2 research outputs found
The Role of Structural Enthalpy in Spherical Nucleic Acid Hybridization
DNA hybridization onto DNA-functionalized
nanoparticle surfaces
(e.g., in the form of a spherical nucleic acid (SNA)) is known to
be enhanced relative to hybridization free in solution. Surprisingly,
via isothermal titration calorimetry, we reveal that this enhancement
is enthalpically, as opposed to entropically, dominated by ∼20
kcal/mol. Coarse-grained molecular dynamics simulations suggest that
the observed enthalpic enhancement results from structurally confining
the DNA on the nanoparticle surface and preventing it from adopting
enthalpically unfavorable conformations like those observed in the
solution case. The idea that structural confinement leads to the formation
of energetically more stable duplexes is evaluated by decreasing the
degree of confinement a duplex experiences on the nanoparticle surface.
Both experiment and simulation confirm that when the surface-bound
duplex is less confined, i.e., at lower DNA surface density or at
greater distance from the nanoparticle surface, its enthalpy of formation
approaches the less favorable enthalpy of duplex formation for the
linear strand in solution. This work provides insight into one of
the most important and enabling properties of SNAs and will inform
the design of materials that rely on the thermodynamics of hybridization
onto DNA-functionalized surfaces, including diagnostic probes and
therapeutic agents
Size Dependence of a Temperature-Induced Solid–Solid Phase Transition in Copper(I) Sulfide
Determination of the phase diagrams for the nanocrystalline forms of materials is crucial for our understanding of nanostructures and the design of functional materials using nanoscale building blocks. The ability to study such transformations in nanomaterials with controlled shape offers further insight into transition mechanisms and the influence of particular facets. Here we present an investigation of the size-dependent, temperature-induced solid–solid phase transition in copper sulfide nanorods from low- to high-chalcocite. We find the transition temperature to be substantially reduced, with the high chalcocite phase appearing in the smallest nanocrystals at temperatures so low that they are typical of photovoltaic operation. Size dependence in phase transformations suggests the possibility of accessing morphologies that are not found in bulk solids under ambient conditions. These otherwise inaccessible crystal phases could enable higher-performing materials in a range of applications, including sensing, switching, lighting, and photovoltaics