Molecular simulations of cytochrome c adsorption on positively charged surfaces: the influence of anion type and concentration

Using polyethylenimine (PEI) as the aqueous reactive monomers, a positively charged thin-film nanocomposite (TFN) nanofiltration (NF) membrane with enhanced performance was developed by successfully incorporating graphene oxide (GO) into the active layer. The effects of GO concentrations on the surface roughness, water contact angle, water flux, salt rejection, heavy metal removals, antifouling property, and chlorine resistance of the TFN membranes were evaluated in depth. The addition of 20 ppm GO facilitated the formation of thin, smooth, and hydrophilic nanocomposite active layers. Thus, the TFN-PEI-GO-20 membrane showed the optimal water flux of 70.3 L·m−2·h−1 without a loss of salt rejection, which was 36.8% higher than the thin-film composite (TFC) blank membrane. More importantly, owing to the positively charged surfaces, both the TFC-PEI-blank and TFN-PEI-GO membranes exhibited excellent rejections toward various heavy metal ions including Zn2+, Cd2+, Cu2+, Ni2+, and Pb2+. Additionally, compared with the negatively charged polypiperazine amide NF membrane, both the TFC-PEI-blank and TFN-PEI-GO-20 membranes demonstrated superior antifouling performance toward the cationic surfactants and basic protein due to their hydrophilic, smooth, and positively charged surface. Moreover, the TFN-PEI-GO membranes presented the improved chlorine resistances with the increasing GO concentration.

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Photodegradation of Rhodamine B in Presence of CaO and NiO-CaO Catalysts

International Journal of Photoenergy ◽

10.1155/2012/398230 ◽

2012 ◽

Vol 2012 ◽

pp. 1-6 ◽

Cited By ~ 10

Author(s):

Tobias Kornprobst ◽

Johann Plank

Keyword(s):

Visible Light ◽

Specific Surface ◽

Surface Area ◽

Rhodamine B ◽

Uv Light ◽

Mechanistic Study ◽

Light Conditions ◽

No Adsorption ◽

Charged Surfaces ◽

Positively Charged

A CaO catalyst was prepared by mild calcination (650°C) of facilely precipitated Ca(OH)2and compared to an NiO-CaO catalyst obtained from an Ni(OH)2/Ca(OH)2coprecipitate as a precursor. Both catalysts degraded rhodamine B (RB) effectively when exposed to ultraviolet light but exhibited slower degradation under visible light conditions. Under UV light, CaO was more effective than NiO-CaO, while in visible light, the opposite was observed. A mechanistic study revealed no influence of the specific surface area of the catalysts on RB degradation, no adsorption of RB on the positively charged surfaces of the catalysts, and only incomplete degradation of RB. Consequently, both materials represent nonconventional photocatalysts.

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Fast coating of hydrophobic upconversion nanoparticles by NaIO4-induced polymerization of dopamine: Positively charged surfaces and in situ deposition of Au nanoparticles

Applied Surface Science ◽

10.1016/j.apsusc.2020.146821 ◽

2020 ◽

Vol 527 ◽

pp. 146821

Author(s):

Wei Zhang ◽

Zhengfang Liao ◽

Xiaoqi Meng ◽

A Erpuding Ai Niwaer ◽

Hongyue Wang ◽

...

Keyword(s):

Au Nanoparticles ◽

Upconversion Nanoparticles ◽

Charged Surfaces ◽

In Situ Deposition ◽

Positively Charged

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The effect of complex-formation with polyanions on the redox properties of cytochrome c

Biochemical Journal ◽

10.1042/bj1920687 ◽

1980 ◽

Vol 192 (2) ◽

pp. 687-693 ◽

Cited By ~ 32

Author(s):

L C Petersen ◽

R P Cox

Keyword(s):

Cytochrome C ◽

Complex Formation ◽

Reaction Rates ◽

Reduced Form ◽

Stable Complex ◽

Phase System ◽

Two Phase ◽

The Difference ◽

Low Ionic Strength ◽

Positively Charged

1. The stable complex formed between mammalian cytochrome c and phosvitin at low ionic strength was studied by partition in an aqueous two-phase system. Oxidized cytochrome c binds to phosvitin with a higher affinity than reduced cytochrome c. The difference was equivalent to a decrease of the redox potential by 22 mV on binding. 2. Complex-formation with phosvitin strongly inhibited the reaction of cytochrome c with reagents that react as negatively charged species, such as ascorbate, dithionite, ferricyanide and tetrachlorobenzoquinol. Reaction with uncharged reagents such as NNN‘N’-tetramethylphenylenediamine and the reduced form of the N-methylphenazonium ion (present as the methylsulphate) was little affected by complex-formation, whereas oxidation of the reduced cytochrome by the positively charged tris-(phenanthroline)cobalt(III) ion was greatly stimulated. 3. A similar pattern of inhibition and stimulation of reaction rates was observed when phosvitin was replaced by other macromolecular polyanions such as dextran sulphate and heparin, indicating that the results were a general property of complex-formation with polyanions. A weaker but qualitatively similar effect was observed on addition of inositol hexaphosphate and ATP. 4. It is suggested that the effects of complex-formation with polyanions on the reactivity of cytochrome c with redox reagents are mainly the result of replacing the positive charge on the free cytochrome by a net negative charge. Any steric effects on polyanion binding are small in comparison with such electrostatic effects.

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