SERRS spectroscopy

Somsen et al. [796] have reported the use of SERR spectroscopy for the in situ selective determination and semi-quantitative analysis of structurally similar dyes separated by TLC. The limits of identification of the TLC-SERRS method (ca. 5ng applied) were sufficient for acquisition of spectra of impurities present in the certified dye standards. SERRS may also be used for in situ identification of highly fluorescent molecules on HPTLC plates. 

S S CONTENTS Preface, C. Allen Bush. Methods in Macromo-lecular Crystallography, Andrew J. Howard and Thomas L. Poulos. Circular Dichroism and Conformation of Unordered Polypeptides, Robert W. Woody. Luminescence Studies with Horse Liver Dehydrogenase Information on the Structure, Dynamics, Transitions and Interactions of this Enzyme, Maurice R. Eftink. Surface-Enhanced Resonance Raman Scattering (SERRS) Spectroscopy A Probe of Biomolecular Structure and Bonding at Surfaces, Therese M. Cotton, Jae-Ho Kim and Randall E. Holt. Three-Dimensional Conformations of Complex Carbohydrates, C. Allen Bush and Perse-veranda Cagas. Index. 

Disentangling interfadal redox processes of proteins by SERR spectroscopy. Chemical Society Reviews,... 

Using biomolecules with chromophoric groups the Raman bands are both resonance (RRS) — and surface enhanced (RRS + SERS = SERRS). Instead of the usual term SERS, the Raman effect is, in this case, called surface enhanced resonance Raman scattering (SERRS). SERRS spectroscopy was first applied to biochemistry of heme chromophores by Cotton et al. Since then, SERS and SERRS have been extended to systematic investigations of biomolecules in the adsorbed state... 

Enhanced Resonance Raman Scattering (SERRS) spectroscopy, are provided by... 

Cotton et al. Already in their preliminary work, the authors explored the potentialities and goals of the SERRS technique for possible applications to bioanalytical problems. The first possibility is enhanced sensitivity for the RR scattering of scarce materials. A second possibility can be added specifically to redox-active chromophores in proteins. Indeed, this new spectroelectrochemical method permits the simultaneous study of an electrochemical reaction in a biological system in conjunction with a specific measurement of subtile variations in the vibrational spectrum of the chromophores. Another striking feature of the SERRS spectroscopy is that fluorescence of the adsorbate can be completely quenched by the metal surface which generates a high-quality Raman spectrum Another common application of SERRS spectroscopy is the study of the adsorption behaviour and conformation of biomolecules at the metal/electrolyte interface. 

As discussed before in the case of nucleic acids the authors have also considered the incidence of the interfacial conformation of the hemoproteins on the appearance of the SERRS signals from the chromophores. Although under their Raman conditions no protein vibration can be observed, the possibility of heme loss or protein denatura-tion are envisaged to explain a direct interaction of the heme chromophores with the electrode surface in the case of the adsorl Mb. extensive denaturation of Cytc at the electrode appears unlikely to the authors on the basis of the close correspondence of the surface and solution spectra. Furthermore, the sluggish electron transfer kinetics measured by cyclic voltammetry in the case of Cytc is also an argument in favour of some structural hindrance for the accessibility to the heme chromophore in the adsorbed state of Cytc. This electrochemical aspect of the behaviour of Cytc has very recently incited Cotton et al. and Tanigushi et al. to modify the silver and gold electrode surface in order to accelerate the electron transfer. The authors show that in the presence of 4,4-bipyridine bis (4-pyridyl)disulfide and purine an enhancement of the quasi-reversible redox process is possible. The SERRS spectroscopy has also permitted the characterization of the surface of the modified silver electrode. It has teen thus shown, that in presence of both pyridine derivates the direct adsorption of the heme chromophore is not detected while in presence of purine a coadsorption of Cytc and purine occurs In the case of the Ag-bipyridyl modified electrode the cyclicvoltammetric and SERRS data indicate that the bipyridyl forms an Ag(I) complex on Ag electrodes with the appropriate redox potential to mediate electron transfer between the electrode and cytochrome c. 

In the case of cytochrome cdi (Cyt cdi) found in many facultative, anaerobic denitrifying bacteria, the SERRS spectroscopy has been used to obtain preliminary heme structure/environment comparisons between cyt cdx from two bacteria sources. Pseudomonas and Paracoccus. The difficulty encountered in preparing sufficient quantities of cyt cdi, can be thus solved by the low product consuming SERRS method. By exciting selectively with the 514.5 nm and 460 nm lines of an Ar laser, it is possible to produce successively an enhancement of RR scattering of reduced heme c, see Fig. 34, and heme di, see Fig. 35, in the protein complexes (3 x 10 M) adsorbed on Ag at —0.6 V vs. SCE. A comparison between the SERRS spectra of cdi proteins from the bacteria suggests differences in the heme chromophore and peripheral substituents. 

