
- Department of Chemistry, University of Utah, Salt Lake City, Utah, USA
| | - Joel M Harris
- Department of Chemistry, University of Utah, Salt Lake City, Utah, USA
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8
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García-López V, Chiang PT, Chen F, Ruan G, Martí AA, Kolomeisky AB, Wang G, Tour JM. Unimolecular Submersible Nanomachines. Synthesis, Actuation, and Monitoring. NANO LETTERS 2015; 15:8229-39. [PMID: 26540377 PMCID: PMC4676417 DOI: 10.1021/acs.nanolett.5b03764] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Revised: 10/30/2015] [Indexed: 05/20/2023]
Abstract
Unimolecular submersible nanomachines (USNs) bearing light-driven motors and fluorophores are synthesized. NMR experiments demonstrate that the rotation of the motor is not quenched by the fluorophore and that the motor behaves in the same manner as the corresponding motor without attached fluorophores. No photo or thermal decomposition is observed. Through careful design of control molecules with no motor and with a slow motor, we found using single molecule fluorescence correlation spectroscopy that only the molecules with fast rotating speed (MHz range) show an enhancement in diffusion by 26% when the motor is fully activated by UV light. This suggests that the USN molecules give ∼9 nm steps upon each motor actuation. A non-unidirectional rotating motor also results in a smaller, 10%, increase in diffusion. This study gives new insight into the light actuation of motorized molecules in solution.
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Affiliation(s)
- Víctor García-López
- Department of Chemistry, Department of Chemical
and Biomolecular Engineering and Center for Theoretical Biological
Physics, Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
| | - Pinn-Tsong Chiang
- Department of Chemistry, Department of Chemical
and Biomolecular Engineering and Center for Theoretical Biological
Physics, Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
| | - Fang Chen
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Gedeng Ruan
- Department of Chemistry, Department of Chemical
and Biomolecular Engineering and Center for Theoretical Biological
Physics, Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
| | - Angel A. Martí
- Department of Chemistry, Department of Chemical
and Biomolecular Engineering and Center for Theoretical Biological
Physics, Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
- E-mail:
| | - Anatoly B. Kolomeisky
- Department of Chemistry, Department of Chemical
and Biomolecular Engineering and Center for Theoretical Biological
Physics, Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
- E-mail:
| | - Gufeng Wang
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
- E-mail:
| | - James M. Tour
- Department of Chemistry, Department of Chemical
and Biomolecular Engineering and Center for Theoretical Biological
Physics, Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
- E-mail:
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9
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Higgins DA, Park SC, Tran-Ba KH, Ito T. Single-Molecule Investigations of Morphology and Mass Transport Dynamics in Nanostructured Materials. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2015; 8:193-216. [PMID: 26132347 DOI: 10.1146/annurev-anchem-071114-040153] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Nanostructured materials such as mesoporous metal oxides and phase-separated block copolymers form the basis for new monolith, membrane, and thin film technologies having applications in energy storage, chemical catalysis, and separations. Mass transport plays an integral role in governing the application-specific performance characteristics of many such materials. The majority of methods employed in their characterization provide only ensemble data, often masking the nanoscale, molecular-level details of materials morphology and mass transport. Single-molecule fluorescence methods offer direct routes to probing these characteristics on a single-molecule/single-nanostructure basis. This article provides a review of single-molecule studies focused on measurements of anisotropic diffusion, adsorption, partitioning, and confinement in nanostructured materials. Experimental methods covered include confocal and wide-field fluorescence microscopy. The results obtained promise to deepen our understanding of mass transport mechanisms in nanostructures, thus aiding in the realization of advanced materials systems.
