Evaluating methods to create protein functionalized catanionic vesicles.

Catanionic surfactant vesicles (SVs) composed of sodium dodecylbenzenesulfonate (SDBS) and cetyltrimethylammonium tosylate (CTAT) have potential applications as targeted drug delivery systems, vaccine platforms, and diagnostic tools. To facilitate these applications, we evaluated various methods to attach proteins to the surface of SDBS/CTAT vesicles. Acid phosphatase from wheat germ was used as a model protein.

Catanionic Vesicles as a Facile Scaffold to Display Natural N-Glycan Ligands for Probing Multivalent Carbohydrate-Lectin Interactions.

Multivalent interactions are a key characteristic of protein-carbohydrate recognition. Phospholipid-based liposomes have been explored as a popular platform for multivalent presentation of glycans, but this platform has been plagued by the instability of typical liposomal formulations in biological media. We report here the exploitation of catanionic vesicles as a stable lipid-based nanoparticle scaffold for displaying large natural N-glycans as multivalent ligands.

Inhibition of Alginate Synthesis by Ebselen Oxide and Its Analogues.

is a Gram-negative opportunistic pathogen that is frequently found in the airways of cystic fibrosis (CF) patients due to the dehydrated mucus that collapses the underlying cilia and prevents mucociliary clearance. During this life-long chronic infection, cell accumulates mutations that lead to inactivation of the gene that results in the constitutive expression of operon and the production of alginate exopolysaccharide. The viscous alginate polysaccharide further occludes the airways of CF patients and serves as a protective matrix to shield from host immune cells and antibiotic therapy.

Extraction of Membrane Components from Using Catanionic Surfactant Vesicles: A New Approach for the Study of Bacterial Surface Molecules.

Identification of antigens is important for vaccine production. We tested extraction protocols using cetyltrimethylammonium tosylate (CTAT) and sodium dodecylbenzenesulfonate (SDBS) to formulate surfactant vesicles (SVs) containing components from . Carbohydrate and protein assays demonstrated that protein and carbohydrates were incorporated into the vesicle leaflet.

Phenotypically distinguishing ESBL-producing pathogens using paper-based surface enhanced Raman sensors.

Antimicrobial stewardship practices are critical in preventing the further erosion of treatment options for bacterial infections. Yet, at the same time, determination of an infection's antimicrobial susceptibility requires multiple rounds of culture and expensive lab automation systems. In this work, we report the use of paper-based surface enhanced Raman spectroscopy (SERS) sensors and portable instrumentation to phenotypically discriminate multi-drug resistance with fewer culture steps than conventional clinical microbiology.

New Trimodal Phenotypic Reporter of Extended-Spectrum β-Lactamase Activity.

Bacterial resistance to β-lactam antibiotics continues to grow as misadministration presents evolutionary pressure that drives bacteria to develop improved resistance enzymes. Known as extended-spectrum β-lactamases (ESBLs), these enzymes are capable of hydrolyzing advanced β-lactam antibiotics such as third-generation (and higher) cephalosporins. Phenotypic detection substrates can be used to rapidly identify a cultured patient sample prior to confirmation by more exhaustive but slower means, critically aiding in the antibiotic stewardship essential in maintaining the effectiveness of not only the cephalosporins but also indirectly the carbapenems, our last-resort β-lactams.

Catanionic Surfactant Vesicles as a New Platform for probing Glycan-Protein Interactions.

Glycomics lags substantially behind proteomics and genomics in its ability to decipher and synthesize complex glycans. The slow progress in deciphering glycan interactions at a molecular level is in large part due to the absence of a functional system to express, on a large scale, carbohydrates of known structure, in the context of a biologically relevant assay system. Here we describe the characterization of a glycan-functionalized catanionic surfactant vesicles (CVs) as a platform for glycan synthesis, and to demonstrate that the resulting glycan-functionalized CVs can serve as a scaffold for the interrogation of protein-glycan interactions.

Novel catanionic surfactant vesicle vaccines protect against Francisella tularensis LVS and confer significant partial protection against F. tularensis Schu S4 strain.

Francisella tularensis is a Gram-negative immune-evasive coccobacillus that causes tularemia in humans and animals. A safe and efficacious vaccine that is protective against multiple F. tularensis strains has yet to be developed.

Construction and characterization of a derivative of Neisseria gonorrhoeae strain MS11 devoid of all opa genes.

