Peptides

Apelin-17 (human, bovine) is derived from the apelin peptide which acts as a ligand for the apelin receptor (APJ) G protein coupled receptor and is a substrate for angiotensin converting enzyme 2. Preprapelin, encoded for by APLN located on Xq25-26.1, is cleaved to form either apelin 36,or apelin 17, 12 and apelin 13. As a member of the adipokine hormone family, which are involved in processes such as vascular homeostasis and angiogenesis, apelin is secreted from adipose tissue.Apelin has been found to be expressed in the spinal cord and the human brain and when performing immunohistochemistry it was observed that apelin-17 is significantly expressed in the human heart, brain, lungs and endothelial cells.Both apelin and the apelin receptor are widely distributed around the body thus apelin has been found to be associated with cardiovascular diseases, obesity, diabetes and cancer. Studies exploring myocardial infarction showed there to be greater apelin mRNA expression during human heart failure compared to in healthy tissue. Apelin protects against heart failure due to, the pyroglutamyl form of apelin, playing a role in decreasing infarct size of myocardial infarctions. Furthermore in rats with hypertension, the expression of apelin and APJ was decreased.

Histone H3 (1-20) K4Me2 is derived from Histone 3 (H3), which is one of the four core histones (H2A, H2B, H3 and H4) fundamental in compacting eukaryotic DNA into the nucleosome. The nucleosome arises when 147 base pairs of DNA wrap around a H3-H4 tetramer and two H2A-H2B dimers, forming the histone octamer core. H4 and H3 are highly conserved and perform roles in binding to segments of DNA which enter and leave the nucleosome and in chromatin formation. Like the other core histone, H3 has a globular domain and a flexible N-terminal domain, 'histone tail' which can undergo modifications such as acetylation, methylation, phosphorylation and ubiquitination. Due to histones containing many lysine and arginine residues, they have a positive net charge which interacts electrostatically with the negatively charged phosphate groups in DNA. The transcriptional activation or silencing of the chromatin is controlled by ATP-dependent chromatin remodelling factors and histone-modifying enzymes which target histone proteins. Both processes change the positioning of the nucleosome, allowing the DNA to be either available to the transcription machinery or inaccessible.Histone tails can undergo multiple modifications, including acetylation, methylation, ubiquitylation and sumoylation.  The modification pattern is believed to alter chromatin function/structure. Histone H3 (1-20) K4Me2-GG-[Lys(5-FAM)] lysine 4 has been dimethylated, has a C-terminal GGK linker labelled with 5-Carboxyfluorescein (5-FAM), a widely used green fluorescent tag. This peptide also has an uncharged C-terminal amide. H3 (1-20) K4Me2 has been investigated to understand its effect on epigenetic regulation through NMR with histone readers such as zinc finger domains. Histone H3 (1-20) K4Me2-GG-[Lys(5-FAM)] can be used to study the function of this pattern on chromatin availability and histone effectors via crystallisation, pull-down assays and protein blots.

[Atto655]-LifeAct (Abp140 1-17) contains the 17 amino acid peptide Lifeact derived from amino acids 1-17 of the Saccharomyces cerevisiae actin binding protein, Abp140. These first 17 amino acids of Abp140 are crucial in allowing Lifeact to localise to actin filaments (F-actin) and therefore it can be used as a cytoskeletal marker. One application of lifeact is in the study of plant development and pathogen defence as filamentous actin within the plant's actin cytoskeleton is important in key processes such as cell division, membrane trafficking and stomatal movements. The addition of the oxazine fluorophore Atto655 which has single molecule (SM) imaging properties allows the location of the LifeAct (Abp140 1-17) to be detected.

SARS-CoV-2 Spike (757-765)

Codesane (COD), is a cationic α-helical amphipathic-anti-microbial-peptide isolated from the venom of the wild bee Colletes daviesanus (Hymenoptera Colletidae). COD exhibits-anti-microbial-activity against Gram-positive and Gram-negative bacteria and Candida albicans but also noticeable haemolytic activity.COD peptide works by permeating both the outer and inner cytoplasmic membranes of Escherichia coli.

Pseudin-2 (Ps) is one of the four pseudin peptides isolated from the skin of the paradoxical frog Pseudis-paradoxa. Pseudins are structurally related, cationic, amphipathic, a-helical anti-microbial peptides (AMP) that share sequence homology with an apoptosis regulating protein. Pseudin-2 is the most abundant and potent of the four pseudins.Pseudin-2 is active against Escherichia coli (with minimum inhibitory concentrations (MIC) of 2.5 mM), Staphylococcus aureus (MIC: 80 mM), and Candida albicans (MIC: 130 mM). Pseudin-2 also has low haemolytic activity against human erythrocytes (the concentration of Pseudin-2 producing 50% haemolysis: >300 mM).In addition to its anti-microbial properties, pseudin-2 has also been shown to stimulate insulin release and may be useful as a therapy for type 2 diabetes. This peptides has a non-amidated C-terminal end, as per the naturally occurring pseudin-2.

The cyclic pentapeptide cyclo(-Arg-Gly-Asp-d-Phe-Lys-) is a highly potent and selective inhibitor for the alphavβ3 integrin receptor. A related compound, cyclo(-Arg-Gly-Asp-d-Phe-Val), is a promising anti-cancer drug candidate- it inhibits angiogenesis and induces apoptosis in vascular cells.Cyclic RGD-containing peptides are selective antagonists of integrins, proteins that play important roles in cell-cell and cell-matrix interactions. In a suitably labelled form, these peptides may serve as useful tools for diagnostic imaging and peptide targeted therapy of some types of cancer.