The copper(I)‐catalyzed cycloaddition reaction between azides and alkynes has been employed to make metal‐adhesive materials. Copper and brass surfaces supply the necessary catalytic Cu ions, and thus the polymerization process occurs selectively on these metals in the absence of added catalysts. Alternatively, copper compounds can be added to monomer mixtures and then introduced to reducing metal surfaces such as zinc to initiate polymerization. The resulting materials were found to possess comparable or superior adhesive strength to standard commercial glues, and structure‐activity correlations have identified several important properties of the monomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4392–4403, 2004

HBV persistence and transmission require HBV replication, which depends on the assembly of a core particle composed of capsid protein (Cp), polymerase, and pregenomic RNA. Reverse transcription to produce infectious DNA-containing particles occurs solely within the core residing in the cytoplasm (9, 10). Thus, core assembly is likely to be a high value target for therapeutics (11).The capsid, the protein shell of the core, is built of 120 Cp dimers arranged with T ϭ 4 symmetry (12, 13). The dimer interfaces are evident as spikes (14-16) that are the major epitope of the capsid (17). Cp in low ionic strength solution is dimeric (18). We have studied ionic strength-dependent capsid assembly extensively in vitro by using the Cp assembly domain (Cp149) (residues 1-149) lacking the 34-residue C-terminal RNA-binding domain (19)(20)(21). Assembly is nucleated by a trimer of Cp dimers and proceeds without accumulating observable populations of intermediates (22). Interactions between dimers are weak but sum to give a globally stable capsid (23). These capsids persist, even under conditions where they are not thermodynamically favored, because of hysteresis to dissociation (24). Some Cp mutations lead to faster assembly and greater stability (25), indicating that wild-type Cp is suboptimal for assembly and suggesting that assembly is regulated in vivo, possibly by conformational change. In support of this assertion, we found that Zn 2ϩ alters the conformation of Cp dimers and enhances the rate of assembly, suggesting that capsid assembly is allosterically regulated (26).Recently, it was discovered that heteroaryldihydropyrimidines (HAPs) (Fig. 1) affect the accumulation of HBV capsids (27,28). HAP drugs decreased the yield of assembled core and HBV genomes from cells that constitutively produce HBV. Electron microscopy showed that Cp assembled in vitro in the presence of HAP drugs led to polymers that had abnormal morphology (29). Similarly, small molecules such as bis ANS {5,5-bis[8-(phenylamino)-1-naphthalenesulfonate]} alter Cp assembly in vitro (30). Recent reports suggest that other small molecules also inhibit normal HBV capsid assembly (31-33).Here, we describe the mechanism of a representative HAP compound, HAP-1 [methyl 4-(2-chloro-4-f luorophenyl)-6-methyl-2-(pyridin-2-yl)-1,4-dihydropyrimidine-5-carboxylate] (Fig. 1). In vitro, low concentrations of HAP-1 enhance both the rate and extent of assembly by favoring an assembly-active state; thus, HAP-1 acts like an allosteric effector. At higher concentrations, HAP-1 led to aberrant noncapsid polymers in vitro, even at the expense of preexisting capsids. We propose that both of these effects on assembly contribute to reducing HBV virion production. Materials and MethodsSynthesis of HAP-1. Preparation of racemic HAP-1 (Fig. 1) was adapted from the patent literature (27,28,34). Condensation of a pyridylamidine with a substituted ␣-carboxymethyl enone gave a 30% yield of Ͼ97% pure HAP-1 after chromatographic purification. HAP-1 was characterized by 1 H, 13 C, and 19 ...

Cyclic peptides and related structures have received attention in a variety of fields pertinent to drug discovery and biochemistry.[1] Peptide cyclization [2] has been managed most commonly by the formation of amide, [3] ester, [4] disulfide, [3b, 5] olefin, [6] and CÀC [7] bonds. Most methods include cyclization as part of solid-phase peptide synthesis, with ring closure performed on the resin support.[8] Olefin metathesis is particularly attractive for ring closure, because terminal alkenes and the transition-metal catalysts used to manipulate them are generally unreactive with protein functional groups.[6] Thus, the "handles" for cyclization can be installed and ignored until the time comes for their connection. We report herein a conceptually similar approach with different chemistry-the copper(i)-catalyzed azide-alkyne cycloaddition reaction [9] -and describe the propensity of this process to give selective dimerization in the ring-closure step.In the course of constructing linear and cyclic versions of the same peptide sequence for display on supramolecular protein scaffolds, we needed a cyclization method compatible with the requirements of side-chain protection/deprotection and with the installation of a reactive group to enable subsequent bioconjugation. The 11-mer and 19-mer Arg-GlyAsp (RGD)-containing peptides 1 and 2 (Scheme 1) contain sequences taken from an adenovirus serotype that binds several a v integrins.[10] They were synthesized by standard 9-fluorenylmethyloxycarbonyl (Fmoc) methods, starting with Fmoc-Phe-Wang resin and l-propargylglycine as the second residue installed. The end of each chain was terminated with side-chain Boc-protected Fmoc-lysine (Boc = tert-butoxycarbonyl), followed by Fmoc deprotection and capping of the N terminus with 5-azidopentanoic acid. The syntheses were also performed with a standard Boc-based protocol, starting[*] Dr.

Successful purification of biological molecules by affinity chromatography requires the attachment of desired ligands to biocompatible chromatographic supports. The Cu(I)-catalyzed cycloaddition of azides and alkynes-the premier example of "click chemistry"-is an efficient way to make covalent connections among diverse molecules and materials. Both azide and alkyne units are highly selective in their reactivity, being inert to most chemical functionalities and stable to wide ranges of solvent, temperature, and pH. We show that agarose beads bearing alkyne and azide groups can be easily made and are practical precursors to functionalized agarose materials for affinity chromatography.