377 research outputs found
Michigan Oil and Gas Update
The Michigan Department of Environment, Great Lakes, and Energy (âEGLEâ), formerly the Michigan Department of Environmental Quality, is in the process of seeking primary enforcement responsibility from the United States Environmental Protection Agency (âEPAâ) for its Underground Injection Control (âUICâ) program for Class II wells pursuant to Part C of the Safe Drinking Water Act (âSDWAâ)
Michigan Oil and Gas Update
On March 23, 2020, the Michigan Court of Claims issued its opinion in Mannes v. Michigan Depât of Treasury. This case considered the meaning of the phrase âexpenses of producing oil and gasâ as such expenses relate to âtaxable incomeâ under the Michigan Income Tax Act of 1967
Structural Insights into DNA Polymerase β Deterrents for Misincorporation Support an Induced-Fit Mechanism for Fidelity
AbstractDNA polymerases generally select the correct nucleotide from a pool of structurally similar molecules to preserve Watson-Crick base-pairing rules. We report the structure of DNA polymerase β with DNA mismatches situated in the polymerase active site. This was achieved by using nicked product DNA that traps the mispair (template-primer, A-C or T-C) in the nascent base pair binding pocket. The structure of each mispair complex indicates that the bases do not form hydrogen bonds with one another, but form a staggered arrangement where the bases of the mispair partially overlap. This prevents closure/opening of the N subdomain that is believed to be required for catalytic cycling. The partially open conformation of the N subdomain results in distinct hydrogen bonding networks that are unique for each mispair. These structures define diverse molecular aspects of misinsertion that are consistent with the induced-fit model for substrate specificity
Provenance and Paleogeography of the 25-17 Ma Rainbow Gardens Formation: Evidence for Tectonic Activity at Ca. 19 Ma and Internal Drainage rather than Throughgoing Paleorivers on the Southwestern Colorado Plateau
The paleogeographic evolution of the Lake Mead region of southern Nevada and northwest Arizona is crucial to understanding the geologic history of the U.S. Southwest, including the evolution of the Colorado Plateau and formation of the Grand Canyon. The ca. 25â17 Ma Rainbow Gardens Formation in the Lake Mead region, the informally named, roughly coeval Jean Conglomerate, and the ca. 24â19 Ma Buck and Doe Conglomerate southeast of Lake Mead hold the only stratigraphic evidence for the Cenozoic pre-extensional geology and paleogeography of this area. Building on prior work, we present new sedimentologic and stratigraphic data, including sandstone provenance and detrital zircon data, to create a more detailed paleogeographic picture of the Lake Mead, Grand Wash Trough, and Hualapai Plateau region from 25 to 18 Ma. These data confirm that sediment was sourced primarily from Paleozoic strata exposed in surrounding Sevier and Laramide uplifts and active volcanic fields to the north. In addition, a distinctive signal of coarse sediment derived from Proterozoic crystalline basement first appeared in the southwestern corner of the basin ca. 25 Ma at the beginning of Rainbow Gardens Formation deposition and then prograded north and east ca. 19 Ma across the southern half of the basin. Regional thermochronologic data suggest that Cretaceous deposits likely blanketed the Lake Mead region by the end of Sevier thrusting. Post-Laramide northward cliff retreat off the Kingman/Mogollon uplifts left a stepped erosion surface with progressively younger strata preserved northward, on which Rainbow Gardens Formation strata were deposited. Deposition of the Rainbow Gardens Formation in general and the 19 Ma progradational pulse in particular may reflect tectonic uplift events just prior to onset of rapid extension at 17 Ma, as supported by both thermochronology and sedimentary data. Data presented here negate the California and Arizona River hypotheses for an âoldâ Grand Canyon and also negate models wherein the Rainbow Gardens Formation was the depocenter for a 25â18 Ma Little Colorado paleoriver flowing west through East Kaibab paleocanyons. Instead, provenance and paleocurrent data suggest local to regional sources for deposition of the Rainbow Gardens Formation atop a stripped low-relief western Colorado Plateau surface and preclude any significant input from a regional throughgoing paleoriver entering the basin from the east or northeast
Revealing the role of the product metal in DNA polymerase β catalysis
