Peptides

3CLpro are the key enzymes required by coronaviruses to replicate. They cleave polyproteins to form replicase. This makes 3CLpro a drug target for protease inhibitors with particular interest to COVID-19. For, example Paxlovid®- has been brought to market as a 3CLpro inhibitor that can be administered orally to reduce coronavirus disease 19 (COVID-19) hospitalisation. Aiming to expand on such advances, synthesis of more substrates for 3CLpro are being generated and tested for their ability to inhibit the protease activity and thus replication cycle of coronaviruses. This product is the natural substrate for 3CLpro, this makes it a useful tool as a control but also for structural manipulation to design inhibitors.

With the rise of multidrug-resistant bacteria like P. aeruginosa, the hunt for low toxicity inhibitors is paramount. A crucial part of their virulence/life cycle is cleavage of signal peptides. Type I signal peptides have a C-terminal hydrophilic domain containing a signal peptidase cleavage site commonly found in P. aeruginosa proteins that are cleaved by type I signal petidases (SPases). P. aeruginosa LasB, a type I signal peptide, is a crucial enzyme for bacterial invasion, it degrades elastin and thus aids tissue invasion, without cleavage by a SPase the protein is inactive. This peptide is an ideal candidate for enzymatic assay work in to SPase inhibitor investigations.Here we provide the substrate LasB sequence with the EDANS-Dabcyl donor quencher pair suitable for SPase inhibitor assays with FRET microscopy analysis. When this peptide is intact, fluorescence from the fluorophore (donor) EDAN is undetectable due to the proximity of the acceptor (quencher) Dabcyl. However, upon cleavage the fluorescence of the EDANS moiety, as measurably by excitation/emission 340/490nm, can be detected due to separation from the Dabcyl quencher.

The heptapeptide Alexamorelin is a member of the Growth Hormone secretagogues (GHS) family. These are synthetic molecules which act through the central nervous system to stimulate the secretion of somatotrophs, prolactin, adrenocorticotrophin and cortisol. Alexamorelin has also been shown to inhibit 125I-Tyr-Ala-HEX binding in tissues. Due to their stimulation of growth hormone release, they are known as non-approved pharmaceuticals and are a concern to sport's drug testing organisations.

Melittin is a 26-residue peptide originally isolated from venom of the European honeybee. Melittin is a cationic, hemolytic peptide from honey bee venom. Melittin lowers the surface tension at the plasma membrane and causes cell lysis. Melittin exhibits potent anti-inflammatory and antimicrobial activity. Melittin has been extensively used as a model peptide for observing membrane lipid-protein interactions.

TAT (48-60) amide is a cell penetrating cationic peptide derived from the N-terminus of the Tat protein, which is a trans-activator of the transcription protein present in the human immunodeficiency virus (HIV). The 48-60 region of the TAT peptide is an arginine-rich bascic domain which as a whole has three domains that function to aid HIV through transactivation, DNA binding and nuclear transport. As a cell penetrating peptide (CPP) TAT aids in the cellular uptake of molecules and hence serves a valuable purpose in transduction methods. This property has been demonstrated through its ability of allowing toxins such as the neurotoxin Botulinum neurotoxin Type A, produced by the Clostridium botulinum type A bacteria to penetrate the skin barrier non-invasively.This peptide has an uncharged C-terminal amide.

β-Amyloid 1-10 (Aβ1-10) is one of many short Aβ species found in vivo and is formed by the cleavage of amyloid β precursor protein by β- and α-secretase.-Amyloid β-protein (Aβ) has been identified as the key subunit of the extracellular plaques found in the brains of patients with Alzheimer disease (AD) and Down syndrome (DS). Aβ has therefore been extensively studied as a potential target for treatment of AD.Aβ is formed from the cleavage of the large, transmembrane protein- APP (amyloid precursor protein). Cleavage of APP by β- and then α-secretases results in the formation of Aβ. Aβ can aggregate to produce amyloid-β oligomers, which are thought to be highly neurotoxic. Over time Aβ can further aggregate to produce the characteristic senile plaques present in AD and DS. Aβ can be degraded by enzymes such as neprilysin, insulin degrading enzyme or endothelin converting enzyme. At physiological levels Aβ may be involved in controlling synaptic activity and neuronal survival. Biotin is C-terminally linked to the peptide via ethylenediamine-for convenient detection and purification. Alternative β-Amyloid fragments and labels are also available, please refer to our peptide catalogue for availability.

Isotocin is a nonapeptide of the arginine vasopressin-oxytocin family produced exclusively in the preoptic area (POA) of teleosts. As a homologue of mammalian oxytocin, studying fish nonapeptides has shown that Isotocin mediates social and reproductive behaviour in fishes. Functional isotocin is stored in granules at the axon terminal with a carrier peptide, neurophysin. Stimuli leads to isotocin dissociation, to be released into the bloodstream or to cross over into the brain. It binds to G-protein coupled receptors (GPCRs), which subtype isotocin binds to defines the following physiological action. It, like other nonapeptides, is a neuromodulator in the CNS, but when distributed by the bloodstream, it acts as a peripheral hormone, such as regulating osmoregulation. Isotocin levels are sex-dependent and linked to the reproductive cycle.HPLC is a sensitive method to detect bioavailable isotocin and other nonapeptides. Measurement of mRNA levels of isotocin has been important to demonstrate the cyclical changes to regulate the endocrine calendar and diurnal rhythm. The level of isotocin is also considered a biomarker for aggression in behavioural indicators of fish welfare studies.