Monodisperse Protein-Based Glycopolymers via a Combined Biosynthetic and Chemical Approach

Glycosylated cellulose derivatives with regioselective distributions of pendant glucose moieties

Inspired by the presence of diverse carbohydrates on the surface of biological systems, we present herein a method for the synthesis of sugar-bearing polymers derived from renewable cellulose. In this paper, novel glycosylated cellulose derivatives were successfully synthesized containing a series of subsequent reactions: (1) synthesis of cellulose derivatives with pendant hydroxyl groups via nucleophilic substitution; (2) further sequential reactions containing a novel TEMPO/[bis(acetoxy)iodo]benzene (BAIB)-mediated oxidation of pendant hydroxyl groups, Schiff base formation and reduction in one-pot reaction; and (3) thiol-ene click reaction as an efficient tool to generate cellulose derivatives with pendant glucosyl groups. Furthermore, the glucosyl groups were only linked with the C6 position of anhydroglucose units (AGUs) of cellulose. Moreover, the glycosylated cellulose derivatives could be reversibly cross-linked by 1,4-phenylenediboronic acid at pH 10 and dissociated into single polymer chains by using glucose, which allow such glycolated cellulose derivatives to be interesting responsive materials.

Straightforward Synthesis of N-Glycan Polymers from Free Glycans via Cyanoxyl Free Radical-Mediated Polymerization

We report a straightforward synthesis of N-glycan polymers from free glycans via glycosylamine intermediates followed by acrylation and polymerization via cyanoxyl-mediated free radical polymerization (CMFRP) in one-pot fashion. No protection and deprotection were used in either glycomonomer or glycopolymer synthesis. A typical synthetic procedure for N-glycan polymers from free monosaccharide and disaccharide, Glc, Gal, Man, GlcNAc, and Lac, was demonstrated. In addition, enzymatic sialylation of the Lac-containing N-glycan polymers and their anti-influenza virus hemagglutination activities were investigated.

Tandem mass spectrometry and ion mobility mass spectrometry for the analysis of molecular sequence and architecture of hyperbranched glycopolymers

Multidimensional mass spectrometry techniques, combining matrix-assisted laser desorption/ionization (MALDI) or electrospray ionization (ESI) with tandem mass spectrometry (MS(2)), multistage mass spectrometry (MS(n)) or ion mobility mass spectrometry (IM-MS), have been employed to gain precise structural insight on the compositions, sequences and architectures of small oligomers of a hyperbranched glycopolymer, prepared by atom transfer radical copolymerization of an acrylate monomer (A) and an acrylate inimer (B), both carrying mannose ester pendants. The MS data confirmed the incorporation of multiple inimer repeat units, which ultimately lead to the hyperbranched material. The various possible structures of n-mers with the same composition were subsequently elucidated based on MS(2) and MS(n) studies. The characteristic elimination of bromomethane molecule provided definitive information about the comonomer connectivity in the copolymeric AB2 trimer and A2B2 tetramer, identifying as present only one of the three possible trimeric isomers (viz. sequence BBA) and only two of the six possible tetrameric isomers (viz. sequences BBA2 and BABA). Complementary IM-MS studies confirmed that only one of the tetrameric structures is formed. Comparison of the experimentally determined collision cross-section of the detected isomer with those predicted by molecular simulations for the two possible sequences ascertained BBA2 as the predominant tetrameric architecture. The multidimensional MS approaches presented provide connectivity information at the atomic level without requiring high product purity (due to the dispersive nature of MS) and, hence, should be particularly useful for the microstructure characterization of novel glycopolymers and other types of complex copolymers.

Cationic charged helical glycopolypeptide using ring opening polymerization of 6-deoxy-6-azido-glyco-N-carboxyanhydride

Glycopolypeptides with a defined secondary structure are of significance in understanding biological phenomena. Synthetic glycopolypeptides, or polypeptides featuring pendant carbohydrate moieties, have been of particular interest in the field of tissue engineering and drug delivery. In this work, we have synthesized charged water-soluble glycopolypeptides that adopt a helical conformation in water. This was carried out by the synthesis of a glyco-N-carboxyanhydride (glyco-NCA) containing an azide group at the sixth position of the carbohydrate ring. Subsequently, the NCA was polymerized to obtain azide-containing glycopolypeptides having good control over molecular weight and polydispersity index (PDI) in high yields. We were also able to control the incorporation of the azide group by synthesizing random co-glycopolypeptide containing 6-deoxy-6-azido and regular 6-OAc functionalized glucose. This azide functionality allows for the easy attachment of a bioactive group, which could potentially enhance the biological activity of the glycopolypeptide. We were able to obtain water-soluble charged glycopolypeptides by both reducing the azide groups into amines and using CuAAC with propargylamine. These charged glycopolypeptides were shown to have a helical conformation in water. Preliminary studies showed that these charged glycopolypeptides showed good biocompatibility and were efficiently taken up by HepG2 cells.

