Surface-Enhanced Resonance Raman Spectroscopic Characterization of the Protein Native Structure

Abstract

Surface-enhanced resonance Raman scattering (SERRS) spectra of biological species are often different from their resonance Raman (RR) spectra. A home-designed Raman flow system is used to determine the factors that contribute to the difference between the SERRS and RR of met-myoglobin (metMb). The results indicate that both the degree of protein-nanoparticles interaction and the laser irradiation contribute to the structural changes and are responsible for the observed differences between the SERRS and RR spectra of metMb. The prolonged adsorption of the protein molecules on the nanoparticle surface, which is the condition normally used for the conventional SERRS experiments, disturbs the heme pocket structure and facilitates the charge transfer process and the photoinduced transformation of proteins. The disruption of the heme pocket results in the loss of the distal water molecule, and the resulting SERRS spectrum of metMb shows a 5-coordinated high-spin heme. The flow system, when operated at a moderately high flow rate, can basically eliminate the factors that disturb the protein structure while maintaining a high enhancement factor. The SERRS spectrum obtained from a 1 x 10 (-7) M metMb solution using this flow system is basically identical to the RR spectrum of a 5 x 10 (-4) M metMb solution. Therefore, the Raman flow system reported here should be useful for characterizing the protein-nanoparticles interaction and the native structure of proteins using SERRS spectroscopy.

Spectro-Electrochemical Investigation of the bc1 Complex from the Yeast Saccharomyces cerevisiae using Surface Enhanced B-Band Resonance Raman Spectroscopy

“…The thickness of the protein layer obtained from fitting the angle scans of 10 nm (inset of Fig. 2A) indicates a submonolayer of bc 1 complex considering a thickness of the protein of 18 nm according to X-ray data (Chase and Parkinson 1991;Feng and Tachikawa 2008) (Table 1). A further thickness increase by 2 nm after dialysis characterizes the formation of lipid bilayer patches between immobilized proteins.…”

“…This phenomenon is associated with the potential dependent surface enhancement effect, which is well known to result from two main effects: an electromagnetic effect and a chemical effect. (Chase and Parkinson 1991;Feng and Tachikawa 2008) On the basis of intensity versus potential profiles measured in electrochemical environments, it has been shown, that the charge transfer mechanism dominates the intensity of SERR spectra of molecules adsorbed on a silver electrode. (Lombardi, Birke et al 1986;Osawa, Matsuda et al 1994) Low Frequency Region (250 -450 cm -1 )…”

Survival of molecular information under surfaced‐enhanced resonance Raman (SERRS) conditions

“…However, as recently pointed out by Feng and Tachikawa, [32] the interest from a biochemists point of view is to obtain information about the native molecule, and since differences between the RS-and SERS-spectra and RRS-and SERRS-spectra are frequently observed, it is necessary to elucidate the mechanisms responsible for these changes. Besides, to benefit fully from the advantages of applying the SERS-technique, it is necessary to explore the kind of molecular information that may be lost or changed, when the molecules are either physisorbed or chemisorbed to a nano-structured surface.…”

“…An example of such a paper is Ref. [32] where it is discussed whether the differences found in RRS-and SERRS-spectra are due to denaturation of the adsorbed species and/or laser photo degradation or due to a selective enhancement of certain vibrational modes. If the interest is the molecule, it is vital to be able to elucidate which information is present due to the native molecule and which is present due to the various combinations of interactions between the molecule and its surroundings.…”

Redox Potential Dependence of Peptide Structure Studied Using Surface Enhanced Raman Spectroscopy

“…Recently, Surface enhanced Raman spectroscopy (SERS) has been used for a large variety of bioanalytical applications, including single molecule studies, 1 oligonucleotide sequencing 2 and for probing peptide and protein structure. [3][4][5][6] SERS can also be used for imaging the intracellular environment of cells and has been demonstrated using a variety of noble metal particles which are readily delivered to mammalian cells. 4,7,8 Gold nanoshells (NS) are engineered nanoparticles and we have recently demonstrated that their characteristics make them ideal for intracellular SERS studies.…”