2-Amidino analogs of glycine-amiloride conjugates: inhibitors of urokinase-type plasminogen activator.

The relative non-toxicity of the diuretic amiloride, coupled with its selective inhibition of the protease urokinase plasminogen activator (uPA), makes this compound class attractive for structure-activity studies. Herein we substituted the C(2)-acylguanidine of C(5)-glycyl-amiloride with amidine and amidoxime groups. The data show the importance of maintaining C(5)-hydrophobicity. The C(5)-benzylglycine analogs containing either C(2)-acylguanidine or amidine inhibited uPA with an IC(50) ranging from 3 to 7 µM and were cytotoxic to human U87 malignant glioma cells.

Highly specific, NIR fluorescent contrast agent with emission controlled by gold nanoparticle.

Nanoparticles are currently being intensively studied for in vivo molecular imaging because of their unique and beneficial properties. Among these particles, some metal particles possess strong surface plasmon fields that can effectively alter fluorescence. Using this fluorescence alteration, an NIR fluorophore based, nanosized contrast agent for breast cancer diagnosis is being developed. The fluorophore is conjugated to gold nanoparticles (GNP) via a short spacer whose length was specially adjusted to have the strong plasmon field to quench the fluorescence. The spacer also has a special molecular sequence that can be cleaved by an enzyme secreted by targeted cancer cells. Normally, the entity does not fluoresce. If it is delivered to the cancer site, the short spacer would be cleaved by the enzyme secreted by the cancer cell at which point the fluorescence would be restored. This entity can incorporate a cancer targeting molecule for a cancer specific delivery. The entity specifically targets cancer cells and fluoresce only when the spacer is cleaved by a specific cancer secreting biomolecule, providing dual specificity for cancer diagnosis. In the future, this entity will be combined with cancer drugs for seamless detection and personalized therapy.

Structural genomics of pathogenic protozoa: an overview.

The Structural Genomics of Pathogenic Protozoa (SGPP) Consortium aimed to determine crystal structures of proteins from trypanosomatid and malaria parasites in a high throughput manner. The pipeline of target selection, protein production, crystallization, and structure determination, is sketched. Special emphasis is given to a number of technology developments including domain prediction, the use of "co-crystallants," and capillary crystallization. "Fragment cocktail crystallography" for medical structural genomics is also described.

Gold nanoparticles as a versatile platform for optimizing physicochemical parameters for targeted drug delivery.

The development of targeted vehicles for systemic drug delivery relies on optimizing both the cell-targeting ligand and the physicochemical characteristics of the nanoparticle carrier. A versatile platform based on modification of gold nanoparticles with thiolated polymers is presented in which design parameters can be varied independently and systematically. Nanoparticle formulations of varying particle size, surface charge, surface hydrophilicity, and galactose ligand density were prepared by conjugation of PEG-thiol and galactose-PEG-thiol to gold colloids. This platform was applied to screen for nanoparticle formulations that demonstrate hepatocyte-targeted delivery in vivo. Nanoparticle size and the presence of galactose ligands were found to significantly impact the targeting efficiency. Thus, this platform can be readily applied to determine design parameters for targeted drug delivery systems.Modified gold nanoparticles are a suitable model for nanoparticle-based gene carriers.

Chemical syntheses of inhibitory substrates of the RNA-RNA ligation reaction catalyzed by the hairpin ribozyme.

The chemical syntheses of RNA oligomers containing modifications on the 5'-carbon of the 5'-terminal nucleoside for crystallographic and mechanistic studies of the hairpin ribozyme are reported. Phosphoramidites 4 and 8 were prepared and used in solid phase syntheses of RNA oligomers containing the sequence 5'-N'UCCUCUCC, where N' indicates either 5'-chloro-5'-deoxyguanosine or 5'-amino-5'-deoxyguanosine, respectively. A ribozyme ligation assay with the 5'-chloro- and 5'-amino-modified RNA oligomers demonstrated their inhibition of the hairpin-catalyzed RNA-RNA ligation reaction.

Transition state stabilization by a catalytic RNA.

The hairpin ribozyme catalyzes sequence-specific cleavage of RNA through transesterification of the scissile phosphate. Vanadate has previously been used as a transition state mimic of protein enzymes that catalyze the same reaction. Comparison of the 2.2 angstrom resolution structure of a vanadate-hairpin ribozyme complex with structures of precursor and product complexes reveals a rigid active site that makes more hydrogen bonds to the transition state than to the precursor or product. Because of the paucity of RNA functional groups capable of general acid-base or electrostatic catalysis, transition state stabilization is likely to be an important catalytic strategy for ribozymes.