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Affiliation(s)
- Daniel A Higgins
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506-0401; ,
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10
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Affiliation(s)
- Lydia Kisley
- Department of Chemistry and Department of Electrical and Computer
Engineering,
Rice Quantum Institute, Rice University, 6100 Main Street, MS-60, Houston, Texas 77005, United States
| | - Christy F. Landes
- Department of Chemistry and Department of Electrical and Computer
Engineering,
Rice Quantum Institute, Rice University, 6100 Main Street, MS-60, Houston, Texas 77005, United States
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11
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Cooper J, Harris JM. Fluorescence-Correlation Spectroscopy Study of Molecular Transport within Reversed-Phase Chromatographic Particles Compared to Planar Model Surfaces. Anal Chem 2014; 86:11766-72. [DOI: 10.1021/ac503250a] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Justin Cooper
- Department of Chemistry, University of Utah, 315 South 1400
East, Salt Lake City, Utah 84112-0805, United States
| | - Joel M. Harris
- Department of Chemistry, University of Utah, 315 South 1400
East, Salt Lake City, Utah 84112-0805, United States
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12
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Mabry JN, Skaug MJ, Schwartz DK. Single-molecule insights into retention at a reversed-phase chromatographic interface. Anal Chem 2014; 86:9451-8. [PMID: 25188676 DOI: 10.1021/ac5026418] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The efficiency of chromatographic separations decreases markedly when peaks exhibit asymmetry (e.g., "peak tailing"). Theoretically, these effects can arise from heterogeneous adsorption kinetics. To investigate the nature and consequences of such heterogeneity, we used a combination of single-molecule imaging and reversed-phase liquid chromatography (RPLC). In both single-molecule and macroscopic RPLC experiments, the stationary phase was hydrophobic end-capped (trimethylsilyl-functionalized) silica, which we exposed to different methanol/water solutions (50%-62% methanol), containing a fluorescent fatty acid analyte. Super-resolution maps based on single-molecule observations revealed rare, strong adsorption sites with activity that varied significantly with methanol concentration. The adsorption and desorption kinetics on the strong sites were heterogeneous and positively correlated, suggesting a broad underlying distribution of site binding energies. Adsorption equilibrium on the strong sites was more sensitive to solution conditions than overall retention measured in RPLC experiments, suggesting that the effect of strong sites on the overall adsorption kinetics should change with solution conditions. Interestingly, in RPLC experiments, peak tailing had a nonmonotonic dependence on methanol concentration within the range studied. Using the stochastic model of chromatography, we showed quantitatively that our single-molecule kinetic results were consistent with this macroscopic trend. This approach to identifying and quantifying adsorption sites should be useful for designing better chromatographic separations and for identifying the role of heterogeneous surface chemistry in molecular dynamics.
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Affiliation(s)
- Joshua N Mabry
- Department of Chemical and Biological Engineering, University of Colorado Boulder, Colorado 80309-0596, United States
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13
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Cooper JT, Harris JM. Imaging Fluorescence-Correlation Spectroscopy for Measuring Fast Surface Diffusion at Liquid/Solid Interfaces. Anal Chem 2014; 86:7618-26. [DOI: 10.1021/ac5014354] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Justin T. Cooper
- Department
of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0805, United States
| | - Joel M. Harris
- Department
of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0805, United States
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14
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Kurc B. Gel electrolytes based on poly(acrylonitrile)/sulpholane with hybrid TiO2/SiO2 filler for advanced lithium polymer batteries. Electrochim Acta 2014. [DOI: 10.1016/j.electacta.2014.01.117] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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15
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Unified superresolution experiments and stochastic theory provide mechanistic insight into protein ion-exchange adsorptive separations. Proc Natl Acad Sci U S A 2014; 111:2075-80. [PMID: 24459184 DOI: 10.1073/pnas.1318405111] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Chromatographic protein separations, immunoassays, and biosensing all typically involve the adsorption of proteins to surfaces decorated with charged, hydrophobic, or affinity ligands. Despite increasingly widespread use throughout the pharmaceutical industry, mechanistic detail about the interactions of proteins with individual chromatographic adsorbent sites is available only via inference from ensemble measurements such as binding isotherms, calorimetry, and chromatography. In this work, we present the direct superresolution mapping and kinetic characterization of functional sites on ion-exchange ligands based on agarose, a support matrix routinely used in protein chromatography. By quantifying the interactions of single proteins with individual charged ligands, we demonstrate that clusters of charges are necessary to create detectable adsorption sites and that even chemically identical ligands create adsorption sites of varying kinetic properties that depend on steric availability at the interface. Additionally, we relate experimental results to the stochastic theory of chromatography. Simulated elution profiles calculated from the molecular-scale data suggest that, if it were possible to engineer uniform optimal interactions into ion-exchange systems, separation efficiencies could be improved by as much as a factor of five by deliberately exploiting clustered interactions that currently dominate the ion-exchange process only accidentally.
