University of Groningen

About: University of Groningen is a education organization based out in Groningen, Groningen, Netherlands. It is known for research contribution in the topics: Population & Context (language use). The organization has 36346 authors who have published 69116 publications receiving 2940370 citations. The organization is also known as: Rijksuniversiteit Groningen & RUG.

Electron transport in a methanofullerene

Abstract: The current-voltage characteristics of methanofullerene [6,6]-phenyl C-61-butyric acid methyl ester (PCBM)-based devices are investigated as a function of temperature. The occurrence of space-charge limited current enables a direct determination of the electron mobility. At room temperature, an electron mobility Of mu(e) = 2 x 10(-7) m(2) V-1 s(-1) has been obtained. This electron mobility is more than three orders of magnitude larger than the hole mobility of donor-type conjugated polymer poly(2-methoxy-5-(3',7'-dimethyloctyloxy)-p-phenylene vinylene) (OC1C10-PPV). As a result, the dark current in PCBM/OC1C10-PPV based devices is completely dominated by electrons. The observed field and temperature-dependence of the electron mobility 1 of PCBM can be described with a Gaussian disorder model. This provides information about the energetic disorder and average transport-site separation in PCBM.

Crystal structure of Agaricus bisporus mushroom tyrosinase: identity of the tetramer subunits and interaction with tropolone.

Abstract: Tyrosinase catalyzes the conversion of phenolic compounds into their quinone derivatives, which are precursors for the formation of melanin, a ubiquitous pigment in living organisms. Because of its importance for browning reactions in the food industry, the tyrosinase from the mushroom Agaricus bisporus has been investigated in depth. In previous studies the tyrosinase enzyme complex was shown to be a H(2)L(2) tetramer, but no clues were obtained of the identities of the subunits, their mode of association, and the 3D structure of the complex. Here we unravel this tetramer at the molecular level. Its 2.3 A resolution crystal structure is the first structure of the full fungal tyrosinase complex. The complex comprises two H subunits of ∼392 residues and two L subunits of ∼150 residues. The H subunit originates from the ppo3 gene and has a fold similar to other tyrosinases, but it is ∼100 residues larger. The L subunit appeared to be the product of orf239342 and has a lectin-like fold. The H subunit contains a binuclear copper-binding site in the deoxy-state, in which three histidine residues coordinate each copper ion. The side chains of these histidines have their orientation fixed by hydrogen bonds or, in the case of His85, by a thioether bridge with the side chain of Cys83. The specific tyrosinase inhibitor tropolone forms a pre-Michaelis complex with the enzyme. It binds near the binuclear copper site without directly coordinating the copper ions. The function of the ORF239342 subunits is not known. Carbohydrate binding sites identified in other lectins are not conserved in ORF239342, and the subunits are over 25 A away from the active site, making a role in activity unlikely. The structures explain how calcium ions stabilize the tetrameric state of the enzyme.

The ctenophore genome and the evolutionary origins of neural systems

Abstract: The origins of neural systems remain unresolved. In contrast to other basal metazoans, ctenophores (comb jellies) have both complex nervous and mesoderm-derived muscular systems. These holoplanktonic predators also have sophisticated ciliated locomotion, behaviour and distinct development. Here we present the draft genome of Pleurobrachia bachei, Pacific sea gooseberry, together with ten other ctenophore transcriptomes, and show that they are remarkably distinct from other animal genomes in their content of neurogenic, immune and developmental genes. Our integrative analyses place Ctenophora as the earliest lineage within Metazoa. This hypothesis is supported by comparative analysis of multiple gene families, including the apparent absence of HOX genes, canonical microRNA machinery, and reduced immune complement in ctenophores. Although two distinct nervous systems are well recognized in ctenophores, many bilaterian neuron-specific genes and genes of 'classical' neurotransmitter pathways either are absent or, if present, are not expressed in neurons. Our metabolomic and physiological data are consistent with the hypothesis that ctenophore neural systems, and possibly muscle specification, evolved independently from those in other animals.