Emerging bioinspired polymers: glycopolypeptides

This article highlights the very recent advances in glycopolypeptide synthesis via NCA polymerization and first studies on stimuli-responsive solution behavior and self-assembling structures. Yet glycopolypeptides are almost exclusively considered as smart biofunctional materials for use in biomedical applications, for instance in targeted drug delivery, but also have high potential for usage as structural materials to fabricate bioinspired hierarchical structures.

Design of monodisperse and well-defined polypeptide-based polyvalent inhibitors of anthrax toxin

The design of polyvalent molecules, presenting multiple copies of a specific ligand, represents a promising strategy to inhibit pathogens and toxins. The ability to control independently the valency and the spacing between ligands would be valuable for elucidating structure-activity relationships and for designing potent polyvalent molecules. To that end, we designed monodisperse polypeptide-based polyvalent inhibitors of anthrax toxin in which multiple copies of an inhibitory toxin-binding peptide were separated by flexible peptide linkers. By tuning the valency and linker length, we designed polyvalent inhibitors that were over four orders of magnitude more potent than the corresponding monovalent ligands. This strategy for the rational design of monodisperse polyvalent molecules may not only be broadly applicable for the inhibition of toxins and pathogens, but also for controlling the nanoscale organization of cellular receptors to regulate signaling and the fate of stem cells.

Iminosugar-based glycopolypeptides: glycosidase inhibition with bioinspired glycoprotein analogue micellar self-assemblies

Glycosidase inhibition with bioinspired glycoprotein analogue micellar self-assemblies.

Synthesis and self-assembly of amphiphilic homoglycopolypeptide

The synthesis of the amphiphilic homoglycopolypeptide was carried out by a combination of NCA polymerization and click chemistry to yield a well-defined polypeptide having an amphiphilic carbohydrate on its side chain. The amphiphilicity of the carbohydrate was achieved by incorporation of an alkyl chain at the C-6 position of the carbohydrate thus also rendering the homoglycopolypeptide amphiphilic. The homoglycopolypeptide formed multimicellar aggregates in water above a critical concentration of 0.9 μM due to phase separation. The multimicellar aggregates were characterized by DLS, TEM, and AFM. It is proposed that hydrophobic interactions of the aliphatic chains at the 6-position of the sugar moieties drives the assembly of these rod-like homoglycopolypeptide into large spherical aggregates. These multimicellar aggregates encapsulate both hydrophilic as well as hydrophobic dye as was confirmed by confocal microscopy. Finally, amphiphilic random polypeptides containing 10% and 20% α-d-mannose in addition to glucose containing a hydrophobic alkyl chain at its 6 position were synthesized by our methodology, and these polymers were also found to assemble into spherical nanostructures. The spherical assemblies of amphiphilic random glycopolypeptides containing 10% and 20% mannose were found to be surface bioactive and were found to interact with the lectin Con-A.

Designed ankyrin repeat proteins as scaffolds for multivalent recognition

Ankyrin repeat (AR) proteins are composed of tandem repeats of a basic structural motif of ca. 33 amino acid residues that form a β-turn followed by two antiparallel α-helices. Multiple repeats stack together in a modular fashion to form a scaffold that is ideally suited for the presentation of multiple functional groups and/or recognition elements. Here we describe a biosynthetic strategy that takes advantage of the modular nature of these proteins to generate multivalent ligands that are both chemically homogeneous and structurally well-defined. Glycosylated AR proteins cluster the tetrameric lectin concanavalin A (Con A) at a rate that is comparable to the rate of Con A aggregation mediated by globular protein conjugates and variable density linear polymers. Thus, AR proteins define a new class of multivalent ligand scaffolds that have significant potential application in the study and control of a variety of multivalent interactions.

