The Constitutional Isomerism of One-Component Ionizable Amphiphilic Janus Dendrimers Orchestrates the Total and Targeted Activities of mRNA Delivery.

Constitutional isomerism has been previously demonstrated by one of our laboratories to represent a powerful design strategy for the elaboration of complex functional self-organizations. Here we report the design, synthesis, and characterization of 14 positional, skeletal, and functional constitutional isomeric one-component, multifunctional, sequence-defined, amphiphilic ionizable Janus dendrimers (IAJDs). Their coassembly by simple injection with luciferase mRNA (Luc-mRNA) to form dendrimersome nanoparticles (DNPs) was studied. Subsequently, the resulting DNPs were employed to investigate, with screening experiments, the delivery of Luc-mRNA in vivo. Constitutional isomerism was shown to produce changes of up to two orders of magnitude of the total-body luciferase activity and targeted luciferase activity to the spleen and liver, of up to three orders of magnitude difference in targeted luciferase activity to the lungs and up to six orders of magnitude to lymph nodes. These results indicate that constitutional isomerism may represent not only a simple but also an important synthetic strategy that most probably may impact the activity of all components of synthetic vectors used in RNA-based nanomedicine, including in mRNA vaccines and therapeutics.

From Frank-Kasper, Quasicrystals, and Biological Membrane Mimics to Reprogramming In Vivo the Living Factory to Target the Delivery of mRNA with One-Component Amphiphilic Janus Dendrimers.

This Perspective is dedicated to the 25th Anniversary of Biomacromolecules. It provides a personal view on the developing field of the polymer and biology interface over the 25 years since the journal was launched by the American Chemical Society (ACS). This Perspective is meant to bridge an article published in the first issue of the journal and recent bioinspired developments in the laboratory of the corresponding author. The discovery of supramolecular spherical helices self-organizing into Frank-Kasper and quasicrystals as models of icosahedral viruses, as well as of columnar helical assemblies that mimic rodlike viruses by supramolecular dendrimers, is briefly presented. The transplant of these assemblies from supramolecular dendrimers to block copolymers, giant surfactants, and other self-organized soft matter follows. Amphiphilic self-assembling Janus dendrimers and glycodendrimers as mimics of biological membranes and their glycans are discussed. New concepts derived from them that evolved in the in vivo targeted delivery of mRNA with the simplest one-component synthetic vector systems are introduced. Some synthetic methodologies employed during the synthesis and self-assembly are explained. Unraveling bioinspired applications of novel materials concludes this brief 25th Anniversary Perspective of Biomacromolecules.

Glycan-Driven Formation of Raft-Like Domains with Hierarchical Periodic Nanoarrays on Dendrimersome Synthetic Cells.

The accurate spatial segregation into distinct phases within cell membranes coordinates vital biochemical processes and functionalities in living organisms. One of nature's strategies to localize reactivity is the formation of dynamic raft domains. Most raft models rely on liquid-ordered L0 phases in a liquid-disordered Ld phase lacking correlation and remaining static, often necessitating external agents for phase separation. Here, we introduce a synthetic system of bicomponent glycodendrimersomes coassembled from Janus dendrimers and Janus glycodendrimers (JGDs), where lactose-lactose interactions exclusively drive lateral organization. This mechanism results in modulated phases across two length scales, yielding raft-like microdomains featuring nanoarrays at the nanoscale. By varying the density of lactose and molecular architecture of JGDs, the nanoarray type and size, shape, and spacing of the domains were controlled. Our findings offer insight into the potential primordial origins of rudimentary raft domains and highlight the crucial role of glycans within the glycocalyx.

Aptamer-Targeted Dendrimersomes Assembled from Azido-Modified Janus Dendrimers "Clicked" to DNA.

