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It protects biological membranes from damage by trapping the lipid peroxyl radicals, ROO • , which would otherwise destroy the membrane lipids, RH, in a two-step chain reaction.This inhibition of lipid peroxidation is effected via a very facile transfer of the phenolic hydrogen atom of TOH to peroxyl radicals. 4,6 To understand and, hopefully, to model the ability of a biological membrane to withstand oxidative stress requires knowledge of the absolute rate constant for reaction 3, k ROO/TOH S , in biologically relevant systems. However, this rate constant is very likely to be highly dependent on the solvent, S, because we have found that rate constants for abstraction of hydroxylic hydrogen atoms show dramatic solvent effects. [7][8][9][10][11] These kinetic solvent effects (KSEs) can be accounted for quantitatively on the basis of hydrogen bonding between the hydrogen bond donor (HBD) substrate (or antioxidant) and hydrogen bond acceptor (HBA) solvent. 7,8,11 Because the extent of the HBD/HBA interaction depends only on the HBD

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The photolysis of gold salts is rarely viewed as the initiation for gold nanoparticle (AuNP) formation. Yet, photolysis of AuCl(4)(-) generates chlorine atoms whose rich hydrogen transfer chemistry can readily generate strongly reducing radicals. Interesting precursors include hydrogen peroxide, 2-propanol, 1,4-cyclohexadiene and tetrahydrofuran; all of them yield strongly reducing radicals. Further, this group of substrates has been selected because of the innocuous and volatile nature of reagents and products, thus allowing a remarkably clean synthesis of gold nanostructures. In the case of H(2)O(2) the by-products are water and oxygen. The methodology reported here opens the door to particles that can be modified in situ or post-synthesis with custom surface covering without concern for chemical debris from the nanostructure synthesis.

We have investigated the structure and properties of dithiothreitol (DTT) monolayers adsorbed on Au(111). Using scanning tunneling microscopy (STM), and Auger electron spectroscopy (AES), we have compared the properties of DTT monolayers with those of more conventional octanethiol layers. STM measurements indicate that much of the DTT layer is disordered; however, small ordered regions with local 2 3× 3 symmetry are observed. STM images of octanethiol films exhibit the characteristic close packed 3× 3 molecular layer with c(4×2) supersymmetry. AES indicates sulfur coverage for both the DTT and octanethiol films is similar. AES studies involving Ellman's reagent, a marker species, suggest a significant fraction of the DTT molecules in the adlayer bind to the gold via two Au-S bonds. On the basis of AES and STM measurements, we propose a structural model in which the majority of DTT molecules bind to the gold surface via two Au-S bonds. The distance between the two Au-S bonds is 5.00 Å, or the same 3a spacing observed between close packed alkanethiol molecules.