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16
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Cooper JT, Peterson EM, Harris JM. Fluorescence Imaging of Single-Molecule Retention Trajectories in Reversed-Phase Chromatographic Particles. Anal Chem 2013; 85:9363-70. [DOI: 10.1021/ac402251r] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Justin T. Cooper
- Department
of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0805, United States
| | - Eric M. Peterson
- Department
of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0805, United States
| | - Joel M. Harris
- Department
of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0805, United States
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17
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Matsui T, Tsukahara S, Watarai H. Single-molecule lactonization of octadecylrhodamine B at a liquid-liquid interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:15428-15432. [PMID: 23095076 DOI: 10.1021/la302375z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The total internal reflection laser fluorescence microscope method was used to observe the lateral diffusion of a single octadecylrhodamine B (C(18)RB) molecule at the toluene-water interface. The interfacial diffusion constant of single fluorescent cation C(18)RB(+) was obtained from the maximum residence time in a small observation area with pH <2. For pH >3, the maximum residence time was remarkably shortened, indicating that single fluorescent zwitterion C(18)RB(±) rapidly converted to the nonfluorescent lactone at the interface. The lactonization rate was completed within 0.13 ms at the toluene-water interface but slowed to 67 ms at an interface saturated with dimyristoylphosphatidylcholine.
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Affiliation(s)
- Tomoko Matsui
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Japan
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18
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Nelson N, Walder R, Schwartz DK. Single molecule dynamics on hydrophobic self-assembled monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:12108-13. [PMID: 22876990 DOI: 10.1021/la302369v] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The interactions between adsorbate molecules and hydrophobic surfaces are of significant interest due to their importance in a variety of biological and separation processes. However, it is challenging to extrapolate macroscopic ensemble-averaged force measurements to molecular-level phenomena. Using total internal reflection fluorescence microscopy to image individual molecules at hydrophobic solid-aqueous interfaces, we directly observed dynamic behavior associated with the interactions between fluorescently labeled dodecanoic acid (our probe molecules) and self-assembled monolayers (SAM) comprising n-alkyltriethoxysilanes with systematically increasing chain length (from n = 4-18). In all cases, we observed at least two characteristic surface residence times and two diffusive modes, suggesting the presence of multiple distinct adsorbed populations. In general, the mean surface residence time increased and the mobility decreased with increasing SAM chain length, consistent with stronger probe-surface interactions. However, these trends were not primarily due to changes in characteristic residence times or diffusion coefficients associated with the individual populations but rather to a dramatic increase in the fraction associated with the long-lived slow-moving population(s) on long-chain SAMs. In particular, on longer (16-18 carbon) alkylsilane monolayers, the probe molecule exhibited far fewer desorption-mediated "flights" than on short (4-6 carbon) monolayers. Additionally, probes on the longer chain surfaces were much more likely to exhibit extended surface residence times as opposed to short transient surface visits.
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Affiliation(s)
- Nathaniel Nelson
- Department of Chemical and Biological Engineering, University of Colorado, Boulder, Colorado 80309, United States
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19
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Kirkeminde AW, Torres T, Ito T, Higgins DA. Multiple Diffusion Pathways in Pluronic F127 Mesophases Revealed by Single Molecule Tracking and Fluorescence Correlation Spectroscopy. J Phys Chem B 2011; 115:12736-43. [DOI: 10.1021/jp208234b] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Alec W. Kirkeminde
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506-0401, United States
| | - Travis Torres
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506-0401, United States
| | - Takashi Ito
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506-0401, United States
| | - Daniel A. Higgins
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506-0401, United States
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20
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Skvortsova YA, Freeney RM, Zhong Z, Geng ML. Tissue phantoms constructed with hydrophobic nanoporous silica particles. Anal Chem 2010; 82:6712-6. [PMID: 20608646 DOI: 10.1021/ac902442g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We describe a protocol to create tissue phantoms with hydrophobic nanoporous particles. The nanopores of the particles are loaded with biological molecules at the desired compositions. Tissue phantoms are prepared by immersing dried particles into aqueous biological matrixes. The hydrophobicity of the pore surface prevents the solution from penetrating into the nanopores, thus preserving the designed molecular composition inside the particles. This protocol provides a unique approach to preparing biological systems in small domains, at micrometer and nanometer dimensions, with well-defined boundaries and tailored biological and optical properties. The nanoporous particle approach is easy when compared to the common preparation methods such as with polymers and vesicles as it involves direct loading of the biological molecules into the pores and does not require complex synthetic steps. The method is adaptable, with tunable pore and particle sizes, and robust, with a rigid boundary to protect the designed biological domain. In addition to tissue phantom preparation, this approach is applicable in systems where a well-defined biological domain is desired.
