Spectroscopic Studies of Structural Changes in Two β-Sheet-Forming Peptides Show an Ensemble of Structures that Unfold Noncooperatively†

Considerable attention has been paid to emulsion gels (EGs) in recent years due to their interesting applications in food. The aim of this work is to shed light on the role played by chia oil in the technological and structural properties of EGs made from soy protein isolates (SPI) and alginate. Two systems were studied: oil-free SPI gels (SPI/G) and the corresponding SPI EGs (SPI/EG) that contain chia oil. The proximate composition, technological properties (syneresis, pH, color and texture) and structural properties using Raman spectroscopy were determined for SPI/G and SPI/EG. No noticeable (p > 0.05) syneresis was observed in either sample. The pH values were similar (p > 0.05) for SPI/G and SPI/EG, but their texture and color differed significantly depending on the presence of chia oil. SPI/EG featured significantly lower redness and more lightness and yellowness and exhibited greater puncture and gel strengths than SPI/G. Raman spectroscopy revealed significant changes in the protein secondary structure, i.e., higher (p < 0.05) α-helix and lower (p < 0.05) β-sheet, turn and unordered structures, after the incorporation of chia oil to form the corresponding SPI/EG. Apparently, there is a correlation between these structural changes and the textural modifications observed.

Download Full-text

Structural control of fibrin bioactivity by mechanical deformation

10.1101/2020.08.24.265611 ◽

2020 ◽

Author(s):

Sachin Kumar ◽

Yujen Wang ◽

Manuel K. Rausch ◽

Sapun H. Parekh

Keyword(s):

Biological Activity ◽

Conformational Changes ◽

Structural Control ◽

Structural Changes ◽

Tensile Deformation ◽

Mechanical Strain ◽

Fibrous Protein ◽

Binding Partners ◽

Blood Clots ◽

Β Sheet

AbstractFibrin is a fibrous protein network that entraps blood cells and platelets to form blood clots following vascular injury. As a biomaterial, fibrin acts a biochemical scaffold as well as a viscoelastic patch that resists mechanical insults. The biomechanics and biochemistry of fibrin have been well characterized independently, showing that fibrin is a hierarchical material with numerous binding partners. However, comparatively little is known about how fibrin biomechanics and biochemistry are coupled: how does fibrin deformation influence its biochemistry at the molecular level? In this study, we show how mechanically-induced molecular structural changes in fibrin affect fibrin biochemistry and fibrin-platelet interaction. We found that tensile deformation of fibrin lead to molecular structural transitions of α-helices to β-sheets, which reduced binding of tissue plasminogen activator (tPA), an enzyme that initiates fibrinolysis, at the network and single fiber level. Moreover, binding of tPA and Thioflavin T (ThT), a commonly used β-sheet marker, was primarily mutually exclusive such that tPA bound to native (helical) fibrin whereas ThT bound to strained fibrin. Finally, we demonstrate that conformational changes in fibrin suppressed the biological activity of platelets on mechanically strained fibrin due to attenuated αIIbβ3 integrin binding. Our work shows that mechanical strain regulates fibrin molecular structure and fibrin biological activity in an elegant mechano-chemical feedback loop, which likely influences fibrinolysis and wound healing kinetics.

Download Full-text

Raman Spectroscopic Studies of Structural Changes of Insulin in Controlled Fluid Flows

10.1063/1.3482707 ◽

2010 ◽

Author(s):

Jonathan Dusting ◽

Grant Webster ◽

Stavroula Balabani ◽

Ewan W. Blanch ◽

P. M. Champion ◽

...

Keyword(s):

Structural Changes ◽

Fluid Flows ◽

Spectroscopic Studies ◽

Raman Spectroscopic

Download Full-text

Effect of the Hydrophilic-Hydrophobic Balance of Antigen-Loaded Peptide Nanofibers on Their Cellular Uptake, Cellular Toxicity, and Immune Stimulatory Properties

International Journal of Molecular Sciences ◽

10.3390/ijms20153781 ◽

2019 ◽

Vol 20 (15) ◽

pp. 3781 ◽

Cited By ~ 3

Author(s):

Tomonori Waku ◽

Saki Nishigaki ◽

Yuichi Kitagawa ◽

Sayaka Koeda ◽

Kazufumi Kawabata ◽

...

