pH-control of the protein resistance of thin hydrogel gradient films

Interactions between phospholipid membranes and selected drugs affecting the central nervous system (CNS) were investigated. Small, unilamellar liposomes were used as biomimetic cell membrane models. Microelectrophoretic experiments on two-component liposomes were performed using the electrophoretic light scattering technique (ELS). The effect of both positively (perphenazine, PF) and negatively (barbituric acid, BA) charged drugs on zwitterionic L-α-phosphatidylcholine (PC) membranes were analyzed. Experimental membrane surface charge density (d) data were determined as a function of pH. Quantitative descriptions of the adsorption equilibria formed due to the binding of solution ions to analyzed two-component membranes are presented. Binding constants of the solution ions with perphenazine and barbituric acid-modified membranes were determined. The results of our research show that both charged drugs change surface charge density values of phosphatidylcholine membranes. It can be concluded that perphenazine and barbituric acid are located near the membrane surface, interacting electrostatically with phosphatidylcholine polar heads.

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Effects of Surface Oxidation on the pH-dependent Surface Charge of oxidized Aluminum Gallium Nitride

Journal of Colloid and Interface Science ◽

10.1016/j.jcis.2021.06.126 ◽

2021 ◽

Author(s):

Jianan Wang ◽

Hua Li ◽

Haoran Li ◽

Stacia Kellern ◽

Umesh K. Mishra ◽

...

Keyword(s):

Gallium Nitride ◽

Surface Charge ◽

Aluminum Gallium Nitride ◽

Surface Oxidation ◽

Ph Dependent

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Tumor-acidity activated surface charge conversion of two-photon fluorescent nanoprobe for enhanced cellular uptake and targeted imaging of intracellular hydrogen peroxide

Chemical Science ◽

10.1039/c9sc03781k ◽

2019 ◽

Vol 10 (40) ◽

pp. 9351-9357 ◽

Cited By ~ 6

Author(s):

Lanlan Chen ◽

Shuai Xu ◽

Wei Li ◽

Tianbing Ren ◽

Lin Yuan ◽

...

Keyword(s):

Hydrogen Peroxide ◽

Surface Charge ◽

Cellular Uptake ◽

Targeted Imaging ◽

Two Photon ◽

Fluorescent Nanoprobe ◽

Tumor Acidity ◽

Ph Dependent ◽

Intracellular Hydrogen Peroxide ◽

Activated Surface

A smart, two-photon fluorescent GC–NABP nanoprobe with pH-dependent surface charge conversion was developed for tumor-targeted visualization of H2O2.

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Evolution of Daptomycin Resistance in Coagulase-Negative Staphylococci Involves Mutations of the Essential Two-Component Regulator WalKR

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01926-18 ◽

2019 ◽

Vol 63 (3) ◽

Cited By ~ 7

Author(s):

Jhih-Hang Jiang ◽

Carina Dexter ◽

David R. Cameron ◽

Ian R. Monk ◽

Sarah L. Baines ◽

...

Keyword(s):