Helical assembly of azobenzene-conjugated carbohydrate hydrogelators with specific affinity for lectins

Carbohydrate-mediated interactions are involved in various biological processes via specific molecular assembly and recognition. Such interactions are enhanced by multivalent effects of the sugar moieties, and thus supramolecular sugar-assembly, i.e., spontaneous association of glycoamphiphiles, is a promising approach to tailor glycocluster formation. In this study, novel sugar-decorated nanofibers were successfully prepared by self-assembly of low molecular weight hydrogelators composed of azobenzene and disaccharide lactones. Circular dichroism measurement of the as-prepared hydrogels indicated that the azobenzene amphiphile containing a lactose moiety possessed (R)-chirality, while the maltose-azobenzene conjugate exhibited (S)-chirality, even though the cellobiose-conjugated azobenzene existed in an achiral form. This suggests that the chiral orientation of the chromophoric azobenzene depended on both the glycosidic linkages and the steric arrangement of hydroxyl groups in the conjugated carbohydrates. Lectin-binding and cell adhesion assays revealed that the nonreducing ends of the conjugated sugar moieties were exposed on the surfaces of self-assembled nanofibrous hydrogels, allowing them to be effectively recognized by the corresponding lectins. In addition, photoisomerization of azobenzene under ultraviolet irradiation induced the sol-gel transitions of the hydrogels. These results demonstrate that the reversibly transformed fibrous glycohydrogels show potential for application as carbohydrate-decorated scaffolds for cell culture engineering.

Conformational and aggregation properties of a PEGylated alanine-rich polypeptide

The conformational and aggregation behavior of PEG conjugates of an alanine-rich polypeptide (PEG-c17H6) were investigated and compared to that of the polypeptide equipped with a deca-histidine tag (17H6). These polypeptides serve as simple and stimuli-responsive models for the aggregation behavior of helix-rich proteins, as our previous studies have shown that the helical 17H6 self-associates at acidic pH and converts to β-sheet structures at elevated temperature under acidic conditions. In the work here, we show that PEG-c17H6 also adopts a helical structure at ambient/subambient temperatures, at both neutral and acidic pH. The thermal denaturation behavior of 17H6 and PEG-c17H6 is similar at neutral pH, where the alanine-rich domain has no self-association tendency. At acidic pH and elevated temperature, however, PEGylation slows β-sheet formation of c17H6, and reduces the apparent cooperativity of thermally induced unfolding. Transmission electron microscopy of PEG-c17H6 conjugates incubated at elevated temperatures showed fibrils with widths of ∼20-30 nm, wider than those observed for fibrils of 17H6. These results suggest that PEGylation reduces β-sheet aggregation in these polypeptides by interfering, only after unfolding of the native helical structure, with interprotein conformational changes needed to form β-sheet aggregates.

Architecture effects on L-selectin shedding induced by polypeptide-based multivalent ligands

Multivalent interactions between selectins and their ligands play key roles in mediating the rolling and tethering of leukocytes in the early steps of the inflammatory response, as well as in lymphocyte circulation. L-selectin shedding, which is the proteolytic cleavage of L-selectin, can be induced by L-selectin clustering through the binding of multivalent ligands to multiple L-selectin molecules, and it has been shown to regulate leukocyte rolling and subsequent integrin activation for firm adhesion. In this paper, we report the production of homogenous glycopolypeptides modified with a 3,6-disulfo-galactopyranoside equipped with a caproyl linker. The saccharide residue was chemically attached to various polypeptide backbones of differing architectures; the composition and purity of the sulfated glycopolypeptides was confirmed via¹H-NMR spectroscopy, amino acid analysis (AAA), and electrophoretic analysis. The retention of the conformation of the polypeptide backbone was confirmed via circular dichroic spectroscopy. The shedding of l-selectin from the surface of Jurkat cells induced by these sulfated glycopolypeptides, determined via ELISA-based methods, varied based on differences in the architectures of the polypeptide scaffolds, suggesting opportunities for these strategies in probing cell-surface receptor arrays and directing cell signaling events.

