10 results on '"Michelman-Ribeiro, Ariel"'
Search Results
2. Fluorescence Correlation Spectroscopy Study of TAMRA Diffusion in Poly(vinyl-alcohol) and Ficoll70 Solutions
- Author
-
Michelman-Ribeiro, Ariel, Horkay, Ferenc, Nossal, Ralph, and Boukari, Hacène
- Published
- 2005
- Full Text
- View/download PDF
3. Biochip for the Detection of Bacillus anthracis Lethal Factor and Therapeutic Agents against Anthrax Toxins.
- Author
-
Silin, Vitalii, Kasianowicz, John J., Michelman-Ribeiro, Ariel, Panchal, Rekha G., Bavari, Sina, and Robertson, Joseph W. F.
- Subjects
BACILLUS anthracis ,ANTHRAX toxin ,BIOCHIPS ,BILAYER lipid membranes ,BIOSENSORS ,MEMBRANE proteins ,ELECTROCHEMICAL apparatus ,IMPEDANCE spectroscopy - Abstract
Tethered lipid bilayer membranes (tBLMs) have been used in many applications, including biosensing and membrane protein structure studies. This report describes a biosensor for anthrax toxins that was fabricated through the self-assembly of a tBLM with B. anthracis protective antigen ion channels that are both the recognition element and electrochemical transducer. We characterize the sensor and its properties with electrochemical impedance spectroscopy and surface plasmon resonance. The sensor shows a sensitivity similar to ELISA and can also be used to rapidly screen for molecules that bind to the toxins and potentially inhibit their lethal effects. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
4. Research Funding and Women in Physics.
- Author
-
Daniels, Karen E., Eblen-Zayas, Melissa, Michelman-Ribeiro, Ariel, and Valentine, Jami M.
- Subjects
RESEARCH funding ,WOMEN in physics ,PHYSICS research - Abstract
A round table discussion on research funding and its relation to women in physics was held during the Second IUPAP International Conference on Women in Physics. Panelists were the director of the Office of Education, Science, and Technology of the Organization of American States; the director of Programs on Women, Science, and Technology for UNESCO; the Minister of Women for Brazil; and a professor of physics from the University of Yamanashi, Japan. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]
- Published
- 2005
- Full Text
- View/download PDF
5. Solution Structures of Bacillus anthracis Protective Antigen Proteins Using Small Angle Neutron Scattering and Protective Antigen 63 Ion Channel Formation Kinetics.
- Author
-
Michelman-Ribeiro, Ariel, Rubinson, Kenneth A., Silin, Vitalii, and Kasianowicz, John J.
- Subjects
- *
SMALL-angle scattering , *BACILLUS anthracis , *BILAYER lipid membranes , *ION channels , *NEUTRON reflectometry , *ANTIGENS , *BACTERIAL toxins - Abstract
We are studying the structures of bacterial toxins that form ion channels and enable macromolecule transport across membranes. For example, the crystal structure of the Staphylococcus aureus α-hemolysin (α-HL) channel in its functional state was confirmed using neutron reflectometry (NR) with the protein reconstituted in membranes tethered to a solid support. This method, which provides sub-nanometer structural information, could also test putative structures of the Bacillus anthracis protective antigen 63 (PA63) channel, locate where B. anthracis lethal factor and edema factor toxins (LF and EF, respectively) bind to it, and determine how certain small molecules can inhibit the interaction of LF and EF with the channel. We report here the solution structures of channel-forming PA63 and its precursor PA83 (which does not form channels) obtained with small angle neutron scattering. At near neutral pH, PA83 is a monomer and PA63 a heptamer. The latter is compared to two cryo-electron microscopy structures. We also show that although the α-HL and PA63 channels have similar structural features, unlike α-HL, PA63 channel formation in lipid bilayer membranes ceases within minutes of protein addition, which currently precludes the use of NR for elucidating the interactions between PA63, LF, EF, and potential therapeutic agents. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
6. Women in Physics in the U.S.: A Progress Report.
- Author
-
Budil, Kimberly S., Daniels, Karen E., Daniels-Race, Theda, Eblen-Zayas, Melissa, Hartline, Beverly K., Hazeltine, Richard, Hodari, Apriel K., Horton, K. Renee, Ivie, Rachel, Kay, Laura, Martínez-Miranda, Luz J., Michelman-Ribeiro, Ariel, Ong, Maria, Rudati, Juana I., Valentine, Jami, Whitten, Barbara, Williams, Elvira, and Zastavker, Yevgeniya V.
