The order of amino acid residues in a peptide, conventionally written from the N-terminus to the C-terminus.
The sequence is a peptide's primary structure — the order of its residues, written N-terminus first. It is normally given in one-letter or three-letter code.
Two peptides with the same composition but different order are different molecules with the same molecular weight, which is why mass alone confirms identity only in combination with other evidence.
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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