Multivalent protein polymers with controlled chemical and physical properties

In this review, we describe our work on the design, characterization, and modification of a series of alanine-rich helical polypeptides with novel functions. Glycosylation of the polypeptides has permitted investigation of polymer architecture effects on multivalent interactions. One of the members of this polypeptide family exhibits polymorphological behavior that is easily manipulated via simple changes in solution pH and temperature. Polypeptide-based fibrils formed at acidic pH and high temperature were shown to direct the one-dimensional organization of gold nanoparticles via electrostatic interactions. As a precursor to fibrils, aggregates likely comprising alanine-rich cores form at low temperatures and acidic pH and reversibly dissociate into monomers upon deprotonation. PEGylation of these polypeptides does not alter the self-association or conformational behavior of the polypeptide, suggesting potential applications in the development of assembled delivery vehicles, as modification of the polypeptides should be a useful strategy for controlling assembly.

Manipulation of electrostatic and saccharide linker interactions in the design of efficient glycopolypeptide-based cholera toxin inhibitors

Multivalent, glycopolymer inhibitors designed for the treatment of disease and pathogen infection have shown improvements in binding correlated with general changes in glycopolymer architecture and composition. We have previously demonstrated that control of glycopolypeptide backbone extension and ligand spacing significantly impacts the inhibition of the cholera toxin B subunit pentamer (CT B(5)) by these polymers. In the studies reported here, we elucidate the role of backbone charge and linker length in modulating the inhibition event. Peptides of the sequence AXPXG (where X is a positive, neutral or negative amino acid), equipped with the alkyne functionality of propargyl glycine, were designed and synthesized via solid-phase peptide synthetic methods and glycosylated via Cu(I)-catalyzed alkyne-azide cycloaddition reactions. The capacity of the glycopeptides to inhibit the binding of the B(5) subunit of cholera toxin was evaluated. These studies indicated that glycopeptides with a negatively charged backbone show improved inhibition of the binding event relative to the other glycopeptides. In addition, variations in the length of the linker between the peptide and the saccharide ligand also affected the inhibition of CT by the glycopeptides. Our findings suggest that, apart from appropriate saccharide spacing and polypeptide chain extension, saccharide linker conformation and the systematic placement of charges on the polypeptide backbone are also significant variables that can be tuned to improve the inhibitory potencies of glycopolypeptide-based multivalent inhibitors.

Chemical conjugation of linear and cyclic RGD moieties to a recombinant elastin-mimetic polypeptide--a versatile approach towards bioactive protein hydrogels

An elastin-mimetic polypeptide, (EMM)(7), with the amino-acid sequence GRDPSS [VPGVG VPGKG VPGVG VPGVG VPGEG VPGIG](7) was used for chemical conjugation of various integrin ligands (RGD peptides) to prepare bioactive hydrogels. The chemical approach involved (1) chemical protection of lysine residues with Fmoc or Boc groups, (2) chemical ligation of a protected linear or cyclic RGD ligand, with or without a hexanoic-acid spacer to the glutamic acid residue, (3) deprotection of the lysine functionalities and the RGD moieties and (4) cross-linking to form a bioactive hydrogel. (1)H NMR spectroscopy was used to quantify the multiple steps in the reaction. The chemical protection was found to be between 65 and 93% for Fmoc and Boc, respectively. The ligands studied included linear RGD cell-binding [H-FGRGDS-OH (1-l-RGD), H-Ahx--FGRGDS-OH (2-Ahx-FGRGDS) and a cyclic -H(2)N-(CH(2))(6)COHN-cyclo(-RGDfK-) (H-Ahx-c(-RGDfK-)) peptide also with a hexanoic-acid spacer. Cell adhesion with mouse osteoblast cells was dependent on the ligand type, ligand density and the use of a spacer.

Synthesis and characterization of a new class of cationic protein polymers for multivalent display and biomaterial applications

Monodisperse protein polymers engineered by biosynthetic techniques are well suited to serve as a basis for creating comb-like polymer architectures for biomaterial applications. We have developed a new class of linear, cationic, random-coil protein polymers designed to act as scaffolds for multivalent display. These polymers contain evenly spaced lysine residues that allow for chemical or enzymatic conjugation of pendant functional groups. Circular dichroism spectroscopy and turbidity experiments have confirmed that these proteins have a random coil structure and are soluble up to at least 65 degrees C. Cell viability assays suggest these constructs are nontoxic in solution up to a concentration of 100 microM. We have successfully attached a small bioactive peptide, a peptoid-peptide hybrid, a poly(ethylene glycol) polymer, and a fluorophore to the protein polymers by chemical or enzymatic coupling, demonstrating their suitability to serve as multivalent scaffolds in solutions or as gels.

