scholarly journals Physicochemical Mechanism for the Lipid Membrane Binding of Polyarginine: The Favorable Enthalpy Change with Structural Transition from Random Coil to α-Helix

2012 ◽  
Vol 41 (10) ◽  
pp. 1374-1376 ◽  
Author(s):  
Yuki Takechi ◽  
Chiharu Mizuguchi ◽  
Masafumi Tanaka ◽  
Toru Kawakami ◽  
Saburo Aimoto ◽  
...  
Keyword(s):  
Structural Transition ◽  
Lipid Membrane ◽  
Membrane Binding ◽  
Enthalpy Change ◽  
Random Coil ◽  
Physicochemical Mechanism ◽  
Α Helix

Conformational Preferences of Aβ25-35 and Aβ35-25 in Membrane Mimicking Environments

2019 ◽  
Vol 26 (5) ◽  
pp. 386-390
Author(s):  
Dhandayuthapani Sambasivam ◽  
Senthilkumar Sivanesan ◽  
Sayeeda Sultana ◽  
Jayakumar Rajadas
Keyword(s):  
Structural Transition ◽  
Conformational Transition ◽  
The Other ◽  
Random Coil ◽  
Structural Modifications ◽  
Sds Micelles ◽  
Conformational Preferences ◽  
Helix Conformation ◽  
Α Helix ◽  
Β Sheet

Background: The structural transition of aggregating Abeta peptides is the key event in the progression of Alzheimer’s Disease (AD). Objective: In the present work, the structural modifications of toxic Aβ25-35 and the scrambled Aβ35-25 were studied in Trifluoroethanol (TFE) and in aqueous SDS micelles. Methods: Using CD spectroscopic investigations, the conformational transition of Aβ25-35 and Aβ35-25 peptides were determined in different membrane mimicking environments such as TFE and SDS. An interval scan CD of the peptides on evaporation of TFE was performed. TFE titrations were carried out to investigate the intrinsic ability of the structural conformations of peptides. Results: We show by spectroscopic evidence that Aβ25-35 prefers beta sheet structures upon increasing TFE concentrations. On the other hand, the non-toxic scrambled Aβ35-25 peptide only undergoes a transition from random coil to α-helix conformation with increasing TFE. In the interval scan studies, Aβ25-35 did not show any structural transitions, whereas Aβ35-25 showed transition from α-helix to β-sheet conformation. In membrane simulating aqueous SDS micelles, Aβ25-35 showed a transition from random coil to α-helix while Aβ35-25 underwent transition from random coil to β-sheet conformation. Conclusion: Overall, the current results seek new insights into the structural properties of amyloidogenic and the truncated sequence in membrane mimicking solvents.

Binding to lipid membrane induces conformational changes in RPE65: implications for its isomerohydrolase activity

2011 ◽  
Vol 436 (3) ◽  
pp. 591-597 ◽  
Author(s):  
Olga Nikolaeva ◽  
Gennadiy Moiseyev ◽  
Karla K. Rodgers ◽  
Jian-xing Ma
Keyword(s):  
Fluorescence Quenching ◽  
Conformational Changes ◽  
Lipid Membrane ◽  
Membrane Binding ◽  
Tryptophan Fluorescence ◽  
Cd Spectroscopy ◽  
Visual Cycle ◽  
Α Helix ◽  
Structural Levels

The visual cycle is a multi-step pathway to recycle 11-cis retinal, the chromophore for both rod and cone visual pigments. The isomerohydrolase RPE65, a membrane-associated enzyme, converts atRE (all-trans-retinyl ester) to 11-cis-retinol, a key step in the visual cycle. Previously, it has been shown that membrane association of RPE65 is essential for its catalytic activity. Using purified recombinant chicken RPE65 and an in vitro liposome-based floatation assay, we present evidence that the RPE65 membrane-binding affinity was significantly facilitated by incorporation of atRE, the substrate of RPE65, into liposomal membrane. Using tryptophan emission fluorescence quenching and CD spectroscopy, we showed that, upon membrane binding, RPE65 undergoes conformational changes at both the tertiary and secondary structural levels. Specifically, tryptophan fluorescence quenching showed that the tertiary RPE65 structure became more open towards the hydrophilic environment upon its association with the membrane. Simultaneously, a decrease in the α-helix content of RPE65 was revealed upon binding with the lipid membrane containing atRE. These results demonstrated that RPE65's functional activity depends on its conformational changes caused by its association with the membrane.