Keyword(s):

Cellular Uptake ◽

Self Assembly ◽

Sheet Forming ◽

Design Guidelines ◽

Cellular Interactions ◽

Antigenic Peptides ◽

Peptide Nanofibers ◽

Dc Line ◽

Chain Lengths ◽

Β Sheet

Recently, nanofibers (NFs) formed from antigenic peptides conjugated to β-sheet-forming peptides have attracted much attention as a new generation of vaccines. However, studies describing how the hydrophilic-hydrophobic balance of NF components affects cellular interactions of NFs are limited. In this report, three different NFs were prepared by self-assembly of β-sheet-forming peptides conjugated with model antigenic peptides (SIINFEKL) from ovalbumin and hydrophilic oligo-ethylene glycol (EG) of differing chain lengths (6-, 12- and 24-mer) to investigate the effect of EG length of antigen-loaded NFs on their cellular uptake, cytotoxicity, and dendritic cell (DC)-stimulation ability. We used an immortal DC line, termed JAWS II, derived from bone marrow-derived DCs of a C57BL/6 p53-knockout mouse. The uptake of NFs, consisting of the EG 12-mer by DCs, was the most effective and activated DC without exhibiting significant cytotoxicity. Increasing the EG chain length significantly reduced cellular entry and DC activation by NFs. Conversely, shortening the EG chain enhanced DC activation but increased toxicity and impaired water-dispersibility, resulting in low cellular uptake. These results show that the interaction of antigen-loaded NFs with cells can be tuned by the EG length, which provides useful design guidelines for the development of effective NF-based vaccines.

Download Full-text

Physicochemical study of the influenza A virus M2 protein and aluminum salt adjuvant interaction as a vaccine candidate model

Future Virology ◽

10.2217/fvl-2019-0019 ◽

2019 ◽

Vol 14 (8) ◽

pp. 523-536

Author(s):

Maryam Saleh ◽

Jamileh Nowroozi ◽

Fatemeh Fotouhi ◽

Behrokh Farahmand

Keyword(s):

Influenza A Virus ◽

Influenza A ◽

Structural Changes ◽

Vaccine Candidate ◽

Human Influenza ◽

M2 Protein ◽

Physicochemical Methods ◽

Α Helix ◽

High Level ◽

Β Sheet

Aim: The present study evaluated the structural changes resulting from the interaction between a recombinant influenza A virus M2 protein and aluminum hydroxide adjuvant to investigate the antigen for further immunological studies. Materials & methods: Membrane protein II was produced from the H1N1 subtype of human influenza A virus. The interaction between M2 protein and alum inum hydroxide adjuvant was evaluated by physicochemical techniques including scanning electron microscope, UV-Vis spectra, Fourier-transform infrared spectroscopy and circular dichroism spectroscopy. Results: Physicochemical methods showed high-level protein adsorption and accessibility to the effective parts of the protein. Conclusion: It was concluded that M2 protein secondary structural perturbations, including the α-helix-to-β-sheet transition, enhanced its mechanical properties toward adsorption.

Download Full-text

Laser Raman Spectroscopic Study Of The β-Sheet Structure Of Fibrinx

10.1055/s-0038-1652272 ◽

1981 ◽

Author(s):

J Marx ◽

G Hudry-Clergeon ◽

L Bernard

Keyword(s):