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Affiliation(s)
- Yulia A Skvortsova
- Department of Chemistry and the Nanoscience and Nanotechnology Institute, The University of Iowa, Iowa City, Iowa 52242, USA
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21
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De Santo I, Causa F, Netti PA. Subdiffusive Molecular Motion in Nanochannels Observed by Fluorescence Correlation Spectroscopy. Anal Chem 2010; 82:997-1005. [DOI: 10.1021/ac902270k] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ilaria De Santo
- Interdisciplinary Research Centre on Biomaterials (CRIB), University Federico II, Piazzale Tecchio 80, 80125, Naples, Italy, Italian Institute of Technology (IIT), Via Morego, 30 Genoa, Italy, and Department of Experimental and Clinical Medicine, University Magna Graecia, Germaneto, 88100, Catanzaro, Italy
| | - Filippo Causa
- Interdisciplinary Research Centre on Biomaterials (CRIB), University Federico II, Piazzale Tecchio 80, 80125, Naples, Italy, Italian Institute of Technology (IIT), Via Morego, 30 Genoa, Italy, and Department of Experimental and Clinical Medicine, University Magna Graecia, Germaneto, 88100, Catanzaro, Italy
| | - Paolo A. Netti
- Interdisciplinary Research Centre on Biomaterials (CRIB), University Federico II, Piazzale Tecchio 80, 80125, Naples, Italy, Italian Institute of Technology (IIT), Via Morego, 30 Genoa, Italy, and Department of Experimental and Clinical Medicine, University Magna Graecia, Germaneto, 88100, Catanzaro, Italy
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22
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Lange JJ, Collinson MM, Culbertson CT, Higgins DA. Single-Molecule Studies of Oligomer Extraction and Uptake of Dyes in Poly(dimethylsiloxane) Films. Anal Chem 2009; 81:10089-96. [DOI: 10.1021/ac902250p] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jeffrey J. Lange
- Departments of Chemistry, Kansas State University, Manhattan, Kansas 66506, and Virginia Commonwealth University, Richmond, Virginia 23284
| | - Maryanne M. Collinson
- Departments of Chemistry, Kansas State University, Manhattan, Kansas 66506, and Virginia Commonwealth University, Richmond, Virginia 23284
| | - Christopher T. Culbertson
- Departments of Chemistry, Kansas State University, Manhattan, Kansas 66506, and Virginia Commonwealth University, Richmond, Virginia 23284
| | - Daniel A. Higgins
- Departments of Chemistry, Kansas State University, Manhattan, Kansas 66506, and Virginia Commonwealth University, Richmond, Virginia 23284
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23
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Carr JK, Himes RD, Keung CH, Burden DL, Walhout PK. Heterogeneous translational dynamics of rhodamine B in polyelectrolyte multilayer thin films observed by single molecule microscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:8330-8339. [PMID: 19505126 DOI: 10.1021/la900573w] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The lateral diffusion dynamics of rhodamine B (RB) in polyelectrolyte multilayer (PEM) thin films has been studied with single-molecule confocal fluorescence microscopy. The films were made with sodium poly(sodium 4-styrenesulfonate) (PSS) and poly(diallydimethlyammonium chloride) (PDDA). Analysis of the real-time emission intensity traces reveals three diverse components of translational motion: (1) fast diffusion of RB through the confocal detection volume; (2) reversible tracer adsorption processes; and (3) nanoconfined diffusion. These processes cover a wide range of time scales. Analysis via fluorescence correlation spectroscopy (FCS) involves multicomponent fitting of the autocorrelated emission data. The model includes a free Brownian diffusion parameter, D, and two rate constants of desorption, k(-1) and k(-2). For RB in a PSS/PDDA thin film made with 0.01 M NaCl in the polyelectrolyte buildup solutions, D = 1.7 x 10(-7) cm(2)/s, k(-1) = 30 s(-1), and k(-2) = 0.1 s(-1). FCS was also performed on RB/PEM samples made with NaCl concentrations of the buildup solutions ranging from 0.01 to 0.7 M. A weak dependence of D and k(-1) on NaCl concentration was observed while k(-2) increased linearly with [NaCl].
