The Ionic Environment and Solution Interactions of Protein Spherical Nucleic Acids Probed by In-situ X-ray Scattering

Krishnamoorthy, Kurinji

doi:https://doi.org/10.21985/n2-fjpk-gy34

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The Ionic Environment and Solution Interactions of Protein Spherical Nucleic Acids Probed by In-situ X-ray Scattering

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Electrostatic interactions mediated by ionic environments play a central role in physical processes across materials science, chemistry and biology. Key biological phenomena, such as the condensation and packaging of DNA, ion transport across cellular membranes and the enzymatic action of proteins, rely on the complex interplay between nanoscale electrostatic, osmotic and entropic forces. A consideration of such interactions is especially relevant to synthetic bioconjugates, which harness the powerful properties of molecules, such as proteins and nucleic acids to realize applications in materials assembly and therapeutic medicine. Spherical nucleic acids (SNAs) defined as a dense three-dimensional arrangement of oligonucleotides on the surface of a particle core are one such striking example of a bioconjugate whose collective properties are distinct from those of its nucleic acid components. For instance, the DNA shell and associated counterionic cloud on an Au nanoparticle SNA results in highly programmable assembly behavior, cooperative hybridization thermodynamics, efficient internalization across more than 200 different cell types and an enhanced resistance to enzymatic degradation in comparison to linear DNA. While the properties and assembly behavior of spherical nucleic acids are well characterized, the nanoscale structure and role of the counterionic cloud surrounding such constructs is poorly understood. Here, we address this challenge in the context of a spherical nucleic acid composed of a functional protein core using in-situ solution x-ray scattering techniques. Our approach provides fundamental insights into the ionic environment around a protein spherical nucleic acid (Pro-SNA) and its influence on the resistance of Pro-SNAs to enzymatic degradation.

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