Cholera toxin inhibitors studied with high-performance liquid affinity chromatography: a robust method to evaluate receptor-ligand interactions

Anti-adhesion drugs may be an alternative to antibiotics to control infection of micro-organisms. The well-characterized interaction between cholera toxin and the cellular glycolipid GM1 makes it an attractive model for inhibition studies in general. In this report, we demonstrate a high-performance liquid affinity chromatography approach called weak affinity chromatography to evaluate cholera toxin inhibitors. The cholera toxin B-subunit was covalently coupled to porous silica and a (weak) affinity column was produced. The K(D) values of galactose and meta-nitrophenyl alpha-D-galactoside were determined with weak affinity chromatography to be 52 and 1 mM, respectively, which agree well with IC(50) values previously reported. To increase inhibition potency multivalent inhibitors have been developed and the interaction with multivalent glycopolypeptides was also evaluated. The affinity of these compounds was found to correlate with the galactoside content but K(D) values were not obtained because of the inhomogeneous response and slow off-rate from multivalent interactions. Despite the limitations in obtaining direct K(D) values of the multivalent galactopolypeptides, weak affinity chromatography represents an additional and valuable tool in the evaluation of monovalent as well as multivalent cholera toxin inhibitors. It offers multiple advantages, such as a low sample consumption, high reproducibility and short analysis time, which are often not observed in other methods of analysis.

Polymer-Based Therapeutics

Polymeric materials have been applied in therapeutic applications, such as drug delivery and tissue regeneration, for decades owing to their biocompatibility and suitable mechanical properties. In addition, select polymer-drug conjugates have been used as bioactive pharmaceuticals owing to their increased drug efficacy, solubility, and target specificity compared with small-molecule drugs. Increased synthetic control of polymer properties has permitted the production of polymer assemblies for the targeted and controlled delivery of drugs, and polymeric sequestrants take advantage of their lack of solubility for the sequestration of target molecules in vivo. In more recent studies reviewed in greater detail here, the properties of polymers that distinguish them from small-molecule drugs, such as their high molecular weight and their ability to display multiple pendant moieties, have been specifically exploited for activating cellular targets or inhibiting the binding of pathogens. The elucidation of relevant structure-function relationships in investigations of this kind has relied on the combination of living polymerization methods with chemical conjugation methods, and protein engineering methods have shown increasing potential in the manipulation of architectural features of such polymer therapeutics. Garnering a detailed understanding of the various mechanisms by which multivalent polymers engage biological targets is certain to expand the role of polymers as therapeutics, by enabling highly specific activities of designed polymers in the biological environment.

Evaluation of conformation and association behavior of multivalent alanine-rich polypeptides

PURPOSE

Helical alanine-rich polypeptides with functional groups displayed along the backbone can display desired molecules such as saccharides or therapeutic molecules at a prescribed spacing. Because these polypeptides have promise for application as biomaterials, the conformation and association of these molecules have been investigated under biologically relevant conditions.

METHODS

Three polypeptide sequences, 17-H-3, 17-H-6, and 35-H-6, have been produced through recombinant techniques. Circular dichroic (CD) spectroscopy was used to monitor the secondary structure of the polypeptides in PBS (phosphate buffered saline, pH 7.4). The aggregation behavior in PBS was monitored via analytical ultracentrifugation and non-denaturing polyacrylamide gel electrophoresis.

RESULTS

The three polypeptides adopt a highly helical structure at low and ambient temperatures, and when heated, undergo a helix-to-coil transition, typical of other alanine-rich peptide sequences. The melting temperatures and van't Hoff enthalpies, extracted from the CD data, suggest similar stability of the sequences. Although alanine-rich sequences can be prone to aggregation, there is no indication of aggregation for the three polypeptides at a range of concentrations relevant for possible biological applications.

CONCLUSIONS

The helical polypeptides are monomeric under biologically relevant conditions enabling application of these polypeptides as useful scaffolds for ligand or drug display.

