The Cationic Host Defense Peptides Could Be Used To Kill Enveloped Novel Coronavirus SARS-CoV-2

Direct antimicrobial mechanisms of cationic host defense peptides

The cationic host defense peptides (CHDP), also known as antimicrobial peptides, could be used to kill enveloped viruses such as the 2019 Novel Coronavirus SARS-CoV-2. The peptides have the potential to destabilize the viral envelope on contact, damaging the virions and inhibiting infectivity. The specific antiviral peptide may bind to cellular receptors involved in viral infection or peptide-mediated aggregation of viral particles. The antiviral peptides could create an ‘antiviral shield’ at mucosal surfaces and prevent replication and spread of the Coronavirus if upregulated after the initial infection.

During pandemics, where there is insufficient time to produce vaccines (such as the outbreak of respiratory illness Covid-19 first detected in Wuhan, China), the cationic host defense peptides could be the first-line antiviral treatments.

Some of the antimicrobial peptides are the human cathelicidin LL-37 and β-defensins. Cathelicidins are immunomodulatory antimicrobials with an important role in the regulation of the inflammatory response. The only human cathelicidin, LL-37, is the most well-studied peptide in this family. LL-37 is an α-helical peptide. While defensins have a common β-sheet core stabilized with three disulfide bridges between six conserved cysteine residues.

Direct antimicrobial mechanisms of cationic host defense peptides can be mediated by membrane translocation of the peptides followed by binding to intracellular targets such as nucleic acids and/or proteins to kill bacteria. Proline-rich antimicrobial peptides use inner membrane transporters as Trojan horses to gain entry and bind to intracellular targets such as nucleic acids or nascent proteins. And subsequently affect cell processes such as replication, transcription, translation, protein folding, and cell wall synthesis.

At this stage, only a few peptide-derived treatments have made it to market such as PAC-113, a histatin analog, and dalbavancin, a semisynthetic lipoglycopeptide.

Despite the limited understanding of structure-function relationships, the potential of peptide-based therapies remains a promising new clinical direction for the Coronavirus.

2019-nCoV Coronavirus Receptor -Binding Motif Directly Contacts ACE2 Receptor

2019-nCoV Coronavirus Receptor -Binding Motif Directly Contacts ACE2 Receptor
2019-nCoV Coronavirus Receptor -Binding Motif

The extensive structural analyses have revealed that interactions between SARS-CoV spike protein receptor-binding domain (RBD) and its host receptor angiotensin-converting enzyme 2 (ACE2), which regulate both the cross-species and human-to-human transmissions of SARS-CoV.

Studies showed that the sequence of 2019-nCoV coronavirus RBD, including its receptor -binding motif (RBM) that directly contacts ACE2 and uses ACE2 as its receptor with much higher affinity (10-20 times higher!) than SARS.

Several critical residues in 2019-nCoV RBM may provide favorable interactions with human ACE2 such as Gln493 and Asn501.

A total of nine cysteine residues are found in the RBD, six of which forming three pairs of disulfide bonds. Among these three pairs, two are in the core (Cys336-Cys361 and Cys379-Cys432) to help stabilize the β sheet structure while the remaining one (Cys480-Cys488) connects loops in the distal end of the RBM.

LifeTein synthesized a 69 amino acid spike glycoprotein in 6 days

Coronavirus SARS-CoV-2
Coronavirus SARS-CoV-2

2019 Novel Coronavirus SARS-CoV-2 is a virus identified as the cause of an outbreak of respiratory illness Covid-19 first detected in Wuhan, China.

To help expedite Covid-19 research, LifeTein synthesized a 69 amino acid spike glycoprotein with one disulfide bond in 6 days. This effort is a partnership with a biotech company for drug development.

Cyclic peptides as broad-spectrum antiviral agents

Cyclic peptides as broad-spectrum antiviral agent

Cyclic peptides as broad-spectrum antiviral agents

Antiviral drugs and vaccines are the most powerful tools to combat viral diseases. Most drugs and vaccines only target a single virus. However, the broad-spectrum antivirals can be used for rapid management of new or drug-resistant viral strains. Cyclized peptides and peptide analogs are excellent examples of broad-spectrum antivirals.

An artificial peptide molecule was found to neutralize a broad range of group 1 influenza A viruses, including H5N1. The peptide design was based on complementarity determining region (CDR) loops have been reported for other viral targets. The optimized peptides bind to the highly conserved stem epitope and block the low pH-induced conformational rearrangements associated with membrane fusion.

These peptidic compounds and their advantageous biological properties should accelerate development of novel small molecule and peptide-based therapeutics against influenza virus.

The linear peptide is Suc-SQLRSLEYFEWLSQ-NH2. Three cyclization strategies were used: head to tail, side chain to side chain and side chain to tail. An ornithine (Orn) side chain was fused with the carboxyl terminus of β-alanine for lactam formation.

Check here for more details: Potent peptidic fusion inhibitors of influenza virus, Science 28 Sep 2017, DOI: 10.1126/science.aan0516

Lately, more broad-spectrum antiviral agents were found to target viruses. It was found that 55 compounds can target eight different RNA and DNA viruses. Dalbavancin is a novel lipo-glycopeptide antibiotic. The lipoglycopeptide disrupts bacterial cell wall formation by binding to
the terminal d-alanyl-d-alanine peptidoglycan sequence in Gram-positive bacteria in a linear, concentration-dependent manner. The dalbavancin has effects on echovirus 1, ezetimibe against HIV1 and Zika virus.

