Analysis of human blood plasma and hen egg white by chiroptical spectroscopic methods (ECD, VCD, ROA)

Abstract

Chiroptical methods are widely used in structural and conformational analyses of biopolymers. The application of these methods to investigations of biofluids would provide new avenues for the molecular diagnosis of protein-misfolding diseases. In this work, samples of human blood plasma and hen egg white were analyzed using a combination of conventional and chiroptical methods: ultraviolet absorption/electronic circular dichroism (UV/ECD), Fourier transform infrared absorption/vibrational circular dichroism (FTIR/VCD), and Raman scattering/Raman optical activity (Raman/ROA). For comparison, the main components of these substances--human serum albumin (HSA) and ovalbumin (Ova)--were also analyzed by these methods. The ultraviolet region of the ECD spectrum was analyzed using the CDNN CD software package to evaluate the secondary structures of the proteins. The UV/ECD, FTIR/VCD, and Raman/ROA spectra of the substances were quite similar to those of the corresponding major proteins, while some differences were also detected and explained. The conclusions drawn from the FTIR/VCD and Raman/ROA data were in good agreement with the secondary structures calculated from ECD. The results obtained in this work demonstrate that the chiroptical methods used here can be applied to analyze not only pure protein solutions but also more complex systems, such as biological fluids.

Complementary analysis of tissue homogenates composition obtained by Vis and NIR laser excitations and Raman spectroscopy

“…For brain, all Raman spectra show only a band at ca. 1265 cm À1 assigned to a-helical structures [6,12,16,38,39]. This is congruent with FTIR spectrum of this sample that exhibited the largest contribution of a-helices in the overall composition of proteins [32].…”

“…Positions of Raman bands (in cm À1 ) with their assignment observed in spectra of tissues for 488 nm excitation line [3][4][5][6][7]10,[12][13][14]16,37,38,[39][40][41]. Tables 1 and 2.…”

Resonance Raman optical activity of the imidazole–Myoglobin complex: Titrating enhancement

“…Nevertheless, with the current experimental setup, it is possible to selectively probe the haem distortion induced by the location of a sixth axial ligand of the iron centre on the plane of the porphyrin and discriminate between two enhanced rROA spectra of met‐Mb, corresponding to the ligated and unligated forms of the protein. Looking forward for theoretical spectra prediction to be available, in order to support experimental data and help to better interpret them, this work is proposed as a contribution to the state of the art concerning the investigation of the haem chromophores via the combined Abs/ECD and rRaman/rROA analysis …”

Where does the Raman optical activity of [Rh(en)3]3+come from? Insight from a combined experimental and theoretical approach

“…With these instruments structural insight has been gained into a wide range of molecular systems: they can record difference spectra of small molecules, e.g., chirally deuterated neopentane 12 , or give valuable information about conformations in polypeptides 13 and the tertiary structures of proteins. 14,15 Recently ROA was used for in situ analysis of human blood plasma and other biofluids 16 . With respect to transition metal complexes, only a few studies have been published [17][18][19][20] ; the opposite is the case, however, for VCD investigations of such compounds, see, e.g., references 21-24. In this paper, we report the vibrational ROA characterization of a chiral transition metal complex, tris(ethylenediamine)rhodium (III), [Rh(en) 3 ] 3+ , in aqueous solution.…”