Intensity of the Polarized Raman Band at 1340−1345 cm^-1 As an Indicator of Protein α-Helix Orientation:  Application to Pf1 Filamentous Virus

Abstract

Raman spectra of oriented alpha-helical protein molecules exhibit a prominent band near 1340-1345 cm(-)(1), the intensity of which is highly sensitive to molecular orientation. Polarization of the 1340-1345 cm(-)(1) marker is evident in Raman spectra of alpha-helical poly-L-alanine (alphaPLA) and alpha-helical poly-gamma-benzyl-L-glutamate (alphaPBLG). Corresponding polarization is also observed in Raman spectra of the filamentous virus Pf1, which is an assembly of alpha-helical coat protein molecules. In alphaPLA and alphaPBLG, we assign the band to a normal mode of symmetry type E(2) and specifically to a vibration localized in the (O=C)-C(alpha)-H linkages of the main chain peptide group. Although strict helical symmetry does not apply to coat subunits of filamentous viruses, an approximate E(2)-type mode may be presumed to account for a corresponding Raman band of Pf1 and fd filamentous viruses. Spectroscopic studies of N-methylacetamide and isotopically-edited fd viruses support the present assignment of the 1340-1345 cm(-)(1) band. Polarization anisotropy indicates that this band may be exploited as a novel indicator of protein alpha-helix orientation. Application of this approach to the polarized Raman spectrum of Pf1 suggests that, on average, the axis of the alpha-helical coat protein subunit in the native virion structure forms an angle of 20 +/- 10 degrees with respect to the virion axis.

Detection of Receptor-Induced Glycoprotein Conformational Changes on Enveloped Virions by Using Confocal Micro-Raman Spectroscopy

“…For example, Raman spectroscopic methods have been used to investigate protein structure (57); alpha-helix hydration in polypeptides, proteins, and viruses (58-62); polypeptide and carbohydrate structures of glycoproteins (63); carbohydrate characterization (64); and the molecular structures of proteins (62,63,(65)(66)(67). Raman spectroscopy has been validated as a highly accurate and reliable method to monitor and determine protein secondary structural variations in situ, such as folding and orientation (68,69), glycosylation status (43), phosphorylation status (42,70), and posttranslational modifications (71). The overall secondary structures of the glycosylated and deglycosylated forms of soluble glycoprotein C of herpes simplex virus were differentiated by using conventional Raman spectroscopy (72).…”

Confocal Laser Raman Microspectroscopy of Biomineralization Foci in UMR 106 Osteoblastic Cultures Reveals Temporally Synchronized Protein Changes Preceding and Accompanying Mineral Crystal Deposition

“…3C). Finally, the band centered at 1340 cm Ϫ1 also decreases slightly over the mineralization period (p Ͻ 0.05 at 82 and 88 h compared with 64 h non-mineralized control); this signal has been assigned to protein ␣-helices where its intensity is sensitive to molecular orientation (36). Although the identities of protein substituents contributing to the 1004, 1340, and 1660 cm Ϫ1 peaks are not yet known, the temporal correlations of these transitions imply these groups may play a direct role in mineral crystal nucleation and propagation within BMF.…”

Characterization of the interactions between chitosan/whey protein at different conditions

“…On present study, the complexation of C/WPO may restrain the C=D stretching vibration of the acetylated amino group in chitosan at pH higher than 5.5 because the peak was less prominent and completely disappeared after heating at pH 6.0 (Figure 5D.). The peak at 1342 cm −1 was attributed to C α -H bending and C-C α stretching of internal coordinates of the main chain (D=C)-C α -H moiety (Tsuboi et al, 2000). At pH 4.0, the intensity of this peak decreased after the addition of chitosan and disappeared at higher chitosan concentration ( Figure 6A).…”

“…Three regions in the FTOR spectra were investigated, i.e., the amide O (1600-1690 cm orientation (Tsuboi et al, 2000). As shown in Figure 5 were seen, and no changes presented before or after heat The chitosan and whey protein with opposite charges at pH 5.5 and 6.0 could combine with each other through electrostatic attraction.…”