Amphiphilic Janus dendrimers (JDs), synthetic alternatives to lipids, have the potential to expand the scope of nanocarrier delivery systems. JDs self-assemble into vesicles called dendrimersomes, encapsulate both hydrophobic cargo and nucleic acids, and demonstrate enhanced stability in comparison to lipid nanoparticles (LNPs). Here, we report the ability to enhance the cellular uptake of Janus dendrimersomes using DNA aptamers. Azido-modified JDs were synthesized and conjugated to alkyne-modified DNAs using copper-catalyzed azide alkyne cycloaddition. DNA-functionalized JDs form nanometer-sized dendrimersomes in aqueous solution via thin film hydration. These vesicles, now displaying short DNAs, are then hybridized to transferrin receptor binding DNA aptamers. Aptamer-targeted dendrimersomes show improved cellular uptake as compared to control vesicles via fluorescence microscopy and flow cytometry. This work demonstrates the versatility of using click chemistry to conjugate functionalized JDs with biologically relevant molecules and the feasibility of targeting DNA-modified dendrimersomes for drug delivery applications.

Self-Assembly of Glycerol-Amphiphilic Janus Dendrimers Amplifies and Indicates Principles for the Selection of Stereochemistry by Biological Membranes.

The principles for the selection of the stereochemistry of phospholipids of biological membranes remain unclear and continue to be debated. Therefore, any new experiments on this topic may help progress in this field. To address this question, three libraries of constitutional isomeric glycerol-amphiphilic Janus dendrimers (JDs) with nonsymmetric homochiral, racemic, and symmetric achiral branching points were synthesized by an orthogonal-modular-convergent methodology. These JDs amplify self-assembly, and therefore, monodisperse vesicles known as dendrimersomes (DSs) with predictable dimensions programmed by JD concentration were assembled by rapid injection of their ethanol solution into water. DSs of homochiral JD enantiomers, racemic, including mixtures of different enantiomers, and achiral exhibited similar DS size-concentration dependence. However, the number of bilayers of DSs assembled from homochiral, achiral, and racemic JDs determined by cryo-TEM were different. Statistical analysis of the number of bilayers and coarse-grained molecular dynamics simulations demonstrated that homochiral JDs formed predominantly unilamellar DSs. Symmetric achiral JDs assembled only unilamellar DSs while racemic JDs favored multilamellar DSs. Since cell membranes are unilamellar, these results indicate a new rationale for nonsymmetric homochiral vs racemic selection. Simultaneously, these experiments imply that the symmetric achiral lipids forming more stable membrane, probably had been the preferable assemblies of prebiotic cell membranes.

Targeted and Equally Distributed Delivery of mRNA to Organs with Pentaerythritol-Based One-Component Ionizable Amphiphilic Janus Dendrimers.

Delivery of nucleic acids with viral and synthetic vectors has pioneered genetic nanomedicine. Four-component lipid nanoparticles (LNPs) consisting of ionizable lipids, phospholipids, cholesterol, and PEG-conjugated lipids, assembled by microfluidic or T-tube, are the benchmark synthetic vector for delivery of mRNA. One-component multifunctional sequence-defined ionizable amphiphilic Janus dendrimer (IAJD) delivery systems for mRNA were developed by us to complement LNPs. IAJDs consist of multifunctional hydrophilic low-generation dendrons or minidendrons conjugated to hydrophobic dendrons. They were inspired by amphiphilic Janus dendrimers and glycodendrimers. IAJDs coassemble with mRNA into predictable-size vesicles, named dendrimersome nanoparticles (DNPs), by simple injection in acetate buffer, rather than by the complex technology required by LNPs. Assembly of DNPs by simple injection together with sequence design in the hydrophilic and hydrophobic modules of IAJDs endowed rapid screening to access discovery. Molecular design principles for targeted delivery were elaborated when the branching points of IAJDs were constructed from symmetrically and nonsymmetrically substituted plant phenolic acids interconnected by pentaerythritol (PE). Here, we report the first library containing simplified IAJDs constructed in only three steps from symmetrically trialkylated PE in the hydrophobic domain and four different piperazine-based ionizable amines in the hydrophilic part. Rapid coassembly with mRNA and in vivo screening led to the discovery of the two most active IAJDs targeting the spleen, liver, and lymph nodes, one predominantly to the spleen and liver and six delivering equally to the spleen, liver, lung, and lymph nodes. These IAJDs represent the simplest synthetic vectors and the first viral or synthetic system delivering equally to multiple organs.

