Studying Protein Binding to Conjugated Gold Nanospheres; Application of Mie Light Scattering to Reaction Kinetics

Abstract

The study of protein interactions is an area of much interest, particularly towards obtaining more detailed information about biological processes. Current methods involve the use of complicated, specialised techniques which are beyond the scope of most laboratories. Here, we show how information about the binding of proteins to conjugated gold nanospheres can be obtained using straightforward experimental techniques. A Perkin Elmer LS 55 luminescence spectrometer was used to observe the changes in light scattering caused by the binding of complementary proteins to conjugated nanoparticles, measured by the intensity change over time. Mie theory simulations have been used to predict the expected observations and to quantify the changes in intensity as a function of surface coverage. Further kinetic studies have been carried out at 530 nm to obtain more detailed information about the processes involved in the binding reaction. Thus, we have demonstrated that the interaction of proteins can be studied using a straightforward method which provides information about surface coverage and reaction kinetics.

Quantitative Studies of the Interactions of Metalloproteins with Gold Nanoparticles: Identification of Dominant Properties of the Protein that Underlies the Spectral Changes

“…Changes in peak maximum were determined using an in-house polynomial curve fit (MATLAB). The analytical protocol defining wavelength changes is outlined in ref .…”

“…Nanoparticles provide a convenient means to study protein−gold interactions, and over the past few years these have proved to offer a versatile platform. − Their optical properties permit study of these interactions using an array of techniques including absorption, SPR, , SERS, and light scattering. , Similarly, nanoparticle conjugates to biomacromolecules have been used in several applications including electron microscopy, immunoassays, and biosensors. , …”

“…Gold nanoparticles have been utilized in a variety of studies with cyt C including electrochemical, structural, and conformational approaches. Proteins bound to gold nanoparticles have been shown to retain their biological activity. ,− Cyt C has been shown to stabilize gold nanoparticles in electrolytes at high pH by the formation of bioconjugated particles. These have been used to study the stability and control of orientation and the effect of particle size on conformational change. − SAM coated particles have been used to facilitate further studies on conformational changes induced by pH and the effects of variation in the SAM headgroup on protein orientation and electrochemical behavior. − …”

Enhanced localized surface plasmon resonance obtained in two step etched silicon nanowires decorated with silver nanoparticles

“…Higher dielectric medium and refractive index were known parameters for the increased scattering efficiency; 35,37 for instance, enhancement in the LSPR mode was obtained by Underwood et al 38 for Au colloids in a high refractive index medium. For Ag, on the other hand, in this work, LSPR mode was obtained even for 12 nm thick Ag deposited sample on the contrary to one-step etched counterpart.…”

Sensitivity of Localized Surface Plasmon Resonances to Bulk and Local Changes in the Optical Environment

“…This change is surprisingly large even for the very thin coating of Al 2 O 3 deposited onto the nanoparticles and substrate, and is the opposite of what one would expect from Mie theory calculations of similarly sized coated and uncoated spheres. The scattering cross section of Au nanoparticles calculated using Mie theory increases when the refractive index of the bulk medium is increased or a thin coating is introduced. , This apparent discrepancy is due to the asymmetric environment being studied here; Mie theory considers a homogeneous environment whereas in the experiment light is incident upon a nanoparticle supported by a substrate. All of the nanoparticles were characterized by obtaining SEM images and then correlating these images with the dark-field spectra.…”