Hydrophobic metals

Upon formation of a metal chelate or complex, the next rate-limiting step in delivering iron to the cell is the diffusion of iron complexes through the. soil in response to diffusion gradients. In the vicinity of plant roots, metal chelates and complexes may also move by bulk flow in the transpiration stream as water moves from the soil into the plant. However, depending on their charge characteristics and hydrophobicity, metal chelators and complexes can become adsorbed to clay and organic matter, which may then decrease their mobility and bioavail-... 

INTERACTION OF HYDROPHOBIC METAL COMPLEXES AND ORGANOMETALLIC COMPOUNDS WITH BIOLOGICAL INTERPHASES... 

Partitioning of metal complexes into the lipid bilayer of membranes is only significant for hydrophobic species. FA and HA, and their metal complexes, are not expected to enter to a significant extent into the lipid bilayer, due to their large molecular size. Uptake of hydrophobic metal species by diffusion across... 

The particular enhancement of a radical dimerisation reaction, Eqs. (45a) and (45b), is observed on hydrophobic metals like Hg, Pb, and Sn at potentials close to their respective point of zero charge where electrosorption is strongest and diminishes at more negative and positive potential. If the reduction potential of the oxo-compound, which in accordance with the equilibrium reaction (45b) is pH dependent (60 mV per pH unit), is shifted by more than 100 mV away from the point of zero charge, then the ketyl radicals are no longer adsorbed strongly enough and they are displaced from the... 

The self-assembly and inhibition of protein adsorption by thiolated dextran monolayers at hydrophobic metal surfaces. In Ratner BD, Castner DG (eds) Surface modification of polymeric biomaterials. Plenum, New York, p 117... 

In 1988, Schiffrin s group [4] claimed that the use of lutetium biphthalocyanine (LuPc2) complex more hydrophobic than Fc enabled observation and investigation of a true , or heterogeneous, ET across the 0/W interface. A series of subsequent papers reported ET systems by other hydrophobic metal complexes including tin diphthalo-cyanine [5], iron and ruthenium metalloporphyrin complexes with pyridine [6] and Fc derivatives [7]. These experimental studies then stimulated theoretical studies on the ET kinetics [8-12]. 

The biochemical reaction performed by the methyltransferase appears to be metal dependent, as determined by chemical inhibition studies, but the exact identity of this metal has yet to be defined [41]. EDTA treatment had no inhibitory effect on Stel4p, but incubation of the protein with 10 - 50 mM of the metal chelating agent 1,10-phenanthroline eliminated catalytic activity [37,41]. Additionally, even more hydrophobic metal sequesterants such as zincon [37], lysine nitriloacetic acid (Lys-NTA) [42], and cholesteryl-Lys-NTA [43] also inhibited the methyltransferase but at much lower concentrations. Together, these data suggest that the metal ion may be buried in a hydrophobic region of the enzyme. 

The LB techniques are a powerful tool used to assemble large-scale monolayers of hydrophobic metallic nanoparticles on a water surface [42]. The advantages of the LB techniques are the good reproducibility of the metallic nanoparticles substrates and the ability to disperse the particles on the surface of water [43]. Recently, the LB methods have received interest as a process for the fabrication of thin films SERS substrates. 

Figure 5.1. Water droplets on a hydrophobized metal surface. (Courtesy J. Maas.)...

In conclusion of this protocol, we have found that the SELDI-TOF-MS technique is a very powerful tool to decipher a variety of complex body fluids. Furthermore, many chips surfaces (strong anion exchange, weak cation exchange, hydrophobic, metal binding, normal phase, etc.) can be used for profiling commonly studied body fluids such as serum/plasma, NAF, and urine. Moreover, each chip provides different but complementary information about the composition and the profile of the samples studied. Thus, SELDI-TOF-MS... 

The location of the reaction step depends on extractant surface activity and hydrophobicity, metal concentration, and hydrodynamics (agitation intensity). Low metal concentration and high hydrodynamics, together with high surface activity and the low solubility of the extractant in the aqueous phase (i.e., high hydrophobicity), favor the interfacial reaction. However, the reaction place may also depend on experimental conditions, i.e., the method used for the studies. In general, case reaction... 

A. Michaelides and K. Morgenstern, Ice nanoclusters at hydrophobic metal surfaces. Nature Materials 6, 597-601 (2007). 

Asymmetric transfer hydrogenation of insoluble ketones (e.g. Q -bromomethyl aryl ketones) catalyzed by hydrophobic metal-amido complexes of Ir and Rh can be carried out... 

In the case of proteins exposed to a hydrophobic metal surface, the behaviour is quite different, and in good agreement with earlier studies of protein adsorption to hydrophobic materials [1]. Thus the values of the thickness and of the refractive index are consistent with the formation of a monolayer. 

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