Why is the capacity hump almost always at positive charge densities?

1984 ◽  
Vol 176 (1-2) ◽  
pp. 383-387 ◽  
Author(s):  
Wolfgang Schmickler ◽  
Douglas Henderson
2018 ◽  
Vol 73 (2) ◽  
pp. 99-108 ◽  
Author(s):  
Peter Luger ◽  
Birger Dittrich ◽  
Leonard Benecke ◽  
Hannes Sterzel

AbstractMotivated by the medical interest in methylene blue as potential anti-Alzheimer agent, the charge densities of three salt structures containing the methylene blue cation with nitrate (as dihydrate), chloride (as pentahydrate) and thiocyanate counter-ions were generated by application of the invariom formalism and examined. The so-obtained charge density distributions were analyzed using the QTAIM formalism to yield bond topological and atomic properties. The atomic charges on the methylene blue cation indicate a delocalized charge distribution; only a small positive charge on the sulfur atom was found. Electrostatic potentials mapped onto iso-surfaces of electron density for the cations, and for the methylene blue cations with anions, were compared. The effect of hydrogen disorder on the molecular electrostatic potential was investigated for the thiocyanate structure.


2018 ◽  
Vol 6 (11) ◽  
pp. 1633-1639 ◽  
Author(s):  
Hainan Sun ◽  
Yin Liu ◽  
Xue Bai ◽  
Xiaofei Zhou ◽  
Hongyu Zhou ◽  
...  

Gold nanoparticles with various positive charge densities and hydrophobicities induce cellular oxidative stress differently and sensitize cancer cells to paclitaxel.


1982 ◽  
Vol 60 (14) ◽  
pp. 1787-1792 ◽  
Author(s):  
Z. Borkowska ◽  
W. R. Fawcett

The entropy of formation of the mercury/methanol interface has been calculated from double layer capacity and interfacial tension measurements. In contrast to results for aqueous and propylene carbonate solutions, the plot of entropy against electrode charge density passes through a minimum at negative charge densities and a maximum at positive charge densities in the same regions where a minimum and maximum are found on the capacity curve. The excess surface entropy of methanol is negative for all charge densities, indicating that the solvent is more structured at the mercury surface than in the bulk. The results have been discussed in terms of the three state model in which the charge dependence of the entropy is attributed to reorientation of solvent dipoles at the interface.


2018 ◽  
Vol 36 (4) ◽  
pp. 979-986 ◽  
Author(s):  
Tinglong Zhang ◽  
Hai Yu ◽  
Fangcong Zhou ◽  
Jie Chen ◽  
Maohua Zhang

Abstract. A balloon-borne instrument was designed to measure the electric field in thunderstorms. One case of thunderstorm was observed in the Pingliang region (35.57∘ N, 106.59∘ E; and 1620 m above sea level, a.s.l.) of a Chinese inland plateau, through penetration by the balloon-borne sounding in the early period of the mature stage. Results showed that the sounding passed through seven predominant charge regions. A negative charge region with a depth of 800 m located near the surface, and a positive charge region appeared in the warm cloud region; their mean charge densities were −0.44 ± 0.136 and 0.43 ± 0.103 nC m−3, respectively. Five charge regions existed in the region colder than 0 ∘C, and charge polarity alternated in a vertical direction with a positive charge at the lowest region. The mean charge densities for these five regions were 0.40±0.037 nC m−3 (−9.5 to −4 ∘C), -0.63±0.0107 nC m−3 (−18 to −14 ∘C), 0.35±0.063 nC m−3 (−27 to −18 ∘C), -0.36±0.057 nC m−3 (−34 to −27 ∘C), and 0.24±0.06 nC m−3 (−38 to −34 ∘C). We speculated that the two independent positive charge regions in the lower portion are the same charge region with a weak charge density layer in the middle. The analysis showed that the real charge structure of the thunderstorm is more complex than the tripole model, and the lower dipole is the most intensive charge region in the thunderstorm. Keywords. Meteorology and atmospheric dynamics (atmospheric electricity)


2007 ◽  
Vol 121-123 ◽  
pp. 747-750
Author(s):  
Leng Nie ◽  
Li Zeng Gao ◽  
Xi Yun Yan ◽  
Tai Hong Wang

