Influence of Backbone Conformational Rigidity in Temperature-Sensitive Amphiphilic Supramolecular Assemblies

Molecular design features that endow amphiphilic supramolecular assemblies with a unique temperature-sensitive transition have been investigated. We find that conformational rigidity in the backbone is an important feature for eliciting this feature. We also find that intramolecular hydrogen-bonding can induce such rigidity in amphiphile backbone. Guest encapsulation stability of these assemblies was found to be significantly altered within a narrow temperature window, which correlates with the temperature-sensitive size transition of the molecular assembly. Molecular design principles demonstrated here could have broad implications in developing future temperature-responsive systems

Activatable Dendritic ¹⁹F Probes for Enzyme Detection

We describe a novel activatable probe for fluorine-19 NMR based on self-assembling amphiphilic dendrons. The dendron probe has been designed to be spectroscopically silent due to the formation of large aggregates. Upon exposure to the specific target enzyme, the aggregates disassemble to give rise to a sharp ¹⁹F NMR signal. The probe is capable of detecting enzyme concentrations in the low nanomolar range. Response time of the probe was found to be affected by the hydrophilic–lipophilic balance of dendrons. Understanding the structural factors that underlie this design principle provides the pathway for using this strategy for a broad range of enzyme-based imaging

Protein AND Enzyme Gated Supramolecular Disassembly

An amphiphilic nanoassembly was designed to respond to the concurrent presence of a protein and an enzyme. We present herein a system, where in the presence of these two stimuli supramolecular disassembly and molecular release occur. This molecular release arises in the form a fluorescence response that has been shown to be specific. We also show that this system can be modified to respond only if light stimulus is also present in addition to the protein and the enzyme. Demonstration of such supramolecular disassembly principles could have broad implications in a variety of biological applications

Temperature-Sensitive Transitions below LCST in Amphiphilic Dendritic Assemblies: Host–Guest Implications

Oligo­(ethylene glycol)-decorated supramolecular assemblies have been of great interest due to their charge-neutral character and thus their propensity to avoid nonspecific interactions. These systems are known to exhibit a macroscopic temperature-sensitive transition, where the assembly phase-separates from the aqueous phase at higher temperatures. While this so-called lower critical solution temperature (LCST) behavior has been well-studied, there have been no studies on the fate of these supramolecular assemblies below this transition temperature. The work here brings to light the presence of a second, sub-LCST transition, observed well below the LCST of oligo­(ethylene glycol) (OEG)-based dendrons, where the host–guest properties of the assembly are significantly altered. This sub-LCST transition is accompanied by changes in the guest encapsulation stability and dynamics of host exchange