Monitoring the Switching from Base-on to Base-off Forms of Vitamin B12 by Natural and Magnetic Circular Dichroism Spectroscopies

Year: 2026

Authors: Machalska E., Mazzeo G., Wierzba A.J., Dybas J., Rode J.E., Abbate S., Gryko D., Baranska M., Longhi G., Fuse M.

Autors Affiliation: Univ Brescia, Dept Mol & Translat Med, I-25123 Brescia, Italy; Jagiellonian Univ, Jagiellonian Ctr Expt Therapeut, PL-30348 Krakow, Poland; Polish Acad Sci, Inst Organ Chem, PL-01224 Warsaw, Poland; Ist Nazl Ottica CNR, Unita Brescia, I-25123 Brescia, Italy; Univ Colorado, Dept Biochem, Boulder, CO 80309 USA; Univ Colorado, BioFrontiers Inst, Boulder, CO 80303 USA; Inst Nucl Chem & Technol, Lab Spect Mol Modeling & Struct Determinat, PL-03195 Warsaw, Poland; Jagiellonian Univ, Fac Chem, PL-30387 Krakow, Poland.

Abstract: This work demonstrates that an approach which makes use of magnetic circular dichroism (MCD) together with electronic circular dichroism (ECD) brings one to a rapid, sensitive, nondestructive, and inexpensive determination of the electronic structure of diamagnetic, chiral, and flexible molecular systems. The subject of this study is cobalamins (Cbls), including vitamin B12, the unique and intricate structure of which determines their selective and strong protein binding. Their existence in two forms (base-on and base-off) not only causes significant structural changes but also influences the reactivity of B12 derivatives in biologically important organometallic reactions. Therefore, recognizing the Cbl forms and understanding how they switch between them is essential. Notably, this study is the first to show that combining MCD and ECD, supported by quantum mechanics calculations, allows differentiation between base-on and base-off Cbls in aqueous environment at pH 7.4 and in acidic conditions, respectively. Furthermore, these techniques are sensitive to Cbl modifications at the meso position of the corrin macrocycle or in the axial upper ligands.

Journal/Review: ANALYTICAL CHEMISTRY

Volume: 98 (5)      Pages from: PMID 370536-1  to: PMID 370536-8

More Information: The authors are grateful for financial support from the National Science Centre, Poland (Project 20 19/33/N/ST4/01986 to E.M., 2021/41/B/NZ3/04146 to J.D.) and the Italian Ministry of University and Research (MUR) through the PRIN 2022 program (INVESTCPE) prot. 2022CXHY3A to G.M., E.M., and M.F., and (SMART HELIX), prot. 2022B3EFJH to G.L. M.F. thanks CINECA for an award under the ISCRA C project CCESTI – HP10CPAAXL. The authors also express their gratitude to Prof. Fabio Zobi (Department of Chemistry, University of Fribourg, Switzerland) for providing the vitamin B12 (Cbl-6) derivative. Lastly, we appreciate Jasco Europe for generously lending us the PMCD-586 module.
KeyWords: Co-c Bond; Electronic-properties; X-ray; B-12; Cobalamin; Coenzyme; Protein; Cofactors; Methylcobalamin; Transcobalamin
DOI: 10.1021/acs.analchem.5c07584