Five in situ observations of live oarfish Regalecus glesne (Regalecidae) by remotely operated vehicles in the oceanic waters of the northern Gulf of Mexico

As part of the SERPENT Project, five observations of apparently healthy oarfish Regalecus glesne by remotely operated vehicles are reported from the northern Gulf of Mexico. Regalecus glesne were observed between 2008 and 2011 at depths from within the epipelagic and mesopelagic zones. These observations include the deepest verified record of R. glesne (463–492 m) and the first record of an arthropod ectoparasite (isopod).     

Methanogens rapidly transition from methane production to iron reduction

Methanogenesis, the microbial methane (CH₄) production, is traditionally thought to anchor the mineralization of organic matter as the ultimate respiratory process in deep sediments, despite the presence of oxidized mineral phases, such as iron oxides. This process is carried out by archaea that have also been shown to be capable of reducing iron in high levels of electron donors such as hydrogen. The current pure culture study demonstrates that methanogenic archaea (Methanosarcina barkeri) rapidly switch from methanogenesis to iron‐oxide reduction close to natural conditions, with nitrogen atmosphere, even when faced with substrate limitations. Intensive, biotic iron reduction was observed following the addition of poorly crystalline ferrihydrite and complex organic matter and was accompanied by inhibition of methane production. The reaction rate of this process was of the first order and was dependent only on the initial iron concentrations. Ferrous iron production did not accelerate significantly with the addition of 9,10‐anthraquinone‐2,6‐disulfonate (AQDS) but increased by 11–28% with the addition of phenazine‐1‐carboxylate (PCA), suggesting the possible role of methanophenazines in the electron transport. The coupling between ferrous iron and methane production has important global implications. The rapid transition from methanogenesis to reduction of iron–oxides close to the natural conditions in sediments may help to explain the globally‐distributed phenomena of increasing ferrous concentrations below the traditional iron reduction zone in the deep ‘methanogenic’ sediment horizon, with implications for metabolic networking in these subsurface ecosystems and in past geological settings.     

Knockout of receptor for advanced glycation end‐products attenuates age‐related renal lesions

Pro‐aging effects of endogenous advanced glycation end‐products (AGEs) have been reported, and there is increasing interest in the pro‐inflammatory and ‐fibrotic effects of their binding to RAGE (the main AGE receptor). The role of dietary AGEs in aging remains ill‐defined, but the predominantly renal accumulation of dietary carboxymethyllysine (CML) suggests the kidneys may be particularly affected. We studied the impact of RAGE invalidation and a CML‐enriched diet on renal aging. Two‐month‐old male, wild‐type (WT) and RAGE^?/? C57Bl/6 mice were fed a control or a CML‐enriched diet (200 μg CML/g_food) for 18 months. Compared to controls, we observed higher CML levels in the kidneys of both CML WT and CML RAGE^?/? mice, with a predominantly tubular localization. The CML‐rich diet had no significant impact on the studied renal parameters, whereby only a trend to worsening glomerular sclerosis was detected. Irrespective of diet, RAGE^?/? mice were significantly protected against nephrosclerosis lesions (hyalinosis, tubular atrophy, fibrosis and glomerular sclerosis) and renal senile apolipoprotein A‐II (ApoA‐II) amyloidosis (p < 0.001). A positive linear correlation between sclerosis score and ApoA‐II amyloidosis score (r = 0.92) was observed. Compared with old WT mice, old RAGE^?/? mice exhibited lower expression of inflammation markers and activation of AKT, and greater expression of Sod2 and SIRT1. Overall, nephrosclerosis lesions and senile amyloidosis were significantly reduced in RAGE^?/? mice, indicating a protective effect of RAGE deletion with respect to renal aging. This could be due to reduced inflammation and oxidative stress in RAGE^?/? mice, suggesting RAGE is an important receptor in so‐called inflamm‐aging.     

Expansion of Bacteriophages Is Linked to Aggravated Intestinal Inflammation and Colitis

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Experimental Infection and Repeat Survey Data Indicate the Amphibian Chytrid Batrachochytrium dendrobatidis May Not Occur on Freshwater Crustaceans in Northern Queensland, Australia

Chytridiomycosis is a fatal disease of amphibians, caused by the amphibian chytrid Batrachochytrium dendrobatidis. The disease is unusual in that it may drive many amphibian species to local extinction during outbreaks. These dramatic declines in host population numbers could be facilitated if the pathogen can grow as a saprobe or on alternative hosts, a feature common to other chytrid species. This is also supported by in vitro work that demonstrates B. dendrobatidis can grow and reproduce in the absence of amphibian cells. In a previous study, B. dendrobatidis was detected on freshwater shrimp from rain forest streams in northern Queensland, Australia, using diagnostic PCR. We set out to confirm and further investigate the presence of B. dendrobatidis on crustaceans by carrying out more extensive sampling of shrimp in the field, experimental B. dendrobatidis infection trials using shrimp and crayfish, and PCR verification of the presence of B. dendrobatidis from shrimp samples that previously tested positive. We could not confirm the presence of B. dendrobatidis on shrimp, and report that original positive tests in shrimp reported by Rowley et al. (2006) were likely false. Thus, we suggest that shrimp may not be an important reservoir host for B. dendrobatidis.     