Nanovesicles displaying functional linear and branched oligomannose self-assembled from sequence-defined Janus glycodendrimers.

Cell surfaces are often decorated with glycoconjugates that contain linear and more complex symmetrically and asymmetrically branched carbohydrates essential for cellular recognition and communication processes. Mannose is one of the fundamental building blocks of glycans in many biological membranes. Moreover, oligomannoses are commonly found on the surface of pathogens such as bacteria and viruses as both glycolipids and glycoproteins. However, their mechanism of action is not well understood, even though this is of great potential interest for translational medicine. Sequence-defined amphiphilic Janus glycodendrimers containing simple mono- and disaccharides that mimic glycolipids are known to self-assemble into glycodendrimersomes, which in turn resemble the surface of a cell by encoding carbohydrate activity via supramolecular multivalency. The synthetic challenge of preparing Janus glycodendrimers containing more complex linear and branched glycans has so far prevented access to more realistic cell mimics. However, the present work reports the use of an isothiocyanate-amine "click"-like reaction between isothiocyanate-containing sequence-defined amphiphilic Janus dendrimers and either linear or branched oligosaccharides containing up to six monosaccharide units attached to a hydrophobic amino-pentyl linker, a construct not expected to assemble into glycodendrimersomes. Unexpectedly, these oligoMan-containing dendrimers, which have their hydrophobic linker connected via a thiourea group to the amphiphilic part of Janus glycodendrimers, self-organize into nanoscale glycodendrimersomes. Specifically, the mannose-binding lectins that best agglutinate glycodendrimersomes are those displaying hexamannose. Lamellar "raft-like" nanomorphologies on the surface of glycodendrimersomes, self-organized from these sequence-defined glycans, endow these membrane mimics with high biological activity.

The Unexpected Importance of the Primary Structure of the Hydrophobic Part of One-Component Ionizable Amphiphilic Janus Dendrimers in Targeted mRNA Delivery Activity.

Viral and synthetic vectors for delivery of nucleic acids impacted genetic nanomedicine by aiding the rapid development of the extraordinarily efficient Covid-19 vaccines. Access to targeted delivery of nucleic acids is expected to expand the field of nanomedicine beyond most expectations. Both viral and synthetic vectors have advantages and disadvantages. The major advantage of the synthetic vectors is their unlimited synthetic capability. The four-component lipid nanoparticles (LNPs) are the leading nonviral vector for mRNA used by Pfizer and Moderna in Covid-19 vaccines. Their synthetic capacity inspired us to develop a one-component multifunctional sequence-defined ionizable amphiphilic Janus dendrimer (IAJD) delivery system for mRNA. The first experiments on IAJDs provided, through a rational-library design combined with orthogonal-modular accelerated synthesis and sequence control in their hydrophilic part, some of the most active synthetic vectors for the delivery of mRNA to lung. The second experiments employed a similar strategy, generating, by a less complex hydrophilic structure, a library of IAJDs targeting spleen, liver, and lung. Here, we report preliminary studies designing the hydrophobic region of IAJDs by using dissimilar alkyl lengths and demonstrate the unexpectedly important role of the primary structure of the hydrophobic part of IAJDs by increasing up to 90.2-fold the activity of targeted delivery of mRNA to spleen, lymph nodes, liver, and lung. The principles of the design strategy reported here and in previous publications indicate that IAJDs could have a profound impact on the future of genetic nanomedicine.

