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Updated: Jul 16, 2026

Collecting Variable-concentration Isothermal Titration Calorimetry Datasets in Order to Determine Binding Mechanisms
Published on: April 7, 2011
Evaluation of the Binding Affinity of Nitrosylcobalamin to Intrinsic Factor as a Predictive Model for Cobalamin
Annette M Sysel1, Joseph A Bauer2
1Bauer Research Foundation, Inc., Akron, OH 44312, USA.
Background:
Intrinsic factor (IF) is a glycoprotein crucial for cobalamin (vitamin B12) absorption in the human body. This study aimed to evaluate the binding affinity of nitrosylcobalamin (NO-Cbl), a cobalamin analog, to recombinant human IF derived from plants, using hydroxocobalamin (OH-Cbl) as a comparative standard.
Methods:
Surface plasmon resonance (SPR) was employed to assess the kinetic parameters of NO-Cbl and OH-Cbl interactions with plant- derived IF across various concentrations.
Results:
SPR analysis demonstrated that NO-Cbl and OH-Cbl exhibited high binding affinities to IF, with equilibrium dissociation constant (KD) values in the picomolar range. OH-Cbl showed a slightly stronger binding affinity (KD = 4.79 × 10-11 M) than NO-Cbl (KD = 8.58 × 10-11 M). Despite NO-Cbl and OH-Cbl both being bound to IF, differences in binding affinity and stability were observed, particularly at higher concentrations.
Conclusion:
Variations in IF binding between NO-Cbl and OH-Cbl may be attributed to the saturation of binding sites or recognition issues specific to plant-derived IF. This study underscores the potential of NO-Cbl as a targeted therapeutic agent capable of leveraging natural cobalamin uptake pathways. These results also highlight the suitability of using recombinant plant-derived IF as a model for predicting the biological activity of cobalamin analogs despite the nuanced differences from native human IF.
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