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https://www.readbyqxmd.com/read/27780075/thermal-intensification-of-microbial-fe-ii-fe-iii-redox-cycling-in-a-pristine-shallow-sand-aquifer-on-the-canadian-shield
#1
V L Shirokova, A M L Enright, C B Kennedy, F G Ferris
This investigation evaluates spatial relationships between summer (July) groundwater temperatures and Fe(II)/Fe(III) biogeochemical cycling over a five year period in a shallow pristine sand aquifer at Meilleurs Bay near Deep River, Ontario, Canada. A warm subsurface thermal island of 12.5-16.1 °C, compared to background conditions of 10-11 °C, was manifest in contour maps of average groundwater temperature over the study period. The warm zone coincided with an area of convergent groundwater flow, implicating horizontal heat transfer by advective convection as the reason for elevated temperatures...
October 19, 2016: Water Research
https://www.readbyqxmd.com/read/26050709/density-functional-theory-insights-into-the-role-of-the-methionine-tyrosine-tryptophan-adduct-radical-in-the-katg-catalase-reaction-o2-release-from-the-oxyheme-intermediate
#2
Bonnie I Kruft, Richard S Magliozzo, Andrzej A Jarzęcki
Density functional theory was employed for a comprehensive study that provided electronic and structural insights into the KatG catalase reaction that involves oxyheme. The catalytic role of a unique amino acid cofactor Met-Tyr-Trp (MYW) in its radical form found in KatG was thereby elucidated. It was established that the MYW-radical is flexible such that a "hinge-like opening" rotation of the Trp-107 ring with respect to the Tyr-229 ring along their covalent C-C bond is an inherent feature of its catalytic properties...
July 2, 2015: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/25157192/slow-science-the-value-of-long-ocean-biogeochemistry-records
#3
Stephanie A Henson
Sustained observations (SOs) have provided invaluable information on the ocean's biology and biogeochemistry for over 50 years. They continue to play a vital role in elucidating the functioning of the marine ecosystem, particularly in the light of ongoing climate change. Repeated, consistent observations have provided the opportunity to resolve temporal and/or spatial variability in ocean biogeochemistry, which has driven exploration of the factors controlling biological parameters and processes. Here, I highlight some of the key breakthroughs in biological oceanography that have been enabled by SOs, which include areas such as trophic dynamics, understanding variability, improved biogeochemical models and the role of ocean biology in the global carbon cycle...
September 28, 2014: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/25043880/natural-product-synthesis-at-the-interface-of-chemistry-and-biology
#4
Jiyong Hong
Nature has evolved to produce unique and diverse natural products that possess high target affinity and specificity. Natural products have been the richest sources for novel modulators of biomolecular function. Since the chemical synthesis of urea by Wöhler, organic chemists have been intrigued by natural products, leading to the evolution of the field of natural product synthesis over the past two centuries. Natural product synthesis has enabled natural products to play an essential role in drug discovery and chemical biology...
August 11, 2014: Chemistry: a European Journal
https://www.readbyqxmd.com/read/24260025/long-noncoding-rnas-promote-transcriptional-poising-of-inducible-genes
#5
Sara C Cloutier, Siwen Wang, Wai Kit Ma, Christopher J Petell, Elizabeth J Tran
Long noncoding RNAs (lncRNAs) are a class of molecules that impinge on the expression of protein-coding genes. Previous studies have suggested that the GAL cluster-associated lncRNAs of Saccharomyces cerevisiae repress expression of the protein-coding GAL genes. Herein, we demonstrate a previously unrecognized role for the GAL lncRNAs in activating gene expression. In yeast strains lacking the RNA helicase, DBP2, or the RNA decay enzyme, XRN1, we find that the GAL lncRNAs specifically accelerate gene expression from a prior repressive state...
