Spatiotemporal control and superselectivity in supramolecular polymers using multivalency

Multivalency has an important but poorly understood role in molecular self-organization. We present the noncovalent synthesis of a multicomponent supramolecular polymer in which chemically distinct monomers spontaneously coassemble into a dynamic, functional structure. We show that a multivalent recruiter is able to bind selectively to one subset of monomers (receptors) and trigger their clustering along the self-assembled polymer, behavior that mimics raft formation in cell membranes. This phenomenon is reversible and affords spatiotemporal control over the monomer distribution inside the supramolecular polymer by superselective binding of single-strand DNA to positively charged receptors. Our findings reveal the pivotal role of multivalency in enabling structural order and nonlinear recognition in water-soluble supramolecular polymers, and it offers a design principle for functional, structurally defined supramolecular architectures

The relationship between observing behavior and food-key response rates under mixed and multiple schedules of reinforcement

Pigeons were trained under an observing response procedure in which pecks on one key (food key) were reinforced under a mixed fixed-interval 30-sec extinction schedule. A response on a second (observing) key replaced the mixed-schedule stimulus with either of two multiple-schedule stimuli (red and green keylights) for 5 sec. Observing response rates were positively correlated with food-key response rates in the presence of multiple-schedule stimuli and inversely related to food-key response rates in the presence of mixed-schedule stimuli. These results suggest that observing response output is controlled not only by the stimuli produced by observing responses but also by the stimuli in the presence of which observing responses occur. The possibility that observing responses alter the probability of reinforcement is advanced