---
title: "Create a monomer"
method: POST
path: "/monomers"
tags: ["monomers"]
---

# Create a monomer

`POST /monomers`

## Request

- Base URL: `https://{tenant_name}.benchling.com/api/v2`
- URL: `https://{tenant_name}.benchling.com/api/v2/monomers`
- Auth: HTTP bearer

Create a monomer.

## Query parameters

- `returning` string

## Request body

- MonomerCreate
  - `color` string, nullable: The hex color code of the monomer visual symbol
  - `customMolecularWeight` number, double, nullable: Optional molecular weight value that the user can provide to override the calculated molecular weight
  - `name` string: Name of the monomer
  - `smiles` string: The chemical structure in SMILES format.
  - `symbol` string: User-defined identifier of the monomer, unique on the monomer type.
  - `visualSymbol` 'DIAMOND_FILLED' | 'DIAMOND_HOLLOW' | 'DIAMOND_DASHED' | 'STAR_FILLED' | 'STAR_HOLLOW' | 'TRIANGLE_FILLED' | 'TRIANGLE_HOLLOW' | 'DYAD_FILLED' | 'DYAD_HOLLOW' | 'CLOVER_FILLED' | 'CLOVER_HOLLOW' | 'TRIAD_FILLED' | 'TRIAD_HOLLOW' | 'RECTANGLE_FILLED' | 'RECTANGLE_HOLLOW' | 'LETTERS_P' | 'LETTERS_PS': The shape of the monomer visual symbol.
  - `naturalAnalog` string: Symbol for the natural equivalent of the monomer. Acceptable natural analog values include IUPAC bases, r, and p.

## Response `201`

Created

- Monomer
  - `archiveRecord` ArchiveRecord
    - `reason` string
  - `attachmentPoints` string[]: A list of the capping group present at each location where the monomer can form a bond with other monomers
  - `calculatedMolecularWeight` number, double: The molecular weight of the monomer as calculated by RDKit based on the monomer chemical structure
  - `canonicalSmiles` string: The canonicalized chemical structure in SMILES format.
  - `createdAt` string, date-time: DateTime the monomer was created.
  - `customMolecularWeight` number, double, nullable: Optional molecular weight value that the user can provide to override the calculated molecular weight
  - `exactMolecularWeight` number, double: The exact molecular weight of the monomer as calculated by RDKit based on the monomer chemical structure
  - `id` string: ID of the monomer
  - `modifiedAt` string, date-time: DateTime the monomer was last modified.
  - `monomerType` 'BACKBONE' | 'BRANCH': The part of the nucleotide structure that the monomer fits into, i.e. backbone or branch
  - `name` string: Name of the monomer
  - `naturalAnalog` string: Symbol for the natural equivalent of the monomer. Acceptable natural analog values include IUPAC bases, r, and p.
  - `originalSmiles` string, nullable: The original chemical structure supplied by the user in SMILES format. Null if the user did not originally supply SMILES.
  - `polymerType` 'RNA': The polymer type of the monomer. Currently only RNA monomers are supported.
  - `symbol` string: User-defined identifier of the monomer, unique on the monomer type.
  - `visualColor` string, nullable: The hex color code of the monomer visual symbol
  - `visualSymbol` 'DIAMOND_FILLED' | 'DIAMOND_HOLLOW' | 'DIAMOND_DASHED' | 'STAR_FILLED' | 'STAR_HOLLOW' | 'TRIANGLE_FILLED' | 'TRIANGLE_HOLLOW' | 'DYAD_FILLED' | 'DYAD_HOLLOW' | 'CLOVER_FILLED' | 'CLOVER_HOLLOW' | 'TRIAD_FILLED' | 'TRIAD_HOLLOW' | 'RECTANGLE_FILLED' | 'RECTANGLE_HOLLOW' | 'LETTERS_P' | 'LETTERS_PS': The shape of the monomer visual symbol.

## Other responses

- `400`: Bad Request
- `403`: Forbidden

---

[API](https://skmtc.dev/benchling/apis/benchling-api-2.md) - [All operations](https://skmtc.dev/benchling/apis/benchling-api-2/llms.txt) - [OpenAPI document](https://skmtc.dev/benchling/apis/benchling-api-2/revisions/01d2fa8523cd?raw)