scholarly journals Morphological Transformation of Peptide Nanoassemblies through Conformational Transition of Core-forming Peptides

Polymers ◽  
2018 ◽  
Vol 11 (1) ◽  
pp. 39
Author(s):  
Tomonori Waku ◽  
Naoyuki Hirata ◽  
Masamichi Nozaki ◽  
Kanta Nogami ◽  
Shigeru Kunugi ◽  
...  
Keyword(s):  
Conformational Transition ◽  
Morphological Transformation ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Solvent Environment ◽  
Ph Conditions ◽  
Α Helix ◽  
Micro Reactors ◽  
External Stimuli ◽  
Β Sheet

Morphological control of nanostructures that are composed of amphiphilic di- or tri-block molecules by external stimuli broadens their applications for molecular containers, nanoreactors, and controlled release materials. In this study, triblock amphiphiles comprising oligo(ethylene glycol), oligo(l-lysine), and tetra(l-phenylalanine) were prepared for the construction of nanostructures that can transform accompanying α-to-β transition of core-forming peptides. Circular dichroic (CD) measurements showed that the triblock amphiphiles adopted different secondary structures depending on the solvent environment: they adopt β-sheet structures in aqueous solution, while α-helix structures in 25% 2,2,2-trifluoroethanol (TFE) solution under basic pH conditions. Transmission electron microscopic (TEM) observation revealed that the triblock amphiphiles formed vesicle structures in 25% TFE aq. Solvent exchange from 25% TFE to water induced morphological transformation from vesicles to arc-shaped nanostructures accompanying α-β conformational transition. The transformable nanostructures may be useful as novel smart nanomaterials for molecular containers and micro reactors.

Effects of salt concentrations on the structural transitions of peptide-amphiphile solution

2014 ◽  
Vol 1622 ◽  
pp. 147-152 ◽  
Author(s):  
Takahiro Otsuka ◽  
Atsushi Hotta
Keyword(s):  
Salt Concentration ◽  
Hierarchical Structures ◽  
Cd Spectroscopy ◽  
Structural Transitions ◽  
Peptide Amphiphile ◽  
Molecular Conformations ◽  
Multi Scale ◽  
Transmission Electron ◽  
Α Helix ◽  
Β Sheet

ABSTRACTA new peptide amphiphile (PA) called C16-W3K has hierarchical structures, presenting unique solution states, micelle structures, and secondary structures. In this work, the effects of salt (sodium dihydrogenorthophosphate) concentration on the hierarchical structural transitions of the C16-W3K solution due to its active hydrogen bonding in the peptide were discussed. In order to analyze the effects of salt on the structural transitions, the mechanical and structural analyses were conducted by viscosity measurements, transmission electron microscopy (TEM), and circular dichroic (CD) spectroscopy. It was found that the C16-W3K solutions with different salt concentrations presented different multi-scale structural transitions from spherical micelles with α-helix molecular conformations in the sol state to wormlike micelles with β-sheet conformations in the gel state. Additionally, we found that the speed of transition increased as the salt concentration increased and the conformational ratio of β-sheet to α-helix in the solutions increased with the increase in the salt concentration.

scholarly journals Synthetic Dimeric Aβ(28–40) Mimics the Complex Epitope of Human Anti-Aβ Autoantibodies against Toxic Aβ Oligomers

2013 ◽  
Vol 288 (38) ◽  
pp. 27638-27645 ◽  
Author(s):  
Andreas M. Roeder ◽  
Yvonne Roettger ◽  
Anne Stündel ◽  
Richard Dodel ◽  
Armin Geyer
Keyword(s):  
Conformational Transition ◽  
Amyloid Peptide ◽  
Cd Spectra ◽  
Aβ Oligomers ◽  
Peptide Epitopes ◽  
Β Amyloid ◽  
Covalently Linked ◽  
Β Amyloid Peptide ◽  
Α Helix ◽  
Β Sheet

Covalently linked carboxyl-terminal segments of the β-amyloid peptide (Aβ) were tested for their qualification as minimal conformational epitopes of the naturally occurring human autoantibodies against β-amyloid (nAbs-Aβ). nAbs-Aβ specifically recognize the toxic oligomers of Aβ and not the monomeric or the fibrillar forms of Aβ. The synthetic dimers of Aβ(28–40) described herein mimic the toxic Aβ oligomers but are not kinetic intermediates with uncertain compositions. CD spectra identified a surprisingly rich conformational behavior of selected miniamyloids. We observed a highly cooperative conformational transition of β-sheet to α-helix upon the addition of the helix enforcing co-solvent hexafluoroisopropanol. The CD curves of dimer 9 resembled, in a completely reversible manner, the CD spectra measured during the irreversible fibrillation of the parent Aβ(1–40). Synthetic peptide epitopes with high affinities for nAbs-Aβ are needed to identify the physiological roles of nAbs-Aβ and are promising epitopes for vaccination experiments.

