The Determinative Role of the Exchange Cation and Layer-Charge Density of Smectite on Aflatoxin Adsorption

2012 ◽  
Vol 60 (4) ◽  
pp. 374-386 ◽  
Author(s):  
Youjun Deng ◽  
Lian Liu ◽  
Ana Luisa Barrientos Velázquez ◽  
Joe B. Dixon
Keyword(s):  
Charge Density ◽  
Layer Charge ◽  
Exchange Cation

scholarly journals Deciphering the Role of π-Interactions in Polyelectrolyte Complexes Using Rationally Designed Peptides

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2074
Author(s):  
Sara Tabandeh ◽  
Cristina Elisabeth Lemus ◽  
Lorraine Leon
Keyword(s):  
Hydrogen Bonding ◽  
Phase Separation ◽  
Liquid Phase ◽  
Charge Density ◽  
Secondary Structures ◽  
Liquid Phase Separation ◽  
Polyelectrolyte Complexes ◽  
Π Interactions ◽  
Liquid Liquid Phase Separation

Electrostatic interactions, and specifically π-interactions play a significant role in the liquid-liquid phase separation of proteins and formation of membraneless organelles/or biological condensates. Sequence patterning of peptides allows creating protein-like structures and controlling the chemistry and interactions of the mimetic molecules. A library of oppositely charged polypeptides was designed and synthesized to investigate the role of π-interactions on phase separation and secondary structures of polyelectrolyte complexes. Phenylalanine was chosen as the π-containing residue and was used together with lysine or glutamic acid in the design of positively or negatively charged sequences. The effect of charge density and also the substitution of fluorine on the phenylalanine ring, known to disrupt π-interactions, were investigated. Characterization analysis using MALDI-TOF mass spectroscopy, H NMR, and circular dichroism (CD) confirmed the molecular structure and chiral pattern of peptide sequences. Despite an alternating sequence of chirality previously shown to promote liquid-liquid phase separation, complexes appeared as solid precipitates, suggesting strong interactions between the sequence pairs. The secondary structures of sequence pairs showed the formation of hydrogen-bonded structures with a β-sheet signal in FTIR spectroscopy. The presence of fluorine decreased hydrogen bonding due to its inhibitory effect on π-interactions. π-interactions resulted in enhanced stability of complexes against salt, and higher critical salt concentrations for complexes with more π-containing amino acids. Furthermore, UV-vis spectroscopy showed that sequences containing π-interactions and increased charge density encapsulated a small charged molecule with π-bonds with high efficiency. These findings highlight the interplay between ionic, hydrophobic, hydrogen bonding, and π-interactions in polyelectrolyte complex formation and enhance our understanding of phase separation phenomena in protein-like structures.

Beyond Charge Density Matching: The Role of C–H···O Interactions in the Formation of Templated Vanadium Tellurites

2011 ◽  
Vol 11 (9) ◽  
pp. 4213-4219 ◽  
Author(s):  
Matthew D. Smith ◽  
Samuel M. Blau ◽  
Kelvin B. Chang ◽  
Matthias Zeller ◽  
Joshua Schrier ◽  
...  
Keyword(s):  
Charge Density

Assessment of surface energetic heterogeneity of synthetic Na- saponites. The role of layer charge

Clay Minerals ◽  
2002 ◽  
Vol 37 (1) ◽  
pp. 39-57 ◽  
Author(s):  
L. J. Michot ◽  
F. Villiéras
Keyword(s):  
Aspect Ratio ◽  
Gas Adsorption ◽  
High Energy ◽  
Layer Charge ◽  
Adsorption Mechanisms ◽  
Energetic Heterogeneity ◽  
Complex Adsorption ◽  
Adsorption Energy Distribution ◽  
Synthetic Saponite

AbstractHigh-resolution gas adsorption techniques were used to analyse the evolution of the aspect ratio and adsorption energy distribution on synthetic saponite samples with increasing layer charge. Using Ar as a gaseous probe, the aspect ratio of the saponite particles can be determined easily by decomposing the derivative adsorption isotherms and taking into account high-energy sites which can be assigned to talc-like ditrigonal cavities. Changes in the shape of the elementary particles are observed for layer charges above 1.30, i.e. when all the ditrigonal cavities contain at least one Al atom substituting for Si. When N2 is used as a probe, high-energy sites that could be wrongly interpreted as micropores on the basis of classical t-plot treatments are observed whatever the layer charge. Using the information obtained from both Ar and N2, schemes for describing adsorption can be proposed for all layer charges and suggest complex adsorption mechanisms for charged clay minerals.

scholarly journals Preparation of hectorite-like swelling silicate with controlled layer charge density

2008 ◽  
Vol 116 (1360) ◽  
pp. 1309-1313 ◽  
Author(s):  
Makoto OGAWA ◽  
Takayuki MATSUTOMO ◽  
Tomohiko OKADA
Keyword(s):  
Charge Density ◽  
Layer Charge
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