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pH‐dependent formation of ethylenediaminetetraacetic acid supramolecular aggregates
Author(s) -
Müller Michele,
Haeberli André
Publication year - 1994
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(94)80164-9
Subject(s) - ethylenediaminetetraacetic acid , supramolecular chemistry , chemistry , biophysics , crystallography , organic chemistry , crystal structure , chelation , biology
Pure ethylenediaminetetraacetic acid tetrasodium salt (EDTA · Na 4 ) in water showed a pH‐dependent change of optical density detected in the ultraviolet region. The most important change was found between pH 4 and 8, corresponding to the deprotonation of the third ionizable group having a pK of 6.2. The absorbance change was reversible and depended on the addition/removal of only 1 proton equivalent. The presence of supramolecular aggregates was suggested by size‐exclusion chromatography, dialysis and cryo‐electronmicroscopy. The molecular weight of EDTA supramolecular aggregates was 10–15,000 and 8–14,000, as determined by gel chromatography and dialysis, respectively. Cryo‐electronmicroscopy revealed structures of 2–4 nm in diameter.