Protein Conformation ◽

Protein Concentration ◽

Structural Changes ◽

Fibre Diameter ◽

Enzymatic Conversion ◽

Raman Spectroscopic ◽

Laser Raman ◽

Sheet Structure ◽

Two Parameters ◽

Β Sheet

Raman spectroscopy has proved to be a useful tool in the study of protein conformation in aqueous solution. Structural changes have been observed by this technique during the enzymatic conversion of fibrinogen into fibrin (J. Marx and col. (1979) Biochim. Biophys. Acta., 578, 107-115), particularly by the study of the Amide I and Amide III regions an important increase in the β-sheet form has been shown to occur. This variation is investigated under various conditions of ionic strength (μ) and protein concentration (c), two parameters which are known to change the fibre diameter (low values of μ and c favor an increase in the fibre diameter). The amount of β-sheet structure in fibrinogen is approximately 10 % and is unaffected by μ or c. In fibrin, the amount of β-sheet increases progressively from 20 % in fine clots (low diameter fibres) to more than 30 % in coarse clots (high diameter fibres). This correlation between the percentage of β-sheet structure and fibre diameter in fibrin indicates that numerous intermonomer hydrogen bonds are formed in the equatorial direction of the fibre. These bonds would greatly consolidate the association between monomers which is probably initiated at a few highly specific sites.

Download Full-text

Nanotubular self-organization of amide dendrons with focal β-sheet forming peptide units

Soft Matter ◽

10.1039/c6sm01408a ◽

2016 ◽

Vol 12 (36) ◽

pp. 7453-7456 ◽

Cited By ~ 1

Author(s):

Jeonghun Lee ◽

Hyunil Jang ◽

Jonghwan Park ◽

Chulhee Kim

Keyword(s):

Sheet Forming ◽

Self Organization ◽

Β Sheet

Download Full-text

Thermodynamics of Micellization of β-Sheet Forming Poly(acrylic acid)-block-poly(l-valine) Hybrids

The Journal of Physical Chemistry B ◽

10.1021/jp801990h ◽

2008 ◽

Vol 112 (37) ◽

pp. 11542-11550 ◽

Cited By ~ 3

Author(s):

A. Sinaga ◽

T. A. Hatton ◽

K. C. Tam

Keyword(s):

Acrylic Acid ◽

Sheet Forming ◽

Thermodynamics Of Micellization ◽

Β Sheet ◽

Poly Acrylic Acid

Download Full-text

Structural Characterization of the C2 Domains of Classical Isozymes of Protein Kinase C and Novel Protein Kinase Cε by using Infrared Spectroscopy

Spectroscopy An International Journal ◽

10.1155/2003/361563 ◽

2003 ◽

Vol 17 (2-3) ◽

pp. 399-416

Author(s):

Senena Corbalán-García ◽

Josefa García-García ◽

M. Susana Sánchez-Carrillo ◽

Juan C. Gómez-Fernández

Keyword(s):

Thermal Stability ◽

Protein Kinase ◽

Secondary Structure ◽

Phosphatidic Acid ◽

Bound States ◽

Thermal Denaturation ◽

Spectroscopic Studies ◽

Lipid Binding ◽

C2 Domain ◽

Β Sheet

The amide I regions in the original infrared spectra of PKCα-C2 in the Ca2+-free and Ca2+-bound states are both consistent with a predominantly β-sheet secondary structure. Spectroscopic studies of the thermal denaturation revealed that for the PKCα-C2 domain alone the secondary structure abruptly changed at 50°C. While in the presence of Ca2+, the thermal stability of the protein increased considerably. Phosphatidic acid binding to the PKCα-C2 domain was characterized, and the lipid–protein binding becoming Ca2+-independent when 100 mol% phosphatidic acid vesicles was used. The effect of lipid binding on secondary structure and thermal stability was also studied. In addition, the secondary structure of the C2 domain from the novel PKCε was also determined by IR spectroscopy and β-sheet was seen to be the major structural component. Spectroscopic studies of the thermal denaturation in D2O showed a broadening in the amide I′band starting at 45°C. Phosphatidic acid containing vesicles were used to characterize the effect of lipid binding on the secondary structure. It was observed through thermal stability experiments that the secondary structure did not change upon lipid binding and the protein stability was very high with no significant changes occurring in the secondary structure after heating.

Download Full-text