Bioactive cell-like hybrids from dendrimersomes with a human cell membrane and its components.

Cell-like hybrids from natural and synthetic amphiphiles provide a platform to engineer functions of synthetic cells and protocells. Cell membranes and vesicles prepared from human cell membranes are relatively unstable in vitro and therefore are difficult to study. The thicknesses of biological membranes and vesicles self-assembled from amphiphilic Janus dendrimers, known as dendrimersomes, are comparable. This feature facilitated the coassembly of functional cell-like hybrid vesicles from giant dendrimersomes and bacterial membrane vesicles generated from the very stable bacterial Escherichia coli cell after enzymatic degradation of its outer membrane. Human cells are fragile and require only mild centrifugation to be dismantled and subsequently reconstituted into vesicles. Here we report the coassembly of human membrane vesicles with dendrimersomes. The resulting giant hybrid vesicles containing human cell membranes, their components, and Janus dendrimers are stable for at least 1 y. To demonstrate the utility of cell-like hybrid vesicles, hybrids from dendrimersomes and bacterial membrane vesicles containing YadA, a bacterial adhesin protein, were prepared. The latter cell-like hybrids were recognized by human cells, allowing for adhesion and entry of the hybrid bacterial vesicles into human cells in vitro.

Encapsulation of hydrophobic components in dendrimersomes and decoration of their surface with proteins and nucleic acids.

Reconstructing the functions of living cells using nonnatural components is one of the great challenges of natural sciences. Compartmentalization, encapsulation, and surface decoration of globular assemblies, known as vesicles, represent key early steps in the reconstitution of synthetic cells. Here we report that vesicles self-assembled from amphiphilic Janus dendrimers, called dendrimersomes, encapsulate high concentrations of hydrophobic components and do so more efficiently than commercially available stealth liposomes assembled from phospholipid components. Multilayer onion-like dendrimersomes demonstrate a particularly high capacity for loading low-molecular weight compounds and even folded proteins. Coassembly of amphiphilic Janus dendrimers with metal-chelating ligands conjugated to amphiphilic Janus dendrimers generates dendrimersomes that selectively display folded proteins on their periphery in an oriented manner. A modular strategy for tethering nucleic acids to the surface of dendrimersomes is also demonstrated. These findings augment the functional capabilities of dendrimersomes to serve as versatile biological membrane mimics.

Encoding biological recognition in a bicomponent cell-membrane mimic.

Self-assembling dendrimers have facilitated the discovery of periodic and quasiperiodic arrays of supramolecular architectures and the diverse functions derived from them. Examples are liquid quasicrystals and their approximants plus helical columns and spheres, including some that disregard chirality. The same periodic and quasiperiodic arrays were subsequently found in block copolymers, surfactants, lipids, glycolipids, and other complex molecules. Here we report the discovery of lamellar and hexagonal periodic arrays on the surface of vesicles generated from sequence-defined bicomponent monodisperse oligomers containing lipid and glycolipid mimics. These vesicles, known as glycodendrimersomes, act as cell-membrane mimics with hierarchical morphologies resembling bicomponent rafts. These nanosegregated morphologies diminish sugar-sugar interactions enabling stronger binding to sugar-binding proteins than densely packed arrangements of sugars. Importantly, this provides a mechanism to encode the reactivity of sugars via their interaction with sugar-binding proteins. The observed sugar phase-separated hierarchical arrays with lamellar and hexagonal morphologies that encode biological recognition are among the most complex architectures yet discovered in soft matter. The enhanced reactivity of the sugar displays likely has applications in material science and nanomedicine, with potential to evolve into related technologies.

Design-functionality relationships for adhesion/growth-regulatory galectins.

