A redetermination of the structure of poly[[μ₄-(R)-2-ammonio-3-sulfonato­propano­ato]aqua­sodium], originally reported as poly[[μ₇-L-cysteato(2−)]disodium]

The structure originally reported as poly[[μ₇-L-cysteato(2−)]disodium], [Na₂(C₃H₅NO₅S)]_n [Liu (2002). Acta Cryst. E67, m1346–m1347], has been redetermined with one of the sodium atoms replaced with a water mol­ecule and an additional proton attached to the amine group, resulting in the revised formula [Na{CO₂CH(CH₂SO₃)NH₃}(H₂O)]_n. The agreement index, wR, has been reduced from 0.159 to 0.087 and the global instability index from 0.56 vu (valence units) to the acceptable value of 0.11 vu.