Role of positive charge in the competitive effect of phosphate on sulfate sorption by an allophanic soil

Soil Research ◽  
1988 ◽  
Vol 26 (1) ◽  
pp. 171 ◽  
Author(s):  
KB Marsh ◽  
JK Syers ◽  
RW Tillman
Keyword(s):  
Soil Ph ◽  
Positive Charge ◽  
High Surface ◽  
Competitive Effect ◽  
High Ph ◽  
Ph Range ◽  
Allophanic Soil ◽  
Reduced Surface

The effect of phosphate (P) on the sorption of sulfate (S) by an allophanic soil with high surface positive charge was investigated in the pH range of 5.3-7.0 obtained by incubation with Ca(OH)2. The effect of P on S sorption was directly related to the effect of P on surface positive charge. At low soil pH, P reduced surface positive charge to a larger extent than at high pH and this was associated with a larger effect of P on S sorption.

Role of the Staphylococcus aureus Extracellular Loop of GraS in Resistance to Distinct Human Defense Peptides in PMN and Invasive Cardiovascular infections

2021 ◽  
Author(s):  
Ambrose L. Cheung ◽  
Junho Cho ◽  
Arnold S. Bayer ◽  
Michael R. Yeaman ◽  
Yan Q. Xiong ◽  
...  
Keyword(s):  
Positive Charge ◽  
Polymyxin B ◽  
Electrostatic Charge ◽  
Cationic Peptides ◽  
Extracellular Loop ◽  
Ph Dependent ◽  
Defense Peptides ◽  
Hospital Acquired ◽  
Reduced Surface

GraS is a membrane sensor in S. aureus that induces mprF and dltABCD expression to alter the surface positive charge upon exposure to cationic human defense peptides (HDPs). The sensing domain of GraS likely resides in the 9-residue extracellular loop (EL). In this study, we assessed a hospital-acquired (HA)-MRSA strain (COL) for the specific role of two distinct EL mutations: F38G (bulk) and D/35/37/41K (charged inversion). Activation of mprF by polymyxin B (PMB) was reduced in the D35/37/41K mutant vs the D35/37/41G mutant, correlating with reduced surface positive charge; in contrast, these effects were less prominent in the F38G mutant, although still lower than the parent. These data indicated that both electrostatic charge and steric bulk of the EL of GraS influence induction of genes impacting HDP resistance. Using mprF expression as a readout, we confirmed GraS signaling was pH-dependent, increasing as pH was lowered (pH 7.5 ≫ 5.5). In contrast to PMB activation, reduction of mprF was comparable at pH 5.5 between the P38G and D35/37/41K point mutants, indicating a likely mechanistic divergence between GraS activation by acidic pH vs. cationic peptides. Survival assays in human blood and purified PMNs revealed lower survival of the D35/37/41K mutant vs. the F38G mutant, with both lower than the parent. Virulence studies in the rabbit endocarditis model mirrored whole blood and PMN killing assay data above. Collectively, these data confirmed the importance of specific residues within the EL of GraS in conferring essential bacterial responses for MRSA survival in infections.

scholarly journals The Staphylococcus aureus Two-Component Regulatory System, GraRS, Senses and Confers Resistance to Selected Cationic Antimicrobial Peptides

2011 ◽  
Vol 80 (1) ◽  
pp. 74-81 ◽  
Author(s):  
Soo-Jin Yang ◽  
Arnold S. Bayer ◽  
Nagendra N. Mishra ◽  
Michael Meehl ◽  
Nagender Ledala ◽  
...  
Keyword(s):  
Antimicrobial Peptides ◽  
Positive Charge ◽  
Efflux Pump ◽  
Regulatory System ◽  
Polymyxin B ◽  
Cationic Antimicrobial Peptides ◽  
Two Component ◽  
Mrsa Strains ◽  
Reduced Surface

ABSTRACTThe two-component regulatory system, GraRS, appears to be involved in staphylococcal responses to cationic antimicrobial peptides (CAPs). However, the mechanism(s) by which GraRS is induced, regulated, and modulated remain undefined. In this study, we used two well-characterized MRSA strains (Mu50 and COL) and their respective mutants ofgraRandvraG(encoding the ABC transporter-dependent efflux pump immediately downstream ofgraRS), and show that (i) the expression of two key determinants of net positive surface charge (mprFanddlt) is dependent on the cotranscription of bothgraRandvraG, (ii) reduced expression ofmprFanddltingraRmutants was phenotypically associated with reduced surface-positive charge, (iii) this net reduction in surface-positive charge ingraRandvraGmutants, in turn, correlated with enhanced killing by a range of CAPs of diverse structure and origin, including those from mammalian platelets (tPMPs) and neutrophils (hNP-1) and from bacteria (polymyxin B), and (iv) the synthesis and translocation of membrane lysyl-phosphatidylglycerol (anmprF-dependent function) was substantially lower ingraRandvraGmutants than in parental strains. Importantly, the inducibility ofmprFanddlttranscription via thegraRS-vraFGpathway was selective, with induction by sublethal exposure to the CAPs, RP-1 (platelets), and polymyxin B, but not by other cationic molecules (hNP-1, vancomycin, gentamicin, or calcium-daptomycin). AlthoughgraRregulates expression ofvraG, the expression ofgraRwas codependent on an intact downstreamvraGlocus. Collectively, these data support an important role of thegraRSandvraFGloci in the sensing of and response to specific CAPs involved in innate host defenses.