Circularly polarized luminescence of Sm (III) and Eu (III) complexes with chiral ligand (R/S)‐BINAPO

Luminescent lanthanide (III) ions have been exploited for circularly polarized luminescence (CPL) for decades. However, very few of these studies have involved chiral samarium (III) complexes. Complexes are prepared by mixing axial chiral ligands (R/S))‐2,2’‐bis(diphenylphosphoryl)‐1,1′‐binaphthyl (BINAPO) with europium and samarium Tris (trifluoromethane sulfonate) (Eu (OTf)₃ and Sm (OTf)₃). Luminescence‐based titration shows that the complex formed is Ln((R/S)‐BINAPO)₂(OTf)₃, where Ln = Eu or Sm. The CPL spectra are reported for Eu((R/S)‐BINAPO)₂(OTf)₃ and Sm((R/S)‐BINAPO)₂(OTf)₃. The sign of the dissymmetry factors, g_em, was dependent upon the chirality of the BINAPO ligand, and the magnitudes were relatively large. Of all of the complexes in this study, Sm((S)‐BINAPO)₂(OTf)₃ has the largest g_em = 0.272, which is one of the largest recorded for a chiral Sm³⁺ complex. A theoretical three‐dimensional structural model of the complex that is consistent with the experimental observations is developed and refined. This report also shows that (R/S)‐BINAPO are the only reported ligands where g_em (Sm³⁺) > g_em (Eu³⁺).     

Oxidation of ultrafast radical clock substrate probes by the soluble methane monooxygenase from Methylococcus capsulatus (Bath)

Radical clock substrate probes were used to assess the viability of a discrete substrate radical species in the mechanism of hydrocarbon oxidation by the soluble methane monooxygenase (sMMO) from Methylococcus capsulatus (Bath). New substituted cyclopropane probes were used with very fast ring-opening rate constants and other desirable attributes, such as the ability to discriminate between radical and cationic intermediates. Oxidation of these substrates by a reconstituted sMMO system resulted in no rearranged products, allowing an upper limit of 150 fs to be placed on the lifetime of a putative radical species. This limit strongly suggests that there is no such substrate radical intermediate. The two enantiomers of trans-1-methyl-2-phenyl-cyclopropane were prepared, and the regioselectivity of their oxidation to the corresponding cyclopropylmethanol and cyclopropylphenol products was determined. The results are consistent with selective orientation of the two enantiomeric substrates in the hydrophobic cavity at the active site of sMMO, specific models for which were examined by molecular modeling.     

An EPR study of the dinuclear iron site in the soluble methane monooxygenase from Methylococcus capsulatus (Bath) reduced by one electron at 77 K: the effects of component interactions and the binding of small molecules to the diiron(III) center

Reduction of the soluble methane monooxygenase hydroxylase (MMOH) from Methylococcus capsulatus (Bath) in frozen 4:1 buffer/glycerol solutions at 77 K by mobile electrons generated by gamma-irradiation produces an EPR-detectable, mixed-valent Fe(II)Fe(III) center. At this temperature the conformation of the enzyme remains essentially unaltered during reduction, so the mixed-valent EPR spectra serve to probe the active site structure of the EPR-silent, diiron(III) state. The EPR spectra of the cryoreduced samples reveal that the diiron(III) cluster of the resting hydroxylase has at least two chemically distinct forms, the structures of which differ from that of the equilibrium Fe(II)Fe(III) site. Their relative populations depend on pH, the presence of component B, and formation of the MMOH/MMOB complex by reoxidation of the reduced, diiron(II) hydroxylase. The formation of complexes between MMOB, MMOR, and the oxidized hydroxylase does not measurably affect the structure of the diiron(III) site. Cryogenic reduction in combination with EPR spectroscopy has also provided information about interaction of MMOH in the diiron(III) state with small molecules. The diiron(III) center binds methanol and phenols, whereas DMSO and methane have no measurable effect on the EPR properties of cryoreduced hydroxylase. Addition of component B favors the binding of some exogenous ligands, such as DMSO and glycerol, to the active site diiron(III) state and markedly perturbs the structure of the diiron(III) cluster complexed with methanol or phenol. The results reveal different reactivity of the Fe(III)Fe(III) and Fe(II)Fe(III) redox states of MMOH toward exogenous ligands. Moreover, unlike oxidized hydroxylase, the binding of exogenous ligands to the protein in the mixed-valent state is allosterically inhibited by MMOB. The differential reactivity of the hydroxylase in its diiron(III) and mixed-valent states toward small molecules, as well as the structural basis for the regulatory effects of component B, is interpreted in terms of a model involving carboxylate shifts of a flexible glutamate ligand at the Fe(II)Fe(III) center.     

Imidazo[1,2-b]pyridazines: a potent and selective class of cyclin-dependent kinase inhibitors

Modification of imidazo[1,2-a]pyridine CDK inhibitors lead to identification of less lipophilic imidazo[1,2-b]pyridazine series of CDK inhibitors. Although several equivalent compounds from these two series have similar structure and show similar CDK activity, the SAR of the two series differs significantly. Protein inhibitor structure determination has confirmed differences in binding mode and given some understanding of these differences in SAR. Potent and selective imidazo[1,2-b]pyridazine inhibitors of CDK2 have been identified, which show >1 microM plasma levels following a 2mg/kg oral dose to mice.