Resonance Raman Spectroscopy Reveals New Insight into the Electronic Structure of β-Hematin and Malaria Pigment

Abstract

Resonance Raman spectra of beta-hematin and hemin are reported for a range of excitation wavelengths including 406, 488, 514, 568, 633, 780, 830, and 1064 nm. Dramatic enhancement of A(1g) modes (1570, 1371, 795, 677, and 344 cm(-1)), ring breathing modes (850-650 cm(-1)), and out-of-plane modes including iron-ligand modes (400-200 cm(-1)) were observed when irradiating with 780- and 830-nm laser excitation wavelengths for beta-hematin and to a lesser extent hemin. Absorbance spectra recorded during the transformation of hemin to beta-hematin showed a red-shift of the Soret and Q (0-1) bands, which has been interpreted as excitonic coupling resulting from porphyrin aggregation. A small broad electronic transition observed at 867 nm was assigned to a z-polarized charge-transfer transition d(xy) --> e(g)(pi). The extraordinary band enhancement observed when exciting with near-infrared excitation wavelengths in beta-hematin when compared to hemin is explained in terms of an aggregated enhanced Raman scattering hypothesis based on the intermolecular excitonic interactions between porphyrinic units. This study provides new insight into the electronic structure of beta-hematin and therefore hemozoin (malaria pigment). The results have important implications in the design and testing of new anti-malaria drugs that specifically interfere with hemozoin formation.

Raman Spectroscopy of Blood and Blood Components

“…95 The following year, they reported a more detailed Raman spectroscopic study of hematin (the synthetic analog of hemozoin). 96 In 2007 the Monash workers co-authored a study in which acoustic levitation was used to suspend RBCs and Plasmodium-infected cells in place, allowing the measurement of the spectral signature of hemozoin in the diseased cells. 97 One of the co-authors of that study, J. Popp, had previously been one of the early workers on LTRS.…”

Carboxylated nanodiamond and re‐oxygenation process of gamma irradiated red blood cells

“…Furthermore, the excitation in the 400-600 nm visible range induces resonant Raman scattering, which depends strongly on the laser wavelength [43]. This phenomenom is produced by electronic transitions associated to the Soret band [44] and the porphyrin ring (Q V and Q 0 bands) [40]. In our work, 488 nm laser excitation enhanced the Soret band scattering and totally symmetric vibrational modes n 2 , n 3 , and n 4 .…”

The HA2 haemagglutinin domain of the lysine-specific gingipain (Kgp) of Porphyromonas gingivalis promotes μ-oxo bishaem formation from monomeric iron(III) protoporphyrin IX

“…In contrast, the HRgpA-and Kgp-haem incubations resulted in a broadening of the Soret band and greater reductions in intensity, indicative of a greater extent of m-oxo dimer formation and aggregation compared to the control or the RgpB protease. Reduction of Soret band absorbance intensity and broadening are measures of the extent of dimerization (Inada & Shibata, 1962) and molecular aggregation of ferrihaems (Wood et al, 2004), respectively. On this basis it was clearly demonstrated that both HRgpA and Kgp mediated greater dimer formation and aggregation than RgpB, which lacks the HA2 domain.…”