Department of Chemistry and Biochemistry

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Browsing Department of Chemistry and Biochemistry by Author "Birrell, G. B."

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    Biological Photocathodes
    (Proceedings of the National Academy of Sciences, 1989-03) Griffith, O. H.; Habliston, D. L.; Birrell, G. B.; Skoczylas, W. P.; Hedberg, K. K.
    Biological surfaces emit electrons when subjected to UV light. This emission is increased greatly after exposure to cesium vapor. Increases from 2 to 3 orders of magnitude are observed, depending on the biochemicals present. Heme and chlorophyll exhibit unusually high photoemission currents, which are increased further after cesiation. Photoemission from proteins and lipids is much less but also is increased by exposure to cesium. The formation of photocathodes with cesium greatly increases the practical magnifications attainable in photoelectron microscopy of organic and biological specimens. Photoelectron micrographs taken at magnifications ;;;: x 100,000 of chlorophyll-rich thylakoid membranes and of colloidal gold-labeled cytoskeleton preparations of cultured epithelial cells demonstrate the improvement in magnification. The selectivity and stability of the photocathodes suggest the possibility of detecting chromophore binding proteins in membranes and the design of photoelectron labels for tagging specific sites on biological surfaces.
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    ESR of an alkylalkoxyamino radical trapped in X‑irradiated decanal oxime O‑methyl ether‑urea inclusion crystals
    (Journal of Chemical Physics, 1972-01-15) Ciecierska‑Tworek, Z; Birrell, G. B.; Griffith, O. H.
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    Immunophotoelectron Microscopy: The Electron Optical Analog of Immunofluorescence Microscopy
    (Proceedings of the National Academy of Sciences, 1985-01) Birrell, G. B.; Habliston, D. L.; Nadakavukaren, K. K.; Griffith, O. H.
    The electron optical analog of immunofluo rescence microscopy combines three developments: (i) photoelectron microscopy to produce a high-resolution image of ex posed components of the cell, (jQ site-specific antibodies, and (iii) photoemissive markers coupled to the antibodies to make the distribution of sites visible. This approach, in theory, pro vides a way to extend the useful immunofluorescence micros copy technique to problems requiring much higher resolution. The resolution limit of fluorescence microscopy is limited to about 200 nm by the wavelength of the light used to form the image, whereas in photoelectron microscopy the image is formed by electrons (current resolution: 10-20 nm; theoretical limit: 5 nm or better depending on the electron optics). As a test system, cytoskeletons of CV-1 epithelial cells were pre pared under conditions that preserve microtubules, and the microtubule networks were visualized by both indirect immu nofluorescence and immunophotoelectron microscopy using colloidal gold coated with antibodies. Colloidal gold serves as a label for immunophotoelectron microscopy, providing en hanced photoemission from labeled cellular components so that they stand out against the darker background of the re maining unlabeled structures. In samples prepared for both immunofluorescence and immunophotoelectron microscopy, individual microtubules in the same cells were visualized by both techniques. The photoemissionof the colloidal gold mark ers is sufficiently high that the microtubules are easily recog nized without reference to the immunofluorescence micro graphs, indicating that this approach can be used, in combina tion with antibodies, to correlate structure and function in cell biological studies.
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    Phorbol ester-induced actin cytoskeletal reorganization requires a heavy metal ion
    (Cell Regulation, 1991-12) Hedberg, Karen K.; Birrell, G. B.; Griffith, O. H.
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    Phorbol ester-induced actin cytoskeletal reorganization requires a heavy metal ion, probably Zn2+.
    (Cell Regulation, 1991-12) Hedberg, K. K.; Birrell, G. B.; Griffith, O. H.
    The cell-permeant heavy metal chelator N,N,N',Ntetrakis( 2-pyridylmethyl)ethylenediamine (TPEN) was found to counteract phorbol ester-induced actin reorganization in PTK2 and Swiss 3T3 cells. By us ing fluorescence and the higher resolution tech nique of photoelectron microscopy to monitor actin patterns, 15-min pretreatment with 25-50 pM TPEN was found to dramatically reduce actin alterations resulting from subsequent phorbol ester treatment in PTK2 cells. Similar results were obtained with Swiss 3T3 cells using 50 mM TPEN for 1.5 h. Phorbol ester-induced actin alterations are thought to de pend on activation of protein kinase C (PKC). In contrast to the phorbol ester effect, the PKC-independent actin cytoskeletal disruption caused by staurosporine and cytochalasin B was unaffected by TPEN pretreatment. TPEN did not block phorbol ester-induced activation of PKC in Swiss 3T3 cells, as observed by the phosphorylation of the 80K PKC substrate protein (MARCKS protein). TPEN also did not inhibit partially purified PKC from Swiss 3T3 cells in an in vitro PKC-specific commercial assay. To establish that the effect of TPEN is the removal of metal ions and not some other nonspecific effect of TPEN, a series of transition metal ions was added at the end of the TPEN pretreatment. The results indicate that the transient but dramatic phorbol ester-induced reorganization of the actin cytoskeleton in cultured cells depends on an inter action of PKC with a heavy metal, probably zinc.