A chain of amino acids joined by peptide bonds — shorter than a protein, with no sharp boundary between the two.
A peptide is a sequence of amino acids linked by peptide bonds, the amide bond formed between one residue's carboxyl group and the next one's amino group. Chains are commonly called peptides up to a few dozen residues and proteins beyond that, but the line is a convention rather than a definition.
Sequence determines molecular formula, molecular weight and how the chain folds, which is why identity testing is ultimately a question about sequence.
Topic: Fundamentals
A foundational overview of what research peptides are, how laboratories handle them as reference compounds, the difference between in-vitro and preclinical models, and why COAs matter.
Read moreA saturable, probe-dependent effect is what separates a modulator from a competitor. This guide covers the cooperativity factor alpha and the ceiling it sets in a binding curve, the operational model of allosterism, probe dependence as both diagnostic and complication, the radioligand dissociation experiment a competitor cannot pass, how to rule out receptor reserve and allosteric agonism, and the extracellular surfaces a peptide ligand can actually reach.
Read moreWhy an axis walk misses the ion-pairing/pH interaction and stalls short of a diagonal optimum, how the screening and response-surface stages divide the work, what replication buys that a lack-of-fit test cannot do without, and the difference between a modelled design space and a range you have actually run.
Read moreThe counterion can be the largest non-peptide term in a lyophilised solid, and it is not inferable from the sequence. How suppressed-conductivity ion chromatography measures trifluoroacetate, acetate, chloride and the common cations; how to dilute into the linear range; what system suitability to fix for a small anion; and how to read a molar ratio that lands far from expectation.
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