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

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.

Ligand-Tuning of the Stability of Pd(II) Conjugates with Cyanocobalamin

“…Formation of 1 was confirmed also by changes in the infrared spectrum (pink line in Figure 3 ), occurring in the range characteristic for the stretching Co–C vibrations [ 34 ], namely the shifts from 496 cm −1 to 515 cm −1 .…”

Resonance Raman analysis of intracellular vitamin B12 analogs in methanogenic archaea

“…see Figure 1). Accumulated resonance Raman spectra of cobalamines (vitamin B 12 derivatives) all indicate that the corrin-ring frequencies are surprisingly similar no matter what the axial ligand 27,31,32,39 or the oxidation state 27,30 of the cobalt atom (Co(II) or Co(III)) is. Close inspection of the spectra, however, reveals that the relative intensities of some minor bands differ substantially among cobalamines.…”

Recognition of the True and False Resonance Raman Optical Activity

“…RROA can be detected at low concentrations (ca. 10 −5 M) [19–22] while maintaining structural sensitivity [12, 21, 23] . Single state resonance usually leads to single signed RROA, [1, 19, 24] whereas pre‐resonance and more resonance states provide RROA spectrum with positive and negative bands, similarly as for the “conventional” non‐resonance case.…”

“…Single state resonance usually leads to single signed RROA, [1, 19, 24] whereas pre‐resonance and more resonance states provide RROA spectrum with positive and negative bands, similarly as for the “conventional” non‐resonance case. However, up to now there is a limited number of reports on RROA, due to the challenges arising during the measurement, including artifacts related to absorption and fluorescence [12–14, 21, 23, 25] …”