Sara Ostrowski - Academia.edu (original) (raw)
Papers by Sara Ostrowski
The Journal of Physical Chemistry A, 2004
... Richard S. Moog,* Daniel D. Kim, Jessica J. Oberle, and Sara G. Ostrowski. Department of Chem... more ... Richard S. Moog,* Daniel D. Kim, Jessica J. Oberle, and Sara G. Ostrowski. Department of Chemistry, Franklin and Marshall College, Lancaster, Pennsylvania 17604-3003. J. Phys. Chem. A , 2004, 108 (42), pp 92949301. DOI ...
Chemical Physics Letters, 1999
Ž. Absorption and emission energies of four coumarins coumarins 1, 102, 152, 153 in a variety of ... more Ž. Absorption and emission energies of four coumarins coumarins 1, 102, 152, 153 in a variety of alcohols and aprotic solvents are analyzed in terms of the solvatochromic parameter and dielectric continuum models. Although the results for all four solutes are well described using the empirical solvatochromic parameters, some deviations from the predictions of the more theoretically based approach are observed in alcohol solvents, particularly for those coumarins expected to exhibit better hydrogen-bond-accepting ability.
Analytical Chemistry, Sep 1, 2003
A frozen water matrix, as found in freeze-fractured frozenhydrated cellular samples, enhances the... more A frozen water matrix, as found in freeze-fractured frozenhydrated cellular samples, enhances the ionization of phosphatidylcholine lipids with static time-of-flight secondary ion mass spectrometry (TOF-SIMS). Isotopic profiles of the phosphocholine ion from deuterated forms of dipalmitoylphosphatidylcholine (DPPC) have been examined under various sample preparation conditions to show that ionization occurs through protonation from the matrix and is enhanced by the water present in freezefractured samples. The ionization of DPPC results in positively charged fragment ions, primarily phosphocholine, with a m/z of 184. Other ions include the M + H ion (m/z 735) and an ion representing the abstraction of the two palmitoyl fatty acid groups (m/z 224). Freezefracture techniques have been used to prepare frozen aqueous samples such as liposomes and cells to expose their membranes for static TOF-SIMS imaging. Due to the importance of surface water during SIMS analyses, sources of gas-phase water resulting from freeze-fracture were examined. Under proper fracturing conditions, water vapor, resulting from water in the sample and water condensed onto the outside of the sample, is released into the vacuum but does not condense back onto the surface. Combining the demonstrated enhancement of phosphatidylcholine lipid signal from water with the freeze-fracture preparation techniques described herein demonstrates potential advantages of studying biological samples in a frozen-hydrated state.
Applied Surface Science, Jun 1, 2004
Molecule-specific imaging using focused ion beams is one of the most powerful applications of ToF... more Molecule-specific imaging using focused ion beams is one of the most powerful applications of ToF-SIMS and offers unique surface characterization information. However, many experiments lack the necessary sensitivity to properly take advantage of the sub-100 nm probe size typical of liquid metal ion sources. The yield of biomolecules using Ga + ions, for example, is very small when compared to that obtained using Cs + ion or SF 5+ cluster ion sources. Most recently, a C 60+ source with a probe size approaching 1×10 -6 m has become available and offers promise to expand imaging applications dramatically. Here, we report on imaging experiments on 50×10 -6 m polystyrene resin particles used in solid phase synthesis of combinatorial libraries and on the assay of the membrane chemistry of single biological cells. Both of these examples allow much higher quality images to be acquired with, in some cases, almost no sample damage. This latter effect opens the possibility of three-dimensional molecule-specific imaging.