Antimicrobial Resistance ◽

Cell Surface ◽

Surface Charge ◽

Sequencing Analysis ◽

Care Hospital ◽

Coagulase Negative Staphylococci ◽

Content Type ◽

Staphylococcus Capitis ◽

Cell Surface Charge ◽

Two Component

ABSTRACTCoagulase-negative staphylococci (CoNS) represent one of the major causes of health care- and medical device-associated infections. Emerging antimicrobial resistance has complicated the treatment of systemic infections caused by CoNS. Here, we describe the prevalence of antimicrobial resistance in clinical CoNS strains from a tertiary care hospital over a 4-year period, and we observed a significant increase in resistance to daptomycin. Notably,Staphylococcus capitisaccounted for the majority of these daptomycin-resistant (DAP-R) CoNS. To further investigate the mechanisms of daptomycin resistance in CoNS, daptomycin-susceptible clinical strains ofS. capitisandStaphylococcus epidermidisunderwentin vitrodaptomycin exposure to generate DAP-R CoNS mutants. Unlike that seen withStaphylococcus aureus, alteration of cell surface charge was not observed in the DAP-R CoNS strains, but biofilm formation was compromised. Whole-genome sequencing analysis of the DAP-R CoNS strains identified single nucleotide polymorphisms (SNPs) inwalKR, the essential two-component regulatory system controlling cell wall biogenesis. PCR and sequencing ofwalKandwalRfrom 17 DAP-R CoNS clinical isolates identified seven nonsynonymous mutations. The results were confirmed by the recreation of thewalKSNP inS. epidermidis, which resulted in reduced susceptibility to daptomycin and vancomycin. This study highlights the significance of CoNS in evolving daptomycin resistance and showed thatwalKRis shared among the staphylococcal species and is involved in antibiotic resistance development. Notably, we did not observe mutations in genes responsible for phospholipid biosynthesis or an altered cell surface charge, suggesting that reduced daptomycin susceptibility in CoNS may emerge in a fashion distinct from that inS. aureus.

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The HP0165-HP0166 Two-Component System (ArsRS) Regulates Acid-Induced Expression of HP1186 α-Carbonic Anhydrase in Helicobacter pylori by Activating the pH-Dependent Promoter

Journal of Bacteriology ◽

10.1128/jb.01492-06 ◽

2007 ◽

Vol 189 (6) ◽

pp. 2426-2434 ◽

Cited By ~ 35

Author(s):

Yi Wen ◽

Jing Feng ◽

David R. Scott ◽

Elizabeth A. Marcus ◽

George Sachs

Keyword(s):

Carbonic Anhydrase ◽

Promoter Region ◽

Low Ph ◽

Start Codon ◽

Two Component System ◽

Component System ◽

Two Component ◽

Ph Dependent ◽

H Pylori

ABSTRACT The periplasmic α-carbonic anhydrase of Helicobacter pylori is essential for buffering the periplasm at acidic pH. This enzyme is an integral component of the acid acclimation response that allows this neutralophile to colonize the stomach. Transcription of the HP1186 α-carbonic anhydrase gene is upregulated in response to low environmental pH. A binding site for the HP0166 response regulator (ArsR) has been identified in the promoter region of the HP1186 gene. To investigate the mechanism that regulates the expression of HP1186 in response to low pH and the role of the HP0165-HP0166 two-component system (ArsRS) in this acid-inducible regulation, Northern blot analysis was performed with RNAs isolated from two different wild-type H. pylori strains (26695 and 43504) and mutants with HP0165 histidine kinase (ArsS) deletions, after exposure to either neutral pH or low pH (pH 4.5). ArsS-dependent upregulation of HP1186 α-carbonic anhydrase in response to low pH was found in both strains. Western blot analysis of H. pylori membrane proteins confirmed the regulatory role of ArsS in HP1186 expression in response to low pH. Analysis of the HP1186 promoter region revealed two possible transcription start points (TSP1 and TSP2) located 43 and 11 bp 5′ of the ATG start codon, respectively, suggesting that there are two promoters transcribing the HP1186 gene. Quantitative primer extension analysis showed that the promoter from TSP1 (43 bp 5′ of the ATG start codon) is a pH-dependent promoter and is regulated by ArsRS in combating environmental acidity, whereas the promoter from TSP2 may be responsible for control of the basal transcription of HP1186 α-carbonic anhydrase.

