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Physics
Biomolecular and Biological Physics
- Laboratory for Fluorescence Dynamics
- Optical Imaging of Thick Tissues
- Optical Monitors for Vascular Insufficiency in Peripheral Tissue
- Transferal Controls from Destructive to Healthy Complex Biological Attractors
^ Laboratory for Fluorescence Dynamics
E. Gratton,* W. W. Mantulin,* R. M. Clegg,* T. Hazlett, S. Sanchez, N. Barry, O. Akcakir, J. Eid, Q. Ruan, J. Sutin, K. Kispetikova
National Institutes of Health, P41-RR-03155
The Laboratory for Fluorescence Dynamics (LFD), a national biomedical resource, has a dual and equal commitment to foster fluorescence research and to provide service in a user-oriented facility.
Fluorescence Research and Development
The research goal of the LFD is to develop new fluorescence instrumentation, design new theoretical formulations of fluorescence phenomena, and compile appropriate software, with the aim of advancing basic research and biomedical applications. Examples of current projects include: instrumentation (frequency domain fluorometer with lifetime and spectral resolution, laser heterodyning, lifetime fluorescence microscopy, ultrastable fluorescence microscope, high-pressure microscopy), software (global analysis of multifrequency data sets), optical imaging (near-infrared images of tissue), and applications (two-photon fluorescence correlation spectroscopy and photon counting histograms). These advances in fluorescence technology are transferred to the user fluorescence and microscopy laboratories.
Fluorescence Laboratory
The laboratory serves both the campus research community and visiting scientists. To date, core and collaborative research has stressed macromolecular assembly and dynamics, membrane structure/function relationships, and fluorescence microscopy of cells. The LFD houses a spectropolarimeter for circular dichroism measurements. Fluorescence equipment includes high-sensitivity, photon-counting, scanning fluorometers (with polarization accessory), three laser-based variable multifrequency phase/modulation fluorometers with different excitation wavelength and modulation frequency options, stopped flow and high pressure accessories. Dedicated personal computers assist in data collection and analysis. Ancillary support for biomedical research is housed in a general biochemistry laboratory, which is equipped for biological sample manipulation.
Fluorescence Microscopy Development Laboratory (FMDL)
FMDL is a technology development laboratory for multiphotonic fluorescence microscopy, which also serves users. A tissue culture facility is also available. It conducts core and collaborative research on a variety of cellular components and systems (membranes, receptors, antibodies, and so forth). The instrumentation includes Ti:sapphire lasers, upright and inverted fluorescence microscopes, and correlation systems for photon counting. The multiphotonic techniques under development include: fluctuation correlation spectroscopy, fluorescence lifetime imaging, photon counting histograms, particle tracking, and single molecular studies.
^ Optical Imaging of Thick Tissues
E. Gratton,* M. Filiaci, V. Toronov, M. Wolf, A. Michalos
National Institutes of Health, 1RO1 CA57032
This project explores the use of frequency-domain methods to obtain near-infrared optical images of thick tissues. The use of near-infrared radiation has been proposed as an attractive alternative to obtain information about the oxygenation state of tissues due to the difference in optical spectra of the oxy- and deoxy-form of hemoglobin. This frequency-domain approach uses the propagation of high-frequency amplitude modulated light. In the frequency-domain, propagation of the AM intensity wave in a highly scattering medium is analogous with wave optics. An object immersed in the medium produces deformation of the propagation wavefront of the amplitude-modulated wave and results in an easy identification of absorbing and scattering objects, such as blood vessels or bone. Computer algorithms display in real-time the wavefront of the AM wave after traversing the tissue. Currently, this optical approach is being used to study activity in the brain in conjunction with MRI measurements.
^ Optical Monitors for Vascular Insufficiency in Peripheral Tissue
E. Gratton,* W. W. Mantulin, A. Paunescu, U. Wolf
National Institutes of Health, 5 R01 RR10966
Peripheral vascular disease (PVD), a chronic disease, afflicts diabetics and others with vascular pathologies. The level of tissue oxygenation in extremities is an important parameter for diagnosis of PVD. Researchers have developed a new technology based on near-IR frequency domain spectroscopy that provides quantitative information on the level of tissue oxygenation. The optical signal is derived from penetration of photon density waves in tissue. The team has designed and built noninvasive, portable, tissue oxygen saturation monitors. Preliminary tests show that the optical oxygen monitor can be clinically useful by providing the clinician with a quantitative physiological parameter that is a meaningful index for the early detection and treatment of PVD. The major advance has been in developing a large mapping sensor, which is applicable to all patients.
^ Transferal Controls from Destructive to Healthy Complex Biological Attractors
E. A. Jackson*
University of Illinois
A method of open-plus-closed-loop control interactions, developed by Jackson and Grosu, was experimentally extended to the transfer of the dynamics of a system between two of its attractors, based on the use of recorded dynamic information in each attractor (rather than information from differential equations). The possibility of using such methods of transferal for living systems, for which equations are not known, has important possibilities. It now appears possible to investigate this method for the control of heart fibrillations, in collaboration with a local cardiologist.