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Affiliation(s)
- Joshua K Carr
- Department of Chemistry, Wheaton College, Wheaton, IL 60187, USA
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24
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Ye F, Collinson MM, Higgins DA. What can be learned from single molecule spectroscopy? Applications to sol-gel-derived silica materials. Phys Chem Chem Phys 2008; 11:66-82. [PMID: 19081909 DOI: 10.1039/b812924j] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Single molecule spectroscopic methods are now being widely employed to probe the nanometer scale properties of sol-gel-derived silica materials. This article reviews a subset of the recent literature in this area and provides salient examples of the new information that can be obtained. The materials covered include inorganic and organically-modified silica, along with surfactant-templated mesoporous materials. Studies of molecule-matrix interactions based on ionic, hydrogen bonding and hydrophobic interactions are reviewed, highlighting the impacts of these interactions on mass transport phenomena. Quantitative investigations of molecular diffusion by single molecule tracking and fluorescence correlation spectroscopy are also covered, focusing on the characterization of anisotropic and hindered diffusion in mesoporous systems. Single molecule polarity studies are described and the new information that can be obtained from the resulting inhomogeneous distributions is discussed. Likewise, single molecule studies of silica acidity properties are reviewed, including observation of nanoscale buffering phenomena due to the chemistry of surface silanols. Finally, related single nanoparticle studies of macroporous silicas are also discussed.
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Affiliation(s)
- Fangmao Ye
- Department of Chemistry, Kansas State University, KS, 66506, Manhattan, USA
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25
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Lange JJ, Culbertson CT, Higgins DA. Single Molecule Studies of Solvent-Dependent Diffusion and Entrapment in Poly(dimethylsiloxane) Thin Films. Anal Chem 2008; 80:9726-34. [DOI: 10.1021/ac8017179] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jeffrey J. Lange
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506
| | | | - Daniel A. Higgins
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506
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Gao Y, Zhong Z, Geng LM. Calibration of probe volume in fluorescence correlation spectroscopy. APPLIED SPECTROSCOPY 2007; 61:956-62. [PMID: 17910792 DOI: 10.1366/000370207781745883] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
In fluorescence correlation spectroscopy (FCS), an accurate evaluation of the probe volume is the basis of correct interpretation of experimental data and solution of an appropriate diffusion model. Poor fitting convergence has been a problem in the determination of the dimensional parameters, the beam radius, omega, and the distance along the optical axis of the probe volume, l. In this work, the instability of fitting during the calibration process is investigated by examining the chi(2) surfaces. We demonstrate that the minimum of chi(2) in the omega dimension is well defined for both converging and diverging data. The difficulty of fitting comes from the l dimension. The uncertainty in l could be significantly larger than that in omega, as determined by F-statistics. A modified calibration process is recommended based on examining two data treatment methods, combining several short data sets into a single long run and averaging the correlation functions of several short data sets. It is found that by using the mean of several converging correlation functions from short data sets instead of a long time correlation, more stable and consistent dimensional parameters are extracted to define the probe volume.
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Affiliation(s)
- Yi Gao
- Department of Chemistry, the Optical Science and Technology Center, the Nanoscience and Nanotechnology Institute, and the Center for Biocatalysis and Bioprocessing, University of Iowa, Iowa City, IA 52242, USA
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27
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Ye F, Collinson MM, Higgins DA. Molecular orientation and its influence on autocorrelation amplitudes in single-molecule imaging experiments. Anal Chem 2007; 79:6465-72. [PMID: 17663532 DOI: 10.1021/ac071255z] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The concentration dependence of autocorrelation amplitudes obtained from orientationally fixed single molecules is explored using theory, simulation, and experimental results. Autocorrelation amplitudes obtained under such circumstances are shown to be approximately 2-fold larger than predicted in previous studies (Koppel, D. E. Phys. Rev. A 1974, 10, 1938-1945 and citing references), which frequently assume polarization-independent excitation and detection. A detailed derivation of the autocorrelation amplitude expected under conditions frequently employed in single-molecule experiments is given. Simulated and experimental single-molecule image data obtained from samples incorporating fixed single molecules are used to verify the correctness of the model. These results are compared to both simulated and experimental time transient data in which the molecules exhibit predominantly fast rotational reorientation and to which previously reported models apply. The experimental results employed are obtained from dye-doped mesoporous silica thin films studied at different levels of hydration. The theory and results obtained are of importance to the determination of molecular concentrations from single-molecule image and time transient autocorrelation data, in situations where the molecules exhibit permanent or reversible adsorption at fixed orientations in or on thin-film materials.
