A General One-Step Synthesis of Alkanethiyl-Stabilized Gold Nanoparticles with Control over Core Size and Monolayer Functionality.

In spite of widespread interest in the unique size-dependent properties and consequent applications of gold nanoparticles (AuNPs), synthetic protocols that reliably allow for independent tuning of surface chemistry and core size, the two critical determinants of AuNP properties, remain limited. Often, core size is inherently affected by the ligand structure in an unpredictable fashion. Functionalized ligands are commonly introduced using postsynthesis exchange procedures, which can be inefficient and operationally delicate.

Probing Multiscale Factors Affecting the Reactivity of Nanoparticle-Bound Molecules.

The structures and physicochemical properties of surface-stabilizing molecules play a critical role in defining the properties, interactions, and functionality of hybrid nanomaterials such as monolayer-stabilized nanoparticles. Concurrently, the distinct surface-bound interfacial environment imposes very specific conditions on molecular reactivity and behavior in this setting. Our ability to probe hybrid nanoscale systems experimentally remains limited, yet understanding the consequences of surface confinement on molecular reactivity is crucial for enabling predictive nanoparticle synthon approaches for postsynthesis engineering of nanoparticle surface chemistry and construction of devices and materials from nanoparticle components.

Quantifying Through-Space Substituent Effects.

The description of substituents as electron donating or withdrawing leads to a perceived dominance of through-bond influences. The situation is compounded by the challenge of separating through-bond and through-space contributions. Here, we probe the experimental significance of through-space substituent effects in molecular interactions and reaction kinetics.

Reconciling Electrostatic and n→π* Orbital Contributions in Carbonyl Interactions.

Interactions between carbonyl groups are prevalent in protein structures. Earlier investigations identified dominant electrostatic dipolar interactions, while others implicated lone pair n→π* orbital delocalisation. Here these observations are reconciled.

Strong Short-Range Cooperativity in Hydrogen-Bond Chains.

Chains of hydrogen bonds such as those found in water and proteins are often presumed to be more stable than the sum of the individual H bonds. However, the energetics of cooperativity are complicated by solvent effects and the dynamics of intermolecular interactions, meaning that information on cooperativity typically is derived from theory or indirect structural data. Herein, we present direct measurements of energetic cooperativity in an experimental system in which the geometry and the number of H bonds in a chain were systematically controlled.

Electrostatic modulation of aromatic rings via explicit solvation of substituents.

Solvent effects are implicated as playing a major role in modulating electrostatic interactions via through-space and polarization effects, but these phenomena are often hard to dissect. By using synthetic molecular torsion balances and a simple explicit solvation model, we demonstrate that the solvation of substituents substantially affects the electrostatic potential of aromatic rings. Although polarization effects are important, we show that a simple additive through-space model also provides a reasonable account of the experimental data.

Transcription forms and remodels supercoiling domains unfolding large-scale chromatin structures.

DNA supercoiling is an inherent consequence of twisting DNA and is critical for regulating gene expression and DNA replication. However, DNA supercoiling at a genomic scale in human cells is uncharacterized. To map supercoiling, we used biotinylated trimethylpsoralen as a DNA structure probe to show that the human genome is organized into supercoiling domains.

Design, synthesis and biological evaluation of non-natural modulators of quorum sensing in Pseudomonas aeruginosa.

Many species of bacteria employ a mechanism of intercellular communication known as quorum sensing which is mediated by small diffusible signalling molecules termed autoinducers. The most common class of autoinducer used by Gram-negative bacteria are N-acylated-L-homoserine lactones (AHLs). Pseudomonas aeruginosa is a clinically important bacterium which is known to use AHL-mediated quorum sensing systems to regulate a variety of processes associated with virulence.

Molecular balances for quantifying non-covalent interactions.

Molecular interactions underlie the whole of chemistry and biology. This tutorial review illustrates the use of rotameric folding molecules, topoisomers, atropoisomers, and tautomers as molecular balances for quantifying non-covalent interactions. This intramolecular approach enables a wide variety of interactions to be examined with a degree of geometric control that is difficult to achieve in supramolecular complexes.