RESUMEN
The appearance of the slow mode, revealed by dynamic light scattering (DLS) measurements in Micrococcus luteus DNA with high GC content, and the effect of guanine sequences on changes of DNA physical state and conformational transitions were investigated. We used two different spectroscopic approaches: DLS, to evidence the relatively slowly diffusing particles arising at high salt concentration, ascribable to the formation of large unspecific molecular aggregates, and circular dichroism spectroscopy, to identify these entities. Our results bring us to conclude that a peculiar, unconventional, structural transition, due to the presence of long guanine stretches, in a well-defined experimental condition, can occur. We comment on the biological implications to detect, by spectroscopic measurements, such an unusual structure involved in the stability, protection and replication maintenance along the human telomeric G-rich strand.
Asunto(s)
ADN/química , Luz , Conformación de Ácido Nucleico/efectos de los fármacos , Conformación de Ácido Nucleico/efectos de la radiación , Dispersión de Radiación , Cloruro de Sodio/farmacología , Animales , Composición de Base , Bovinos , ADN Bacteriano/química , Micrococcus luteus , Microscopía , Desnaturalización de Ácido Nucleico , Soluciones , Temperatura de Transición , Agua/químicaRESUMEN
Gold nanoparticles (AuNPs) conjugated to DNA are widely used for biomedical targeting and sensing applications. DNA functionalization is easily reached on laser generated gold nanoparticles because of their unique surface chemistry, not reproducible by other methods. In this context, we present an extensive investigation concerning the attachment of DNA to the surface of laser generated nanoparticles using Dynamic Light Scattering and UV-Vis spectroscopy. The DNA conjugation is highlighted by the increase of the hydrodynamic radius and by the UV-Vis spectra behavior. Our investigation indicates that Dynamic Light Scattering is a suitable analytical tool to evidence, directly and qualitatively, the binding between a DNA molecule and a gold nanoparticle, therefore it is ideal to monitor changes in the conjugation process when experimental conditions are varied.
Asunto(s)
Dispersión Dinámica de Luz , Oro/química , Nanopartículas del Metal/química , ADN/química , Hidrodinámica , Rayos Láser , Nanotecnología/métodos , Oligonucleótidos/genética , Sales (Química) , Cloruro de Sodio , Espectrofotometría Ultravioleta , Resonancia por Plasmón de SuperficieRESUMEN
This work reports light scattering measurements on DNA in aqueous solutions (100mM NaCl, 1mM EDTA and 10mM Tris-HCl buffer, pH 7.8) over a wide range of molecular weights (10(2)-10(5) base pairs) and shows that, in the above standard solvent, shorter chains (<10(4) base pairs) behave as a "wormlike chain" and their diffusion coefficients as obtained by dynamic light scattering measurements, confirm the prediction of standard wormlike model, whilst longer chains (>10(4) base pairs) behave in a different manner. Dynamic and static light scattering and SEM analysis indicate that DNA molecules 10(5) base pairs long, condense into compact structures in our solvent conditions. Calculations done using a wormlike model are also presented and discussed in comparison both to our experimental data and to other data reported in the literature.