scholarly journals Calculation and Analysis of Fractal Descriptors for Protein Amino Acids in Various Conformational States

2018 ◽  
Vol 1 (3) ◽  
pp. e00070
Author(s):  
V.Yu. Grigorev ◽  
L.D. Grigoreva
Keyword(s):  
Amino Acids ◽  
Conformational Transition ◽  
Van Der Waals ◽  
Conformational State ◽  
Conformational States ◽  
Protein Amino Acids ◽  
Α Helix ◽  
Β Sheet ◽  
Fractal Descriptor

A series of 20 proteinogenic amino acids was studied. Four types of fractal descriptors for 2 conformational states are calculated: α-helix and 1-strand β-sheet. Based on the analysis of the results obtained, it is established that when the conformational state of the amino acids (α-helix→β-sheet) changes, significant changes in the fractal descriptor Dtot, in the calculation of which all the atoms of the molecule are used, are not observed. However, the more specific descriptors Dval, Dvdw and Dunb, which reflect the aggregate of valence-coupled, van der Waals contact and unbound atoms, respectively, are more sensitive to the conformational transition. The increase Dval, Dvdw and the decrease Dunb values were established for a series of 7 amino acids.

Raman Spectroscopic Investigation of the Denaturation Process of Silk Fibroin

1989 ◽  
Vol 43 (7) ◽  
pp. 1269-1272 ◽  
Author(s):  
Siding Zheng ◽  
Guanxian Li ◽  
Wenhuo Yao ◽  
Tongyin Yu
Keyword(s):  
Raman Spectroscopy ◽  
Silk Fibroin ◽  
Conformational Transition ◽  
Transition Process ◽  
Random Coil ◽  
Helical Conformation ◽  
Extension Rate ◽  
Α Helix ◽  
Β Sheet ◽  
Denaturation Process

The mechanical denaturation process of silk fibroin is examined by Raman spectroscopy. The fresh silk fibroins from the middle gland of mature silkworms are drawn to various ratios on a tensile tester ( R = ldrawn/ linitial, where l is length) and their conformations are measured with Raman spectroscopy. Undrawn silk fibroin is mainly in the random coil structure with some α-helical conformation, the characteristic bands appearing at 1252 and 1660 (random coil) and at 942, 1106, and 1270 cm−1 (α-helix). When the samples are drawn up to R = 4 at an extension rate of 500 mm/min, two peaks at 1233 cm−1 (the amide III band) and 1085 cm−1 appear; it is shown that the β-sheet conformation is then formed. With an increase in drawing ratios, the intensities of these β-sheet bands increase and those of the random coil and α-helical bands decrease gradually. These changes indicate that, under the action of stress, the conformation of fibroin is altered from random coil and α-helix to β-sheet structures. This result is quite similar to the results achieved by the spinning of the silkworm. The effect of the water content in liquid silk on this conformational transition process is revealed and discussed.

scholarly journals Thermal, chemical and chemothermal denaturation of yeast enolase

2003 ◽  
Vol 17 (2-3) ◽  
pp. 453-467 ◽  
Author(s):  
Ping Huang ◽  
Aichun Dong
Keyword(s):  
Fourier Transform ◽  
Thermal Denaturation ◽  
Conformational Transition ◽  
Denaturant Concentration ◽  
Unfolded State ◽  
Random Structures ◽  
Α Helix ◽  
Heterogeneous Ensemble ◽  
Β Sheet ◽  
Yeast Enolase

We studied the temperature‒ and denaturant‒induced denaturation of yeast enolase by means of Fourier transform infrared spectroscopy. The temperature‒induced denaturation/aggregation of the enzyme in the absence of denaturant was highly cooperative and occurred between 55 and 65°C with a midpoint of ~58°C. Above 55°C, the intensity at 1656 cm−1(predominantly α‒helix) decreases as a function of temperature, accompanied by the appearance of two new bands at 1622 and 1696 cm−1, indicating the formation of intermolecular β‒sheet aggregates. Five clearly defined isosbestic points were observed, indicating a two‒state conformational transition. Addition of a non‒denaturing concentration of gdnHCl (0.4 M) caused the thermal denaturation/aggregation of the enzyme to proceed faster, but this revealed no unfolding intermediate. The gdnHCl‒induced unfolding was first detected at a gdnHCl concentration of above 0.4 M, evidenced by loss of α‒helix and β‒sheet structures as functions of denaturant concentration. The fully unfolded state was reached at a gdnHCl concentration of 1.6 M. A significant amount of intermolecular β‒sheet aggregate was detected at gdnHCl concentrations between 0.6 and 1.0 M, which disappeared as the denaturant concentration increased further. The gdnHCl‒unfolded state is a heterogeneous ensemble of turns, helix/loops, and random structures, which continues to change at higher concentrations of denaturant.

scholarly journals Membrane-Dependent Amyloid Aggregation of Human BAX α9 (173-192)

