Research Peptide Index Compound directory

Index note

Methodology

Every record in Research Peptide Index is built with the same rules. A fact is stored only when a public source supports it for that exact molecule. When that cannot be shown, the field says “Not verified” and the record explains why.

This page describes those rules: where facts come from, how a name is matched to a registry entry, the rule for each field, and how a record is labeled and reviewed.

Sources

  • PubChem is the main registry source. A record cites a specific PubChem compound by its CID, and the formula, molecular weight, and structure image come from that compound.
  • UniProt is used when it is the entry that actually states a sequence, which is common for naturally occurring peptides.
  • Peptide Sequence Database is linked when it has a page for the same compound. It is not used to fill fields that PubChem or UniProt do not support.

Supplier catalogs, certificates of analysis, forum posts, and marketing pages are not used as sources for identity facts.

Matching a name to a molecule

Most errors in peptide references come from names, not chemistry. A lookup for a common name can return a salt, a metal complex, a fragment, an acetylated or amidated form, or a longer parent molecule. Each of those is a different registry entry with a different formula and mass.

Before a registry entry is attached to a record, the index checks that it is the molecule the name usually means. Where a sequence is shown, the formula of the registry entry is compared with the sequence. If the lookup lands on a related but different substance, that registry entry is not used for the record. Any field it would have filled stays blank, and the naming note says what was found instead.

When one name is used for two molecules, the index keeps them on separate records rather than merging their facts.

Rules for each field

  • One-letter sequence and length. Shown only when a standard one-letter sequence describes the molecule. If the molecule has D-amino acids, unusual residues, cyclization, lipid chains, or other modifications that one-letter code would hide, the line stays blank and the naming note explains why.
  • Molecular formula and weight. Copied from the registry entry the record cites. They are not calculated from a sequence or taken from a supplier label.
  • CAS number. Shown only when the number resolves back to the same PubChem compound already on the record. Registries often list CAS numbers that belong to a salt, a parent, or a related compound. Those are not shown.
  • PubChem CID. The identifier of the registry entry the record relies on, linked to the public PubChem page.
  • Sequence database. Linked only when that site has a page for the same compound.

Each field is checked on its own. A record can have a confirmed formula and still have a blank CAS number. A filled field does not mean the other fields were confirmed.

What “Not verified” means

“Not verified” means the value could not be confirmed for that molecule from the sources above. It does not mean the value is unknown everywhere, and it does not mean the compound is suspect. It means the index will not print a number it cannot trace to the right registry entry.

Research status

Every record carries one of four labels:

  • Identity established: a registry record matched the name and the stored chemistry.
  • Sequence reported, registry incomplete: a sequence or partial registry fact is on the page, and something important is still open.
  • Fragment or analogue: the common name covers more than one molecule, or the record is deliberately not the parent registry entry.
  • Research name only: the name is in use, and a registry identity was not verified.

Status describes how well the identity is documented. It is not a rating of the compound, its safety, its quality, or its research value.

Research categories

Categories are editorial groupings that make the index easier to browse. They describe the area of research a compound is studied in. A compound can belong to more than one category. A category is not an indication, and it does not mean the compound has a clinical result in that area.

Review and changes

Every record shows the date it was last reviewed. A record is reviewed again when a correction is received, when a cited registry entry changes, or when a new source makes a blank field checkable.

When a fact changes, the new value must meet the same rules as the old one. Corrections are checked against the source they cite before a record changes. To report a problem, use the corrections page.

What this methodology does not cover

The methodology covers identity only. The index does not evaluate efficacy, safety, dosing, purity, or legal status, and it does not summarize study outcomes. Sources on a record support that record’s identity facts. They are not citations for any biological effect. See the references page for how sources are cited.