November 2013: PLoS Biology
https://www.readbyqxmd.com/read/23452258/lumped-pathway-metabolic-model-of-organic-carbon-accumulation-and-mobilization-by-the-alga-chlamydomonas-reinhardtii
#6
Jeremy S Guest, Mark C M van Loosdrecht, Steven J Skerlos, Nancy G Love
Phototrophic microorganisms have significant potential as bioenergy feedstocks, but the sustainability of large-scale cultivation will require the use of wastewater as a renewable resource. A key barrier to this advancement is a lack of bioprocess understanding that would enable the design and implementation of efficient and resilient mixed community, naturally lit cultivation systems. In this study, a lumped pathway metabolic model (denoted the phototrophic process model or PPM) was developed for mixed phototrophic communities subjected to day/night cycling...
April 2, 2013: Environmental Science & Technology
https://www.readbyqxmd.com/read/21466217/an-lc-ms-based-chemical-and-analytical-method-for-targeted-metabolite-quantification-in-the-model-cyanobacterium-synechococcus-sp-pcc-7002
#7
Nicholas B Bennette, John F Eng, G Charles Dismukes
Herein, we detail the development of a method for the chemical isolation and tandem LC-MS/MS quantification of a targeted subset of internal metabolites from cyanobacteria. We illustrate the selection of target compounds; requirements for and optimization of mass spectral detection channels, screening, and optimization of chromatography; and development of a sampling protocol that seeks to achieve complete, representative, and stable metabolite extraction on the seconds time scale. Several key factors influencing the separation by reversed-phase ion pairing chromatography, specifically the hydrophobicity of the sample matrix and sensitivity to mobile phase acidity, are identified and resolved...
May 15, 2011: Analytical Chemistry
https://www.readbyqxmd.com/read/21214177/efficient-bioelectronic-actuation-of-the-natural-catalytic-pathway-of-human-metabolic-cytochrome-p450s
#8
Sadagopan Krishnan, Dhanuka Wasalathanthri, Linlin Zhao, John B Schenkman, James F Rusling
Cytochrome (cyt) P450s comprise the enzyme superfamily responsible for human oxidative metabolism of a majority of drugs and xenobiotics. Electronic delivery of electrons to cyt P450s could be used to drive the natural catalytic cycle for fundamental investigations, stereo- and regioselective synthesis, and biosensors. We describe herein 30 nm nanometer-thick films on electrodes featuring excess human cyt P450s and cyt P450 reductase (CPR) microsomes that efficiently mimic the natural catalytic pathway for the first time...
February 9, 2011: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/20696933/scanning-ultrafast-electron-microscopy
#9
Ding-Shyue Yang, Omar F Mohammed, Ahmed H Zewail
Progress has been made in the development of four-dimensional ultrafast electron microscopy, which enables space-time imaging of structural dynamics in the condensed phase. In ultrafast electron microscopy, the electrons are accelerated, typically to 200 keV, and the microscope operates in the transmission mode. Here, we report the development of scanning ultrafast electron microscopy using a field-emission-source configuration. Scanning of pulses is made in the single-electron mode, for which the pulse contains at most one or a few electrons, thus achieving imaging without the space-charge effect between electrons, and still in ten(s) of seconds...
August 24, 2010: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/19214583/juggling-carbon-allocation-patterns-of-a-dominant-tree-in-a-fire-prone-savanna
#10
Alexander Ernest Noel Schutz, William J Bond, Michael D Cramer
In frequently burnt mesic savannas, trees can get trapped into a cycle of surviving fire-induced stem death (i.e. topkill) by resprouting, only to be topkilled again a year or two later. The ability of savanna saplings to resprout repeatedly after fire is a key component of recent models of tree-grass coexistence in savannas. This study investigated the carbon allocation and biomass partitioning patterns that enable a dominant savanna tree, Acacia karroo, to survive frequent and repeated topkill. Root starch depletion and replenishment, foliage recovery and photosynthesis of burnt and unburnt plants were compared over the first year after a burn...