- Subjects
WOMEN in physics ,PHYSICS ,ACADEMIC degrees ,MINORITY women - Abstract
Discusses progress made by women in terms of their participation in physics in the United States. Academic degrees in physics; Challenges for women in physics; Appeal to cultivate the talent and ideas of women, minorities, and others who are underrepresented in physics.
- Published
- 2005
- Full Text
- View/download PDF
7. Cross-validating FRAP and FCS to quantify the impact of photobleaching on in vivo binding estimates.
- Author
-
Stasevich TJ, Mueller F, Michelman-Ribeiro A, Rosales T, Knutson JR, and McNally JG
- Subjects
- Animals, Biophysical Phenomena, Cell Line, Tumor, Facilitated Diffusion, Fluorescent Dyes, Green Fluorescent Proteins metabolism, Mice, Protein Binding, Receptors, Glucocorticoid metabolism, Recombinant Fusion Proteins metabolism, Fluorescence Recovery After Photobleaching methods, Photobleaching, Spectrometry, Fluorescence methods
- Abstract
Binding can now be quantified in live cells, but the accuracy of such measurements remains uncertain. To address this uncertainty, we compare fluorescence recovery after photobleaching (FRAP) and fluorescence correlation spectroscopy (FCS) measurements of the binding kinetics of a transcription factor, the glucocorticoid receptor, in the nuclei of live cells. We find that the binding residence time measured by FRAP is 15 times longer than that obtained by FCS. We show that this discrepancy is not likely due to the significant differences in concentrations typically used for FRAP and FCS, nor is it likely due to spatial heterogeneity of the nucleus, improper calibration of the FCS focal volume, or the intentional FRAP photobleach. Instead, our data indicate that photobleaching of bound molecules in FCS is mainly responsible. When this effect is minimized, FRAP and FCS measurements nearly agree, although cross-validation by other approaches is now required to rule out mutual errors. Our results demonstrate the necessity of a photobleach correction for FCS measurements of GFP-tagged molecules that are bound for >0.25 s, and represent an important step forward in establishing a gold standard for in vivo binding measurements., (Copyright © 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.)
- Published
- 2010
- Full Text
- View/download PDF
8. Direct measurement of association and dissociation rates of DNA binding in live cells by fluorescence correlation spectroscopy.
- Author
-
Michelman-Ribeiro A, Mazza D, Rosales T, Stasevich TJ, Boukari H, Rishi V, Vinson C, Knutson JR, and McNally JG
- Subjects
- Algorithms, Animals, Binding Sites genetics, DNA metabolism, Diffusion, Fluorescence Recovery After Photobleaching, Mice, Microscopy, Confocal, Models, Theoretical, NIH 3T3 Cells, Protein Binding drug effects, Protein Binding genetics, Transcription Factors genetics, Transcription Factors metabolism, Vitellogenins chemistry, Vitellogenins genetics, Vitellogenins metabolism, DNA chemistry, Spectrometry, Fluorescence methods, Transcription Factors chemistry
- Abstract
Measurement of live-cell binding interactions is vital for understanding the biochemical reactions that drive cellular processes. Here, we develop, characterize, and apply a new procedure to extract information about binding to an immobile substrate from fluorescence correlation spectroscopy (FCS) autocorrelation data. We show that existing methods for analyzing such data by two-component diffusion fits can produce inaccurate estimates of diffusion constants and bound fractions, or even fail altogether to fit FCS binding data. By analyzing live-cell FCS measurements, we show that our new model can satisfactorily account for the binding interactions introduced by attaching a DNA binding domain to the dimerization domain derived from a site-specific transcription factor (the vitellogenin binding protein (VBP)). We find that our FCS estimates are quantitatively consistent with our fluorescence recovery after photobleaching (FRAP) measurements on the same VBP domains. However, due to the fast binding interactions introduced by the DNA binding domain, FCS generates independent estimates for the diffusion constant (6.7 +/- 2.4 microm2/s) and the association (2 +/- 1.2 s(-1)) and dissociation (19 +/- 7 s(-1)) rates, whereas FRAP produces only a single, but a consistent, estimate, the effective-diffusion constant (4.4 +/- 1.4 microm2/s), which depends on all three parameters. We apply this new FCS method to evaluate the efficacy of a potential anticancer drug that inhibits DNA binding of VBP in vitro and find that in vivo the drug inhibits DNA binding in only a subset of cells. In sum, we provide a straightforward approach to directly measure binding rates from FCS data.