The orientation of sickle hemoglobin fibers within fascicles

1988 ◽  
Vol 46 ◽  
pp. 400-401
Author(s):  
Christopher A. Miller ◽  
Bridget Carragher ◽  
William A. McDade ◽  
Robert Josephs
Keyword(s):  
Sickle Cell ◽  
Sickle Cell Anemia ◽  
Relative Orientation ◽  
Unit Cell ◽  
Red Cell ◽  
High Ph ◽  
Sickle Hemoglobin ◽  
Polar Crystal ◽  
Helical Configuration

Highly ordered bundles of deoxyhemoglobin S (HbS) fibers, termed fascicles, are intermediates in the high pH crystallization pathway of HbS. These fibers consist of 7 Wishner-Love double strands in a helical configuration. Since each double strand has a polarity, the odd number of double strands in the fiber imparts a net polarity to the structure. HbS crystals have a unit cell containing two double strands, one of each polarity, resulting in a net polarity of zero. Therefore a rearrangement of the double strands must occur to form a non-polar crystal from the polar fibers. To determine the role of fascicles as an intermediate in the crystallization pathway it is important to understand the relative orientation of fibers within fascicles. Furthermore, an understanding of fascicle structure may have implications for the design of potential sickling inhibitors, since it is bundles of fibers which cause the red cell distortion responsible for the vaso-occlusive complications characteristic of sickle cell anemia.

scholarly journals The Role of the Disulfide Bridge in the Copper (II) Binding by the Cyclic His4-Peptide

2021 ◽  
Vol 22 (12) ◽  
pp. 6458
Author(s):  
Aleksandra Pieniężna ◽  
Weronika Witak ◽  
Aneta Szymańska ◽  
Justyna Brasuń
Keyword(s):  
Metal Ions ◽  
Coordination Mode ◽  
Transition Metal Ions ◽  
Disulfide Bridge ◽  
Chain Flexibility ◽  
Vis Spectroscopy ◽  
Ph Range ◽  
Cd Studies ◽  
Metal Ratios

In this paper, we present studies on the influence of the disulfide bridge on the copper (II) ions’ binding abilities by the cyclic His4-peptide. The studied ligand HKHPHRHC-S-S-C consists of nine amino acids. The cyclic structure was obtained through a disulfide bridge between two cysteinyl groups. Moreover, this peptide is characterized by the presence of four His residues in the sequence, which makes it an interesting ligand for transition metal ions. The potentiometric and spectroscopic (UV-Vis spectroscopy and circular dichroism spectroscopy (CD)) studies were carried out in various molar ligand to metal ratios: 2:1, 1:1, and 1:2, in the pH range of 2.5–11 at 25 °C. The results showed that the cyclic His4-peptide promotes dinuclear complexes in each of these systems and forms the final dinuclear species with the {NIm, 3N-amide}{NIm, 3N-amide} coordination mode. The obtained data shows that cyclization by the formation of the disulfide bond has an impact on the peptide chain flexibility and appearance of additional potential donors for metal ions and influences the copper (II) ions’ coordination.

scholarly journals The Unusual Role of Pro in Cu(II) Binding by His2-Cyclopentapeptide

2021 ◽  
Vol 22 (12) ◽  
pp. 6628
Author(s):  
Aleksandra Pieniężna ◽  
Aleksandra Kotynia ◽  
Justyna Brasuń
Keyword(s):  
Amino Acid ◽  
Potentiometric Titration ◽  
Amino Acid Residue ◽  
Strong Impact ◽  
Mononuclear Complexes ◽  
Study Results ◽  
Metal Ratio ◽  
Ph Range ◽  
L1 And L2

In this paper, we present findings from studying the interaction of copper(II) ions with the His2-cyclopentapeptide and the role of proline used for the purpose of potentiometric titration and UV-Vis, CD and EPR spectroscopic measurements. Experiments of two homodetic peptides differing by one amino acid residue were conducted for a ligand to metal ratio of 1:1 in the pH range 2.5–11.0. The presented studies reveal that peptides form only mononuclear complexes, and the CuH2L complex appears in the system first (for both L1 and L2). Study results show that the presence of Pro influences the structure of formed complexes and their stabilities and has a strong impact on the efficiency of copper(II) coordination.