Analytical Chemistry, Nov 1, 2005
Investigation of the spatial distribution of lipids in cell membranes can lead to an improved und... more Investigation of the spatial distribution of lipids in cell membranes can lead to an improved understanding of the role of lipids in biological function and disease. Time-offlight secondary ion mass spectrometry is capable of molecule-specific imaging of biological molecules across single cells and has demonstrated potential for examining the functional segregation of lipids in cell membranes. In this paper, standard SIMS spectra are analyzed for phosphatidylethanolamine, phosphatidylglycerol, phosphatidylserine, phosphatidylinositol, cholesterol, and sulfatide. Importantly, each of the lipids result in signature mass spectral peaks that allow them to be identified. These signature peaks are also useful for imaging experiments and are utilized here to simultaneously image lipids on a micrometer scale in picoliter vials. Because the low secondary ion signal achieved for lipids from an atomic primary ion source makes cell-imaging experiments challenging, improving signal with cluster primary ion sources is of interest. Here, we compare the secondary ion yield for seven lipids using atomic (Ga + or In + ) ion sources and a buckminsterfullerene (C 60 + ) primary ion source. A 40-1000-fold improvement in signal is found with C 60 + relative to the other two ion sources, indicating great promise for future cellular imaging applications using the C 60 + probe. Figure 6. (A) + SIMS spectrum of an equimolar mixture of PC, PE, PG, PS, PI, cholesterol (C), and sulfatide (S) with a C60 + source. (B) -SIMS spectrum of the same mixture.
Langmuir, Mar 1, 2010
Past literature investigations have optimized various single factors used in the formation of thi... more Past literature investigations have optimized various single factors used in the formation of thiolated, single stranded DNA (ss-DNA) monolayers on gold. In this study a more comprehensive approach is taken, where a design of experiment (DOE) is employed to simultaneously optimize all of the factors involved in construction of the capture monolayer used in a fluorescence-based hybridization assay. Statistical analysis of the fluorescent intensities resulting from the DOE provides empirical evidence for the importance and the optimal levels of traditional and novel factors included in this investigation. We report on the statistical importance of a novel factor, temperature of the system during monolayer formation of the capture molecule and lateral spacer molecule, and how proper usage of this temperature factor increased the hybridization signal 50%. An initial theory of how the physical factor of heat is mechanistically supplementing the function of the lateral spacer molecule is provided.
Single-Cell Level Mass Spectrometric Imaging Sara G. Ostrowski Andrew G. Ewing Nicholas Winograd ... more Single-Cell Level Mass Spectrometric Imaging Sara G. Ostrowski Andrew G. Ewing Nicholas Winograd Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania, USA INTRODUCTION ... (From Ref.[12].) (View this art in color at www.dekker.com.) Fig. ...
Review of Scientific Instruments, 2007
Combinatorial materials libraries are becoming more complicated; successful screening of these li... more Combinatorial materials libraries are becoming more complicated; successful screening of these libraries requires the development of new high throughput screening methodologies. Time of flight secondary ion mass spectrometry (ToF-SIMS) is a surface analytical technique that is able to detect and image all elements (including hydrogen which is problematic for many other analysis instruments) and molecular fragments, with high mass resolution,
The Review of scientific instruments, 2007
Combinatorial materials libraries are becoming more complicated; successful screening of these li... more Combinatorial materials libraries are becoming more complicated; successful screening of these libraries requires the development of new high throughput screening methodologies. Time of flight secondary ion mass spectrometry (ToF-SIMS) is a surface analytical technique that is able to detect and image all elements (including hydrogen which is problematic for many other analysis instruments) and molecular fragments, with high mass resolution, during a single measurement. Commercial ToF-SIMS instruments can image 500 microm areas by rastering the primary ion beam over the region of interest. In this work, we will show that large area analysis can be performed, in one single measurement, by rastering the sample under the ion beam. We show that an entire 70 mm diameter wafer can be imaged in less than 90 min using ToF-SIMS stage (macro)rastering techniques. ToF-SIMS data sets contain a wealth of information since an entire high mass resolution mass spectrum is saved at each pixel in an ...
