---
title: "Protein Properties"
method: POST
path: "/protein_properties"
tags: ["Proteins & peptides"]
---

# Protein Properties

`POST /protein_properties`

## Request

- Base URL: `https://seqbench.com/api/v1`
- URL: `https://seqbench.com/api/v1/protein_properties`
- Auth: none required

Protein properties: molecular weight, isoelectric point, GRAVY, extinction coefficient and composition.

Batchable via `POST /batch`.

## Request body

- object
  - `sequence` string, required: Protein sequence (one-letter amino-acid codes; non-AA characters ignored).
  - `chargeStep` number: pH step along the net-charge titration curve, which always spans pH 0-14. Between 0.001 and 14.
  - `a280` number: A measured absorbance at 280 nm. When given, the response adds `concentration` in mg/mL and µM for both extinction coefficients.
  - `pathLengthCm` number: Path length of the A280 reading in cm (a NanoDrop already reports values normalised to 1 cm).
  - `dilution` number: How many-fold the sample was diluted before the A280 was read.

## Response `200`

Tool ran successfully.

- SuccessResponse: Standard success envelope returned by every single-tool call.
  - `ok` unknown, required
  - `tool` string, required: The tool slug that ran.
  - `result` object, required: Tool-specific output object. Its shape depends on the tool — call `GET /{tool}` or see the docs for each tool's fields.
  - `gate` GateResult
    - `pass` boolean, required: True if and only if every hard check passed.
    - `checks` GateCheck[], required
      - `id` string, required
      - `label` string, required
      - `severity` 'hard' | 'soft', required
      - `pass` boolean, required
      - `message` string, required
      - `value` number
      - `threshold` string
    - `notChecked` string[], required: Honest list of what this gate does NOT verify.
  - `provenance` Provenance, required
    - `apiVersion` string, required
    - `tool` union, required: Tool slug, or an array of slugs (one per step) for a workflow.
      - string
      - string[]
    - `generatedAt` string, date-time, required: ISO 8601 timestamp of when the result was generated.

## Other responses

- `400`: Invalid argument or the tool could not run.
- `404`: Unknown tool.
- `429`: Rate limited (metered tools only). Body carries code `rate_limited` and retryable `true`; honor the Retry-After header.
- `503`: A metered tool is momentarily at capacity. The identical request should succeed after Retry-After; body carries code `upstream_unavailable`.

---

[API](https://skmtc.dev/seqbench/apis/seqbench-api.md) · [All operations](https://skmtc.dev/seqbench/apis/seqbench-api/llms.txt) · [OpenAPI document](https://skmtc.dev/seqbench/apis/seqbench-api/revisions/132575216865?raw)