To better understand the role of Opa in gonococcal infections, we created and characterized a derivative of MS11 (MS11Δopa) that had the coding sequence for all 11 Opa proteins deleted. The MS11Δopa bacterium lost the ability to bind to purified lipooligosaccharide (LOS). While nonpiliated MS11Δopa and nonpiliated Opa-expressing MS11 cells grew at the same rate, nonpiliated MS11Δopa cells rarely formed clumps of more than four bacteria when grown in broth with vigorous shaking.

Multiphoton-absorption-induced-luminescence (MAIL) imaging of tumor-targeted gold nanoparticles.

We demonstrate that multiphoton-absorption-induced luminescence (MAIL) is an effective means of monitoring the uptake of targeted nanoparticles into cells. Gold nanoparticles (AuNPs) with diameters of 4.5 and 16 nm were surface-functionalized with monocyclic RGDfK, an RGD peptide analogue that specifically targets the α(v)β₃ integrin, a membrane protein that is highly overexpressed in activated endothelial cells during tumor angiogenesis.

Carbohydrate modified catanionic vesicles: probing multivalent binding at the bilayer interface.

This article reports on the synthesis, characterization, and binding studies of surface-functionalized, negatively charged catanionic vesicles. These studies demonstrate that the distribution of glycoconjugates in the membrane leaflet can be controlled by small alterations of the chemical structure of the conjugate. The ability to control the glycoconjugate concentration in the membrane provides a method to explore the relationship between ligand separation distance and multivalent lectin binding at the bilayer interface.

Biofabrication of antibodies and antigens via IgG-binding domain engineered with activatable pentatyrosine pro-tag.

We report the assembly of seven different antibodies (and two antigens) into functional supramolecular structures that are specifically designed to facilitate integration into devices using entirely biologically based bottom-up fabrication. This is enabled by the creation of an engineered IgG-binding domain (HG3T) with an N-terminal hexahistidine tag that facilitates purification and a C-terminal enzyme-activatable pentatyrosine "pro-tag" that facilitates covalent coupling to the pH stimuli-responsive polysaccharide, chitosan. Because we confer pH-stimuli responsiveness to the IgG-binding domain, it can be electrodeposited or otherwise assembled into many configurations.

Studies on the mechanism of allylic coupling reactions: a hammett analysis of the coupling of aryl silicate derivatives.

Hammett analysis of the palladium-catalyzed allyl-aryl coupling reaction has demonstrated that the rate of the coupling reaction is enhanced by electron-withdrawing groups on the aryl siloxane. The positive slope of the Hammett plot indicated involvement of a charged transition state in which negative charge on the aryl ring is stabilized inductively. This result is consistent with either transmetalation or reductive elimination being the rate-determining step in the coupling process.

Reductive cyclization of o-nitrophenyl propargyl alcohols: facile synthesis of substituted quinolines.

Reduction of secondary and tertiary o-nitrophenyl propargyl alcohols followed by acid-catalyzed Meyer-Schuster rearrangement gave 2-substituted and 2,4-disubstituted quinolines, respectively. Tertiary propargyl alcohols gave excellent yields of the quinoline derivative, while the yields of quinolines were slightly reduced when secondary propargyl alcohol derivatives were utilized.

Synthesis and structural characterization of glucopyranosylamide films on gold.

Self-assembled monolayers (SAMs) of glucose derivatives on gold have been prepared from alpha- and beta-glucopyranosylamide derivatives. The glucosyl conjugates were synthesized stereoselectively via the in situ generation of glucosyl isoxazolines followed by treatment with thiopyridyl esters. The resulting film structures were characterized by atomic force microscopy, reflection Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy.

Application of palladium-catalyzed allylic arylation to the synthesis of a (+/-)-7-deoxypancratistatin analogue.

Palladium-catalyzed coupling of an aryl siloxane and an allylic carbonate proceeded in good yield to give an adduct that was converted to an analogue of (+/-)-7-deoxypancratistatin.

Application of aryl siloxane cross-coupling to the synthesis of allocolchicinoids.

In this communication, we report a new approach to the allocolchicine carbocyclic skeleton based upon an aryl siloxane coupling reaction and a phenanthrol ring expansion. These key steps allow for the selective functionalization of every carbon within the carbocyclic framework. The siloxane coupling-phenanthrol sequence was applied to the synthesis of two allocolchicinoids, including the first fully synthetic approach to N-acetyl colchinol-O-methyl ether (NCME).

