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Dec 2002

Volume 73, Issue 12, pp. 4057-4404

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back to top BIOLOGY and MEDICINE

A combined confocal and magnetic resonance microscope for biological studies

Paul D. Majors, Kevin R. Minard, Eric J. Ackerman, Gary R. Holtom, Derek F. Hopkins, Christopher I. Parkinson, Thomas J. Weber, and Robert A. Wind

Rev. Sci. Instrum. 73, 4329 (2002); http://dx.doi.org/10.1063/1.1517146 (10 pages) | Cited 10 times

Online Publication Date: 21 November 2002

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Complementary data acquired with different microscopy techniques provide a basis for establishing a more comprehensive understanding of cell function in health and disease, particularly when results acquired with different methodologies can be correlated in time and space. In this article, a novel microscope is described for studying live cells simultaneously with both confocal scanning laser fluorescence optical microscopy and magnetic resonance microscopy. The various design considerations necessary for integrating these two complementary techniques are discussed, the layout and specifications of the instrument are given, and examples of confocal and magnetic resonance images of large frog cells and model tumor spheroids obtained with the compound microscope are presented. © 2002 American Institute of Physics.
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87.64.mk Confocal
07.60.Pb Conventional optical microscopes
07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
87.64.K- Spectroscopy
87.17.-d Cell processes

Novel resonant-frequency sensor to detect the kinetics of protein adsorption

Alison J. Clark, Lorne A. Whitehead, Charles A. Haynes, and Andrzej Kotlicki

Rev. Sci. Instrum. 73, 4339 (2002); http://dx.doi.org/10.1063/1.1520731 (8 pages) | Cited 1 time

Online Publication Date: 21 November 2002

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Proteins prefer interfaces, and in aqueous solutions they rapidly adsorb to available solid–liquid interfaces. The adsorption process often involves a change in protein conformation at the surface that can result in functional inactivation of the protein. These changes in protein conformation, which are thought to lead to the formation of an entangled gel-like layer of denatured protein, are responsible for a number of deliterious processes, including biofouling on contact lenses and medical implants. The adsorption process is generally irreversible; dilution of protein in the solution phase does not result in protein desorption from the solid. Presumably, this is due to the effects of the protein denaturation and entanglement process on the rate constant for desorption. Nonspecific protein adsorption to solid–liquid interfaces is, therefore, a kinetically controlled process. Hence, measuring and understanding the kinetics of protein adsorption to solid surfaces, including the kinetics of protein conformational changes, is of considerable interest. We have developed a sensor that responds to protein adsorption kinetics and also, we believe, is sensitive to protein conformational changes during adsorption. The device is operated by monitoring the change in resonant frequency of an elastomeric film (25 μm thick), as an aqueous protein solution is exposed to the surface. Since the mass of a monolayer of the protein or other adsorbent is an extremely small fraction of the mass of the film, the observed change in resonant frequency is due almost entirely to changes in the surface tension of the film. Upon exposing the elastomeric film to a protein solution, we observe a continuing change in resonant frequency for more than 24 h, which is well beyond the time it would take for the population of proteins on the surface to equilibrate under diffusion-limited kinetics. This prolonged response is likely due to the surface energy changes of the sensor as the adsorbed protein molecules change their conformation. We present a description of the basic operation of this sensor as well as some examples of its response to bulk protein and surfactant concentrations. © 2002 American Institute of Physics.
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87.15.R- Reactions and kinetics
87.14.E- Proteins
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
87.80.-y Biophysical techniques (research methods)
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