Dekker Encyclopedia of Nanoscience and Nanotechnology, Second Edition - Six Volume Set (Print Version), 2008
Single-Cell Level Mass Spectrometric Imaging Sara G. Ostrowski Andrew G. Ewing Nicholas Winograd ... more Single-Cell Level Mass Spectrometric Imaging Sara G. Ostrowski Andrew G. Ewing Nicholas Winograd Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania, USA INTRODUCTION ... (From Ref.[12].) (View this art in color at www.dekker.com.) Fig. ...
ABSTRACT The continued pressure for increasing c-Si solar efficiency is generating many innovativ... more ABSTRACT The continued pressure for increasing c-Si solar efficiency is generating many innovative and novel approaches. In this manuscript we present the results of a chemical cleaning approach for targeted removal of efficiency degrading metallic contaminants. The application of this cleaning approach, in both alkaline and acidic cleaning processes has demonstrated 0.2 to 0.3% absolute cell efficiency improvement for both mc-Si and c-Si production lines. This improvement is not dependent on cell architectures, but addresses a universal complication arising from crystalline silicon photovoltaic wafering manufacture. We also disclose the potential of utilizing this chemistry to enable a spectroscopic method for real time monitoring of trace metal loading in the cleaning baths. And by extension a method to provide process endpoint detection based on metallic loading levels in aqueous solutions.
The Journal of Physical Chemistry A, 2004
... Richard S. Moog,* Daniel D. Kim, Jessica J. Oberle, and Sara G. Ostrowski. Department of Chem... more ... Richard S. Moog,* Daniel D. Kim, Jessica J. Oberle, and Sara G. Ostrowski. Department of Chemistry, Franklin and Marshall College, Lancaster, Pennsylvania 17604-3003. J. Phys. Chem. A , 2004, 108 (42), pp 92949301. DOI ...
Surface and Interface Analysis, 2009
ABSTRACT Time-of-flight secondary ion mass spectrometry (ToF-SIMS) instruments produce raw data s... more ABSTRACT Time-of-flight secondary ion mass spectrometry (ToF-SIMS) instruments produce raw data sets with a tremendous quantity of data. Multivariate statistical analysis (MVA) tools are being used to reduce the massive amount of chemical information into a smaller set of components that are easier to interpret and understand as a result of species association. Standard principal component analysis (PCA) is the most heavily used MVA algorithm in the ToF-SIMS community, and is frequently computed using the singular value decomposition (SVD). Other algorithms such as multivariate curve resolution (MCR) have also gained popularity over the past few years. In this work, we compare the as-measured ToF-SIMS spectrum and ion images with four MVA data analysis protocols: standard PCA, image-rotated SVD, spectra-rotated SVD, and a PCA-based MCR procedure. Image-rotated SVD and spectra-rotated SVD are closely connected to PCA and involve abstract rotations of the singular vectors that naturally arise during computation of the principal components via SVD. These rotations are designed to enhance either spatial contrast or spectral contrast in the components, respectively. We will show that the four MVA protocols provide essentially the same information, but accentuate different aspects of the sample's composition and lateral distribution, and that taken together these methods provide a more complete understanding of the sample. We will demonstrate that the component spectra estimated by MVA protocols assist the analyst in discovering minor constituents and understanding species correlation that would have been difficult, if not impossible, using univariate analysis protocols. For the data set described here, MVA tools identified unexpected species, which were not obvious in the as-measured data. Copyright © 2008 John Wiley & Sons, Ltd.
Science, 2004
Biological membrane fusion is crucial to numerous cellular events, including sexual reproduction ... more Biological membrane fusion is crucial to numerous cellular events, including sexual reproduction and exocytosis. Here, mass spectrometry images demonstrate that the low-curvature lipid phosphatidylcholine is diminished in the membrane regions between fusing Tetrahymena, where a multitude of highly curved fusion pores exist. Additionally, mass spectra and principal component analysis indicate that the fusion region contains elevated amounts of 2-aminoethylphosphonolipid, a high-curvature lipid. This evidence suggests that biological fusion involves and might in fact be driven by a heterogeneous redistribution of lipids at the fusion site.
