eoe sub articles

EoE Sub Articles

1. Characterization of Supramolecular Self-Assembly Structures
<ol>
	<li>Formation of Amyloid Fibers
	<ol>
		<li>To prepare a self-assembly solution, weigh out 1 mg of the peptide powder using an analytical balance. Dissolve into a mixture (pH 7.5) of 20% acetonitrile and 10 mM (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) in a 1.5 mL microcentrifuge tube, to a final concentration of 1 mg/mL peptide assembly mixture. Vortex the assembly solution and leave it to assemble at room temperatur...

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Acetonitrile</td>
			<td>Fisher Scientific</td>
			<td>A998-4</td>
			<td>Flammable; irritating to eyes; Use personal protective equipment; Use only under a fume hood; keep away from open flame or hot surface; if contacted rinse wiith water for at least 15 minutes and obtain medical attention</td>
		</tr>
		<tr>
			<td>4-(2-Hydroxyethyl)piperazine-1-ethanesulfonic acid</td>
			<td>Acros Organics</td>
			<td>AC172571000</td>
			<td>Do not inhale; use outdoors or in well-ventilated area</td>
		</tr>
		<tr>
			<td>Fourier-Transform Infrared Spectrometer</td>
			<td>Alpha Tensor, Bruker</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

a fourier transform infrared spectroscopy technique to study peptide self-assembly

Source: Neves, R., et al. <a href="https://app.jove.com/v/58135/synthesis-characterization-12-dithiolane-modified-self-assembling">Synthesis and Characterization of 1,2-Dithiolane Modified Self-Assembling Peptides.</a> J. Vis. Exp. (2018)
This video demonstrates the self-assembly of amyloid peptides into a beta sheet-rich supramolecular structure using Fourier transform infrared spectroscopy. An infrared beam is passed through a crystal with a high refractive index, and energy absorption across the interface of the crystal and the sample is recorded. The secondary structures of the sample proteins are identified by analyzing their characteristic absorption peaks at specific regions of the infrared spectrum, which aids in identifying the formation of the supramolecular assembly.

<img alt="Figure 1" src="/files/ftp_upload/21466/21466_Figure1.jpg" /> 
Figure 1. Supramolecular characterization of 1,2-dithiolane modified peptide. (A) FT-IR of 1 mg/mL 1,2-dithiolane-KLVFFAQ-NH2 fibers assembled in 10mM HEPES, pH 7.5 in 20% CH3CN. The peak at 1627 cm-1 is consistent with the peptides assembled in a &#946;-sheet conformation. (B) CD of 1 mg/mL 1,2-dithiolane-KLVFFAQ-NH2 fibers assembled i...

Watch this Scientific Journal Video about A Fourier Transform Infrared Spectroscopy Technique to Study Peptide Self-Assembly at JoVE.com

A Fourier Transform Infrared Spectroscopy Technique to Study Peptide Self-Assembly

Source: Neves, R., et al. Synthesis and Characterization of 1,2-Dithiolane Modified Self-Assembling Peptides. J. Vis. Exp. (2018)
This video demonstrates ...

Fourier transform infrared spectroscopy &#8212; FTIR &#8212; helps to study peptide self-assembly into supramolecular structures held together by non-covalent interactions.
Begin by taking an unassembled protein sample &#8212; a suspension of amyloid peptides with the ability to form a beta sheet-rich supramolecular structure. Place the sample in an FTIR instrument equipped with an ATR crystal.
Direct an infrared beam at a critical angle onto the crystal; the beam passes through it and hits the interface between the crystal and sample. Crystals with a higher refractive index than the sample cause internal reflection of the beam.
A small fraction of the beam extends into the sample as an evanescent wave &#8212; a standing wave at the reflection points. Interaction of this wave with the sample causes absorption of the wave&#39;s energy, leading to attenuation of the reflected beam, recorded by a detector.
Depending on the peptide&#39;s structure, the sample absorbs in specific regions of the infrared spectrum. The absorption spectrum &#8212; obtained by Fourier transformation of the signal &#8212; shows a broad peak at a specific wavenumber, characteristic of the unassembled protein sample.
Incubate the sample, allowing self-assembly, to form beta sheet-rich amyloid fibers. Post-incubation, record the absorption spectrum.
A sharp peak at a wavenumber different from the previous broad peak indicates conversion into a beta-sheet assembly.

A Fourier Transform Infrared Spectroscopy Technique to Study Peptide Self-Assembly

Abstract