Glycan-lectin recognition is assumed to elicit its broad range of (patho)physiological functions via a combination of specific contact formation with generation of complexes of distinct signal-triggering topology on biomembranes. Faced with the challenge to understand why evolution has led to three particular modes of modular architecture for adhesion/growth-regulatory galectins in vertebrates, here we introduce protein engineering to enable design switches. The impact of changes is measured in assays on cell growth and on bridging fully synthetic nanovesicles (glycodendrimersomes) with a chemically programmable surface. Using the example of homodimeric galectin-1 and monomeric galectin-3, the mutual design conversion caused qualitative differences, i.e., from bridging effector to antagonist/from antagonist to growth inhibitor and vice versa. In addition to attaining proof-of-principle evidence for the hypothesis that chimera-type galectin-3 design makes functional antagonism possible, we underscore the value of versatile surface programming with a derivative of the pan-galectin ligand lactose. Aggregation assays with N,N'-diacetyllactosamine establishing a parasite-like surface signature revealed marked selectivity among the family of galectins and bridging potency of homodimers. These findings provide fundamental insights into design-functionality relationships of galectins. Moreover, our strategy generates the tools to identify biofunctional lattice formation on biomembranes and galectin-reagents with therapeutic potential.

From examining the relationship between (corona)viral adhesins and galectins to glyco-perspectives.

Glycan-lectin recognition is vital to processes that impact human health, including viral infections. Proceeding from crystallographical evidence of case studies on adeno-, corona-, and rotaviral spike proteins, the relationship of these adhesins to mammalian galectins was examined by computational similarity assessments. Intrafamily diversity among human galectins was in the range of that to these viral surface proteins. Our findings are offered to inspire the consideration of lectin-based approaches to thwart infection by present and future viral threats, also mentioning possible implications for vaccine development.

Targeted Delivery of mRNA with One-Component Ionizable Amphiphilic Janus Dendrimers.

Targeted and efficient delivery of nucleic acids with viral and synthetic vectors is the key step of genetic nanomedicine. The four-component lipid nanoparticle synthetic delivery systems consisting of ionizable lipids, phospholipids, cholesterol, and a PEG-conjugated lipid, assembled by microfluidic or T-tube technology, have been extraordinarily successful for delivery of mRNA to provide Covid-19 vaccines. Recently, we reported a one-component multifunctional sequence-defined ionizable amphiphilic Janus dendrimer (IAJD) synthetic delivery system for mRNA relying on amphiphilic Janus dendrimers and glycodendrimers developed in our laboratory. Amphiphilic Janus dendrimers consist of functional hydrophilic dendrons conjugated to hydrophobic dendrons. Co-assembly of IAJDs with mRNA into dendrimersome nanoparticles (DNPs) occurs by simple injection in acetate buffer, rather than by microfluidic devices, and provides a very efficient system for delivery of mRNA to lung. Here we report the replacement of most of the hydrophilic fragment of the dendron from IAJDs, maintaining only its ionizable amine, while changing its interconnecting group to the hydrophobic dendron from amide to ester. The resulting IAJDs demonstrated that protonated ionizable amines play dual roles of hydrophilic fragment and binding ligand for mRNA, changing delivery from lung to spleen and/or liver. Replacing the interconnecting ester with the amide switched the delivery back to lung. Delivery predominantly to liver is favored by pairs of odd and even alkyl groups in the hydrophobic dendron. This simple structural change transformed the targeted delivery of mRNA mediated with IAJDs, from lung to liver and spleen, and expands the utility of DNPs from therapeutics to vaccines.

An Accelerated Modular-Orthogonal Ni-Catalyzed Methodology to Symmetric and Nonsymmetric Constitutional Isomeric AB2 to AB9 Dendrons Exhibiting Unprecedented Self-Organizing Principles.