May 2009: Oecologia
https://www.readbyqxmd.com/read/17180178/in-vitro-continuous-amperometric-monitoring-of-5-hydroxytryptamine-release-from-enterochromaffin-cells-of-the-guinea-pig-ileum
#11
Bhavik Anil Patel, Xiaochun Bian, Veronika Quaiserová-Mocko, James J Galligan, Greg M Swain
A diamond microelectrode was used to sensitively, reproducibly and stably record overflow of 5-hydroxytryptamine (5-HT, serotonin) from enterochromaffin cells (EC) of the intenstinal mucosal layer. 5-HT is an important neurotransmitter and paracrine signalling molecule in the gastrointestinal tract. The diamond microelectrode was formed by overcoating a sharpened 76 microm diameter Pt wire with a thin layer of conducting diamond. After insulation with polypropylene, the conically-shaped microelectrode had a diameter of about 10 microm at the tip and 80 microm at the cylindrical portion...
January 2007: Analyst
https://www.readbyqxmd.com/read/16943492/metabolite-uptake-stoichiometry-and-chemoautotrophic-function-of-the-hydrothermal-vent-tubeworm-riftia-pachyptila-responses-to-environmental-variations-in-substrate-concentrations-and-temperature
#12
Peter R Girguis, James J Childress
The hydrothermal vent tubeworm Riftia pachyptila is a dominant member of many hydrothermal vent communities along the East Pacific rise and is one of the fastest growing metazoans known. Riftia flourish in diffuse hydrothermal fluid flows, an environment with high spatial and temporal heterogeneity in physical and chemical conditions. To date, physiological and biochemical studies of Riftia have focused on Riftia's adaptations to its chemoautotrophic bacterial symbionts. However the relation between in situ physico-chemical heterogeneity and Riftia host and symbiont metabolism, in particular symbiont chemoautotrophic function, remain poorly understood...
September 2006: Journal of Experimental Biology
https://www.readbyqxmd.com/read/12033879/an-oxygen-cathode-operating-in-a-physiological-solution
#13
Nicolas Mano, Hyug-Han Kim, Yongchao Zhang, Adam Heller
We report the electroreduction of O(2) to water under physiological conditions (pH 7.4, 0.15 M NaCl, 37.5 degrees C) at a current density of 5 mA cm(-2) and at a potential only 0.18 V reducing versus that of the reversible O(2)/H(2)O electrode at pH 7.4. The immobilized electrocatalyst enabling the reduction is the electrostatic adduct of bilirubin oxidase from Myrothecium verrucaria, a polyanion at pH >4.1, and the polycationic redox copolymer of polyacrylamide and poly (N-vinylimidazole) complexed with [Os (4,4'-dichloro-2,2'-bipyridine)(2)Cl](+/2+), cross-linked on carbon cloth...
June 5, 2002: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/7782226/holmium-yag-surgical-lasers
#14
(no author information available yet)
"Holmium:YAG (Ho:YAG)" is the shorthand name for a family of solid-state lasers that use the doping element holmium in a laser crystal (e.g., YAG [yttrium-aluminum-garnet]) and that emit energy at approximately 2.1 microns. This wavelength is relatively new to medicine and has been used in laser surgery for only about the last six years. Like the carbon dioxide (CO2) laser when it was first used clinically, the Ho:YAG laser is poised for rapid and wide-spread use. Ho:YAG lasers, like CO2 lasers, offer precise cutting with minimal damage to adjacent tissue; however, unlike CO2 lasers, they also offer fiberoptic delivery (which is ideal for endoscopic use) and the ability to treat tissue in a liquid-filled environment (e...
March 1995: Health Devices
https://www.readbyqxmd.com/read/2104979/active-site-zinc-ligands-and-activated-h2o-of-zinc-enzymes
#15
COMPARATIVE STUDY
B L Vallee, D S Auld
The x-ray crystallographic structures of 12 zinc enzymes have been chosen as standards of reference to identify the ligands to the catalytic and structural zinc atoms of other members of their respective enzyme families. Universally, H2O is a ligand and critical component of the catalytically active zinc sites. In addition, three protein side chains bind to the catalytic zinc atom, whereas four protein ligands bind to the structural zinc atom. The geometry and coordination number of zinc can vary greatly to accommodate particular ligands...
January 1990: Proceedings of the National Academy of Sciences of the United States of America
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