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Affiliation(s)
- Fangmao Ye
- Department of Chemistry, Kansas State University, Manhattan, KS 66506, USA
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28
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Zhong Z, Geng ML. Microscopic Origins of Band Broadening in Chromatography. Polarity Distribution in C18 Stationary Phase Probed by Confocal Ratiometric Imaging of Nile Red. Anal Chem 2007; 79:6709-17. [PMID: 17663533 DOI: 10.1021/ac071272o] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Band broadening is a major factor that influences the efficiency and resolution of chromatographic separations. Studies of microscopic origins of band broadening, such as the micropolarity distribution of chromatographic stationary phase, can provide a better understanding of many chromatographic phenomena and retention behavior. In this work, we probe the chemical environments of C18 chromatographic stationary phase with quantitative confocal fluorescence microscopy under real reversed-phase liquid chromatography conditions. Ratiometric imaging of C18 interface is achieved by loading the stationary phase with a polarity-sensitive dye, Nile red, and optical sectioning with confocal microscopy. The results reveal that there are uniform micropolarity distributions inside individual chromatographic beads, but the polarity may differ between stationary-phase particles. The homogeneity of micropolarity of individual beads suggests that there are not any spatially large exposed silica sites beyond the optical resolution in C18 stationary phase. The strong adsorption sites are smaller in size than the optical resolution of a few hundred nanometers. The heterogeneity between chromatographic beads indicates that the interactions of Nile red with C18 bonded phase are different between beads. This contributes to the broad overall polarity distribution of the C18 stationary phase and can be one of the factors that cause band broadening in separations. With its high spatial resolution and optical sectioning capabilities, confocal fluorescence imaging is shown to be an ideal method to probe the chromatographic stationary phase. The distribution of micropolarity sheds light on the microscopic heterogeneity in chromatographic processes and its influence on chemical separations.
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Affiliation(s)
- Zhenming Zhong
- Department of Chemistry, Nanoscience and Nanotechnology Institute and the Optical Science and Technology Center, University of Iowa, Iowa City, IA 52242, USA
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29
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Abstract
Single-molecule spectroscopy has emerged as a valuable tool in probing kinetics and dynamic equilibria in adsorption because advances in instrumentation and technology have enabled researchers to obtain high signal-to-noise ratios for common dyes at room temperature. Single-molecule spectroscopy was applied to the study of an important problem in chromatography: peak broadening and asymmetry in the chromatograms of pharmaceuticals, peptides, and proteins. Using DiI, a cationic dye that exhibits the same problematic chromatographic behavior, investigators showed that the adsorption sites that cause chromatographic problems are located at defects on the silica crystal surface.
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Affiliation(s)
- Mary J Wirth
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA.
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Culbertson MJ, Williams JTB, Cheng WWL, Stults DA, Wiebracht ER, Kasianowicz JJ, Burden DL. Numerical fluorescence correlation spectroscopy for the analysis of molecular dynamics under nonstandard conditions. Anal Chem 2007; 79:4031-9. [PMID: 17447726 DOI: 10.1021/ac062013m] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The suitability of mathematical models used to extract kinetic information from correlated data constitutes a significant issue in fluorescence correlation spectroscopy (FCS). Standard FCS equations are derived from a simple Gaussian approximation of the optical detection volume, but some investigations have suggested this traditional practice can lead to inaccurate and misleading conclusions under many experimental circumstances, particularly those encountered in one-photon confocal measurements. Furthermore, analytical models cannot be derived for all measurement scenarios. We describe a novel numerical approach to FCS that circumvents conventional analytical models, enabling meaningful analyses even under extraordinarily unusual measurement conditions. Numerical fluorescence correlation spectroscopy (NFCS) involves quantitatively matching experimental correlation curves with synthetic curves generated via diffusion simulation or direct calculation based on an experimentally determined 3D map of the detection volume. Model parameters are adjusted iteratively to minimize the residual differences between synthetic and experimental correlation curves. In order to reduce analysis time, we distribute calculations across a network of processors. As an example of this new approach, we demonstrate that synthetic autocorrelation curves correspond well with experimental data and that NFCS diffusion measurements of Rhodamine B remain constant, regardless of the distortion present in a confocal detection volume.
