Characterization of sub-peak b4.2, middle molecule.
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.
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*
D005965:Glucuronates; D014118:Toxins, Biological; C026865:uremia middle molecule toxins