Hole Hopping Across a Protein-Protein Interface.

We have investigated photoinduced hole hopping in a Pseudomonas aeruginosa azurin mutant Re126WWCuI, where two adjacent tryptophan residues (W124 and W122) are inserted between the CuI center and a Re photosensitizer coordinated to a H126 imidazole (Re = ReI(H126)(CO)3(dmp)+, dmp = 4,7-dimethyl-1,10-phenanthroline). Optical excitation of this mutant in aqueous media (//(CuII)' back ET that occurs over 12 Å, in contrast to the 23 Å, 120 us step in Re126WWCuI. Importantly, dimerization makes Re126FWCuI photoreactive and, in the case of {Re126WWCuI}2, channels the photoproduced "hole" to the molecule that was not initially photoexcited, thereby shortening the lifetime of ReI(H126)(CO)3(dmp•-)//CuII. Whereas two adjacent W124 and W122 indoles dramatically enhance CuI->*Re intramolecular multistep ET, the tryptophan quadruplex in {Re126WWCuI}2 does not accelerate intermolecular electron transport; instead, it acts as a hole storage and crossover unit between inter- and intramolecular ET pathways. Irradiation of {Re126WWCuII}2 or {Re126FWCuII}2 also triggers intermolecular *Re////(W122•+)' intermolecular charge recombination. Our findings shed light on the factors that control interfacial hole/electron hopping in protein complexes and on the role of aromatic amino acids in accelerating long-range electron transport

Optical and infrared spectroelectrochemical studies of CN-substituted bipyridyl complexes of Ruthenium(II)

Ruthenium(II) polypyridyl complexes [Ru(CNMe-bpy)x(bpy)3−x]2+ (CN-Me-bpy = 4,4′-dicyano-5,5′-dimethyl2,2′-bipyridine, bpy = 2,2′-bipyridine, and x =1−3, abbreviated as 12+, 22+, and 32+) undergo four (12+) orfive (22+ and 32+) successive one-electron reduction steps between −1.3 and −2.75 V versus ferrocenium/ferrocene (Fc+/Fc) in tetrahydrofuran. The CN-Me-bpy ligands are reduced first, with successive one-electron reductions in 22+ and 32+ being separated by 150−210 mV; reduction of the unsubstituted bpy ligand in 12+ and 22+ occurs only when all CN-Me-bpy ligands have been converted to their radical anions. Absorption spectra of the first three reduction products of each complex were measured across the UV, visible, near-IR (NIR), and mid-IR regions and interpreted with the help of density functional theory calculations. Reduction of the CN-Mebpy ligand shifts the ν(CN) IR band by ca. −45 cm−1, enhances its intensity ∼35 times, and splits the symmetrical and antisymmetrical modes. Semireduced complexes containing two and three CN-derivatized ligands 2+, 3+, and 30 show distinct ν(C N) features due to the presence of both CN-Me-bpy and CN-Me-bpy•−, confirming that each reduction is localized on a single ligand. NIR spectra of 10, 1−, and 2− exhibit a prominent band attributable to the CN-Me-bpy•− moiety between 6000 and 7500 cm−1, whereas bpy•−-based absorption occurs between 4500 and 6000 cm−1; complexes 2+, 3+, and 30 also exhibit a band at ca. 3300 cm−1 due to a CN-Me-bpy•− → CN-Me-bpy interligand charge-transfer transition. In the UV−vis region, the decrease of π → π* intraligand bands of the neutral ligands and the emergence of the corresponding bands of the radical anions are most diagnostic. The first reduction product of 12+ is spectroscopically similar to the lowest triplet metal-to-ligand charge-transfer excited state, which shows pronounced NIR absorption, and its ν(CN) IR band is shifted by −38 cm−1 and 5−7-fold-enhanced relative to the ground state

Soil Food Web Changes during Spontaneous Succession at Post Mining Sites: A Possible Ecosystem Engineering Effect on Food Web Organization?

