surface-enhanced Raman spectrometry
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A new, simple photo-deposition method of silver nanoparticles induced by laser inside a fused-silica capillary is described and tested. Silver nanoparticles are immobilized using Ar-ion laser beam of a wavelength of 488 nm and power of 3.6 mW for 60 min. The photodeposited compact spot of a size of ∼10 μm is temporary and spatially stable and resistant to a hydrodynamic flow. The deposit has very good properties for surface-enhanced Raman scattering and serves well for detection in capillary electrophoresis. The advantage of this approach is that neither the silver nanoparticles nor the chemicals for their preparation are components of the background electrolyte during the electrophoretic separation. Thus, the substrate formation and separation of analytes are two independent processes and can be performed under their optimum conditions. The zone broadening due to the sorption of analytes on the immobilized nanoparticles can be significantly reduced by an addition of 20% solution of methanol. The efficiency of capillary electrophoresis and detection selectivity of surface-enhanced Raman scattering induced by He-Ne laser at 632.8 nm is demonstrated by the 3D electropherograms of rhodamines 123 and B as model samples. The limits of detection of about 49 and 150 fmol (1 and 2 μM) have been reached for rhodamine B and 123, respectively.
- MeSH
- chemické modely MeSH
- elektroforéza kapilární metody MeSH
- fotochemické procesy MeSH
- kovové nanočástice chemie MeSH
- limita detekce MeSH
- methanol chemie MeSH
- Ramanova spektroskopie přístrojové vybavení metody MeSH
- rhodaminy analýza izolace a purifikace MeSH
- stříbro chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
A surface enhanced Raman scattering (SERS) spectrometry is an interesting alternative for a rapid molecular recognition of analytes at very low concentration levels. The hyphenation of this technique with advanced separation methods enhances its potential as a detection technique. Until now, it has been hyphenated mainly with common chromatographic and electrophoretic techniques. This work demonstrates for a first time a power of preparative isotachophoresis-surface enhanced Raman scattering spectrometry (pITP-SERS) combination on the analysis of model analyte (buserelin) in a complex biological sample (urine). An off-line identification of target analyte was performed using a comparison of Raman spectra of buserelin standard with spectra obtained by the analyses of the fractions from preparative isotachophoretic runs. SERS determination of buserelin was based on the method of standard addition to minimize the matrix effects. The linearity of developed method was obtained in the concentration range from 0.2 to 1.5 nmol L(-1) with coefficient of determination 0.991. The calculated limit of detection is in tens of pico mols per liter.
- MeSH
- buserelin moč MeSH
- izotachoforéza metody MeSH
- kovové nanočástice chemie MeSH
- lidé MeSH
- Ramanova spektroskopie metody MeSH
- senzitivita a specificita MeSH
- stříbro chemie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The Pro-Gly sequence in designed peptides and proteins is often used to mimic natural beta-hairpin turns. Shorter peptides containing this moiety, however, adopt multiple conformations, and their propensity to form the turn is not obvious. In this study, conformational flexibility of Pro-Gly was investigated with the aid of NMR, Raman scattering, and Raman optical activity (ROA). The spectra of a model tetrapeptide NH3+-D-Ala-L-Pro-Gly-D-Ala-CO2- were analyzed on the basis of statistical methods and density functional computations. Other peptide derivatives were adopted as supporting theoretical and experimental models. The results suggest that the loop conformation of the Pro-Gly core is not inherently stable in vacuum. On the other hand, in aqueous environment the propensity to form the beta-hairpin loops is an intrinsic property of the Pro-Gly sequence. It was observed also in a shorter Ac-D-Pro-Gly-NH-Me dipeptide. The attached alanine residues in the tetrapeptide stabilize the structure only partially. Thus an inclusion of the solvent in the calculations is important for correct description of peptide folding in the aqueous environment. The agreement of the optical spectra with the experiment was determined from overlaps between simulated and measured spectral curves. The comparison of the computed NMR, Raman, and ROA was hampered by experimental noise and limited accuracy of the computations. However, the statistical analysis of the spectroscopic data provided conformer distribution consistent with the computation of the relative energies. The combination of the NMR and Raman techniques with the quantum computations appeared very beneficial for the investigation of Pro-Gly conformational behavior, and can be recommended for future peptide folding studies.
- MeSH
- aminokyselinové motivy MeSH
- diferenciální skenovací kalorimetrie MeSH
- difrakce rentgenového záření MeSH
- financování organizované MeSH
- konformace proteinů MeSH
- nukleární magnetická rezonance biomolekulární metody MeSH
- oligopeptidy chemie MeSH
- Ramanova spektroskopie metody MeSH
- spektrometrie hmotnostní - ionizace laserem za účasti matrice MeSH
Surface-enhanced Raman scattering (SERS) spectroscopy and surface-enhanced infrared absorption (SEIRA) spectroscopy are analytical tools suitable for the detection of small amounts of various analytes adsorbed on metal surfaces. During recent years, these two spectroscopic methods have become increasingly important in the investigation of adsorption of biomolecules and pharmaceuticals on nanostructured metal surfaces. In this work, the adsorption of B-group vitamins pyridoxine, nicotinic acid, folic acid and riboflavin at electrochemically prepared gold and silver substrates was investigated using Fourier transform SERS spectroscopy at an excitation wavelength of 1,064 nm. Gold and silver substrates were prepared by cathodic reduction on massive platinum targets. In the case of gold substrates, oxidation-reduction cycles were applied to increase the enhancement factor of the gold surface. The SERS spectra of riboflavin, nicotinic acid, folic acid and pyridoxine adsorbed on silver substrates differ significantly from SERS spectra of these B-group vitamins adsorbed on gold substrates. The analysis of near-infrared-excited SERS spectra reveals that each of B-group vitamin investigated interacts with the gold surface via a different mechanism of adsorption to that with the silver surface. In the case of riboflavin adsorbed on silver substrate, the interpretation of surface-enhanced infrared absorption (SEIRA) spectra was also helpful in investigation of the adsorption mechanism.