scholarly journals Astrocytes Are More Vulnerable than Neurons to Silicon Dioxide Nanoparticle Toxicity in Vitro

Toxics ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 51
Author(s):  
Jorge Humberto Limón-Pacheco ◽  
Natalie Jiménez-Barrios ◽  
Alejandro Déciga-Alcaraz ◽  
Adriana Martínez-Cuazitl ◽  
Mónica Maribel Mata-Miranda ◽  
...  
Keyword(s):  
Nucleic Acids ◽  
Silicon Dioxide ◽  
Culture Media ◽  
Brain Cell ◽  
Attenuated Total Reflection ◽  
Random Coil ◽  
Silicon Dioxide Nanoparticles ◽  
Neurotoxic Effects ◽  
Α Helix

Some studies have shown that silicon dioxide nanoparticles (SiO2-NPs) can reach different regions of the brain and cause toxicity; however, the consequences of SiO2-NPs exposure on the diverse brain cell lineages is limited. We aimed to investigate the neurotoxic effects of SiO2-NP (0–100 µg/mL) on rat astrocyte-rich cultures or neuron-rich cultures using scanning electron microscopy, Attenuated Total Reflection-Fourier Transform Infrared spectroscopy (ATR-FTIR), FTIR microspectroscopy mapping (IQ mapping), and cell viability tests. SiO2-NPs were amorphous particles and aggregated in saline and culture media. Both astrocytes and neurons treated with SiO2-NPs showed alterations in cell morphology and changes in the IR spectral regions corresponding to nucleic acids, proteins, and lipids. The analysis by the second derivative revealed a significant decrease in the signal of the amide I (α-helix, parallel β-strand, and random coil) at the concentration of 10 µg/mL in astrocytes but not in neurons. IQ mapping confirmed changes in nucleic acids, proteins, and lipids in astrocytes; cell death was higher in astrocytes than in neurons (10–100 µg/mL). We conclude that astrocytes were more vulnerable than neurons to SiO2-NPs toxicity. Therefore, the evaluation of human exposure to SiO2-NPs and possible neurotoxic effects must be followed up.

Influence of Post-Treatment with Methanol Vapor on the Properties of SF/P(LLA-CL) Nanofibrous Scaffolds

2011 ◽  
Vol 236-238 ◽  
pp. 2221-2224
Author(s):  
Kui Hua Zhang ◽  
Xiu Mei Mo
Keyword(s):  
Electrospun Nanofibers ◽  
Random Coil ◽  
Methanol Vapor ◽  
Nanofibrous Scaffolds ◽  
Nanofibrous Structure ◽  
Α Helix ◽  
Β Sheet ◽  
Ideal Method ◽  
C Nmr

In order to improve water-resistant ability silk fibroin (SF) and SF/P(LLA-CL) blended nanofibrous scaffolds for tissue engineering applications, methanol vapor were used to treat electrospun nanofibers. SEM indicated SF and SF/ P(LLA-CL) scaffolds maintained nanofibrous structure after treated with methanol vapor and possessed good water-resistant ability. Characterization of 13C NMR clarified methanol vapor induced SF conformation from random coil or α- helix to β-sheet. Moreover, treated SF/ P (LLA-CL) nanofibrous scaffolds still kept good mechanical properties. Methanol vapor could be ideal method to treat SF and SF/ P(LLA-CL) nanofibrous scaffolds for biomedical applications.

scholarly journals Lipid Membrane Binding of Computationally-Designed DNA Aptamers Specific for Phosphatidylserine

2013 ◽  
Vol 104 (2) ◽  
pp. 93a-94a
Author(s):  
Md Ashrafuzzaman ◽  
H.M. Embark ◽  
H.B. Jagirdar ◽  
A. Alsenaidy ◽  
C.Y. Tseng ◽  
...  
Keyword(s):  
Lipid Membrane ◽  
Membrane Binding ◽  
Dna Aptamers

