Forms of vitamin B12 in radioisotope dilution assays.

Begley, James A.; Hall, Charles A.

doi:10.1136/jcp.34.6.630

Cited by 14 publications

(5 citation statements)

References 16 publications

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“…At that time, studies of Cbl analogs in biological samples were based on extraction procedures that involved acidic or alkaline solutions, addition of KCN, and sometimes heating before quantification of the corrinoids with radioisotope dilution assays (20,21 ). There has been discussion as to whether these extraction procedures could alter the molecular form of Cbl, thereby creating the Cbl analogs as artifacts (22,23 ). We have circumvented this problem by using an enzymatic degradation of the binding proteins, thereby ensuring that Cbl analogs observed are not caused by the extraction procedure (12 ).…”

Section: Discussionmentioning

confidence: 99%

A New Principle for Measurement of Cobalamin and Corrinoids, Used for Studies of Cobalamin Analogs on Serum Haptocorrin

Hardlei

Nexø

2009

Clinical Chemistry

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Section: Discussionmentioning

confidence: 99%

A New Principle for Measurement of Cobalamin and Corrinoids, Used for Studies of Cobalamin Analogs on Serum Haptocorrin

Hardlei

Nexø

2009

Clinical Chemistry

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“…Some microorganisms can synthesize cobalamin whereas delivery to mammals is through dietary intake. Vitamin B 12 has been recognized as an efficient transporter of proteins, anticancer drugs, and radioisotopes to eukaryotic cells. − Therefore, it may be also successful in delivering PNA to some prokaryotic cells which need to take up vitamin B 12 from the environment. Indeed our experiments have shown that such uptake is possible (data not shown).…”

Section: Introductionmentioning

confidence: 99%

Conformational Dynamics of Cyanocobalamin and Its Conjugates with Peptide Nucleic Acids

et al. 2017

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Vitamin B also called cobalamin (Cbl) is an important enzymatic cofactor taken up by mammalian and also by many bacterial cells. Peptide nucleic acid (PNA) is a synthetic DNA analogue that has the ability to bind in a complementary manner to natural nucleic acids. Provided that PNA is efficiently delivered to cells, it could act as a steric blocker of functional DNA or RNA and regulate gene expression at the level of transcription or translation. Recently, Cbl has been examined as a transporter of various molecules to cells. Also, PNA, if covalently linked with Cbl, can be delivered to bacterial cells, but it is crucial to verify that Cbl does not change the desired PNA biological properties. We have analyzed the structure and conformational dynamics of conjugates of Cbl with a PNA monomer and oligomer. We synthesized a cyanocobalamin derivative with a PNA monomer C connected via the triazole linker and determined its NMR spectra. Using microsecond-long molecular dynamics simulations, we examined the internal dynamics of cyanocobalamin-C, its conjugate with a 14-mer PNA, and free PNA. The results suggest that all compounds acquire rather compact structures but the PNA oligomer conformations vary. For the Cbl-C conjugate the cross-peaks from the ROESY spectrum corroborated with the clusters from molecular dynamics trajectories. Within PNA the dominant interaction is stacking but the stacking bases are not necessarily neighboring in the PNA sequence. More bases stack in free PNA than in PNA of the conjugate, but stacking is less stable in free PNA. PNA in the conjugate is slightly more exposed to solvent. Overall, cyanocobalamin attached to a PNA oligomer increases the flexibility of PNA in a way that could be beneficial for its hybridization with natural nucleic acid oligomers.

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“…Since IF only binds Cbl and HC binds both Cbl and CorA [3], it was suggested that the discrepancy in the results obtained with the two radioimmunoassay-measurements, was caused by the presence of CorA in the extracts of plasma corrinoids. Following the initial description of CorA in humans it was discussed whether CorA were native compounds, or whether they were derived from Cbl as a result from a harsh extraction procedure [4], [5].…”

Section: Introductionmentioning

confidence: 99%

Cobalamin Analogues in Humans: A Study on Maternal and Cord Blood

et al. 2013

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BackgroundHaptocorrin (HC) carries cobalamin analogues (CorA), but whether CorA are produced in the body is unknown. All cobalamins (Cbl) to the foetus are delivered by the Cbl-specific protein transcobalamin (TC), and therefore analysis of cord serum for CorA may help to clarify the origin of CorA.MethodsHC-CorA were quantified in paired samples of cord serum from newborns and serum from mothers (n = 69).ResultsThe CorA-concentration was higher in cord serum (median = 380, range: 41–780 pmol/L) than in serum from the mothers (median = 160, range: 64–330 pmol/L), (p<0.0001). HPLC-analysis showed CorA-peaks with retention times of 13.5, 14,5 and 16.5 min in samples from both the mother and cord serum. The peak with retention time 16.5 min constituted 24% (mother) and 45% (cord serum) of the total amount CorA, and eluted as does dicyanocobinamide.ConclusionOur results support that CorA in the human body are derived from Cbl.

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Forms of vitamin B12 in radioisotope dilution assays.

Cited by 14 publications

References 16 publications

A New Principle for Measurement of Cobalamin and Corrinoids, Used for Studies of Cobalamin Analogs on Serum Haptocorrin

A New Principle for Measurement of Cobalamin and Corrinoids, Used for Studies of Cobalamin Analogs on Serum Haptocorrin

Conformational Dynamics of Cyanocobalamin and Its Conjugates with Peptide Nucleic Acids

Cobalamin Analogues in Humans: A Study on Maternal and Cord Blood

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