Techsighting. Cell biology. Sorting on silicon.
Explore the source record for details and available documents.
Cell Separation↗
Biomedical subjects
R Peters
Publications and source records attributed to R Peters.
Optical recording of signal-mediated protein transport through single nuclear pore complexes.
Optical single-transporter recording, a recently established fluorescence microscopic method, was used to study the selective transport of proteins through single nuclear pore complexes (NPCs) of Xenopus oocytes. Recombinant proteins containing either a nuclear localization signal (import protein) or a nuclear export signal (export protein) were generated as transport substrates. To approximate in vivo conditions as closely as possible, a Xenopus egg extract was applied to the cytosolic side and a Xenopus oocyte nuclear extract to the nuclear side of the NPCs. It was found that protein transport through functionally isolated, "patched" NPCs depended on signal sequences, extracts, and metabolic energy, as in vivo. All NPCs were competent for both import and export. The transport direction was strictly determined by the transport signal, and at none of the conditions explored was the import protein exported or the export protein imported, even when the application sides of the extracts were reversed. The mean transport rates of the single NPC were approximately 2 dimers/s for the import protein and approximately 4 dimers/s for the export protein ( approximately 15 microM substrate concentration, 22-24 degrees C), in good agreement with in vivo rates estimated for mammalian cells by microinjection experiments. The study shows that optical single-transporter recording permits the analysis of membrane transport processes not previously accessible to single-transporter recording and thus provides additional possibilities for the elucidation of nucleocytoplasmic transport mechanisms.
Animals↗
Protein expression. Folding to green.
Explore the source record for details and available documents.
Archaeal Proteins↗
Techsighting. Test tube kidneys.
Explore the source record for details and available documents.
Animals↗
Techsigting. Neural regeneration. Some nerve!
Explore the source record for details and available documents.
Animals↗
Polymer chemistry. Designer jell-o.
Explore the source record for details and available documents.
Acrylamides↗
The cutting edge: surgery sites on the World Wide Web.
Explore the source record for details and available documents.
General Surgery↗
Gene sequencing. Size matters.
Explore the source record for details and available documents.
Base Pairing↗
Scanning microphotolysis: three-dimensional diffusion measurement and optical single-transporter recording.
Scanning microphotolysis (SCAMP) is a combination of fluorescence microphotolysis and confocal laser scanning microscopy. A laser scanning microscope is equipped with an optical switch able to modulate the power or/and wavelength of the laser beam in less than a microsecond while a dedicated computer program is employed to precisely coordinate scanning process and laser beam modulation. By these means it becomes possible to vary the power or/and wavelength of the laser beam during scanning at a precision of one resolution element. Patterns of almost arbitrary design can be written into the object by photolysis, e.g., photobleaching or photoactivation. The dissipation of the photolysis pattern by diffusion or other types of molecular transport can be followed at confocal resolution and used to characterize the transport process. SCAMP can be employed in conjunction with single-photon or multiphoton excitation. Furthermore, it can be easily installed on virtually any confocal laser scanning microscope. We summarize at first the conceptual and practical basis of SCAMP. Then, two novel applications are discussed: (i) measurements of translational diffusion coefficients in truly three-dimensional systems at diffraction-limited resolution, and (ii) optical recording of single transporters in membrane patches.
Diffusion↗
Perforated jejunal diverticulitis as a rare cause of acute abdomen.
Jejunal diverticula is rare and in most cases without any symptoms. They become clinically relevant when complications, such as diverticulitis, malabsorption caused by bacterial overgrowth, intestinal hemorrhage, or obstruction, occur. In this case report a case of perforated jejunal diverticulitis is presented and the problems in finding the correct diagnosis are discussed.
Abdomen, Acute↗
Permeability of single nuclear pores.
In this first application of optical single transporter recording (OSTR), a recently established technique for optically monitoring the activity of single transporters in membrane patches (Tschödrich-Rotter and Peters. 1998. J. Microsc. 192:114-125), the passive permeability of the nuclear pore complex (NPC) was measured for a homologous series of hydrophilic probe molecules. Nuclei were isolated from Xenopus oocytes and firmly attached to filters containing small cylindrical pores. Transport through membrane patches spanning filter pores was measured by scanning microphotolysis. Thus the permeability coefficients of single NPCs were determined for fluorescently labeled dextrans of approximately 4, 10, and 20 kDa. Dextrans of >/=40 kDa could not permeate the NPC. The data were consistent with a model in which the NPC contains a single diffusion channel. By application of established theories for the restricted diffusion through small pores, the diffusion channel was approximated as a cylinder with a radius of 4.4-6.1 nm (mean 5. 35 nm). Because the transport rate constant of the single NPC was known, the equivalent length of the channel could be also determined and was found to be 40-50 nm (mean 44.5 nm). The symmetry of the NPC implies that a singular component such as the diffusion channel is located at the center of the NPC. Therefore a common transport pathway apparently mediates both passive and signal-dependent transport. To test this hypothesis, measurements of signal-dependent transport and of the mutual effects signal-dependent and passive transport may exert on each other are in progress.
Animals↗