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31
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Zhong Z, Wang G, Geng ML. Probing strong adsorption of individual solute molecules at solid/liquid interfaces with model-based statistical two-dimensional correlation analysis. J Mol Struct 2006. [DOI: 10.1016/j.molstruc.2006.04.031] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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32
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Parida SK, Dash S, Patel S, Mishra BK. Adsorption of organic molecules on silica surface. Adv Colloid Interface Sci 2006; 121:77-110. [PMID: 16879799 DOI: 10.1016/j.cis.2006.05.028] [Citation(s) in RCA: 347] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2005] [Revised: 05/17/2006] [Accepted: 05/17/2006] [Indexed: 11/29/2022]
Abstract
The adsorption behaviour of various organic adsorbates on silica surface is reviewed. Most of the structural information on silica is obtained from IR spectral data and from the characteristics of water present at the silica surface. Silica surface is generally embedded with hydroxy groups and ethereal linkages, and hence considered to have a negative charged surface prone to adsorption of electron deficient species. Adsorption isotherms of the adsorbates delineate the nature of binding of the adsorbate with silica. Aromatic compounds are found to involve the pi-cloud in hydrogen bonding with silanol OH group during adsorption. Cationic and nonionic surfactants adsorb on silica surface involving hydrogen bonding. Sometimes, a polar part of the surfactants also contributes to the adsorption process. Styryl pyridinium dyes are found to anchor on silica surface in flat-on position. On modification of the silica by treating with alkali, the adsorption behaviour of cationic surfactant or polyethylene glycol changes due to change in the characteristics of silica or modified silica surface. In case of PEG-modified silica, adsolubilization of the adsorbate is observed. By using a modified adsorption equation, hemimicellization is proposed for these dyes. Adsorptions of some natural macromolecules like proteins and nucleic acids are investigated to study the hydrophobic and hydrophilic binding sites of silica. Artificial macromolecules like synthetic polymers are found to be adsorbed on silica surface due to the interaction of the multifunctional groups of the polymers with silanols. Preferential adsorption of polar adsorbates is observed in case of adsorbate mixtures. When surfactant mixtures are considered to study competitive adsorption on silica surface, critical micelle concentration of individual surfactant also contributes to the adsorption isotherm. The structural study of adsorbed surface and the thermodynamics of adsorption are given some importance in this review.
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Affiliation(s)
- Sudam K Parida
- Centre of Studies in Surface Science and Technology, Department of Chemistry, Jyoti Vihar, 768 019, Orissa, India
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Fletcher KA, Fakayode SO, Lowry M, Tucker SA, Neal SL, Kimaru IW, McCarroll ME, Patonay G, Oldham PB, Rusin O, Strongin RM, Warner IM. Molecular fluorescence, phosphorescence, and chemiluminescence spectrometry. Anal Chem 2006; 78:4047-68. [PMID: 16771540 PMCID: PMC2662353 DOI: 10.1021/ac060683m] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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34
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Fu Y, Ye F, Sanders WG, Collinson MM, Higgins DA. Single Molecule Spectroscopy Studies of Diffusion in Mesoporous Silica Thin Films. J Phys Chem B 2006; 110:9164-70. [PMID: 16671729 DOI: 10.1021/jp054178p] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Single molecule spectroscopy is applied in studies of diffusion and surface adsorption in sol-gel-derived mesoporous silica thin films. Mesoporous films are obtained by spin casting surfactant-templated sols onto glass substrates. Small-angle X-ray diffraction results are consistent with hexagonally ordered mesophases in as-synthesized (i.e., surfactant-containing) films. Upon calcination, a 30% contraction and disordering of these structures occurs. Nile Red is used as a fluorescent probe of both the as-synthesized and calcined films. It is loaded into the samples at subnanomolar levels either prior to spin casting or after calcination. Fluorescence imaging and single-point fluorescence time transients show the dye molecules to be relatively mobile in the as-synthesized samples. In contrast, the molecules appear entrapped at fixed locations in dry calcined films. In calcined films rehydrated under high humidity conditions, the Nile Red molecules again become mobile. Time transients obtained from the as-synthesized and rehydrated samples provide clear evidence for frequent reversible adsorption of the dye to the silica surfaces. Autocorrelations of the time transients provide quantitative data on the mean diffusion coefficients (D = 2.4 x 10(-10) and 2.6 x 10(-10) cm2/s) and mean desorption times (1/k = 25 and 40 s) for the as-synthesized and rehydrated films, respectively. The results prove both water and surfactant play important roles in governing matrix interactions and mass transport.
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Affiliation(s)
- Yi Fu
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506, USA
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