Efforts directed toward the synthesis of colchicine: application of palladium-catalyzed siloxane cross-coupling methodology.

[reaction: see text] Colchicine is an important and synthetically challenging natural product. The key synthetic step in this approach to the synthesis of colchicine involved a palladium-catalyzed cross-coupling reaction between 5-bromotropolone (4) and an aryl siloxane to form the aryl-tropolone bond. The coupling of a variety of highly functionalized aryl siloxane derivatives was investigated and optimized coupling conditions were developed.

Improved synthesis of aryltrialkoxysilanes via treatment of aryl Grignard or lithium reagents with tetraalkyl orthosilicates.

General reaction conditions for the synthesis of aryl(trialkoxy)silanes from aryl Grignard and lithium reagents and tetraalkyl orthosilicates (Si(OR)(4)) have been developed. Ortho-, meta-, and para-substituted bromoarenes underwent efficient metalation and silylation at low temperature to provide aryl siloxanes. Mixed results were obtained with heteroaromatic substrates: 3-bromothiophene, 3-bromo-4-methoxypyridine, 5-bromoindole, and N-methyl-5-bromoindole underwent silylation in good yield, whereas a low yield of siloxane was obtained from 2-bromofuran, and 2-bromopyridine failed to give silylated product.

Palladium-catalyzed cross-coupling of aryl triethylammonium bis(catechol) silicates with aryl bromides using microwave irradiation.

The scope of the palladium-catalyzed cross-coupling reaction of aryl bis(catechol) silicates has been extended to include the coupling of aryl bromides by employing microwave irradiation. This new set of coupling conditions is tolerant of electron-rich and -deficient aryl bromides. In addition, a variety of substituted aryl bis(catechol) silicates have been successfully cross-coupled.

Application of directed orthometalation toward the synthesis of aryl siloxanes.

A selection of ortho-substituted aryl siloxanes have been prepared by directed orthometalation protocols. These siloxanes can be prepared in high yields and purity by use of a diverse selection of ortho-directing groups and electrophilic siloxane derivatives. The siloxanes are employed in palladium-catalyzed cross-coupling reactions with aryl bromides to generate unsymmetrical ortho-substituted biaryls in good to excellent yields.

Preparation and palladium-catalyzed cross-coupling of aryl triethylammonium bis(catechol) silicates with aryl triflates.

Pentavalent aryl and heteroaryl bis(catechol) silicates undergo palladium-catalyzed cross-coupling with aryl and heteroaryl triflates in the presence of a fluoride source in excellent yields. These solid, air-stable bis(catechol) silicates are prepared from a high-yielding displacement reaction between catechol and an aryl siloxane in the presence of an amine base. The cross-coupling reaction is tolerant of a wide range of electron-donating and electron-withdrawing groups.

Siloxane-based cross-coupling of bromopyridine derivatives: studies for the synthesis of streptonigrin and lavendamycin.

Highly functionalized 4-bromopyridines were prepared and found to undergo fluoride-promoted, Pd-catalyzed cross-coupling with aryltrialkoxysilanes to give sterically demanding biaryls. The 3-nitro-4-bromopyridine derivative coupled in good yield with TBAT (tetrabutylammonium triphenyldifluorosilicate) to provide a biaryl adduct that serves as a model system for the total synthesis of the antitumor antibiotics streptonigrin and lavendamycin. [reaction: see text]

Application of silicon-based cross-coupling technology to triflates.

Aryl silatranes undergo fluoride-induced cross-coupling with aryl triflates to provide unsymmetrical biaryl derivatives in good to excellent yields. Silatranes also couple with aryl iodides and bromides, although the yields of adduct are lower than with the corresponding siloxane derivates. Aryl siloxanes (which had previously failed to couple with triflates) can be employed for triflate couplings using the Denmark modification, although the yields are lower than the corresponding silatrane reactions.

Stereoselective synthesis of alpha- and beta-glycosylamide derivatives from glycopyranosyl azides via isoxazoline intermediates.

Treatment of 2-acetoxy glycopyranosyl azides with Ph3P gave isoxazolines by ring closure of the phosphorimine. Coupling of in situ generated isoxazolines with acylating reagents gave mixtures of alpha- or beta-glycopyranosyl amides. The alpha/beta ratio depended upon the acylating reagent and metal salts employed.