scholarly journals Distribution and function of carbamate hydrolase genes cehA and mcd in soils: the distinct role of soil pH

2018 ◽  
Vol 94 (6) ◽  
Author(s):  
Constantina Rousidou ◽  
Dionysis Karaiskos ◽  
Despoina Myti ◽  
Evangelos Karanasios ◽  
Panagiotis A Karas ◽  
...  
Keyword(s):  
Soil Ph ◽  
And Function ◽  
Distinct Role

scholarly journals Single and Dual Metal Oxides as Promising Supports for Carbon Monoxide Removal from an Actual Syngas: The Crucial Role of Support on the Selectivity of the Au–Cu System

Catalysts ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 852 ◽  
Author(s):  
Bernay Cifuentes ◽  
Felipe Bustamante ◽  
Martha Cobo
Keyword(s):  
Metal Oxides ◽  
High Surface ◽  
High Surface Area ◽  
Carbon Deposits ◽  
Promising Strategy ◽  
Cu Catalysts ◽  
Dual Metal ◽  
Effect Of The Support ◽  
Lower Capacity

A catalytic screening was performed to determine the effect of the support on the performance of an Au–Cu based system for the removal of CO from an actual syngas. First, a syngas was obtained from reforming of ethanol. Then, the reformer outlet was connected to a second reactor, where Au–Cu catalysts supported on several single and dual metal oxides (i.e., CeO2, SiO2, ZrO2, Al2O3, La2O3, Fe2O3, CeO2-SiO2, CeO2-ZrO2, and CeO2-Al2O3) were evaluated. AuCu/CeO2 was the most active catalyst due to an elevated oxygen mobility over the surface, promoting CO2 formation from adsorption of C–O* and OH− intermediates on Au0 and CuO species. However, its lower capacity to release the surface oxygen contributes to the generation of stable carbon deposits, which lead to its rapid deactivation. On the other hand, AuCu/CeO2-SiO2 was more stable due to its high surface area and lower formation of formate and carbonate intermediates, mitigating carbon deposits. Therefore, use of dual supports could be a promising strategy to overcome the low stability of AuCu/CeO2. The results of this research are a contribution to integrated production and purification of H2 in a compact system.

scholarly journals Springtime high surface ozone events over the western United States: Quantifying the role of stratospheric intrusions

2012 ◽  
Vol 117 (D21) ◽  
pp. n/a-n/a ◽  
Author(s):  
Meiyun Lin ◽  
Arlene M. Fiore ◽  
Owen R. Cooper ◽  
Larry W. Horowitz ◽  
Andrew O. Langford ◽  
...  
Keyword(s):  
United States ◽  
Surface Ozone ◽  
High Surface ◽  
Western United States ◽  
Stratospheric Intrusions

The role of calcium in high pH excursions for reactivated GAC

Carbon ◽  
2005 ◽  
Vol 43 (3) ◽  
pp. 511-518 ◽  
Author(s):  
David W. Mazyck ◽  
Fred S. Cannon ◽  
Morgana T. Bach ◽  
Ljubisa R. Radovic
Keyword(s):  
High Ph

Biological weathering in soil: the role of symbiotic root-associated fungi biosensing minerals and directing photosynthate-energy into grain-scale mineral weathering

2008 ◽  
Vol 72 (1) ◽  
pp. 85-89 ◽  
Author(s):  
J. R. Leake ◽  
A. L. Duran ◽  
K. E. Hardy ◽  
I. Johnson ◽  
D. J. Beerling ◽  
...  
Keyword(s):  
Carbon Allocation ◽  
High Surface ◽  
Turgor Pressure ◽  
High Surface Area ◽  
Volume Ratio ◽  
Mineral Weathering ◽  
Mycorrhizal Associations ◽  
P Content ◽  
Biological Weathering

AbstractBiological weathering is a function of biotic energy expenditure. Growth and metabolism of organisms generates acids and chelators, selectively absorbs nutrient ions, and applies turgor pressure and other physical forces which, in concert, chemically and physically alter minerals. In unsaturated soil environments, plant roots normally form symbiotic mycorrhizal associations with fungi. The plants provide photosynthate-carbohydrate-energy to the fungi in return for nutrients absorbed from the soil and released from minerals. In ectomycorrhiza, one of the two major types of mycorrhiza of trees, roots are sheathed in fungus, and 15—30% of the net photosynthate of the plants passes through these fungi into the soil and virtually all of the water and nutrients taken up by the plants are supplied through the fungi. Here we show that ectomycorrhizal fungi actively forage for minerals and act as biosensors that discriminate between different grain sizes (53—90 μm, 500—1000 μm) and different minerals (apatite, biotite, quartz) to favour grains with a high surface-area to volume ratio and minerals with the highest P content. Growth and carbon allocation of the fungi is preferentially directed to intensively interact with these selected minerals to maximize resource foraging.

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