Review of Scientific Instruments, 2007
Microscopy and Microanalysis, 2007
Microscopy and Microanalysis, 2006
Langmuir, 2010
Past literature investigations have optimized various single factors used in the formation of thi... more Past literature investigations have optimized various single factors used in the formation of thiolated, single stranded DNA (ss-DNA) monolayers on gold. In this study a more comprehensive approach is taken, where a design of experiment (DOE) is employed to simultaneously optimize all of the factors involved in construction of the capture monolayer used in a fluorescence-based hybridization assay. Statistical analysis of the fluorescent intensities resulting from the DOE provides empirical evidence for the importance and the optimal levels of traditional and novel factors included in this investigation. We report on the statistical importance of a novel factor, temperature of the system during monolayer formation of the capture molecule and lateral spacer molecule, and how proper usage of this temperature factor increased the hybridization signal 50%. An initial theory of how the physical factor of heat is mechanistically supplementing the function of the lateral spacer molecule is provided.
Analytical Chemistry, 2007
Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is a well-established bioanalytical met... more Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is a well-established bioanalytical method for directly imaging the chemical distribution across single cells. Here we report a protocol for the use of SIMS imaging to comparatively quantify the relative difference in cholesterol level between the plasma membranes of two cells. It should be possible to apply this procedure to the study of other selected lipids. This development enables direct comparison of the chemical effects of different drug treatments and incubation conditions in the plasma membrane at the single-cell level. Relative, quantitative TOF-SIMS imaging has been used here to compare macrophage cells treated to contain elevated levels of cholesterol with respect to control cells. In situ fluorescence microscopy with two different membrane dyes was used to discriminate morphologically similar but differentially treated cells prior to SIMS analysis. SIMS images of fluorescently identified cells reveal that the two populations of cells have distinct outer leaflet membrane compositions with the membranes of the cholesterol-treated macrophages containing more than twice the amount of cholesterol of control macrophages. Relative quantification with SIMS to compare the chemical composition of single cells can provide valuable information about normal biological functions, causative agents of diseases, and possible therapies for diseases.
The Journal of Physical Chemistry A, 2004
... Richard S. Moog,* Daniel D. Kim, Jessica J. Oberle, and Sara G. Ostrowski. Department of Chem... more ... Richard S. Moog,* Daniel D. Kim, Jessica J. Oberle, and Sara G. Ostrowski. Department of Chemistry, Franklin and Marshall College, Lancaster, Pennsylvania 17604-3003. J. Phys. Chem. A , 2004, 108 (42), pp 92949301. DOI ...
Chemical Physics Letters, 1999
Ž. Absorption and emission energies of four coumarins coumarins 1, 102, 152, 153 in a variety of ... more Ž. Absorption and emission energies of four coumarins coumarins 1, 102, 152, 153 in a variety of alcohols and aprotic solvents are analyzed in terms of the solvatochromic parameter and dielectric continuum models. Although the results for all four solutes are well described using the empirical solvatochromic parameters, some deviations from the predictions of the more theoretically based approach are observed in alcohol solvents, particularly for those coumarins expected to exhibit better hydrogen-bond-accepting ability.
Analytical Chemistry, Sep 1, 2003
A frozen water matrix, as found in freeze-fractured frozenhydrated cellular samples, enhances the... more A frozen water matrix, as found in freeze-fractured frozenhydrated cellular samples, enhances the ionization of phosphatidylcholine lipids with static time-of-flight secondary ion mass spectrometry (TOF-SIMS). Isotopic profiles of the phosphocholine ion from deuterated forms of dipalmitoylphosphatidylcholine (DPPC) have been examined under various sample preparation conditions to show that ionization occurs through protonation from the matrix and is enhanced by the water present in freezefractured samples. The ionization of DPPC results in positively charged fragment ions, primarily phosphocholine, with a m/z of 184. Other ions include the M + H ion (m/z 735) and an ion representing the abstraction of the two palmitoyl fatty acid groups (m/z 224). Freezefracture techniques have been used to prepare frozen aqueous samples such as liposomes and cells to expose their membranes for static TOF-SIMS imaging. Due to the importance of surface water during SIMS analyses, sources of gas-phase water resulting from freeze-fracture were examined. Under proper fracturing conditions, water vapor, resulting from water in the sample and water condensed onto the outside of the sample, is released into the vacuum but does not condense back onto the surface. Combining the demonstrated enhancement of phosphatidylcholine lipid signal from water with the freeze-fracture preparation techniques described herein demonstrates potential advantages of studying biological samples in a frozen-hydrated state.