Phospholipids modulate the biophysical properties and vasoactivity of PACAP-(1—38)

2002 ◽  
Vol 93 (4) ◽  
pp. 1377-1383 ◽  
Author(s):  
Takaya Tsueshita ◽  
Salil Gandhi ◽  
Hayat Önyüksel ◽  
Israel Rubinstein
Keyword(s):  
Conformational Transition ◽  
Critical Micellar Concentration ◽  
Random Coil ◽  
Cheek Pouch ◽  
Hamster Cheek Pouch ◽  
Pituitary Adenylate Cyclase ◽  
Peripheral Microcirculation ◽  
Α Helix

The purpose of this study was to elucidate the interactions between pituitary adenylate cyclase-activating peptide (PACAP)-(1—38) and phospholipids in vitro and to determine whether these phenomena modulate, in part, the vasorelaxant effects of the peptide in the intact peripheral microcirculation. We found that the critical micellar concentration of PACAP-(1—38) was 0.4–0.9 μM. PACAP-(1—38) significantly increased the surface tension of a dipalmitoylphosphatidylcholine monolayer and underwent conformational transition from predominantly random coil in saline to α-helix in the presence of distearoyl-phosphatidylethanolamine-polyethylene glycol (molecular mass of 2,000 Da) sterically stabilized phospholipid micelles (SSM) ( P < 0.05). Using intravital microscopy, we found that aqueous PACAP-(1—38) evoked significant concentration-dependent vasodilation in the intact hamster cheek pouch that was significantly potentiated when PACAP-(1—38) was associated with SSM ( P < 0.05). The vasorelaxant effects of aqueous PACAP-(1—38) were mediated predominantly by PACAP type 1 (PAC1) receptors, whereas those of PACAP-(1—38) in SSM predominantly by PACAP/vasoactive intestinal peptide type 1 and 2 (VPAC1/VPAC2) receptors. Collectively, these data indicate that PACAP-(1—38) self-associates and interacts avidly with phospholipids in vitro and that these phenomena amplify peptide vasoactivity in the intact peripheral microcirculation.

Electrochemistry of Alzheimer Disease Amyloid Beta Peptides

2018 ◽  
Vol 25 (33) ◽  
pp. 4066-4083 ◽  
Author(s):  
Ana-Maria Chiorcea-Paquim ◽  
Teodor Adrian Enache ◽  
Ana Maria Oliveira-Brett
Keyword(s):  
Amino Acid ◽  
Amyloid Beta ◽  
Biological Fluids ◽  
Electron Transfer Reaction ◽  
Random Coil ◽  
Sequence Length ◽  
Dependent Manner ◽  
Aβ Peptide ◽  
Aβ Peptides ◽  
Α Helix

Alzheimer’s disease (AD) is a widespread form of dementia that is estimated to affect 44.4 million people worldwide. AD pathology is closely related to the accumulation of amyloid beta (Aβ) peptides in fibrils and plagues, the small oligomeric intermediate species formed during the Aβ peptides aggregation presenting the highest neurotoxicity. This review discusses the recent advances on the Aβ peptides electrochemical characterization. The Aβ peptides oxidation at a glassy carbon electrode occurs in one or two steps, depending on the amino acid sequence, length and content. The first electron transfer reaction corresponds to the tyrosine Tyr10 amino acid residue oxidation, and the second to all three histidine (His6, His13 and His14) and one methionine (Met35) amino acid residues. The Aβ peptides aggregation and amyloid fibril formation are electrochemically detected via the electroactive amino acids oxidation peak currents decrease that occurs in a time dependent manner. The Aβ peptides redox behaviour is correlated with changes in the adsorption morphology from initially random coiled structures, corresponding to the Aβ peptide monomers in random coil or in α-helix conformations, to aggregates, protofibrils and two types of fibrils, corresponding to the Aβ peptides in a β-sheet configuration, observed by atomic force microscopy. Electrochemical studies of Aβ peptides aggregation, mediated by the interaction with metal ions, particularly zinc, copper and iron, and different methodologies concerning the detection of Aβ peptide biomarkers of AD in biological fluids, using electrochemical biosensors, are also discussed.

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