The successful integration of 2D nanomaterials into functional devices hinges on developing fabrication methods that afford hierarchicalcontrol across length scales of the entire assembly.W ed emonstrate structural control over ac lass of crystalline 2D nanosheets assembled from collagen triple helices.Bylengthening the triple helix unit through sequential additions of Pro-Hyp-Gly triads,w ea chieved sub-angstrom tuning over the 2D lattice.T hese subtle changes influence the overall nanosheet size, which can be adjusted across the mesoscale size regime.The internal structure was observed by cryo-TEM with direct electron detection, whichprovides realspace high-resolution images,inwhich individual triple helices comprising the lattice can be clearly discerned. These results establish ag eneral strategy for tuning the structural hierarchy of 2D nanomaterials that employr igid, cylindrical structural units.

Engineering free-standing 2D nanomaterials with compositional, spatial, and functional control across size regimes from the nano- to mesoscale represents a significant challenge. Herein, we demonstrate a straightforward strategy for the thermodynamically controlled fabrication of multicomponent sectored nanosheets in which each sector can be chemically and spatially addressed independently and orthogonally. Collagen triple helices, comprising collagen-mimetic peptides (CMPs), are employed as molecularly programmable crystallizable units. Modulating their thermodynamic stability affords the controlled synthesis of 2D core–shell nanostructures via thermally driven heteroepitaxial growth. Structural information, gathered from SAXS and cryo-TEM, reveals that the distinct peptide domains maintain their intrinsic lattice structure and illuminates various mechanisms employed by CMP triple helices to alleviate the elastic strain associated with the interfacial lattice mismatch. Finally, we demonstrate that different sectors of the sheet surface can be selectively functionalized using bioorthogonal conjugation chemistry. Altogether, we establish a robust platform for constructing multifunctional 2D nanoarchitectures in which one can systematically program their compositional, spatial, and functional properties, which is a significant step toward their deployment into functional nanoscale devices.

The fabrication of dynamic, transformable biomaterials that respond to environmental cues represents a significant step forward in the development of synthetic materials that rival their highly functional, natural counterparts. Here, we describe the design and synthesis of crystalline supramolecular architectures from charge-complementary heteromeric pairs of collagen-mimetic peptides (CMPs). Under appropriate conditions, CMP pairs spontaneously assemble into either 1D ultraporous (pore diameter > 100 nm) tubes or 2D bilayer nanosheets due to the structural asymmetry that arises from heteromeric self-association. Crystalline collagen tubes represent a heretofore unobserved morphology of this common biomaterial. In-depth structural characterization from a suite of biophysical methods, including TEM, AFM, high-resolution cryo-EM, and SAXS/WAXS measurements, reveals that the sheet and tube assemblies possess a similar underlying lattice structure. The experimental evidence suggests that the tubular structures are a consequence of the self-scrolling of incipient 2D layers of collagen triple helices, and that the scrolling direction determines the formation of two distinct structural isoforms. Furthermore, we show that nanosheets and tubes can spontaneously interconvert through manipulation of the assembly pH and systematic adjustment of the CMP sequence. Altogether, we establish initial guidelines for the construction of dynamically responsive 1D and 2D assemblies that undergo a structurally programmed morphological transition.

Dopamine (DA) release in the ventral and dorsal striatum has been linked to reward processing and motivation, but there are longstanding controversies about whether DA release in these key target structures primarily reflects costs or benefits, and how these signals vary with motivation. Here we apply behavioral economic principles to generate demand curves for rewards while directly measuring DA release in the nucleus accumbens (NAc) and dorsolateral striatum (DLS) via a genetically-encoded sensor. By independently varying costs and benefits, we reveal that DA release in both structures incorporates reward magnitude and sunk cost. Surprisingly, motivation was inversely correlated with reward-evoked DA release; the higher the motivation for rewards the lower the reward-evoked DA release. These relationships between DA release, cost and motivation remained identical when we used optogenetic activation of striatal DA inputs as a reward. Our results reconcile previous disparate findings by demonstrating that during operant tasks, striatal DA release simultaneously encodes cost, benefit and motivation but in distinct manners over different time scales.

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