Five libraries of natural and synthetic phenolic acids containing five AB3, ten constitutional isomeric AB2, one AB4, and one AB5 were previously synthesized and reported by our laboratory in 5 to 11 steps. They were employed to construct seven libraries of self-assembling dendrons, by divergent generational, deconstruction, and combined approaches, enabling the discovery of a diversity of supramolecular assemblies including Frank-Kasper phases, soft quasicrystals, and complex helical organizations, some undergoing deracemization in the crystal state. However, higher substitution patterns within a single dendron were not accessible. Here we report three libraries consisting of 30 symmetric and nonsymmetric constitutional isomeric phenolic acids with unprecedented sequenced patterns, including two AB2, three AB3, eight AB4, five AB5, six AB6, three AB7, two AB8, and one AB9 synthesized by accelerated modular-orthogonal Ni-catalyzed borylation and cross-coupling. A single etherification step with 4-(n-dodecyloxy)benzyl chloride transformed all these phenolic acids, of interest also for other applications, into self-assembling dendrons. Despite this synthetic simplicity, they led to a diversity of unprecedented self-organizing principles: lamellar structures of interest for biological membrane mimics, helical columnar assemblies from rigid-solid angle dendrons forming Tobacco Mosaic Virus-like assemblies, columnar organizations from adaptable-solid angle dendrons forming disordered micellar-like nonhelical columns, columns from supramolecular spheres, five body-centered cubic phases displaying supramolecular orientational memory, rarely encountered in previous libraries forming predominantly Frank-Kasper phases, and two Frank-Kasper phases. Lessons from these self-organizing principles, discovered within a single generation of self-assembling dendrons, may help elaborate design principles for complex helical and nonhelical organizations of synthetic and biological matter.

One-Component Multifunctional Sequence-Defined Ionizable Amphiphilic Janus Dendrimer Delivery Systems for mRNA.

Efficient viral or nonviral delivery of nucleic acids is the key step of genetic nanomedicine. Both viral and synthetic vectors have been successfully employed for genetic delivery with recent examples being DNA, adenoviral, and mRNA-based Covid-19 vaccines. Viral vectors can be target specific and very efficient but can also mediate severe immune response, cell toxicity, and mutations. Four-component lipid nanoparticles (LNPs) containing ionizable lipids, phospholipids, cholesterol for mechanical properties, and PEG-conjugated lipid for stability represent the current leading nonviral vectors for mRNA. However, the segregation of the neutral ionizable lipid as droplets in the core of the LNP, the "PEG dilemma", and the stability at only very low temperatures limit their efficiency. Here, we report the development of a one-component multifunctional ionizable amphiphilic Janus dendrimer (IAJD) delivery system for mRNA that exhibits high activity at a low concentration of ionizable amines organized in a sequence-defined arrangement. Six libraries containing 54 sequence-defined IAJDs were synthesized by an accelerated modular-orthogonal methodology and coassembled with mRNA into dendrimersome nanoparticles (DNPs) by a simple injection method rather than by the complex microfluidic technology often used for LNPs. Forty four (81%) showed activity in vitro and 31 (57%) in vivo. Some, exhibiting organ specificity, are stable at 5 °C and demonstrated higher transfection efficiency than positive control experiments in vitro and in vivo. Aside from practical applications, this proof of concept will help elucidate the mechanisms of packaging and release of mRNA from DNPs as a function of ionizable amine concentration, their sequence, and constitutional isomerism of IAJDs.

Unraveling topology-induced shape transformations in dendrimersomes.

The vital functions of cell membranes require their ability to quickly change shape to perform complex tasks such as motion, division, endocytosis, and apoptosis. Membrane curvature in cells is modulated by very complex processes such as changes in lipid composition, the oligomerization of curvature-scaffolding proteins, and the reversible insertion of protein regions that act like wedges in the membrane. But, could much simpler mechanisms support membrane shape transformation? In this work, we demonstrate how the change of amphiphile topology in the bilayer can drive shape transformations of cell membrane models. To tackle this, we have designed and synthesized new types of amphiphiles-Janus dendrimers-that self-assemble into uni-, multilamellar, or smectic-ordered vesicles, named dendrimersomes. We synthesized Janus dendrimers containing a photo-labile bond that upon UV-Vis irradiation cleavage lose a part of the hydrophilic dendron. This leads to a change from a cylindrically to a wedge-shaped amphiphile. The high mobility of these dendrimers allows for the concentration of the wedge-shaped amphiphiles and the generation of transmembrane asymmetries. The concentration of the wedges and their rate of segregation allowed control of the budding and generation of structures such as tubules and high genus vesicles.