- Published
- 2009
- Full Text
- View/download PDF
9. Probe diffusion in aqueous poly(vinyl alcohol) solutions studied by fluorescence correlation spectroscopy.
- Author
-
Michelman-Ribeiro A, Horkay F, Nossal R, and Boukari H
- Subjects
- Diffusion, Models, Chemical, Solutions chemistry, Water chemistry, Polyvinyl Alcohol chemistry, Spectrometry, Fluorescence methods
- Abstract
We report fluorescence correlation spectroscopy measurements of the translational diffusion coefficient of various probe particles in dilute and semidilute aqueous poly(vinyl alcohol) solutions. The range of sizes of the particles (fluorescent molecules, proteins, and polymers) was chosen to explore various length scales of the polymer solutions as defined by the polymer-polymer correlation length. For particles larger than the correlation length, we find that the diffusion coefficient, D, decreases exponentially with the polymer concentration. This can be explained by an exponential increase in the solution viscosity, consistent with the Stokes-Einstein equation. For probes on the order of the correlation length, the decrease of the diffusion coefficient cannot be accounted for by the Stokes-Einstein equation, but can be fit by a stretched exponential, D approximately exp(-alphacn), where we find n = 0.73-0.84 and alpha is related to the probe size. These results are in accord with a diffusion model of Langevin and Rondelez (Polymer 1978, 19, 1875), where these values of n indicate a good solvent quality.
- Published
- 2007
- Full Text
- View/download PDF
10. Electrolysis induces gradients and domain orientation in agarose gels.
- Author
-
Michelman-Ribeiro A, Nossal R, Morris R, Lange S, Kuo CS, and Bansil R
- Subjects
- Anisotropy, Hydrogen-Ion Concentration, Light, Polymers chemistry, Protons, Scattering, Radiation, Time Factors, Biophysics methods, Electrolysis methods, Gels chemistry, Sepharose chemistry
- Abstract
We have used small-angle light-scattering (SALS), microscopy, and measurements to study structural changes produced in unbuffered agarose gels as ions migrate under applied electric fields (3-20 V/cm). Anisotropic, bowtielike, light-scattering patterns were observed, whose development occurred more quickly at higher fields. The horizontal lobes were more pronounced at higher polymer concentration. Analysis of the SALS data with a simple model of scattering from anisotropic rods in an electric field is consistent with anisotropic rodlike domains on the order of 10-15 microm in length, which align perpendicular to the electric field. The anisotropic domains in the gel reach almost the same level of orientation, regardless of the field strength. Microscope imaging revealed anisotropic domains on the same length scale, also aligned perpendicular to the field. Profiles of pH variation across the gel, measured by video photography, indicate that the anisotropic patterns appear when the H+ and OH- ions, migrating in opposite directions, meet. Calculations of pH profiles using a model based on electrodiffusion reproduce several features of measured pH profiles, including the power-law dependence on the electric field of the time at which the oppositely charged fronts meet. Ions migrating from both ends of the gel produce pH changes that are correlated with macroscopic shrinking and orientation of the gel.
- Published
- 2006
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.