Applied Surface Science, Jun 1, 2004
Molecule-specific imaging using focused ion beams is one of the most powerful applications of ToF... more Molecule-specific imaging using focused ion beams is one of the most powerful applications of ToF-SIMS and offers unique surface characterization information. However, many experiments lack the necessary sensitivity to properly take advantage of the sub-100 nm probe size typical of liquid metal ion sources. The yield of biomolecules using Ga + ions, for example, is very small when compared to that obtained using Cs + ion or SF 5+ cluster ion sources. Most recently, a C 60+ source with a probe size approaching 1×10 -6 m has become available and offers promise to expand imaging applications dramatically. Here, we report on imaging experiments on 50×10 -6 m polystyrene resin particles used in solid phase synthesis of combinatorial libraries and on the assay of the membrane chemistry of single biological cells. Both of these examples allow much higher quality images to be acquired with, in some cases, almost no sample damage. This latter effect opens the possibility of three-dimensional molecule-specific imaging.
Analytical Chemistry, Nov 1, 2005
Investigation of the spatial distribution of lipids in cell membranes can lead to an improved und... more Investigation of the spatial distribution of lipids in cell membranes can lead to an improved understanding of the role of lipids in biological function and disease. Time-offlight secondary ion mass spectrometry is capable of molecule-specific imaging of biological molecules across single cells and has demonstrated potential for examining the functional segregation of lipids in cell membranes. In this paper, standard SIMS spectra are analyzed for phosphatidylethanolamine, phosphatidylglycerol, phosphatidylserine, phosphatidylinositol, cholesterol, and sulfatide. Importantly, each of the lipids result in signature mass spectral peaks that allow them to be identified. These signature peaks are also useful for imaging experiments and are utilized here to simultaneously image lipids on a micrometer scale in picoliter vials. Because the low secondary ion signal achieved for lipids from an atomic primary ion source makes cell-imaging experiments challenging, improving signal with cluster primary ion sources is of interest. Here, we compare the secondary ion yield for seven lipids using atomic (Ga + or In + ) ion sources and a buckminsterfullerene (C 60 + ) primary ion source. A 40-1000-fold improvement in signal is found with C 60 + relative to the other two ion sources, indicating great promise for future cellular imaging applications using the C 60 + probe. Figure 6. (A) + SIMS spectrum of an equimolar mixture of PC, PE, PG, PS, PI, cholesterol (C), and sulfatide (S) with a C60 + source. (B) -SIMS spectrum of the same mixture.
Langmuir, Mar 1, 2010
Past literature investigations have optimized various single factors used in the formation of thi... more Past literature investigations have optimized various single factors used in the formation of thiolated, single stranded DNA (ss-DNA) monolayers on gold. In this study a more comprehensive approach is taken, where a design of experiment (DOE) is employed to simultaneously optimize all of the factors involved in construction of the capture monolayer used in a fluorescence-based hybridization assay. Statistical analysis of the fluorescent intensities resulting from the DOE provides empirical evidence for the importance and the optimal levels of traditional and novel factors included in this investigation. We report on the statistical importance of a novel factor, temperature of the system during monolayer formation of the capture molecule and lateral spacer molecule, and how proper usage of this temperature factor increased the hybridization signal 50%. An initial theory of how the physical factor of heat is mechanistically supplementing the function of the lateral spacer molecule is provided.
