Temperature and pH Effects on Biodegradation of Hexachlorocyclohexane Isomers in Water and a Soil Slurry

2002 ◽  
Vol 50 (18) ◽  
pp. 5070-5076 ◽  
Author(s):  
Tariq Siddique ◽  
Benedict C. Okeke ◽  
Muhammad Arshad ◽  
William T. Frankenberger
Keyword(s):  
Ph Effects ◽  
Soil Slurry ◽  
Hexachlorocyclohexane Isomers

Anaerobic degradation of hexachlorocyclohexane isomers in liquid and soil slurry systems

Chemosphere ◽  
2005 ◽  
Vol 61 (4) ◽  
pp. 528-536 ◽  
Author(s):  
Juan Carlos Quintero ◽  
Maria Teresa Moreira ◽  
Gumersindo Feijoo ◽  
Juan M. Lema
Keyword(s):  
Anaerobic Degradation ◽  
Soil Slurry ◽  
Hexachlorocyclohexane Isomers

Reductive Dechlorination of α-, β-, γ-, and δ-Hexachlorocyclohexane Isomers with Hydroxocobalamin, in Soil Slurry Systems

2010 ◽  
Vol 44 (18) ◽  
pp. 7063-7069 ◽  
Author(s):  
B. Rodríguez-Garrido ◽  
T. A. Lú-Chau ◽  
G. Feijoo ◽  
F. Macías ◽  
M.C. Monterrroso
Keyword(s):  
Reductive Dechlorination ◽  
Soil Slurry ◽  
Hexachlorocyclohexane Isomers

Rationalizing the pH-Activity Response for Escherichia Coli’s Glycinamide Ribonucleotidetransformylase Through Computational Methods

2019 ◽  
Author(s):  
Adrian Roitberg ◽  
Pancham Lal Gupta
Keyword(s):  
Transfer Reaction ◽  
Catalytic Mechanism ◽  
Ph Dependence ◽  
Ph Effects ◽  
Dependent Manner ◽  
E Coli ◽  
Gar Tfase ◽  
Activity Curve ◽  
Ph Dependent ◽  
Formyl Transfer

<div>Human Glycinamide ribonucleotide transformylase (GAR Tfase), a regulatory enzyme in the de novo purine biosynthesis pathway, has been established as an anti-cancer target. GAR Tfase catalyzes the formyl transfer reaction from the folate cofactor to the GAR ligand. In the present work, we study E. coli GAR Tfase, which has high sequence similarity with the human GAR Tfase with most functional residues conserved. E. coli GAR Tfase exhibits structural changes and the binding of ligands that varies with pH which leads to change the rate of the formyl transfer reaction in a pH-dependent manner. Thus, the inclusion of pH becomes essential for the study of its catalytic mechanism. Experimentally, the pH-dependence of the kinetic parameter kcat is measured to evaluate the pH-range of enzymatic activity. However, insufficient information about residues governing the pH-effects on the catalytic activity leads to ambiguous assignments of the general acid and base catalysts and consequently its catalytic mechanism. In the present work, we use pH-replica exchange molecular dynamics (pH-REMD) simulations to study the effects of pH on E. coli GAR Tfase enzyme. We identify the titratable residues governing the pH-dependent conformational changes in the system. Furthermore, we filter out the protonation states which are essential in maintaining the structural integrity, keeping the ligands bound and assisting the catalysis. We reproduce the experimental pH-activity curve by computing the population of key protonation states. Moreover, we provide a detailed description of residues governing the acidic and basic limbs of the pH-activity curve.</div>

Organochlorine Contaminants in Headwater Peatlands, and Selected Estuary Sites of the Moose River

1986 ◽  
Vol 21 (2) ◽  
pp. 251-256 ◽  
Author(s):  
Robert C. McCrea ◽  
Greg M. Wickware
Keyword(s):  
Atmospheric Deposition ◽  
Organochlorine Pesticides ◽  
River Basin ◽  
Vascular Plants ◽  
Typha Latifolia ◽  
Coastal Marshes ◽  
Surficial Sediments ◽  
Organochlorine Contaminants ◽  
Hexachlorocyclohexane Isomers ◽  
Moose River

Abstract Peatland waters of the Moose River basin, as well as surficial sediments and vascular plants of the estuary were sampled in 1982. Elevated levels of PCBs were found at all five peatland sites; concentrations ranged from 28 to 65 ng/L. Of the seventeen organochlorine pesticides investigated, the hexachlorocyclohexane isomers (a-and y-BHC) were the most prominent with total BHC concentrations ranging from 1.5 to 13.7 ng/L. The presence of these contaminants in ombrotrophic bogs indicated that there was atmospheric deposition of organochlorine contaminants in the basin. Analyses of surficial sediments, collected from tidal flats and coastal marshes, showed that PCBs and organochlorine pesticides were not present. Samples of Triglochin maritima L. seed heads and Typha latifolia L. roots were also free of PCBs.

Surfactant concentration and pH effects on the zeta potential values of alumina nanofluids to inspect stability

2019 ◽  
Vol 583 ◽  
pp. 123960 ◽  
Author(s):  
Karen Cacua ◽  
Fredy Ordoñez ◽  
Camilo Zapata ◽  
Bernardo Herrera ◽  
Elizabeth Pabón ◽  
...  
Keyword(s):  
Zeta Potential ◽  
Surfactant Concentration ◽  
Ph Effects

scholarly journals Chitosan Adsorbent Derivatives for Pharmaceuticals Removal from Effluents: A Review

Macromol ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 130-154
Author(s):  
Efstathios V. Liakos ◽  
Maria Lazaridou ◽  
Georgia Michailidou ◽  
Ioanna Koumentakou ◽  
Dimitra A. Lambropoulou ◽  
...  
Keyword(s):  
Emerging Contaminants ◽  
Low Cost ◽  
Value Added ◽  
Ph Effects ◽  
Hydroxyl Groups ◽  
Research Papers ◽  
Natural Polysaccharide ◽  
Best Fitting ◽  
Isotherm And Kinetic Models ◽  
Published Research

Chitin is mentioned as the second most abundant and important natural biopolymer in worldwide scale. The main sources for the extraction and exploitation of this natural polysaccharide polymer are crabs and shrimps. Chitosan (poly-β-(1 → 4)-2-amino-2-deoxy-d-glucose) is the most important derivative of chitin and can be used in a wide variety of applications including cosmetics, pharmaceutical and biomedical applications, food, etc., giving this substance high value-added applications. Moreover, chitosan has applications in adsorption because it contains amino and hydroxyl groups in its molecules, and can thus contribute to many possible adsorption interactions between chitosan and pollutants (pharmaceuticals/drugs, metals, phenols, pesticides, etc.). However, it must be noted that one of the most important techniques of decontamination is considered to be adsorption because it is simple, low-cost, and fast. This review emphasizes on recently published research papers (2013–2021) and briefly describes the chemical modifications of chitosan (grafting, cross-linking, etc.), for the adsorption of a variety of emerging contaminants from aqueous solutions, and characterization results. Finally, tables are depicted from selected chitosan synthetic routes and the pH effects are discussed, along with the best-fitting isotherm and kinetic models.

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