Class Polypeptide

constructor

• new Polypeptide(mRNA): Polypeptide

• Parameters

  • mRNA: MRNA

    A mature mRNA sequence that codes for a sequence of amino acids

  Returns Polypeptide

  Throws

  InvalidSequenceError Thrown if the mRNA coding sequence length is not divisible by 3 (invalid codons)

  Throws

  InvalidCodonError Thrown if any codon is invalid (doesn't code for an amino acid and is not a stop codon)

  Example

  const mRNA = new MRNA('GAUGAAAGGGAAAUAG', 'AUGAAAGGGAAAUAG', 1, 16);
  const polypeptide = new Polypeptide(mRNA); // 4 codons: Met-Lys-Gly-Lys, stops at UAG
  console.log(polypeptide.aminoAcidSequence.length); // 4
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Readonly aminoAcidSequence

Readonly mRNA

contains

• contains(subsequence): boolean

• Checks if the polypeptide contains the specified amino acid subsequence

  Parameters

  • subsequence: string | Polypeptide

    The amino acid subsequence to search for (string or Polypeptide)

  Returns boolean

  True if the subsequence is found, false otherwise

  Example

  const polypeptide = new Polypeptide(mRNA); // sequence: 'MKGK'
  console.log(polypeptide.contains('KG')); // true
  console.log(polypeptide.contains('AA')); // false
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endsWith

• endsWith(suffix): boolean

• Checks if the polypeptide ends with the specified amino acid suffix

  Parameters

  • suffix: string | Polypeptide

    The amino acid suffix to check for (string or Polypeptide)

  Returns boolean

  True if the sequence ends with the suffix, false otherwise

  Example

  const polypeptide = new Polypeptide(mRNA); // sequence: 'MKGK'
  console.log(polypeptide.endsWith('GK')); // true
  console.log(polypeptide.endsWith('MK')); // false
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getSequence

• getSequence(): string

• Returns the single-letter amino acid sequence as a string

  Returns string

  String representation of the amino acid sequence

  Example

  const polypeptide = new Polypeptide(mRNA);
  console.log(polypeptide.getSequence()); // 'MKGK' (single letter codes)
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getSubsequence

• getSubsequence(start, end?): Polypeptide

• Returns a sub-polypeptide from the specified start position to the end position

  Parameters

  • start: number

    The starting position (inclusive, 0-based)
  • Optional end: number

    The ending position (exclusive, 0-based). If not specified, goes to end of sequence

  Returns Polypeptide

  A new Polypeptide instance containing the amino acid subsequence

  Example

  const polypeptide = new Polypeptide(mRNA); // sequence: 'MKGK'
  const sub = polypeptide.getSubsequence(1, 3); // Creates polypeptide with 'KG'
  console.log(sub.getSequence()); // 'KG'
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indexOf

• indexOf(subsequence, startPosition?): number

• Returns the index of the first occurrence of the specified amino acid subsequence

  Parameters

  • subsequence: string | Polypeptide

    The amino acid subsequence to search for (string or Polypeptide)
  • startPosition: number = 0

    The position to start searching from (default: 0)

  Returns number

  The index of the first occurrence, or -1 if not found

  Example

  const polypeptide = new Polypeptide(mRNA); // sequence: 'MKGK'
  console.log(polypeptide.indexOf('K')); // 1 (first K)
  console.log(polypeptide.indexOf('K', 2)); // 3 (second K)
  console.log(polypeptide.indexOf('AA')); // -1 (not found)
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length

• length(): number

• Returns the length of the polypeptide in amino acids

  Returns number

  The number of amino acids in the sequence

  Example

  const mRNA = new MRNA('GAUGAAAGGGAAAUAG', 'AUGAAAGGGAAAUAG', 1, 16);
  const polypeptide = new Polypeptide(mRNA);
  console.log(polypeptide.length()); // 4 amino acids
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startsWith

• startsWith(prefix): boolean

• Checks if the polypeptide starts with the specified amino acid prefix

  Parameters

  • prefix: string | Polypeptide

    The amino acid prefix to check for (string or Polypeptide)

  Returns boolean

  True if the sequence starts with the prefix, false otherwise

  Example

  const polypeptide = new Polypeptide(mRNA); // sequence: 'MKGK'
  console.log(polypeptide.startsWith('MK')); // true
  console.log(polypeptide.startsWith('GK')); // false
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