Single-Cell Level Mass Spectrometric Imaging Sara G. Ostrowski Andrew G. Ewing Nicholas Winograd ... more Single-Cell Level Mass Spectrometric Imaging Sara G. Ostrowski Andrew G. Ewing Nicholas Winograd Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania, USA INTRODUCTION ... (From Ref.[12].) (View this art in color at www.dekker.com.) Fig. ...
Review of Scientific Instruments, 2007
Combinatorial materials libraries are becoming more complicated; successful screening of these li... more Combinatorial materials libraries are becoming more complicated; successful screening of these libraries requires the development of new high throughput screening methodologies. Time of flight secondary ion mass spectrometry (ToF-SIMS) is a surface analytical technique that is able to detect and image all elements (including hydrogen which is problematic for many other analysis instruments) and molecular fragments, with high mass resolution,
The Review of scientific instruments, 2007
Combinatorial materials libraries are becoming more complicated; successful screening of these li... more Combinatorial materials libraries are becoming more complicated; successful screening of these libraries requires the development of new high throughput screening methodologies. Time of flight secondary ion mass spectrometry (ToF-SIMS) is a surface analytical technique that is able to detect and image all elements (including hydrogen which is problematic for many other analysis instruments) and molecular fragments, with high mass resolution, during a single measurement. Commercial ToF-SIMS instruments can image 500 microm areas by rastering the primary ion beam over the region of interest. In this work, we will show that large area analysis can be performed, in one single measurement, by rastering the sample under the ion beam. We show that an entire 70 mm diameter wafer can be imaged in less than 90 min using ToF-SIMS stage (macro)rastering techniques. ToF-SIMS data sets contain a wealth of information since an entire high mass resolution mass spectrum is saved at each pixel in an ...
Dekker Encyclopedia of Nanoscience and Nanotechnology, Second Edition - Six Volume Set (Print Version), 2008
Single-Cell Level Mass Spectrometric Imaging Sara G. Ostrowski Andrew G. Ewing Nicholas Winograd ... more Single-Cell Level Mass Spectrometric Imaging Sara G. Ostrowski Andrew G. Ewing Nicholas Winograd Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania, USA INTRODUCTION ... (From Ref.[12].) (View this art in color at www.dekker.com.) Fig. ...
ABSTRACT The continued pressure for increasing c-Si solar efficiency is generating many innovativ... more ABSTRACT The continued pressure for increasing c-Si solar efficiency is generating many innovative and novel approaches. In this manuscript we present the results of a chemical cleaning approach for targeted removal of efficiency degrading metallic contaminants. The application of this cleaning approach, in both alkaline and acidic cleaning processes has demonstrated 0.2 to 0.3% absolute cell efficiency improvement for both mc-Si and c-Si production lines. This improvement is not dependent on cell architectures, but addresses a universal complication arising from crystalline silicon photovoltaic wafering manufacture. We also disclose the potential of utilizing this chemistry to enable a spectroscopic method for real time monitoring of trace metal loading in the cleaning baths. And by extension a method to provide process endpoint detection based on metallic loading levels in aqueous solutions.
The Journal of Physical Chemistry A, 2004
... Richard S. Moog,* Daniel D. Kim, Jessica J. Oberle, and Sara G. Ostrowski. Department of Chem... more ... Richard S. Moog,* Daniel D. Kim, Jessica J. Oberle, and Sara G. Ostrowski. Department of Chemistry, Franklin and Marshall College, Lancaster, Pennsylvania 17604-3003. J. Phys. Chem. A , 2004, 108 (42), pp 92949301. DOI ...