Exploring functional pairing between surface glycoconjugates and human galectins using programmable glycodendrimersomes.

Precise translation of glycan-encoded information into cellular activity depends critically on highly specific functional pairing between glycans and their human lectin counter receptors. Sulfoglycolipids, such as sulfatides, are important glycolipid components of the biological membranes found in the nervous and immune systems. The optimal molecular and spatial design aspects of sulfated and nonsulfated glycans with high specificity for lectin-mediated bridging are unknown. To elucidate how different molecular and spatial aspects combine to ensure the high specificity of lectin-mediated bridging, a bottom-up toolbox is devised. To this end, negatively surface-charged glycodendrimersomes (GDSs), of different nanoscale dimensions, containing sulfo-lactose groups are self-assembled in buffer from a synthetic sulfatide mimic: Janus glycodendrimer (JGD) containing a 3'-O-sulfo-lactose headgroup. Also prepared for comparative analysis are GDSs with nonsulfated lactose, a common epitope of human membranes. These self-assembled GDSs are employed in aggregation assays with 15 galectins, comprising disease-related human galectins, and other natural and engineered variants from four families, having homodimeric, heterodimeric, and chimera architectures. There are pronounced differences in aggregation capacity between human homodimeric and heterodimeric galectins, and also with respect to their responsiveness to the charge of carbohydrate-derived ligand. Assays reveal strong differential impact of ligand surface charge and density, as well as lectin concentration and structure, on the extent of surface cross-linking. These findings demonstrate how synthetic JGD-headgroup tailoring teamed with protein engineering and network assays can help explain how molecular matchmaking operates in the cellular context of glycan and lectin complexity.

Enhanced Concanavalin†A Binding to Preorganized Mannose Nanoarrays in Glycodendrimersomes Revealed Multivalent Interactions.

The effect of the two-dimensional glycan display on glycan-lectin recognition remains poorly understood despite the importance of these interactions in a plethora of cellular processes, in (patho)physiology, as well as its potential for advanced therapeutics. Faced with this challenge we utilized glycodendrimersomes, a type of synthetic vesicles whose membrane mimics the surface of a cell and offers a means to probe the carbohydrate biological activity. These single-component vesicles were formed by the self-assembly of sequence-defined mannose-Janus dendrimers, which serve as surrogates for glycolipids. Using atomic force microscopy and molecular modeling we demonstrated that even mannose, a monosaccharide, was capable of organizing the sugar moieties into periodic nanoarrays without the need of the formation of liquid-ordered phases as assumed necessary for rafts. Kinetics studies of Concanavalin A binding revealed that those nanoarrays resulted in a new effective ligand yielding a ten-fold increase in the kinetic and thermodynamic constant of association.

Monodisperse Macromolecules by Self-Interrupted Living Polymerization.

Biological macromolecules such as proteins and nucleic acids are monodisperse just as low-molar-mass organic compounds are. However, synthetic macromolecules contain mixtures of different chain lengths, the most uniform being generated by living polymerizations, which exhibit a maximum of 1-3% of chains with the desired length. Monodisperse natural and synthetic oligomers can be obtained in low quantities by tedious, multistep iterative methods. Here we report a methodology to synthesize monodisperse synthetic macromolecules by self-interrupted living polymerization. This methodology relies on a concept that combines supramolecular and macromolecular chemistry and differs from the conventional reactivity principles employed in the synthesis of polymers for over 100 years.