RESUMO
In a previous work we demonstrated that toxic aggregates of the protein ß-amyloid (ATAß) involved in the Alzheimer's disease (AD) can be destabilized upon electromagnetic irradiation of the peptide Cys-Leu-Pro-Phe-Phe-Asp (CLPFFD) adsorbed on gold nanospheres (AuNSs). For a selective recognition of the therapeutic target (i.e. ATAß) of AD by the conjugates peptide-nanoparticle it is relevant to understand how the interaction between attached ligands and nanoparticles occurs. In this work a surface enhanced Raman scattering spectroscopy (SERS) study of the interactions of CLPFFD with AuNSs of 10nm average diameter was carried out. The SERS data suggest that phenylalanine displays its aromatic ring coplanar to the surface which is supported by theoretical data obtained from molecular mechanics (MM) and Extended Hückel Theory (EHT) calculations.
Assuntos
Peptídeos beta-Amiloides/metabolismo , Ouro/química , Nanosferas/química , Peptídeos/química , Ácido Aspártico/química , Cisteína/química , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Nanopartículas Metálicas/química , Modelos Moleculares , Peptídeos/farmacologia , Fenilalanina/química , Conformação Proteica , Espectrofotometria Ultravioleta , Análise Espectral Raman/métodosRESUMO
Prismatic silver nanoparticles (PNps) were used in the surface enhanced Raman scattering (SERS) study of the antioxidant alkaloid boldine (5,6,6a,7-tetrahydro-1,10-dimethoxy-6-methyl-4H-dibenzo[de,g]quinoline-2,9-diol). Prismatic and quasi-spherical (QsNps) silver nanoparticles were synthesized and characterized by UV-Vis spectra, topographic profile (AFM) and zeta potential measurements. Raman and infrared (IR) spectra of the boldine were registered. Theoretical model calculations of the boldine onto the Ag surface predict a nearly coplanar orientation of the benzo[de]quinoline moiety and non-bonded interactions (electrostatic).
Assuntos
Antioxidantes/química , Aporfinas/química , Nanopartículas Metálicas/química , Prata/química , Análise Espectral Raman/métodos , Modelos MolecularesRESUMO
Raman and surface-enhanced Raman scattering (SERS) spectra of the synthetic carboxy terminal peptide of human chorionic gonadatropin ß-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
Assuntos
Gonadotropina Coriônica Humana Subunidade beta/química , Sequência de Aminoácidos , Gonadotropina Coriônica Humana Subunidade beta/genética , Humanos , Interações Hidrofóbicas e Hidrofílicas , Técnicas In Vitro , Nanopartículas Metálicas , Modelos Moleculares , Oligopeptídeos/química , Oligopeptídeos/genética , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/genética , Análise Espectral Raman/métodos , Eletricidade EstáticaRESUMO
Arginine amino acid (Arg) has been vibrationally studied through its infrared, Raman and surface-enhanced Raman scattering (SERS) spectra, and theoretical calculations. Net charge is used to predict the possibility to obtain the SERS spectrum of Arg in colloidal solution. The interpretation of the SERS spectral data suggests that the Arg-Ag nanoparticles interaction in a colloidal solution and in the case of the Arg coated by Ag is mainly verified through the guanidinium moiety. Theoretical calculations performed by using extended Hückel theory method for a model of Arg interacting with an Ag cluster support the observed SERS experimental result.
Assuntos
Arginina/química , Análise Espectral Raman/métodos , Nanopartículas Metálicas/química , Modelos Moleculares , Modelos Teóricos , Estrutura Molecular , Prata/químicaRESUMO
Organochlorine pesticide endosulfan has been detected for the first time by using surface-enhanced Raman scattering (SERS) at trace concentrations. The bis-acridinium dication lucigenine was successfully used as a molecular assembler in the functionalization of metal nanoparticles to facilitate the approach of the pesticide to the metal surface. From the SERS spectra valuable information about the interaction mechanism between the pesticide and lucigenin can be deduced. In fact, endosulfan undergoes an isomerization upon adsorption onto the metal, while the viologen undergoes a rotation of the acridinium planes to better accommodate the pesticide molecule. An interaction between the N atom of the central acridinium ring and the pesticide Cl-CC-Cl fragment is verified through a charge-transfer complex. The present study affords important information which can be applied to the design of chemical sensor systems of persistent organic pollutants based on the optical detection on functionalized metal nanoparticle.