scholarly journals A pH-dependent conformational transition of Aβ peptide and physicochemical properties of the conformers in the glial cell

2002 ◽  
Vol 361 (3) ◽  
pp. 547 ◽  
Author(s):  
Yoichi MATSUNAGA ◽  
Nobuhiro SAITO ◽  
Akihiro FUJII ◽  
Junichi YOKOTANI ◽  
Tadakazu TAKAKURA ◽  
...  
Keyword(s):  
Physicochemical Properties ◽  
Glial Cell ◽  
Conformational Transition ◽  
Aβ Peptide ◽  
Ph Dependent

A pH-dependent conformational transition of Aβ peptide and physicochemical properties of the conformers in the glial cell

2002 ◽  
Vol 361 (3) ◽  
pp. 547-556 ◽  
Author(s):  
Yoichi MATSUNAGA ◽  
Nobuhiro SAITO ◽  
Akihiro FUJII ◽  
Junichi YOKOTANI ◽  
Tadakazu TAKAKURA ◽  
...  
Keyword(s):  
Glial Cell ◽  
Conformational Changes ◽  
Conformational Transition ◽  
Early Stage ◽  
Ph Dependence ◽  
Amyloid Β ◽  
Proteinase K ◽  
Aβ Peptide ◽  
Ph Dependent ◽  
Insight Into

In the present study we identified the epitopes of antibodies against amyloid β-(1–42)-peptide (Aβ1–42): 4G8 reacted with peptides corresponding to residues 17–21, 6F/3D reacted with peptides corresponding to residues 9–14, and anti 5-10 reacted with peptides corresponding to residues 5–10. The study also yielded some insight into the Aβ1–42 structures resulting from differences in pH. An ELISA study using monoclonal antibodies showed that pH-dependent conformational changes occur in the 6F/3D and 4G8 epitopes modified at pH 4.6, but not in the sequences recognized by anti 1-7 and anti 5-10. This was unique to Aβ1–40 and Aβ1–42 and did not occur with Aβ1–16 or Aβ17–42. The reactivity profile of 4G8 was not affected by blockage of histidine residues of pH-modified Aβ1–40 and Aβ1–42 with diethyl pyrocarbonate; however, the mutant [Gln11]Aβ1–40 abrogated the unique pH-dependence towards 4G8 observed with Aβ1–40. These findings suggest that these epitopes are cryptic at pH4.6, and that Glu11 is responsible for the changes. We suggest that the abnormal folding of 6F/3D epitope affected by pH masked the 4G8 epitope. A study of the binding of metal ions to Aβ1–42 suggested that Cu2+ and Zn2+ induced a conformational transition around the 6F/3D region at pH7.4, but did not affect the region when it was modified at pH4.6. However, Fe2+ had no effect, irrespective of pH. Aβ modified at pH 4.6 appeared to be relatively resistant to proteinase K compared with Aβs modified at pH7.4, and the former might be preferentially internalized and accumulated in a human glial cell. Our findings suggest the importance of microenvironmental changes, such as pH, in the early stage of formation of Aβ aggregates in the glial cell.

Carbon nanospheres with dual-color emission and their application in ratiometric pyrophosphate sensing

The Analyst ◽  
2019 ◽  
Vol 144 (2) ◽  
pp. 550-558 ◽  
Author(s):  
Zhong-Xia Wang ◽  
Yuan-Fei Gao ◽  
Xian-He Yu ◽  
Fen-Ying Kong ◽  
Wen-Juan Wang ◽  
...  
Keyword(s):  
Physicochemical Properties ◽  
Carbon Nanospheres ◽  
One Pot ◽  
Aqueous Synthesis ◽  
Dual Color ◽  
Ph Dependent ◽  
The One ◽  
Solubility Equilibrium ◽  
Color Emission ◽  
Fluorescent Carbon

Herein, we employ pH-dependent solubility equilibrium to develop the one-pot aqueous synthesis of dual-color emission fluorescent carbon nanosphere (DFCSs) with novel physicochemical properties.

scholarly journals A Slow pH-dependent Conformational Transition Underlies a Novel Mode of Activation of the Epithelial Na+/H+Exchanger-3 Isoform

2002 ◽  
Vol 277 (13) ◽  
pp. 11090-11096 ◽  
Author(s):  
Hisayoshi Hayashi ◽  
Katalin Szászi ◽  
Natasha Coady-Osberg ◽  
John Orlowski ◽  
James L. Kinsella ◽  
...  
Keyword(s):  
Conformational Transition ◽  
Ph Dependent

The study of pH-dependent complexation between gelatin and gum arabic by morphology evolution and conformational transition

2013 ◽  
Vol 30 (1) ◽  
pp. 323-332 ◽  
Author(s):  
Yi Lv ◽  
Xiaoming Zhang ◽  
Haiyang Zhang ◽  
Shabbar Abbas ◽  
Eric Karangwa
Keyword(s):  
Conformational Transition ◽  
Gum Arabic ◽  
Morphology Evolution ◽  
Ph Dependent

The pH-dependent conformational transition of β-lactoglobulin modulates the binding of protoporphyrin IX

