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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.
Insights
Researchers identified a specific middle molecule, b4.2, linked to uremic toxicity and polyneuropathy. This glucuronide solute, distinct from Stockholm
Area of Science:
- Nephrology
- Toxicology
- Biochemistry
Background:
- Middle molecules (MM) are implicated in uremic toxicity.
- The specific solutes responsible remain largely unidentified.
Purpose of the Study:
- To isolate and characterize middle molecules associated with uremic toxicity.
- To differentiate between MM isolated by different research groups.
Main Methods:
- Thin layer chromatography for purity assessment.
- Enzymatic and acidic hydrolysis.
- Mass spectrometry (desorption chemical ionization and electron-impact ionization).
Main Results:
- A distinct solute, b4.2, was isolated and purified.
- b4.2 was identified as a glucuronide with a molecular weight of 568 daltons (or 526 in native form).
- b4.2 is chemically different from Stockholm's peak 7c and is found in both normal urine and uremic hemofiltrate.
Conclusions:
- The isolated solute b4.2 is a potential contributor to uremic toxicity and polyneuropathy.
- b4.2 is a glucuronoconjugate of an aglycon with a molecular weight of 392 daltons (or 350 in native form).
- The characterization of b4.2 provides a new target for understanding and potentially treating uremic toxicity.