Fluorescence and surface-enhanced vibrational spectroscopies of lawsone and plumbagin

© 2016, Copyright © Taylor & Francis Group, LLC. The natural dyes lawsone and plumbagin (1,4-naphthoquinones) were studied by using fluorescence, Raman, infrared (IR), surface-enhanced Raman scattering (SERS), and surface-enhanced IR absorption. From the absorption spectrum, it was possible to infer that the enol-lawsone tautomer concentration decreases in silver colloidal solution. Plumbagin dimers, both in water and in silver colloidal solution, were identified from the fluorescence band profile and surface-SERS spectrum. The SERS spectrum of lawsone was obtained by using silver colloidal solution after 12-hour settle; the keto and enol lawsone silver colloid interaction occurs. The assignment of Raman and IR bands of both dyes was calculated with density functional theory calculations. Only a monomeric structure of lawsone interacting with a silver cluster model was predicted. The monomer adopts a nearly coplanar orientation onto the silver surface; the shortest distance is 3.2 Å,

Fluorescence and surface-enhanced vibrational spectroscopies of lawsone and plumbagin

<p>The natural dyes lawsone and plumbagin (1,4-naphthoquinones) were studied by using fluorescence, Raman, infrared (IR), surface-enhanced Raman scattering (SERS), and surface-enhanced IR absorption. From the absorption spectrum, it was possible to infer that the enol-lawsone tautomer concentration decreases in silver colloidal solution. Plumbagin dimers, both in water and in silver colloidal solution, were identified from the fluorescence band profile and surface-SERS spectrum. The SERS spectrum of lawsone was obtained by using silver colloidal solution after 12-hour settle; the keto and enol lawsone silver colloid interaction occurs. The assignment of Raman and IR bands of both dyes was calculated with density functional theory calculations. Only a monomeric structure of lawsone interacting with a silver cluster model was predicted. The monomer adopts a nearly coplanar orientation onto the silver surface; the shortest distance is 3.2 Å, suggesting an electrostatic interaction.</p

Surface-enhanced Raman scattering and theoretical studies of the C-terminal peptide of the β-subunit human chorionic gonadotropin without linked carbohydrates

Raman and surface-enhanced Raman scattering (SERS) spectra of the synthetic carboxy terminal peptide of human chorionic gonadatropin β-subunit free of carbohydrate moieties (P37) are reported. The spectral analysis is performed on the basis of our reported Raman spectrum and SERS data of oligopeptides displaying selected amino acids sequences MRKDV, ADEDRDA, and LGRGISL. SERS samples of P37 were prepared by coating the solid peptide with metal colloids on a quartz slide. This treatment makes possible to obtain high spectral batch to batch reproducibility. Amino acids components of P37 display net charges and hydrophobic characteristics, which are related to particular structural aspects of the adsorbate-substrate interaction. The spectroscopic results are supported by quantum chemical calculations performed by using extended Hückel theory method for a model of P37 interacting with an Ag surface. The P37-metal interaction is drove by positively charged fragments of selected amino acids

Surface-enhanced Raman scattering and theoretical studies of the C-terminal peptide of the β-subunit human chorionic gonadotropin without linked carbohydrates

Raman and surface-enhanced Raman scattering (SERS) spectra of the synthetic carboxy terminal peptide of human chorionic gonadatropin β-subunit free of carbohydrate moieties (P37) are reported. The spectral analysis is performed on the basis of our reported Raman spectrum and SERS data of oligopeptides displaying selected amino acids sequences MRKDV, ADEDRDA, and LGRGISL. SERS samples of P37 were prepared by coating the solid peptide with metal colloids on a quartz slide. This treatment makes possible to obtain high spectral batch to batch reproducibility. Amino acids components of P37 display net charges and hydrophobic characteristics, which are related to particular structural aspects of the adsorbate-substrate interaction. The spectroscopic results are supported by quantum chemical calculations performed by using extended Hückel theory method for a model of P37 interacting with an Ag surface. The P37-metal interaction is drove by positively charged fragments of selected amino acids, mainly threonine 109, lysine 122, and arginine in positions 114 and 133. Data here reported intend to contribute to the knowledge about the antigen-antibody interaction and to the drugs delivery research area. © 2010 Wiley Periodicals, Inc.Contract grant sponsor: CSIC-CONICYT Contract grant number: 2007-145 Contract grant sponsors: Fondecyt Contract grant number: 1070078, 1085124, and 1090074 Contract grant sponsors: Ministerio de Educacio´n y Ciencia of Spain Contract grant number: FIS2007-63065 Contract grant sponsors: Comunidad de Madrid Contract grant number: S2009/TIC-1476 MICROSERES II Contract grant sponsors: Doctoral Fellowship CONICYT (to A.E.A.) Contract grant number: AT-24090050 (to A.E.A.)Peer Reviewe

SERS spectrum of red dyes in the Mapuche belts from the beginning of the XXth century

Red dyes in seven belts (trariwe) belonging to the Mapuche culture, dated as beginning of the XXth century and stored in Museo Regional de la Araucania, Chile, were studied by using ultraviolet-visible, liquid chromatography coupled to mass spectrometry, Raman and Surface Enhanced Raman Scattering spectroscopies. Red dyes were extracted and analysed; the spectral analysis allowed identifying that the principal red dye in five samples is highly consistent with a commercial synthetic aniline, the azopigment PR57. Another monoazopigment, an orange benzimidazolone, was identified in two samples. A molecular model for the PR57/Ag surface interaction supports the idea that the dye mainly exposes to the metal the carboxylate and sulphonate groups; the red azopigment is oriented rather tilted with the two aromatic rings being almost coplanar to the surface. The electrostatic interactions are the main factor of the PR57/Ag layer interaction.Fondecyt, 1140524, 3140492, 315022

Surface enhanced Raman scattering study of l-lysine

Different SERS spectra of lysine (Lys) in Ag colloidal surface were obtained. No identical SERS spectra of Lys were observed after a stabilization period, suggesting that a unique conformation and orientation on the metal surface of lysine do not exist at neutral pH. In general, Lys molecules interact with the surface through both the carboxylate and amino groups; the aliphatic moiety is close to the surface. The interpretation of the experimental results is supported by theoretical analysis of the molecule on the silver surface. © 2008 Elsevier B.V. All rights reserved

Surface-enhanced Raman scattering study of L-tryptophan

Surface-enhanced Raman scattering (SERS) spectra of tryptophan (Trp) were obtained. A unique SERS spectrum of Trp, corresponding to the most stable conformation and orientation on the metal surface, is observed after a stabilization period. The Trp molecules interact with the surface through both the carboxylate and amino groups; the aliphatic moiety is close to the surface. The pyrrole ring of the indolemoiety is farther from the surface than the benzene fragment. The observed spectra vary depending on both the preparation of the silver colloid and the aggregation time. The interpretation of the experimental results is supported by theoretical treatment of themolecule on the silver surface. Copyright © 2008 John Wiley & Sons, Ltd