Amino-modified tetrapod-like ZnO nanostructures were tried as novel carriers for mammalian cell transfections. The nanostructures consisted of four needle-shaped tetrahedrally arranged legs connected at the center. After silica coating and amino modification, ZnO nanostructures complexes bound plasmid DNA through electrostatic interactions in aqueous solution. When mixed with cells, DNA-nanostructures attached easily onto cell membranes and entered the cells for gene expressions. Due to high positive charge densities on surfaces and needle-shaped tetrahedral structures, functionalized ZnO used as carriers for cell transfections with both high transfection efficiency and little cytotoxicity. And a possible transfection machamism was proposed in this report.


1968 ◽  
Vol 9 (37) ◽  
pp. 4009-4012 ◽  
Author(s):  
V. Koptyug ◽  
A. Rezvukhin ◽  
E. Lippmaa ◽  
T. Pehk

2020 ◽  
pp. 124-135
Author(s):  
I. N. G. Wardana ◽  
N. Willy Satrio

Tofu is main food in Indonesia and its waste generally pollutes the waters. This study aims to change the waste into energy by utilizing the electric charge in the pores of tofu waste to produce hydrogen in water. The tofu pore is negatively charged and the surface surrounding the pore has a positive charge. The positive and negative electric charges stretch water molecules that have a partial charge. With the addition of a 12V electrical energy during electrolysis, water breaks down into hydrogen. The test was conducted on pre-treated tofu waste suspension using oxalic acid. The hydrogen concentration was measured by a MQ-8 hydrogen sensor. The result shows that the addition of turmeric together with sodium bicarbonate to tofu waste in water, hydrogen production increased more than four times. This is due to the fact that magnetic field generated by delocalized electron in aromatic ring in turmeric energizes all electrons in the pores of tofu waste, in the sodium bicarbonate, and in water that boosts hydrogen production. At the same time the stronger partial charge in natrium bicarbonate shields the hydrogen proton from strong attraction of tofu pores. These two combined effect are very powerful for larger hydrogen production in water by tofu waste.


2020 ◽  
Author(s):  
Egle Maximowitsch ◽  
Tatiana Domratcheva

Photoswitching of phytochrome photoreceptors between red-absorbing (Pr) and far-red absorbing (Pfr) states triggers light adaptation of plants, bacteria and other organisms. Using quantum chemistry, we elucidate the color-tuning mechanism of phytochromes and identify the origin of the Pfr-state red-shifted spectrum. Spectral variations are explained by resonance interactions of the protonated linear tetrapyrrole chromophore. In particular, hydrogen bonding of pyrrole ring D with the strictly conserved aspartate shifts the positive charge towards ring D thereby inducing the red spectral shift. Our MD simulations demonstrate that formation of the ring D–aspartate hydrogen bond depends on interactions between the chromophore binding domain (CBD) and phytochrome specific domain (PHY). Our study guides rational engineering of fluorescent phytochromes with a far-red shifted spectrum.


2018 ◽  
Author(s):  
Daniel D. Brauer ◽  
Emily C. Hartman ◽  
Daniel L.V. Bader ◽  
Zoe N. Merz ◽  
Danielle Tullman-Ercek ◽  
...  

<div> <p>Site-specific protein modification is a widely-used strategy to attach drugs, imaging agents, or other useful small molecules to protein carriers. N-terminal modification is particularly useful as a high-yielding, site-selective modification strategy that can be compatible with a wide array of proteins. However, this modification strategy is incompatible with proteins with buried or sterically-hindered N termini, such as virus-like particles like the well-studied MS2 bacteriophage coat protein. To assess VLPs with improved compatibility with these techniques, we generated a targeted library based on the MS2-derived protein cage with N-terminal proline residues followed by three variable positions. We subjected the library to assembly, heat, and chemical selections, and we identified variants that were modified in high yield with no reduction in thermostability. Positive charge adjacent to the native N terminus is surprisingly beneficial for successful extension, and over 50% of the highest performing variants contained positive charge at this position. Taken together, these studies described nonintuitive design rules governing N-terminal extensions and identified successful extensions with high modification potential.</p> </div>


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