Antimicrobial Peptide Dendrimers and Quorum-Sensing Inhibitors in Formulating Next-Generation Anti-Infection Cell Therapy Dressings for Burns

Multidrug resistance infections are the main cause of failure in the pro-regenerative cell-mediated therapy of burn wounds. The collagen-based matrices for delivery of cells could be potential substrates to support bacterial growth and subsequent lysis of the collagen leading to a cell therapy loss. In this article, we report the development of a new generation of cell therapy formulations with the capacity to resist infections through the bactericidal effect of antimicrobial peptide dendrimers and the anti-virulence effect of anti-quorum sensing MvfR (PqsR) system compounds, which are incorporated into their formulation. Anti-quorum sensing compounds limit the pathogenicity and antibiotic tolerance of pathogenic bacteria involved in the burn wound infections, by inhibiting their virulence pathways. For the first time, we report a biological cell therapy dressing incorporating live progenitor cells, antimicrobial peptide dendrimers, and anti-MvfR compounds, which exhibit bactericidal and anti-virulence properties without compromising the viability of the progenitor cells.     

Semisynthesis of fluorescent metabolite sensors on cell surfaces

Progress in understanding signal transduction and metabolic pathways is hampered by a shortage of suitable sensors for tracking metabolites, second messengers, and neurotransmitters in living cells. Here we introduce a class of rationally designed semisynthetic fluorescent sensor proteins, called Snifits, for measuring metabolite concentrations on the cell surface of mammalian cells. Functional Snifits are assembled on living cells through two selective chemical labeling reactions of a genetically encoded protein scaffold. Our best Snifit displayed fluorescence intensity ratio changes on living cells significantly higher than any previously reported cell-surface-targeted fluorescent sensor protein. This work establishes a generally applicable and rational strategy for the generation of cell-surface-targeted fluorescent sensor proteins for metabolites of interest.     

Migrastatin and analogues: New anti-metastatic agents

Migrastatin and some migrastatin analogues are potent anti-metastatic agents. The biological activity as well as the chemical syntheses of migrastatin and its analogues is discussed.     

A cyclodecapeptide ligand to vitamin B12

Libraries of cyclic decapeptides were screened with vitamin B(12) derivatives to give cyclic peptide ligands incorporating histidine and cysteine as coordinating residues and negatively charged amino acids. Two hits, cyclo-(HisAspGluProGlyIleAlaThrProdGln) and cyclo-(ValAspGluProGlyGluAspCysProdGln) were resynthesized in good yields for solution experiments. The peptides bind aquocobalamin with coordination of His or Cys to the cobalt with high affinities (K(a) approximately 10(5) M(-1)). Additional interactions between the peptide side chains and the vitamin B(12) corrin moiety were determined by studying the (1)H NMR solution structure. The cyclopeptide-cobalamin complex with the histidine residue showed enhanced stability towards cyanide exchange, demonstrating the shielding effect of the ligand on the metal center.     

A peptide dendrimer enzyme model with a single catalytic site at the core

Catalytic esterase peptide dendrimers with a core active site were discovered by functional screening of a 65,536-member combinatorial library of third-generation peptide dendrimers using fluorogenic 1-acyloxypyrene-3,6,8-trisulfonates as substrates. In the best catalyst, RMG3, ((AcTyrThr)(8)(DapTrpGly)(4)(DapArgSerGly)(2)DapHisSerNH2), ester hydrolysis is catalyzed by a single catalytic histidine residue at the dendrimer core. A pair of arginine residues in the first-generation branch assists substrate binding. The catalytic proficiency of dendrimer RMG3 (kcat/KM = 860 M(-1) min(-1) at pH 6.9) per catalytic site is comparable to that of the multivalent esterase dendrimer A3 ((AcHisSer)(8)(DapHisSer)(4)(DapHisSer)2DapHisSerNH2) which has fifteen histidines and five catalytic sites (Delort, E. et al. J. Am. Chem. Soc. 2004, 126, 15642-15643). Remarkably, catalysis in the single site dendrimer RMG3 is enhanced by the outer dendritic branches consisting of aromatic amino acids. These interactions take place in a relatively compact conformation similar to a molten globule protein as demonstrated by diffusion NMR. In another dendrimer, HG3 ((AcIlePro)(8)(DapIleThr)(4)(DapHisAla)(2)DapHisLeuNH2) by contrast, catalysis by a core of three histidine residues is unaffected by the outer dendritic layers. Dendrimer HG3 or its core HG1 exhibit comparable activity to the first-generation dendrimer A1 ((AcHisSer)(2)DapHisSerNH2). The compactness of dendrimer HG3 in solution is close to that a denatured peptide. These experiments document the first esterase peptide dendrimer enzyme models with a single catalytic site and suggest a possible relationship between packing and catalysis in these systems.     

Formal chemoselective synthesis of leucascandrolide A

A chemoselective synthesis of the macrocyclic core of leucascandrolide A has been achieved, utilizing highly enantioselective allylmetalations, an enantioselective Noyori reduction of a propargylic ketone and olefin metatheses as the key steps.     

Identification of protease substrates by combinatorial profiling on TentaGel beads

Reacting a 65,536 member combinatorial library of octapeptides on TentaGel beads with various proteases followed by selective staining of the free amino termini at the reacted bead surface and sequence determination by amino acid analysis allowed the rapid identification of protease substrates.