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Cystine

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C6H12N2O4S2 · 240.3 g/mol

IUPAC name: (2R)-2-amino-3-[[(2R)-2-amino-2-carboxyethyl]disulfanyl]propanoic acid

Also called L-cystine, disulfide, cysteine dimer

Amino acids
Open in Athanor
The structure of Cystine
Drawn from its SMILES with RDKit

Names and identifiers

IUPAC name
(2R)-2-amino-3-[[(2R)-2-amino-2-carboxyethyl]disulfanyl]propanoic acid
Synonyms
L-cystine, disulfide, cysteine dimer
+ 37 more

L-Dicysteine, beta,beta'-Dithiodialanine, L-Cysteine disulfide, 1-Cystine, Cystine, L-, Dicysteine, Cystine (L)-, Cystine acid, Cysteine disulfide, Cystin, (-)-Cystine, Alanine, 3,3'-dithiodi-, Alanine, 3,3'-dithiobis-, beta,beta'-Dithioalanine, L-, L-Alanine, 3,3'-dithiobis-, DTXSID2046418, L-alpha-Diamino-beta-dithiolactic acid, 3,3'-Dithiobis(2-aminopropanoic acid), 3,3'-Dithiodialanine, cistina, Bis(beta-amino-beta-carboxyethyl)disulfide, (R-(R*,R*))-3,3'-Dithiobis(2-aminopropanoic acid), 48TCX9A1VT, beta,beta'-Diamino-beta,beta'-dicarboxydiethyl disulfide, (2R,2'R)-3,3'-disulfanediylbis(2-aminopropanoic acid), beta,beta'-Diamino-beta,beta'-dicarboxydiethyldisulfide, 3,3'-Dithiobis(2-aminopropanoic acid), (R-(R*,R*))-, Propanoic acid, 3,3'-dithiobis(2-amino-, (R-(R*,R*))-, NSC-13203, (2R)-2-amino-3-{[(2R)-2-amino-2-carboxyethyl]disulfanyl}propanoic acid, DTXCID0026418, CHEBI:16283, (R,R)-3,3'-dithiobis(2-aminopropanoic acid), (2R)-2-amino-3-[[(2R)-2-amino-2-carboxyethyl]disulfanyl]propanoic acid, alpha-Diamino-beta-dithiolactic acid, L Cystine, CHEBI:17376

Molecular formula
C6H12N2O4S2
Empirical formula
C3H6NO2S
Molecular weight
240.3 g/mol
Exact mass
240.02385
CAS number
56-89-3
PubChem CID
67678
Canonical SMILES
C(C(C(=O)O)N)SSCC(C(=O)O)N
Isomeric SMILES
C([C@@H](C(=O)O)N)SSC[C@@H](C(=O)O)N
InChI
InChI=1S/C6H12N2O4S2/c7-3(5(9)10)1-13-14-2-4(8)6(11)12/h3-4H,1-2,7-8H2,(H,9,10)(H,11,12)/t3-,4-/m0/s1
InChIKey
LEVWYRKDKASIDU-IMJSIDKUSA-N
Molfile

Names, InChI and the identifiers from PubChem, retrieved 2026-10-14.

Calculated

Heavy atoms
14
Rings
0
Aromatic rings
0
Fraction sp³ carbons (Fsp3)
0.67
H-bond donors
4
H-bond acceptors
6 computed here · PubChem 8
Rotatable bonds
7
TPSA (Ų)
126.6 computed here · PubChem 177
Formal charge
0
XLogP3
-6.3 PubChem
Complexity
192 PubChem
Stereocenters
2 definedCIP: C2: R · C7: R
Double-bond geometry
None specified
Point group
C1 of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

  • C29.99%
  • H5.03%
  • N11.66%
  • O26.63%
  • S26.69%

Isotope pattern

100%240.0249.1%241.02610%242.021243.023244.019

Each peak is a nominal mass with its abundance-weighted exact mass, as a percentage of the tallest, from IUPAC natural isotope abundances.

Computed from the structure with RDKit 2026.09 when this page was built, beside PubChem's own computed values from its record; where the two differ, both are shown.

Predicted

log P
-0.81 Crippen (Wildman and Crippen 1999)
log S (water solubility)
-0.36 ESOL (Delaney 2004), log mol/L
Synthetic accessibility
3.5 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

  • Molecular weight ≤ 500: 240.31
  • log P ≤ 5 (Crippen): -0.81
  • H-bond donors ≤ 5: 4
  • H-bond acceptors ≤ 10: 6

Passes all four rules.

¹³C NMR shifts, predicted

Predictions, not measurements; each names its method. A measured log P, where a source reports one, is under Physical properties.

Safety

This chemical does not meet GHS hazard criteria for 97.8% (182 of 186) of all reports.[1]

Safety data sheets on the supplier’s page: LGC Standards, Sigma-Aldrich, DempoChem.

Always read the supplier’s safety data sheet before working with it.

Spectra

Experimental spectra held by these sources; each link opens the source's own record.

Literature

Reading PubChem, OpenAlex and GSRS…

Bioactivity

Reading ChEMBL…

References

  1. [1]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
  2. [2]Human Metabolome Database (HMDB) · Linked only · via PubChem · retrieved 2026-10-14
  3. [3]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
  4. [4]MassBank Europe · Linked only · via PubChem · retrieved 2026-10-14
  5. [5]MassBank of North America (MoNA) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
  6. [6]NIST Mass Spectrometry Data Center · Linked only · via PubChem · retrieved 2026-10-14
  7. ·Calculated values: computed by Athanor with RDKit 2026.09 from the structure.
  8. ·Literature on PubChem

Data last updated 2026-10-14.