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Soil Chemistry

Tropical Soils ◽

10.1093/oso/9780195115987.003.0006 ◽

2003 ◽

Author(s):

Anthony S. R. Juo ◽

Kathrin Franzluebbers

Keyword(s):

Surface Charge ◽

Functional Groups ◽

Soil Chemistry ◽

Chemical Properties ◽

Hydroxyl Groups ◽

Oh Groups ◽

Surface Hydroxyl ◽

Mineral Structure ◽

Ph Dependent ◽

Soil Colloids

Soil chemistry deals with the chemical properties and reactions of soils. It is essentially the application of electrochemistry and colloid chemistry to soil systems. Major topics include surface charge properties of soil colloids, cation and anion sorption and exchange, soil acidity, soil alkalinity, soil salinity, and the effects of these chemical properties and processes on soil biological activity, plant growth, and environmental quality. The ability of the electrically charged surface of soil colloids to retain nutrient cations and anions is an important chemical property affecting the fertility status of the soil. There are two major sources of electrical charges on soil organic and inorganic colloids, namely, permanent or constant charges and variable or pH-dependent charges. Permanent or constant charges are the result of the charge imbalance brought about by isomorphous substitution in a mineral structure of one cation by another of similar size but differing valence (see also section 2.3.2). For example, the substitution of Mg2+ for Al3+ that occurs in Al-dominated octahedral sheets of 2:1 clay minerals results in a negative surface charge in smectite, vermiculite, and chlorite. The excess negative charges are then balanced by adsorbed cations to maintain electrical neutrality. Permanent negative charges of all 2:1 silicate minerals arise from isomorphous substitutions. The l:l-type clay mineral, kaolinite, has only a minor amount of permanent charge due to isomorphic substitution. The negative charges on kaolinite originate from surface hydroxyl groups on the edge of the mineral structure and are pH-dependent. Variable or pH-dependent charges occur on the surfaces of Fe and Al oxides, allophanes, and organic soil colloids. This type of surface charge originates from hydroxyl groups and other functional groups by releasing or accepting H+ ions, resulting in either negative or positive charges. Other functional groups are hydroxyl (OH) groups of Fe and/or Al oxides and allophanes and the COOH and OH groups of soil organic matter. Variable-charge soil colloids bear either a positive or a negative net surface charge depending on the pH of the soil. The magnitude of the charge varies with the electrolyte concentration of the soil solution.

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The ionogenic nature of the secretory-granule membrane. Electrokinetic properties of isolated chromaffin granules

Biochemical Journal ◽

10.1042/bj1300825 ◽

1972 ◽

Vol 130 (3) ◽

pp. 825-832 ◽

Cited By ~ 32

Author(s):

E. K. Matthews ◽

R. J. Evans ◽

P. M. Dean

Keyword(s):

Surface Charge ◽

Negative Charge ◽

Single Type ◽

Chromaffin Granules ◽

Chromaffin Granule ◽

Granule Membrane ◽

Dose Dependent Fashion ◽

Ph Dependent ◽

Dose Dependent ◽

Anionic Surface

1. Chromaffin granules isolated from the bovine adrenal medulla possess an electrophoretic mobility of -1.12μm·s-1·cm·V-1, corresponding to a surface ζ potential of -14.4mV and surface charge density of 1.38×10-6C·cm-2. 2. The mobility of chromaffin granules is pH-dependent, indicating an amphoteric surface with an isoelectric point at pH3.0 and acidic groups with a pKa of 3.11. 3. Addition of bi- and ter-valent cations decreased the mobility of chromaffin granules in a dose-dependent fashion with a relative potency of La3+»Mn2+>Ca2+ >Sr2+>Mg2+>Ba2+. 4. Treatment with neuraminidase decreased the mobility of erythrocytes by 84%, whereas chromaffin-granule mobility was decreased by only 14%. This correlates well with the small complement of neuraminic acid present in the granule membrane. 5. The nature, origin and significance of the anionic surface charge of the chromaffin granule is discussed. It is concluded that the net negative charge at the surface of shear derives chiefly from a single type of chemical group, namely -CO2-, contributed by the α-carboxyl group of constituent proteins, the phospholipid phosphatidylserine and, to a lesser extent, the sialic acid component of glycoproteins.

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