Characterization of middle molecule compounds.
Gel filtration and subsequent ion exchange chromatography were used to separate middle molecule (MM) fractions in the molecular weight range of 350-2,000 daltons from uremic biological fluids. Three of these fractions (71, 7b, and 7c) were further investigated. Although these fractions after ion exchange chromatography appeared to be chromatographically pure, isotachophoretic analyses revealed at least two compounds in each fraction and the distribution of the constituents varied in different patients. Middle molecule 7c from one patient was pure enough to allow further characterization. After hydrolysis, glycine was the only amino acid recovered. The compound had a blocked N-terminus but the C-terminal amino acid was free. The blocking groups were investigated by partial acid hydrolysis, high voltage electrophoresis, isotachophoresis, mass spectrometry, and by enzymatic hydrolysis. The results suggested that the major compound in fraction 7c is a beta-glucuronidated conjugate of o-OH-benzoic acid and glycine.
D002850:Chromatography, Gel; D005965:Glucuronates / Q000097:blood* / Q000302:isolation & purification; D006801:Humans; D006435:Renal Dialysis; D014118:Toxins, Biological / Q000302:isolation & purification*; D014462:Ultrafiltration; D014511:Uremia / Q000097:blood*
D005965:Glucuronates; D014118:Toxins, Biological; C026865:uremia middle molecule toxins