More details: https://www.ncbi.nlm.nih.gov/pubmed/29698664

Tips for Working with Magnetic Beads

Magnetic beads

Protein purification with magnetic beads is an excellent choice for high-throughput microscale purification, pull-down/CoIP, and protein/protein or protein/DNA interaction studies. Magnetic beads can be coated with specific affinity ligands for antigens, antibodies, proteins, or nucleic acids.

Magnetic beads have a defined diameter and non-porous. There are no hidden surfaces for the molecules to stick to. So the background, purification, and washing steps are all reduced. Separation using magnetic beads is the quickest, cleanest, and most efficient technique out of all the bead separation methods using agarose, sepharose, or silica beads.

Here are some tips for new users.

  1. Resuspend your beads thoroughly to ensure consistency between the aliquots

Magnetic beads need to have enough magnetic contents to allow simple pull-down by a magnet. Our Magnetic Beads are nano-superparamagnetic beads covalently coated with highly functional groups. The increased beads surface area results in increased binding capacity and improved dispersion. Magnetic beads are massive particles comprised of iron oxide, so they sediment over time. It is crucial to vortex and thoroughly resuspend the magnetic beads before use to redisperse the beads.

2. Wash your beads to reduce non-specific binding

Increase the number of washing steps helps to reduce non-specific binding to the beads. When washing the magnetic beads with either ethanol or recommended wash buffer, use enough wash solution to cover the pellet. Understand the functional groups of your beads
Our beads covalently coated with maleimide, primary amine, NHS, carboxylic acid, purified streptavidin, protein A, reduced glutathione, nickel-charged nitrilotriacetic acid, or groups for DNA/RNA purification. The coatings, buffer conditions, and functional groups will affect the properties of the beads. It is essential to understand the necessary information about the beads to handle them better.

3. Capture the beads to ensure all beads are recovered

Generally, the magnetic beads are attracted to the magnet and form a pellet within a minute. Prolong the attraction of the magnetic beads to the magnet helps.

4. Do not disturb the bead pellet when removing the wash solution

Angle the pipette tip when removing the wash solution or supernatant. Do not let the tip touch the pellet of magnetic beads.

New Publication: Cell Cited LifeTein Biotinylated Peptide Products

Pull-down assay using biotinylated peptides

Giantin, a novel conserved Golgi membrane protein, is a disulfide-linked homodimer. It was found that BFA-induced Golgi disorganization is associated with the monomerization of giantin.

The pull-down experiment was performed. The control peptide biotin-GHGTGSTGSGSMLRTLLRRRL synthesized by LifeTein was incubated with lysate and Dynabeads, as well as the lysate incubated with Dynabeads only served as a control. Dynabeads carrying MGAT1 peptide were able to pull-down giantin from the lysate of HeLa cells, however, giantin was not detected in the pull-down fraction from the lysate exposed to the Dynabeads or in combination with control peptide. It is logical to hypothesize that the MGAT1 binding domain of giantin lies within its N-terminal non-coiled-coil area.

The Dynabeads function similarly to LifeTein magnetic beads:
https://www.lifetein.com/peptide-product/amineactivated-peptide-conjugation-magnetic-beads-p-3647.html

Cells 2019, 8(12), 1631; https://doi.org/10.3390/cells8121631

Full list of Cell-Penetrating Peptides

Table 1 Selection of cell-penetrating peptides

(Reference: https://doi.org/10.1007/978-981-13-8747-0, Ülo Langel, CPP, Cell-Penetrating Peptides, 2019)

Rush Peptide Synthesis in Action

LifeTein Peptide Synthesis Service

LifeTein provides the fastest turnaround time and most reliable quality in the industry. Peptides are made in New Jersey, USA. Projects move from conception to bench in only 3–5 days so you can deal with your research deadlines.

Introducing LifeTein‘s faster microwave peptide synthesis technology!
LifeTein’s new platform is designed for maximized speed and efficiency. Unparalleled peptide quality, greater flexibility, and improved reliability make LifeTein the vendor of choice for all your peptide synthesis needs.

Remarkably Fast:

How to form the fibrillary structure using beta-amyloid peptides?

Aβ-(1–42) was dissolved to 1 mM in 100% hexafluoroisopropanol, hexafluoroisopropanol was removed under vacuum, and the peptide was stored at −20 °C. For the aggregation protocols, the peptide was first resuspended in dry Me2SO (DMSO) to 5 mM. For oligomeric conditions, F-12 (without phenol red) culture media was added to bring the peptide to a final concentration of 100 μM, and the peptide was incubated at 4 °C for 24 h. For fibrillar conditions, 10 mM HCl was added to bring the peptide to a final concentration of 100 μM, and the peptide was incubated for 24 h at 37 °C. ADDLS, amyloid derived diffusible ligands.

Aducanumab is a human monoclonal antibody that has been studied for the treatment of Alzheimer’s disease.