Lagomorphs (a group that consists of pikas, hares, rabbits and allies) are notable for their conservative morphology retained for most of their over 50 million years evolutionary history. On the other hand, their remarkable morphological uniformity partly stems from a considerable number of homoplasies in cranial and dental structures that hamper phylogenetic analyses. The premolar foramen, an opening in the palate of lagomorphs, has been characterized as an important synapomorphy of one clade, Ochotonidae (pikas). Within Lagomorpha, however, its phylogenetic distribution is much wider, the foramen being present not only in all ochotonids but also in leporids and stem taxa; its morphology and incidence also varies considerably across the order, even intraspecifically. In this study, we provide a broad survey of the taxonomic distribution of the premolar foramen in extant and fossil Lagomorpha and describe in detail the morphological variation of this character within the group. Micro-computed tomography was used to examine the hard palate and infraorbital groove morphology in Poelagus (Leporidae) and Ochotona. Scans revealed the course and contacts of the canal behind the premolar foramen and structural differences between the two crown clades. We propose that the premolar foramen has evolved independently in several lineages of Lagomorpha, and we discuss development and function of this foramen in the lagomorph skull. This study shows the importance of comprehensive studies on phylogenetically informative non-dental characters in Lagomorpha

Comunidades de minhocas em um ecótono entre floresta e campo arável e suas relações com as propriedades do solo

The objective of this work was to assess the effects of a forest-field ecotone on earthworm assemblages. Five sites (blocks) differing in the type of crop rotation used in the field were studied in Central Bohemia, Czech Republic. In each block, sampling was carried out in seven parallel rows perpendicular to a transect from a forest (oak or oak-pine) to the centre of a field, both in spring and autumn 2001–2003. Individual rows were located in the forest (5 m from the edge), in the forest edge, and in the field (at 5, 10, 25, 50 and 100 m distances from the forest edge). The density and biomass of earthworms were lowest in the forest, increased markedly in the forest edge, decreased again at 5 or 10 m distance from the forest edge and then continuously increased along the distance to the field boundary. The highest number of species was found in the forest edge and in the field boundary. Individual species differed in their distribution along the transect. Both density and biomass of earthworms were correlated with distance from forest edge, soil organic matter content, soil porosity, and water infiltration rate.O objetivo deste trabalho foi avaliar os efeitos de um ecótono entre floresta e campo arável sobre comunidades de minhocas. Cinco locais (blocos) com diferentes tipos de rotação de culturas utilizados no campo foram estudados na Boêmia Central, República Tcheca. Em cada bloco, amostragens foram feitas em sete linhas paralelas perpendiculares a um transecto de floresta (carvalho ou carvalho e pinheiro), em direção ao centro de um campo, na primavera e no outono de 2001–2003. Linhas individuais foram marcadas na floresta (a 5 m da borda), na borda da floresta e no campo (a 5, 10, 25, 50 e 100 m da borda da floresta). A densidade e biomassa das minhocas foi menor na floresta, aumentou marcadamente na borda da floresta, decaiu novamente a 5 ou 10 m de distância da borda da floresta e aumentou continuamente com a distância até o limite do campo. O maior número de espécies foi encontrado na borda da floresta e no limite do campo. As espécies apresentaram distribuições diferentes ao longo do transecto. Tanto a densidade quanto a biomassa de minhocas foram correlacionadas com a distância da borda da floresta, o conteúdo de matéria orgânica do solo, a porosidade do solo e a infiltração de água

A new case of consensual decision: collective movement in earthworms

Collective movements are reported for many species from microorganisms to humans. But except for a few soil-inhabiting species, intra-specific interactions in soil are poorly studied. Some intra-specific interactions occur in earthworms. Most of them are negative, concerning parameters like the rate of survival, maturation, food ingestion or growth. Virtually nothing is known about collective movement in earthworms that represent the dominant biomass of the soil. This study, the first one on annelids, highlights a consensual decision phenomenon based only on contact between followers. Using an olfactometer set-up and modelling, we show that earthworms Eisenia fetida influence each other to select a common direction during their migration. Experiments in a binary choice test showed that contacts between individuals are responsible for collective movement. This coordination in movement could allow earthworms to benefit from forming clusters. The resulting local higher densities, enhancing individual survival and favouring the cooperation, may be at the origin of Allee effects reported for these species. © 2010 University of Liege, Gembloux Agro BioTech.SCOPUS: ar.jFLWINinfo:eu-repo/semantics/publishe