Mixing the Light Spin with Plasmon Orbit by Nonlinear Light-Matter Interaction in Gold

Transformation of light carrying spin angular momentum (SAM) to optical field vortices carrying orbital angular momentum (OAM) has been of wide interest in recent years. The interactions between two optical fields, each carrying one of those degrees of freedom, and furthermore, the transfer of the resulting angular momentum product to matter are seldom discussed. Here, we measure the interaction between 3D light carrying axial SAM and 2D plasmon-polariton vortices carrying high-order transverse OAM. The interaction is mediated by two-photon absorption within a gold surface, imprinting the resulting angular-momentum mixing into matter by excitation of electrons that are photo-emitted into vacuum. Interestingly, the spatial distribution of the emitted electrons carries the signature of a subtraction of the spin from the orbit angular momenta. We show experimentally and theoretically that the absorptive nature of this interaction leads to both single and double photon-plasmon angular momentum mixing processes by one- and two- photon interactions. Our results demonstrate high order angular momenta light-matter interactions, provide a glimpse into specific electronic excitation routes, and may be applied in future electronic sources and coherent control

Metabolites of xenobiotica and mineral oil constituents linked to macromolecular organic matter in polluted environments

The type of association between pollutants and humic substances of soils, sediments and river waters has been investigated. Metabolites, which can arise from the microbiological degradation of polyaromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCB), were cleaved from the macromolecular matrix by selective chemical degradation techniques (OH−, BCl3, Rh/H2). Hydrolysis reactions performed with Na18OH proved that some metabolites of pollutants form stable ester bonds by condensation processes with functional groups of humic substances, a phenomenon which has major implications for transport, toxicity and bioavailability of xenobiotica

Identification of crucial amino acids in mouse aldehyde oxidase 3 that determine substrate specificity.

In order to elucidate factors that determine substrate specificity and activity of mammalian molybdo-flavoproteins we performed site directed mutagenesis of mouse aldehyde oxidase 3 (mAOX3). The sequence alignment of different aldehyde oxidase (AOX) isoforms identified variations in the active site of mAOX3 in comparison to other AOX proteins and xanthine oxidoreductases (XOR). Based on the structural alignment of mAOX3 and bovine XOR, differences in amino acid residues involved in substrate binding in XORs in comparison to AOXs were identified. We exchanged several residues in the active site to the ones found in other AOX homologues in mouse or to residues present in bovine XOR in order to examine their influence on substrate selectivity and catalytic activity. Additionally we analyzed the influence of the [2Fe-2S] domains of mAOX3 on its kinetic properties and cofactor saturation. We applied UV-VIS and EPR monitored redox-titrations to determine the redox potentials of wild type mAOX3 and mAOX3 variants containing the iron-sulfur centers of mAOX1. In addition, a combination of molecular docking and molecular dynamic simulations (MD) was used to investigate factors that modulate the substrate specificity and activity of wild type and AOX variants. The successful conversion of an AOX enzyme to an XOR enzyme was achieved exchanging eight residues in the active site of mAOX3. It was observed that the absence of the K889H exchange substantially decreased the activity of the enzyme towards all substrates analyzed, revealing that this residue has an important role in catalysis

Determination of the cofactor composition of the mAOX3 variants.

<p>µM molybdenum/µM enzyme) and iron (µM 2 x [2Fe2S]/µM enzyme) contents were determined by ICP-OES (see Experimental procedures).¹ Molybdenum (</p><p>%.² Determined after conversion to the stable oxidized fluorescent product FormA. mAOX3-WT was set to 100</p><p> Relative molybdopterin (MPT) saturation, molybdenum and iron saturation and ratio of absorbance at 280 nm, 444 nm and 550 nm of mAOX3 variants in comparison to reported values for the wild type enzyme.</p

Steady-state kinetic parameters for mAOX3 wild type and mAOX3 variants containing numerous amino acids present in the active site of bovine XOR.

<p>µM DCPIP in 50 mM Tris (HCl) pH 8.00 at 37°C; k_cat was corrected for molybdenum content¹ Determined in the presence of 100 </p><p><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0082285#pone.0082285-Coelho1" target="_blank">[23]</a> and corrected for molybdenum content.² Values from </p><p> n.d. none detectable.</p><p>⁴ phthalazine:DCPIP reaction was biphasic.</p

Steady-state kinetic parameters of mAOX3 wild type and mAOX3 variants containing the FeS-domains of mAOX1.

<p>µM DCPIP was used as terminal electron receptor.¹ 100 </p><p>² Molecular oxygen in air saturated buffer was used as terminal electron acceptor.</p><p>°C; k_cat was corrected for molybdenum content³ Determined in 50 mM Tris HCl pH 8.00 at 37</p><p><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0082285#pone.0082285-Coelho1" target="_blank">[23]</a> and corrected for molybdenum content.⁴ Values from </p