Resonance Raman Optical Activity Spectroscopy in Probing Structural Changes Invisible to Circular Dichroism Spectroscopy: A Study on Truncated Vitamin B12 Derivatives.

Ewa Machalska,Monika Halat,Dorota Gryko,Grzegorz Zajac,Aleksandra J Wierzba,Malgorzata Baranska

doi:10.3390/molecules25194386

Abstract

This work demonstrates resonance Raman optical activity (RROA) spectra of three truncated vitamin B12 derivatives modified within the nucleotide loop. Since truncated cobalamins possess sufficiently high rotational strength in the range of ROA excitation (532 nm), it was possible to record their spectra in the resonance condition. They showed several distinct spectral features allowing for the distinguishing of studied compounds, in contrast to other methods, i.e., UV-Vis absorption, electronic circular dichroism, and resonance Raman spectroscopy. The improved capacity of the RROA method is based here on the excitation of molecules via more than two electronic states, giving rise to the bisignate RROA spectrum, significantly distinct from a parent Raman spectrum. This observation is an important step in the dissemination of using RROA spectroscopy in studying the complex structure of corrinoids which may prove crucial for a better understanding of their biological role.

Highlights

IntroductionVitamin B12 (cyanocobalamin, (CN)Cbl), belonging to the best studied among all corrinoid molecules, is a micronutrient isolated from specific bacterial sources e.g., Propionibacteria and Pseudomonas denitnpcans [8,9]
Natural cobalt-corrinoids and their synthetic analogs have recently been widely explored as transporters of biologically important molecules into eukaryotic or prokaryotic cells [1,2], fluorophore probes [3], antivitamins [4,5], and a catalyst [6] like other commonly known catalytic materials [7].Vitamin B12 (cyanocobalamin, (CN)Cbl), belonging to the best studied among all corrinoid molecules, is a micronutrient isolated from specific bacterial sources e.g., Propionibacteria and Pseudomonas denitnpcans [8,9]
Based on the changes in the color of the (CN)Cbl solution in water compared to its incomplete derivatives: from red for cobalamin to rosy for (CN)(H2 O)Cby(OMe)7 and purple for (CN)2 Cbi and (CN)2 Cbi-P, the absorption spectra of these compounds differs with regard to the position of distinctive bands

Summary

Introduction

Vitamin B12 (cyanocobalamin, (CN)Cbl), belonging to the best studied among all corrinoid molecules, is a micronutrient isolated from specific bacterial sources e.g., Propionibacteria and Pseudomonas denitnpcans [8,9]. This coordination complex (Figure 1) comprises several relevant structural entities:. Molecules 2020, 25, x FOR PEER REVIEW of substrates [13] or the reduction of ribonucleotides [14], while MeCbl participates in the transfer of radical-induced rearrangement of substrates [13] or the reduction of ribonucleotides [14], while the methyl cation [15].

Methods

Results

Conclusion