Global amine and acid functional group modification of proteins

A sequential reaction methodology is employed for the complete derivatization of protein thiols, amines, and acids in high purity under denaturing conditions. Following standard thiol alkylation, protein amines are modified via reductive methylation with formaldehyde and pyridine-borane. Protein acids are subsequently amidated under buffered conditions in DMSO using the coupling reagent (7-azabenzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate. The generality of the approach is demonstrated with four proteins and with several amines yielding near-quantitative transformations as characterized by high-resolution Fourier transform mass spectrometry. The developed approach has numerous implications for protein characterization and general protein chemistry. Applications in mass spectrometry (MS) based proteomics of intact proteins (top-down MS) are explored, including the addition of stable isotopes for relative quantitation and protein identification through functional group counting. The methodology can be used for altering the physical and chemical properties of proteins, as demonstrated with amidation to modify protein isoelectric point and through derivatization with quaternary amines. Additionally, the chemistry has applications in the semisynthesis of monodisperse polymers based on protein scaffolds. We prepare proteins modified with azides and alkynes to enable further functionalization via copper(I)-catalyzed 1,3-dipolar Huisgen cycloaddition ("click") chemistry.

Effects of Saccharide Spacing and Chain Extension on Toxin Inhibition by Glycopolypeptides of Well-Defined Architecture

Many recognition events important in biology are mediated via multivalent interactions between relevant oligosaccharides and multiple saccharide receptors present on lectins, viruses, toxins, and cell surfaces. Because of the important role played by protein-carbohydrate interactions in these pathogenic recognition events and in other human diseases, considerable effort has been devoted toward the development of multivalent polymeric ligands for carbohydrate-binding proteins. In this work, we report the synthesis of new polypeptide-based glycopolymers produced via a combination of protein engineering and chemical methods. These methodologies permit control over the number and the spacing of saccharides on the scaffold, as well as the conformation of the polymer backbone, and allow a more purposeful design of polymers for manipulation of multivalent binding events. Two families of galactose-bearing glycopolypeptides with random coil conformations, [(AG)(3)PEG](y) (y = 10 and 16) and {[(AG)(2)PSG](2)[(AG)(2)PEG][(AG)(2)PSG](2)}(y) (y = 6), have been synthesized. The carboxylic acid functionality of the glutamic acid residues allowed subsequent modification with amino-saccharides to yield the desired glycopolypeptides; selective placement of the glutamic acid group permitted investigation of the effects of multivalency and saccharide spacing on toxin inhibition. In addition, a family of galactose-functionalized PGA-based glycopolymers of varying molecular weights was also synthesized to compare the effects of backbone flexibility and hydrodynamic volume, relative to the recombinant glycopolypeptides, on toxin inhibition. Glycopolypeptides were characterized via (1)H NMR, MALDI-TOF mass spectrometry, SDS-PAGE analysis, and spectrophotometric assays. They were tested as inhibitors of the binding of the cholera toxin B subunit via direct enzyme-linked assays. The data from these experiments confirm the relevance of appropriate saccharide spacing on controlling the binding event and also indicate the influence of chain extension in improving inhibition.

Romping the cellular landscape: linear scaffolds for molecular recognition

Multivalent molecules with a precise array of recognition elements that interact with specific cell types are important for characterizing the topology of molecules on a cell surface. Applications ranging from the control of cellular signaling to drug delivery and tissue imaging rely on these surface-mapping molecules. Linear polymers provide a molecular scaffold that is advantageous for these types of applications and their synthesis can be amenable to the introduction of different recognition elements. Recently, advances have been made in the development of synthetic approaches for preparing linear polymeric substrates with highly controlled lengths and recognition element spacing.

Binding of monomeric and dimeric Concanavalin A to mannose-functionalized dendrimers

Because of the central role of Concanavalin A (Con A) in the study of protein-carbohydrate interactions, a thorough understanding of the multivalent functions of Con A is imperative. Here, the association of monomeric and dimeric derivatives of Con A with mannose-functionalized generation two through six PAMAM dendrimers is reported. Hemagglutination assay results indicate relatively low activity of the dendrimers for monomeric Con A, with small increases as the dendrimer generation increases. Isothermal titration microcalorimetry experiments indicate monovalent binding by the dendrimers with monomeric Con A and divalent binding by the dendrimers with dimeric Con A. Continuous (and comparable) but narrowing increases in enthalpy and entropy and the slight increase in association constants with monomeric Con A as the dendrimer generation increases suggest favorable proximity effects on binding. Both the hemagglutination assay and the calorimetry experiments suggest that statistical binding enhancements can be observed with monomeric Con A. The results described here should allow for a more quantitative evaluation of the enhancements that are often observed in protein-carbohydrate interactions for glycosylated frameworks binding to Con A.