2020 ◽  
Author(s):  
David A. Price ◽  
Tayler D. Hill ◽  
Kaitlyn A. Hutson ◽  
Blaze W. Rightnowar ◽  
Sean D. Moran
Keyword(s):  
Mitochondrial Outer Membrane ◽  
Mitochondrial Outer Membrane Permeabilization ◽  
2D Ir ◽  
Transmission Electron ◽  
Amyloid Aggregates ◽  
Family Protein ◽  
Small Unilamellar Vesicles ◽  
Α Helix ◽  
Β Sheet ◽  
Prior Models

ABSTRACTMitochondrial outer membrane permeabilization, which is a critical step in apoptosis, is initiated upon transmembrane insertion of the C-terminal α-helix (α9) of the pro-apoptotic Bcl-2 family protein BAX. The isolated α9 fragment (residues 173-192) is also competent to disrupt model membranes, and the structures of its membrane-associated oligomers are of interest in understanding the potential roles of this sequence in apoptosis. Here, we used ultrafast two-dimensional infrared (2D IR) spectroscopy, thioflavin T binding, and transmission electron microscopy to show that the synthetic BAX α9 peptide (α9p) forms amyloid aggregates in solution and on the surfaces of anionic small unilamellar vesicles (SUVs). Its inherent amyloidogenicity was predicted by sequence analysis, and 2D IR spectra reveal that SUVs modulate the β-sheet structures of the resulting amyloid species. These results contradict prior models of transmembrane α9p pores and motivate further examination of the formation or suppression of BAX amyloids in apoptosis.

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.

Effect of Concentration on Structure and Properties of Concentrated Regenerated Silk Fibroin Solution

2011 ◽  
Vol 311-313 ◽  
pp. 1653-1656 ◽  
Author(s):  
Fang Xie ◽  
Hao Liang
Keyword(s):  
Silk Fibroin ◽  
Conformational Transition ◽  
Random Coil ◽  
Scanning Calorimetry ◽  
Regenerated Silk Fibroin ◽  
Lower Temperature ◽  
Α Helix ◽  
Β Sheet ◽  
Dsc Curves ◽  
Fibroin Solution

The thermal properties and rheological behavior of concentrated regenerated silk fibroin aqueous solution from 15% to 37% was investigated by differential scanning calorimetry (DSC) and rheometer. Also the conformation of solutions was characterized by Raman spectra. It was discovered that the major endothermic peak in the DSC curves shifted toward the lower temperature region with increasing the concentration. This behavior suggests increasing the concentration can accelerate conformational transition of silk fibroin from random coil and α-helix to β-sheet structure. In addition, it was found that the viscosity of solution increased with increasing concentration in favor of spinning.

scholarly journals Effect of Active Coatings Containing Lippa citriodora Kunth. Essential Oil on Bacterial Diversity and Myofibrillar Proteins Degradation in Refrigerated Large Yellow Croaker

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1787
Author(s):  
Bo Li ◽  
Xuesong Wang ◽  
Xin Gao ◽  
Jun Mei ◽  
Jing Xie
Keyword(s):  
Essential Oil ◽  
Bacterial Diversity ◽  
Carbonyl Compounds ◽  
Large Yellow Croaker ◽  
Myofibrillar Proteins ◽  
Refrigerated Storage ◽  
Tertiary Structures ◽  
Transmission Electron ◽  
Α Helix ◽  
Β Sheet

The research evaluated the effects of locust bean gum (LBG) and sodium alginate (SA) active coatings containing 0.15, 0.30 or 0.60% lemon verbena (Lippa citriodora Kunth.) essential oil (LVEO) on the bacterial diversity and myofibrillar proteins (MPs) of large yellow croaker during refrigerated storage at 4 °C for 18 days. Variability in the dominant bacterial community in different samples on the 0, 9th and 18th day was observed. Pseudomonas and Shewanella were the two major genera identified during refrigerated storage. At the beginning, the richness of Pseudomonas was about 37.31% and increased for control (CK) samples during refrigerated storage, however, the LVEO-treated samples increased sharply from day 0 to the 9th day and then decreased. LBG-SA coatings containing LVEO treatments significantly delayed MPs oxidation by retarding the formation of free carbonyl compounds and maintaining higher sulfhydryl content, higher Ca2+-ATPase activity, better organized secondary (higher contents of α-helix and β-sheet) and tertiary structures during refrigerated storage. The transmission electron microscope (TEM) images showed that the integrity of the sarcomere was damaged; the boundaries of the H-, A-, and I-bands, Z-disk, and M-line were fuzzy in the CK samples at the end of storage. However, the LVEO-treated samples were still regular in appearance with distinct dark A-bands, light I-bands, and Z-disk. In brief, LBG-SA active coatings containing LVEO treatments suggested a feasible method for protecting the MPs of large yellow croaker during refrigerated storage.

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