---
title: "Update AaMonomer"
method: PATCH
path: "/api/v3/aa-monomer/{aa_monomer_id}"
tags: ["AA Monomer"]
---

# Update AaMonomer

`PATCH /api/v3/aa-monomer/{aa_monomer_id}`

## Request

- Base URL: `https://{tenant_name}.benchling.com`
- URL: `https://{tenant_name}.benchling.com/api/v3/aa-monomer/{aa_monomer_id}`
- Auth: HTTP bearer

Update AaMonomer.

## Path parameters

- `aa_monomer_id` string, required

## Headers

- `EARLY-ACCESS` string

## Request body

- UpdateAaMonomerInput
  - `archiveReason` string: Why it is being archived. Required when `archived` is `true`, and not allowed when unarchiving.
  - `archived` boolean: Set to `true` to archive or `false` to unarchive it. Archiving requires `archiveReason`.
  - `chemicalStructure` AaMonomerChemicalStructureInput
    - `structureFormat` 'smiles', required
    - `value` string, required
  - `customMolecularWeight` number, double, nullable: Optional molecular weight value that the user can provide to override the calculated value.
  - `name` string
  - `symbol` string: User-defined identifier of the monomer, unique per tenant.

## Response `200`

OK

- AaMonomer: An amino acid monomer is a building block for modified peptide sequences. Each AA monomer has a symbol identifier, chemical structure (SMILES/molfile), molecular weight, and attachment points defining where it bonds to other monomers. The naturalAnalog field links modified monomers to their standard amino acid counterpart (e.g., a modified alanine analog links to natural 'A'). AA monomers define the chemistry of non-standard amino acids used in peptide and protein engineering.
  - `__typename` string
  - `archiveReason` string, nullable
  - `archived` boolean
  - `attachmentPoints` AaMonomerAttachmentPointsItems[]: The capping groups present at each attachment point where the monomer bonds to other monomers.
  - `calculatedMolecularWeight` number, double: The molecular weight of the monomer with capping groups removed, computed using the average atomic weights of each element weighted by natural isotopic frequency.
  - `canonicalSmiles` string: The SMILES representation of the chemical structure after being standardized.
  - `createdAt` string, datetime
  - `creator` PrincipalRef
    - `__typename` string
    - `id` string, api_id
  - `customMolecularWeight` number, double, nullable: Optional molecular weight value that the user can provide to override the calculated value.
  - `exactMolecularWeight` number, double: The exact (monoisotopic) molecular weight of the monomer with capping groups removed, computed using the atomic weight of the most frequent isotope of each element.
  - `id` string
  - `isNatural` boolean: Whether this monomer represents a natural (unmodified) amino acid, as opposed to a modified or synthetic variant.
  - `modifiedAt` string, datetime
  - `molfile` string: The molfile representation of the chemical structure.
  - `name` string
  - `naturalAnalog` 'A' | 'B' | 'C' | 'D' | 'E' | 'F' | 'G' | 'H' | 'I' | 'J' | 'K' | 'L' | 'M' | 'N' | 'O' | 'P' | 'Q' | 'R' | 'S' | 'T' | 'U' | 'V' | 'W' | 'X' | 'Y' | 'Z': The standard amino acid single-letter code that this monomer is an analog of.
  - `originalSmiles` string, nullable: The SMILES string that was originally provided upon creation. Null if the user did not originally provide SMILES.
  - `symbol` string: User-defined identifier of the monomer, unique per tenant.

## Other responses

- `400`: Bad Request
- `403`: Forbidden
- `404`: Not Found
- `409`: Conflict
- `429`: Too Many Requests
- `500`: Internal Server Error

---

[API](https://skmtc.dev/benchling/apis/benchling-api.md) - [All operations](https://skmtc.dev/benchling/apis/benchling-api/llms.txt) - [OpenAPI document](https://skmtc.dev/benchling/apis/benchling-api/revisions/c9f087b98b8b?raw)