“Molecular Clusters” on the Surface of an Oxidizing Metal
FIELD ion microscopy, which holds the possibility of resolving the individual atoms in a metallic surface, should in principle be a powerful tool for the study of reactions on surfaces. As part of an extensive study of the mechanism of oxidation of several metals, we have recently observed the formation of characteristic, reproducible, small clusters of atoms of regular shape when a perfect iridium surface is exposed to oxygen.
SOME APPLICATIONS OF ION‐ELECTRON IMAGE CONVERSION IN FIELD ION MICROSCOPE STUDIES OF SURFACE REACTIONS
An ion‐electron image converter has been applied to field ion studies of surface reactions. Argon imaging has been used to study oxygen and carbon monoxide adsorption on tungsten while the effect of using the reactive imaging gases, oxygen, nitrogen, and carbon monoxide, has also been investigated. The reaction of nitrogen is of particular interest in the context of field‐induced rearrangement processes.
The peculiar thermo-structural behavior of the anionic lipid DMPG.
Aqueous dispersions of the anionic phospholipid dimyristoyl phosphatidylglycerol (DMPG), around 100 mM ionic strength, are known to exhibit a thermal behavior similar to that of the largely studied lipid dimyristoyl phosphatidylcholine (DMPC), which undergoes a gel to liquid crystalline phase transition at 23 degrees C, well characterized by differential scanning calorimetry (DSC), and other methods. However, at low ionic strength, DMPG has been shown to present a large gel-fluid transition region, ranging from 18 to 35 degrees C. This intermediate phase is optically transparent and characterized by a continuous change in membrane packing. Structural properties of the DMPG gel-fluid transition region will be discussed, based on results obtained by several techniques: electron spin resonance (ESR) of spin labels at the membrane surface and intercalated at different depths in the bilayer; light scattering; DSC; small angle X-ray scattering (SAXS); and fluorescence spectroscopy of probes in the bilayer.