2006 ◽  
Vol 1760 (1) ◽  
pp. 38-46 ◽  
Author(s):  
Fang Tian ◽  
Katrina Johnson ◽  
Andrea E. Lesar ◽  
Harry Moseley ◽  
James Ferguson ◽  
...  
Keyword(s):  
Conformational Transition ◽  
Protoporphyrin Ix ◽  
Ph Dependent ◽  
Β Lactoglobulin

scholarly journals Caffeine Adsorption by Fique Bagasse Biochar Produced at Various Pyrolysis Temperatures

2019 ◽  
Vol 35 (2) ◽  
pp. 538-546 ◽  
Author(s):  
Yaned Milena Correa-Navarro ◽  
Juan Carlos Moreno-Piraján ◽  
Liliana Giraldo ◽  
Paola Rodríguez-Estupiñan
Keyword(s):  
Experimental Data ◽  
Hydrogen Bonding ◽  
Physicochemical Properties ◽  
Agricultural Residues ◽  
Layer Adsorption ◽  
Different Temperatures ◽  
Π Stacking Interaction ◽  
Ph Dependent ◽  
Bagasse Biochar ◽  
Adsorption Capability

Biochar obtained from agricultural residues is ever more recognized as a multifunctional porous solid for multiples applications. In this study, fique bagasse biochars were produced at different temperatures and their corresponding deashing. These materials were investigated about physicochemical properties and adsorption capability of caffeine. The pH solution was an influential parameter, and it was determined that a pH =2.0 for washed biochar and pH= 6.0 for not washed biochar were the best conditions for adsorption. Langmuir, Freundlich and Redlich-Peterson isotherms models provided a good fit for the experimental data, indicating a surface and multi-layer adsorption. From the adsorption capacity at equilibrium of fique bagasse biochars it was concluded that pH-dependent interactions, hydrogen bonding and π- π stacking interaction were found to be responsible for caffeine adsorption. The results allow to visualize the biochar obtained from fique bagasse as a sustainable alternative for the waste derived from the production of the cabuya.

scholarly journals Two protonation switches control rhodopsin activation in membranes

2008 ◽  
Vol 105 (46) ◽  
pp. 17795-17800 ◽  
Author(s):  
Mohana Mahalingam ◽  
Karina Martínez-Mayorga ◽  
Michael F. Brown ◽  
Reiner Vogel
Keyword(s):  
Transmembrane Domain ◽  
Conformational Transition ◽  
Salt Bridge ◽  
Receptor Activation ◽  
Activation Mechanism ◽  
Partial Activation ◽  
Ph Dependent ◽  
G Protein Coupled ◽  
Receptor Conformation ◽  
Receptor Family

Activation of the G protein-coupled receptor (GPCR) rhodopsin is initiated by light-induced isomerization of the retinal ligand, which triggers 2 protonation switches in the conformational transition to the active receptor state Meta II. The first switch involves disruption of an interhelical salt bridge by internal proton transfer from the retinal protonated Schiff base (PSB) to its counterion, Glu-113, in the transmembrane domain. The second switch consists of uptake of a proton from the solvent by Glu-134 of the conserved E(D)RY motif at the cytoplasmic terminus of helix 3, leading to pH-dependent receptor activation. By using a combination of UV–visible and FTIR spectroscopy, we study the activation mechanism of rhodopsin in different membrane environments and show that these 2 protonation switches become partially uncoupled at physiological temperature. This partial uncoupling leads to ≈50% population of an entropy-stabilized Meta II state in which the interhelical PSB salt bridge is broken and activating helix movements have taken place but in which Glu-134 remains unprotonated. This partial activation is converted to full activation only by coupling to the pH-dependent protonation of Glu-134 from the solvent, which stabilizes the active receptor conformation by lowering its enthalpy. In a membrane environment, protonation of Glu-134 is therefore a thermodynamic rather than a structural prerequisite for activating helix movements. In light of the conservation of the E(D)RY motif in rhodopsin-like GPCRs, protonation of this carboxylate also may serve a similar function in signal transduction of other members of this receptor family.

scholarly journals Nanodiamond surface redox chemistry: influence of physicochemical properties on catalytic processes

2014 ◽  
Vol 172 ◽  
pp. 349-364 ◽  
Author(s):  
Thomas S. Varley ◽  
Meetal Hirani ◽  
George Harrison ◽  
Katherine B. Holt
Keyword(s):  
Electron Transfer ◽  
Proton Transfer ◽  
Physicochemical Properties ◽  
Redox Chemistry ◽  
Redox Species ◽  
Redox Active ◽  
Ph Dependent ◽  
Catalytic Processes ◽  
Surface Redox

Modification of an electrode with an immobilised layer of nanodiamond is found to significantly enhance the recorded currents for reversible oxidation of ferrocene methanol (FcMeOH). Current enhancement is related to nanodiamond diameter, with enhancement increasing in the order 1000 nm < 250 nm < 100 nm < 10 nm < 5 nm. We attribute the current enhancement to two catalytic processes: i) electron transfer between the solution redox species and redox-active groups on the nanodiamond surface; ii) electron transfer mediated by FcMeOH+ adsorbed onto the nanodiamond surface. The first process is pH dependent as it depends on nanodiamond surface functionalities for which electron transfer is coupled to proton transfer. The adsorption-mediated process is observed most readily at slow scan rates and is due to self-exchange between adsorbed FcMeOH+ and FcMeOH in solution. FcMeOH+ has a strong electrostatic affinity for the nanodiamond surface, as confirmed by in situ infrared (IR) experiments.

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