Water vapor spectroscopy at 5 μ using a tunable SFR laser

Electron microscopy and diffraction of biological materials in the hydrated state requires the construction of a chamber in which the water vapor pressure can be maintained at saturation for a given specimen temperature, while minimally affecting the normal vacuum of the remainder of the microscope column. Initial studies with chambers closed by thin membrane windows showed that at the film thicknesses required for electron diffraction at 100 KV the window failure rate was too high to give a reliable system. A single stage, differentially pumped specimen hydration chamber was constructed, consisting of two apertures (70-100μ), which eliminated the necessity of thin membrane windows. This system was used to obtain electron diffraction and electron microscopy of water droplets and thin water films. However, a period of dehydration occurred during initial pumping of the microscope column. Although rehydration occurred within five minutes, biological materials were irreversibly damaged. Another limitation of this system was that the specimen grid was clamped between the apertures, thus limiting the yield of view to the aperture opening.

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Hydration Chamber for Jeolco 200 Kv Microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100069703 ◽

1970 ◽

Vol 28 ◽

pp. 542-543

Author(s):

V. R. Matricardi ◽

G. G. Hausner ◽

D. F. Parsons

Keyword(s):

Electron Microscope ◽

Water Vapor ◽

Vapor Pressure ◽

Pressure Gradient ◽

Room Temperature ◽

List Type ◽

Type Number ◽

Equilibrium Vapor Pressure

In order to observe room temperature hydrated specimens in an electron microscope, the following conditions should be satisfied: The specimen should be surrounded by water vapor as close as possible to the equilibrium vapor pressure corresponding to the temperature of the specimen.The specimen grid should be inserted, focused and photo graphed in the shortest possible time in order to minimize dehydration.The full area of the specimen grid should be visible in order to minimize the number of changes of specimen required.There should be no pressure gradient across the grid so that specimens can be straddled across holes.Leakage of water vapor to the column should be minimized.

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Warm and freeze-fracture of cotton seed radicles

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100129206 ◽

1987 ◽

Vol 45 ◽

pp. 984-985

Author(s):

E. L. Vigil ◽

E. F. Erbe

Keyword(s):

Thin Film ◽

Water Vapor ◽

Fracture Surface ◽

Membrane Structure ◽

Room Temperature ◽

Freeze Fracture ◽

Longitudinal Axis ◽

Fracture Plane ◽

Cotton Seeds ◽

Condensed Water

In cotton seeds the radicle has 12% moisture content which makes it possible to prepare freeze-fracture replicas without fixation or cryoprotection. For this study we have examined replicas of unfixed radicle tissue fractured at room temperature to obtain data on organelle and membrane structure.Excised radicles from seeds of cotton (Gossyplum hirsutum L. M-8) were fractured at room temperature along the longitudinal axis. The fracture was initiated by spliting the basal end of the excised radicle with a razor. This procedure produced a fracture through the tissue along an unknown fracture plane. The warm fractured radicle halves were placed on a thin film of 100% glycerol on a flat brass cap with fracture surface up. The cap was rapidly plunged into liquid nitrogen and transferred to a freeze- etch unit. The sample was etched for 3 min at -95°C to remove any condensed water vapor and then cooled to -150°C for platinum/carbon evaporation.

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