title: Characterization of sub-peak b4.2, middle molecule.
abstract: The Middle Molecules (MM) within the molecular weight (MW) range of vitamin B12 (1355 daltons) are assumed to be partly responsible for uremic toxicity. We have isolated a solute, b4.2, the purity of which is controlled by thin layer chromatography on silica gel. It correlates with active clinical polyneuropathy. The Stockholm group is dealing with a MM they call peak 7c. After exchange of purified solutes between the Stockholm group and us, comparative analyses demonstrate that 7c and b4.2 are different. The b4.2 solute is a glucuronide but it is impossible to obtain the aglycon moiety after enzymatic or acidic hydrolysis. Desorption chemical ionization and electron-impact ionization mass spectrometry results of b4.2 after transformation in methyl ester trimethylsilyl derivative are compatible with a b4.2 MW of 568 daltons (or 526 in native form) corresponding to a glucuronoconjugate of an aglycon with a MW 392 daltons (or 350 in native form). Moreover mass spectrometry confirms that b4.2 isolated from normal human urine and from uremic RP6 hemofiltrate fluid are identical.
mesh_terms: D008401:Gas Chromatography-Mass Spectrometry; D005965:Glucuronates / Q000032:analysis / Q000652:urine; D006801:Humans; D013058:Mass Spectrometry; D008970:Molecular Weight; D014118:Toxins, Biological / Q000097:blood / Q000302:isolation & purification*; D014511:Uremia / Q000097:blood*
chemical_list: D005965:Glucuronates; D014118:Toxins, Biological; C026865:uremia middle molecule toxins