Surface and Interface Analysis, 2009
ABSTRACT Time-of-flight secondary ion mass spectrometry (ToF-SIMS) instruments produce raw data s... more ABSTRACT Time-of-flight secondary ion mass spectrometry (ToF-SIMS) instruments produce raw data sets with a tremendous quantity of data. Multivariate statistical analysis (MVA) tools are being used to reduce the massive amount of chemical information into a smaller set of components that are easier to interpret and understand as a result of species association. Standard principal component analysis (PCA) is the most heavily used MVA algorithm in the ToF-SIMS community, and is frequently computed using the singular value decomposition (SVD). Other algorithms such as multivariate curve resolution (MCR) have also gained popularity over the past few years. In this work, we compare the as-measured ToF-SIMS spectrum and ion images with four MVA data analysis protocols: standard PCA, image-rotated SVD, spectra-rotated SVD, and a PCA-based MCR procedure. Image-rotated SVD and spectra-rotated SVD are closely connected to PCA and involve abstract rotations of the singular vectors that naturally arise during computation of the principal components via SVD. These rotations are designed to enhance either spatial contrast or spectral contrast in the components, respectively. We will show that the four MVA protocols provide essentially the same information, but accentuate different aspects of the sample's composition and lateral distribution, and that taken together these methods provide a more complete understanding of the sample. We will demonstrate that the component spectra estimated by MVA protocols assist the analyst in discovering minor constituents and understanding species correlation that would have been difficult, if not impossible, using univariate analysis protocols. For the data set described here, MVA tools identified unexpected species, which were not obvious in the as-measured data. Copyright © 2008 John Wiley & Sons, Ltd.
Science, 2004
Biological membrane fusion is crucial to numerous cellular events, including sexual reproduction ... more Biological membrane fusion is crucial to numerous cellular events, including sexual reproduction and exocytosis. Here, mass spectrometry images demonstrate that the low-curvature lipid phosphatidylcholine is diminished in the membrane regions between fusing Tetrahymena, where a multitude of highly curved fusion pores exist. Additionally, mass spectra and principal component analysis indicate that the fusion region contains elevated amounts of 2-aminoethylphosphonolipid, a high-curvature lipid. This evidence suggests that biological fusion involves and might in fact be driven by a heterogeneous redistribution of lipids at the fusion site.
Review of Scientific Instruments, 2007
Microscopy and Microanalysis, 2007
Microscopy and Microanalysis, 2006
Langmuir, 2010
Past literature investigations have optimized various single factors used in the formation of thi... more Past literature investigations have optimized various single factors used in the formation of thiolated, single stranded DNA (ss-DNA) monolayers on gold. In this study a more comprehensive approach is taken, where a design of experiment (DOE) is employed to simultaneously optimize all of the factors involved in construction of the capture monolayer used in a fluorescence-based hybridization assay. Statistical analysis of the fluorescent intensities resulting from the DOE provides empirical evidence for the importance and the optimal levels of traditional and novel factors included in this investigation. We report on the statistical importance of a novel factor, temperature of the system during monolayer formation of the capture molecule and lateral spacer molecule, and how proper usage of this temperature factor increased the hybridization signal 50%. An initial theory of how the physical factor of heat is mechanistically supplementing the function of the lateral spacer molecule is provided.
Analytical Chemistry, 2007
Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is a well-established bioanalytical met... more Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is a well-established bioanalytical method for directly imaging the chemical distribution across single cells. Here we report a protocol for the use of SIMS imaging to comparatively quantify the relative difference in cholesterol level between the plasma membranes of two cells. It should be possible to apply this procedure to the study of other selected lipids. This development enables direct comparison of the chemical effects of different drug treatments and incubation conditions in the plasma membrane at the single-cell level. Relative, quantitative TOF-SIMS imaging has been used here to compare macrophage cells treated to contain elevated levels of cholesterol with respect to control cells. In situ fluorescence microscopy with two different membrane dyes was used to discriminate morphologically similar but differentially treated cells prior to SIMS analysis. SIMS images of fluorescently identified cells reveal that the two populations of cells have distinct outer leaflet membrane compositions with the membranes of the cholesterol-treated macrophages containing more than twice the amount of cholesterol of control macrophages. Relative quantification with SIMS to compare the chemical composition of single cells can provide valuable information about normal biological functions, causative agents of diseases, and possible therapies for diseases.