Prochazka et al. demonstrated the suitability of surface-enhanced resonance Raman scattering (SERRS) spectroscopy to monitor silver coordination of free base 5,10,15,20-tetrakis(l-methyl-4-pyridyl) porphyrin adsorbed on the Ag colloidal surface. The approach was based on factor analysis (FA) which allows the analysis of the time development of SERRS spectra in terms of varying content of particular porphyrin forms. Their SERRS spectra can be isolated even if none of them is present singularly in any SERRS spectmm. Depending on the chemical properties of the molecular systems, SERRS spectra of two different porphyrin metalated forms have been obtained Ag+ and Ag metalated. The latter form was found to be evoked by pre-treatment of the laser-ablated Ag colloids by the thiosulphate ions. The metalation kinetics obtained show a substantially slower metalation by Ag than that by Ag+ cations. 

Vlckova, B., R Smejkal, M. Michl, M. Prochazka, P. Mojzes, F. Lednicky, and J. Pfleger (2000). SERRS spectroscopy of porphyrin and metalloporphyrin species in systems with Ag nanoparticles and their assemblies. J. Inorg. Biochem. 79, 295. 

SURFACE-ENHANCED RESONANCE RAMAN SCATTERING (SERRS) SPECTROSCOPY OF BACTERIAL MEMBRANES THE FLAVOPROTEINS. 

Surface-Enhanced Resonance Raman Scattering (Serrs) Spectroscopy of Bacterial... 

Flavodoxin from M. elsdenii was studied by the SERRS spectroscopy at liquid N2 temperature [98]. It has been shown, on the basis of comparison with the RR spectrum in the solution, that SERRS spectrum arises from the protein-bound FMN. The SERRS spectra of flavoproteins such as choline oxidase and sarcosine oxidase, whose FAD is covalently bound to the apoprotein, were reported by Taniguchi et al. [100]. The results of these two studies indicate the possibility of detecting the SERRS spectra of native flavoproteins. The close similarity between the solution resonance Raman and SERRS spectra [98] reveals that there is no strong chemical interaction between FMN and the silver electrode surface. It is thus reasonable to conclude that the electromagnetic enhancement contributes significantly to the overall enhancement of the SERRS spectra of flavoproteins under the conditions used in these studies. 

The electrode reaction of tetraheme cytochrome C3 adsorbed at the silver electrode surface was monitored by SERRS spectroscopy [104, 105] and compared with the results obtained by voltammetric techniques. The formal potential determined on the basis of the SERS measurement is more positive compared to the potential determined by the voltammetry, but it is in good agreement with the macroscopic formal potential of the heme-1. This is because cytochrome C3 is adsorbed on the silver electrode particularly via lysine residues surrounding heme-1, which is in fact responsible for the SERRS spectrum of this protein [105]. 

Many results indicate that SERS or SERRS spectroscopy is also useful in the investigation of molecules in interfacial situations. This feature seems to be of particular importance since many functions of biological molecules are realized through their association with biological or other electrically charged surfaces. 

ATR-SEIRAS) [19] and surface-enhanced Raman resonance scattering (SERRS) spectroscopy [23] have been performed on suspended cells and hving biofilms. They thereby unprecedented insights in the bacterial electron transfer mechanisms and the identification of the respective proteins, including the coordination of the central atom [23], was possible. 

Rodger et al. (1998) demonstrated the use of surface-enhanced resonance Raman scattering (SERRS) spectroscopy, without any separation procedure, to analyze dyes and pigments in lipsticks. Lipsticks smeared on glass and cotton surfaces required treatment with a surfactant, for example, poly(L-lysine), and silver colloid prior to the analysis. This in situ SERRS method was applied to six commercial lipstick samples. Discrimination between the samples and identification of some of the pigments present were achieved. The method is qualitative in nature and was suggested to have potential for forensic and quality-control applications. 

In other studies, however, efforts to observe reversible electrochemistry for this protein in the absence of mediators or chemical modification of the electrode surface have met with failure. The reasons for the slow electron transfer kinetics of GO are not understood. Our goal has been to apply surface enhanced resonance Raman scattering (SERRS) spectroscopy to the study of protein electrochemistry. The present study is concerned with GO, its interaction with the electrode and the location of the FAD group with respect to the electrode surface. These issues are related to steps two and three in Hill s mechanism. 

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