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At least 217 records · Page 12Linked to original sources

PubMed1990

Interaction of antibodies with Fc receptors in substrate-supported planar membranes measured by total internal reflection fluorescence microscopy.

A procedure for constructing substrate-supported planar membranes using membrane fragments isolated from the macrophage-related cell line J774A.1 is described. Total internal reflection (TIR) fluorescence microscopy is employed to demonstrate that fluorescently labeled Fab fragments of a monoclonal antibody (2.4G2) with specificity for a murine macrophage cell-surface receptor for IgG (moFc gamma RII) bind to the planar model membranes. These measurements show that the planar membranes contain moFc gamma RII and yield a value for the association constant of 2.4G2 Fab fragments with moFc gamma RII equal to (9.6 +/- 0.4) x 10(8) M-1 and indicate that the surface density of reconstituted moFc gamma RII is approximately 50 molecules/microns 2. In addition, TIR fluorescence microscopy is used to investigate the Fc-mediated competition of unlabeled, polyclonal murine IgG with labeled 2.4G2 Fab fragments for moFc gamma RII in the planar membranes. These measurements indicate that the reconstituted moFc gamma RII recognized by 2.4G2 Fab fragments also retains the ability to bind murine IgG Fc regions and yield a value for the association constant of polyclonal murine IgG with moFc gamma RII equal to (1-5) x 10(5) M-1. This work represents one of the first applications of TIR fluorescence microscopy to specific ligand-receptor interactions.

Animals↗

PubMed1989

Confocal fluorescence microscopy with the tandem scanning light microscope.

Applications of the tandem scanning confocal microscope (TSM) to fluorescence microscopy and its ability to resolve fluorescent biological structures are described. The TSM, in conjunction with a cooled charge-coupled device (cooled CCD) and conventional epifluorescence light source and filter sets, provided high-resolution, confocal data, so that different fluorescent cellular components were distinguished in three dimensions within the same cell. One of the unique features of the TSM is the ability to image fluorochromes excited by ultraviolet light (e.g. Hoechst, DAPI) in addition to fluorescein and rhodamine. Since the illumination is dim, photobleaching is insignificant and prolonged viewing of living specimens is possible. Series of optical sections taken in the Z-axis with the TSM were reproduced as stereo images and three-dimensional reconstructions. These data show that the TSM is potentially a powerful tool in fluorescence microscopy for determining three-dimensional relationships of complex structures within cells labeled with multiple fluorochromes.

Animals↗

PubMed1981

Sequential alterations in the nuclear chromatin region during mitosis of the fission yeast Schizosaccharomyces pombe: video fluorescence microscopy of synchronously growing wild-type and cold-sensitive cdc mutants by using a DNA-binding fluorescent probe.

Video-connected fluorescence microscopy was introduced to study the yeast nuclear chromatin region. It was defined as the nuclear area where a DNA-binding fluorescent probe 4',6-diamidino-2-phenylindole specifically bound and fluoresced. The 3-dimensional feature of the mitotic chromatin region was deduced by analysing the successive video images of a cell viewed at different angles. By investigating synchronous culture of the wild-type fission yeast Schizosaccharomyces pombe, we found sequential structural alterations in the chromatin region during mitosis. The steps found include the compaction of the chromatin region from the regular hemispherical form, the formation of a U-shaped intermediate and the rapid segregation into 2 daughter hemispherical forms. Six cs cdc mutants, apparently blocked in mitosis, were observed by fluorescence microscopy. Under the restrictive conditions their chromatin regions exhibited either hemispherical, compact, disk-like, U-shaped or partially segregated chromatin regions. Two mutants showed anomalous nuclear locations. The results of the temperature shift-up experiments of the highly reversible KM52 and KM108 strains supported the above scheme of sequential alterations in the chromatin region.

Ascomycota↗

PubMed2002

Simple method for reduction of autofluorescence in fluorescence microscopy.

Autofluorescence of aldehyde-fixed neural tissue often complicates the use of fluorescence microscopy. Background fluorescence can be notably reduced or eliminated by irradiation with light before treatment with fluorescence probes, resulting in a higher contrast without adversely affecting the staining probabilities.

Animals↗

PubMed2005

Molecular photobleaching kinetics of Rhodamine 6G by one- and two-photon induced confocal fluorescence microscopy.

Under high-excitation irradiance conditions in one- and two-photon induced fluorescence microscopy, the photostability of fluorescent dyes is of crucial importance for the detection sensitivity of single molecules and for the contrast in fluorescence imaging. Herein, we report on the dependence of photobleaching on the excitation conditions, using the dye Rhodamine 6G as a typical example. The different excitation modes investigated include 1) one-photon excitation into the first-excited singlet state in the range of 500 to 528 nm by continuous wave and picosecond-pulsed lasers and 2) two- and one-photon excitation to higher-excited singlet states at 800 and 350 nm, respectively, by femtosecond pulses. Experimental strategies are presented, which allow resolving the photophysics. From single-molecule trajectories and fluorescence correlation spectroscopy, as well as with a simple theoretical model based on steady-state solutions of molecular rate equation analysis, we determined the underlying photobleaching mechanisms and quantified the photokinetic parameters describing the dependence of the fluorescence signal on the excitation irradiance. The comparison with experimental data and an exact theoretical model show that only minor deviations between the different theoretical approaches can be observed for high-pulsed excitation irradiances. It is shown that fluorescence excitation is in all cases limited by photolysis from higher-excited electronic states. In contrast to picosecond-pulsed excitation, this is extremely severe for both one- and two-photon excitation with femtosecond pulses. Furthermore, the photostability of the higher-excited electronic states is strongly influenced by environmental conditions, such as polarity and temperature.

Biochemistry↗

PubMed1989