Structural alterations, metal-induced

Biggart NW, Murphy E Jr. 1988. Analysis of metal-induced mutations altering the expression or structure of a retroviral gene in a mammalian cell line. Mutat Res 198 115-130. 

When metallic glasses begin to experience plastic deformation at temperatures well below Tg they tend to undergo rapid localization of deformation into shear bands (Spaepen 1977 Argon 1979). However, the localization of deformation by a perturbation in flow is always preceded by a brief stretch of quasi-homogeneous plastic flow (Section 7.8). The discussion of this must await the development of an essential understanding of evolutionary processes of plastic-strain-induced structural alterations in Section 7.6. 

Heat, strong acids or bases, ethanol, or heavy-metal ions irreversibly alter the secondary structure of proteins (see below). This process, known as denaturation, is exemplified by the heat-induced coagulation and hardening of egg white (albumin). Denaturation destroys the physiological activity of proteins. 

Mavrikakis et al.I have nicely shown that the strain induced on the metal-metal bonds by the misalignment of the metal lattice to the registry of the oxide support leads to a shift in the center of the d-band. This change in the electronic structure alters the adsorbate bond strength at these sites, which ultimately dictates the reactivity of the metal. While these effects may die off for large particles on the support, they can clearly play a role for smaller nanoparticles that are in direct contact with the support. 

Plants are constantly subject to adverse environmental conditions such as drought, flooding, extreme temperatures, excessive salts, heavy metals, high-intensity irradiation and infection by pathogenic agents. Because of their immobility, plants have to make necessary metabolic and structural adjustments to cope with the stress conditions. To this end, the expression of the genetic programme in plants is altered by the stress stimuli to induce and/or suppress the production of specific proteins which are either structural proteins or enzymes for specific metabolic pathways. 

Another technique that uses the fluorescence properties of trivalent lanthanides is that of the detection of fluorescence emission decay induced by pulsed dye laser excitation. Horrocks and Sudnick (17) have applied this technique to the study of water molecules bound to metal ions in small complexes and proteins. In one study they found that the exponential decay of Tb3+ fluorescence is altered when H20 is replaced by D20 and that this change can be used to determine the number of coordinated water molecules on the metal ion. With thermolysin, bound Tb3+ had 1-2 water molecules in the first coordination shell. This number is consistent with the x-ray structure. 

The growth of filamentous carbon along with the gas phase product analysis has been used to determine the influence of sulfur on the iron catalyzed decomposition of carbon containing gas mixtures at 600°C. Pretreatment of the metal in H2S was found to initially suppress the reactions leading to carbon deposition from the decomposition of CO/H2 mixtures. After a short time the activity was restored to approximately the same level as that exhibited by an unadulterated iron powder, suggesting that most of the sulfur atoms were being removed from the surface. The small residual fraction of adatoms did, however, induce modifications in the structural characteristics of the filamentous carbon deposit and also altered the reactivity pattern of the iron towards decomposition of a CO/C2H4/H2 mixture. 

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