DNA polymerases catalyze a metal-dependent nucleotidyl transferase reaction during extension of a DNA strand using the complementary strand as a template. The reaction has long been considered to require two magnesium ions. Recently, a third active site magnesium ion was identified in some DNA polymerase product crystallographic structures, but its role is not known. Using quantum mechanical/ molecular mechanical calculations of polymerase β, we find that a third magnesium ion positioned near the newly identified product metal site does not alter the activation barrier for the chemical reaction indicating that it does not have a role in the forward reaction. This is consistent with time-lapse crystallographic structures following insertion of Sp-dCTPιS. Although sulfur substitution deters product metal binding, this has only a minimal effect on the rate of the forward reaction. Surprisingly, monovalent sodium or ammonium ions, positioned in the product metal site, lowered the activation barrier. These calculations highlight the impact that an active site water network can have on the energetics of the forward reaction and how metals or enzyme side chains may interact with the network to modulate the reaction barrier. These results also are discussed in the context of earlier findings indicating that magnesium at the product metal position blocks the reverse pyrophosphorolysis reaction
Insights into the Conformation of Aminofluorene-Deoxyguanine Adduct in a DNA Polymerase Active Site
The active site conformation of the mutagenic fluoroaminofluorene-deoxyguanine adduct (dG-FAF, N-(2â˛-deoxyguanosin-8-yl)-7-fluoro-2-aminofluorene) has been investigated in the presence of Klenow fragment of Escherichia coli DNA polymerase I (Kfexoâ) and DNA polymerase β (pol β) using 19F NMR, insertion assay, and surface plasmon resonance. In a single nucleotide gap, the dG-FAF adduct adopts both a major-groove- oriented and base-displaced stacked conformation, and this heterogeneity is retained upon binding pol β. The addition of a non-hydrolysable 2â˛-deoxycytosine-5â˛-[(Îą,β)-methyleno]triphosphate (dCMPcPP) nucleotide analog to the binary complex results in an increase of the major groove conformation of the adduct at the expense of the stacked conformation. Similar results were obtained with the addition of an incorrect dAMPcPP analog but with formation of the minor groove binding conformer. In contrast, dG-FAF adduct at the replication fork for the Kfexoâ complex adopts a mix of the major and minor groove conformers with minimal effect upon the addition of non-hydrolysable nucleotides. For pol β, the insertion of dCTP was preferred opposite the dG-FAF adduct in a single nucleotide gap assay consistent with 19F NMR data. Surface plasmon resonance binding kinetics revealed that pol β binds tightly with DNA in the presence of correct dCTP, but the adduct weakens binding with no nucleotide specificity. These results provide molecular insights into the DNA binding characteristics of FAF in the active site of DNA polymerases and the role of DNA structure and sequence on its coding potential
Structural Comparison of DNA Polymerase Architecture Suggests a Nucleotide Gateway to the Polymerase Active Site
Herbivores at the Highest Risk of Extinction Among Mammals, Birds, and Reptiles
As a result of their extensive home ranges and slow population growth rates, predators have often been perceived to suffer higher risks of extinction than other trophic groups. Our study challenges this extinction-risk paradigm by quantitatively comparing patterns of extinction risk across different trophic groups of mammals, birds, and reptiles. We found that trophic level and body size were significant factors that influenced extinction risk in all taxa. At multiple spatial and temporal scales, herbivores, especially herbivorous reptiles and large-bodied herbivores, consistently have the highest proportions of threatened species. This observed elevated extinction risk for herbivores is ecologically consequential, given the important roles that herbivores are known to play in controlling ecosystem function
Mismatch-Induced Conformational Distortions in Polymerase β Support an Induced-Fit Mechanism for Fidelity â
The Vehicle, 1966, Vol. 8
Vol. 8
Table of Contents
CommentaryBill Moser & Avis Eaglestonpage 3
The Vengeance of the DeadStephen W. Gibbspage 5
Ode To A MeadowKathleen McCormackpage 12
Row OnDavid Helmpage 13
Sonnet 63R.L. Hudsonpage 14
UntitledKathleen McCormackpage 14
The Pure GoldDavid Helmpage 15
CommunionDavid Helmpage 15
PreludeMichael Baldwinpage 15
The AlbatrossKaren Cooleypage 16
The Albatross (photo)DeWittpage 17
Ruff and the VaseDavid Helmpage 18
LaBelleKathleen McCormackpage 19
Not Quite SoR.L. Hudsonpage 20
Feeling (no number)David Reifpage 21
Song at DuskDavid Helmpage 21
Arcadia RuminationsR.L. Hudsonpage 22
The BarWayne Johnsonpage 25
HelloWilliam Framepage 26
The ProcessJerry DeWittpage 27
The KillingAdrian Beardpage 30
The Amusement Park GameStephen W. Gibbspage 38
DamnMel Tylerpage 40
PainWilliam Framepage 40
UntitledSusan Champlinpage 41
Portrait of A Scholar As A Young ManStephen W. Gibbspage 42
The TimesW.D.Mpage 46
ParadoxW.D.M.page 46
MankindDavid Helmpage 47https://thekeep.eiu.edu/vehicle/1014/thumbnail.jp
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