Contrast in the Photoelectric Effect of Organic and Biochemical Surfaces

Birrell, G. Bruce; Burke, Charles A.; Dehlinger, P.; Griffith, O. Hayes

doi:10.1016/s0006-3495(73)85999-5

Cited by 17 publications

(6 citation statements)

References 3 publications

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“…On the other hand, our observations are also consistent with the hypothesis that a-tocopherol (a-T-3) may facilitate the molecular packing within biological membranes of polyunsaturated phospholipid molecules, and hence the vitamin may stabilize biological membranes containing high proportions of polyunsaturated phospholipid molecules (cf. the disorder in the interior of bilayers of egg phosphatidylcholine discussed by Birrell & Griffith, 1976). Recent experiments have shown that a-tocopherol (a-T-3) influences the permeability properties of liposomes containing polyunsaturated phospholipids (A. T. Diplock & J.…”

Section: Discussionmentioning

confidence: 99%

Interactions of tocopherols and ubiquinones with monolayers of phospholipids

Maggio¹,

Diplock²,

Lucy³

1977

Biochemical Journal

115

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1. The penetration of alpha-tocopherol and seven of its derivatives, and five compounds in the ubiquinone series, having differing chain lengths, into monolayers at the air/water interface of 11 different synthetic phospholipids and cholesterol was investigated; the properties of mixed monolayers of the tocopherols and of ubiquinones with phospholipids were also studied. 2. Penetration of alpha-tocopherol into diarachidonylglycerylphosphorycholine was approximately constant for molar ratios of tocopherol/phospholipid ranging from 0.4:1.0 to 2.0:1.0. 3. Tocopherols with shorter or longer side chains than alpha-tocopherol had a lesser ability to penetrate monolayers of phospholipid molecules with 16 or more carbon atoms in their acyl chains. 4. All the tocopherols penetrated more readily as unsaturation in the phospholipids was increased, and their penetration into mixed monolayers of phospholipids was greatly facilitated by the presence of relatively small quantities of unsaturated phospholipid molecules. 5. There was relatively little interaction between the tocopherols and cholesterol, or between the ubiquinones and phospholipids. 6. The possible significance of the observed interactions between alpha-tocopherol and polyunsaturated phospholipids is discussed in relation to the biochemical actions of alpha-tocopherol in vivo. 7. It is suggested that fluidity of the lipid bilayer in membranes containing polyunsaturated phospholipids may allow alpha-tocopherol to interact in a dynamic manner with a number of phospholipid molecules.

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Section: Discussionmentioning

confidence: 99%

Interactions of tocopherols and ubiquinones with monolayers of phospholipids

Maggio¹,

Diplock²,

Lucy³

1977

Biochemical Journal

115

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“…Material contrast is provided by differences in photoelectron quantum yield (electrons produced per incident photon) just as contrast in fluorescence microscopy is due to differences in fluorescent quantum yields (7)(8)(9). It has been suggested that the photoelectron quantum yields of some dyes might be sufficiently larger than that of the background to permit these dyes to act as photoelectron labels (23)(24)(25). However, this type of material contrast was not observed under the experimental conditions used in this study.…”

Section: Methodsmentioning

confidence: 64%

Photoelectron microscopy and immunofluorescence microscopy of cytoskeletal elements in the same cells.

Nadakavukaren¹,

Chen²,

Habliston³

et al. 1983

Proc. Natl. Acad. Sci. U.S.A.

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Pt K2 rat kangaroo epithelial cells and Rat-I fibroblasts were grown on conductive glass discs, fixed, and permeabilized, and the cytoskeletal elements actin, keratin, and vimentin were visualized by indirect immunofluorescence. After the fluorescence microscopy, the cells were postfixed and dehydrated for photoelectron microscopy. The contrast in these photoelectron micrographs is primarily topographical in origin, and the presence of fluorescent dyes at low density does not contribute significantly to the material contrast. By comparison with fluorescence micrographs obtained on the same individual cells, actincontaining stress fibers, keratin filaments, and vimentin filaments were identified in the photoelectron micrographs. The apparent volume occupied by the cytoskeletal network in the cells as judged from the photoelectron micrographs is much less than it appears to be from the fluorescence micrographs because the higher resolution of photoelectron microscopy shows the fibers closer to their true dimensions. Photoelectron microscopy is a surface technique, and the images highlight the exposed cytoskeletal structures and suppress those extending along the substrate below the nuclei. The results reported here show marked improvement in image quality of photoelectron micrographs and that this technique has the potential of contributing to higher resolution studies of cytoskeletal structures.Photoelectron microscopy (photoemission electron microscopy or PEM) has recently been introduced into the study of whole cells (1, 2) although the origins of this technique are old, predating both transmission electron microscopy and scanning electron microscopy (for review, see ref. 3 for physics and refs. 4 and 5 for biological applications). Photoelectron microscopy differs significantly from the established techniques of transmission and scanning electron microscopy even though the image is formed by electrons. The photoelectron microscope can be considered to be the electron optics analogue of the fluorescence microscope. UV light from a short arc lamp is focused on the specimen as in fluorescence microscopy but, instead of imaging the emitted fluorescent light with a light optics system, emitted electrons are accelerated and imaged with an electron lens system. Photoelectron microscopy has several advantages, including high sensitivity to topographic detail (3, 6), a new source of contrast based on the photoelectric effect (7-9), and an unusually short depth of information (10). The increase in image quality during the development of the photoelectron microscope over the past few years has been substantial. Although the basic mechanisms by which the photoelectron microscopy image arises are understood, the interpretation of photoelectron microscopy images of biological specimens is the focus of current research. Here we report the comparison of photoelectron micrographs with fluorescence micrographs of the same cells that have been labeled by indirect immunofluorescence techniques with antibodies specific fo...

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“…A bright image from the conjugated fluorescein residues can be anticipated because of the low ionization potential of aromatic compounds (7 to 8 eV) relative to the ionization potential of aliphatic compounds (10 to 11 eV) (2). Similar theoretical considerations of the photoelectric effect have recently been shown to have promise as a new method of mapping the positions of biological surface components (1,5,6). Utilizing these principles in conjunction with the magnification power of the electron microscope and with the specificity of fluorescent antibody labeling, we were able to identify and distinguish between two viruses, parainfluenza 1 and influenza A.…”

mentioning

confidence: 76%