Noel K. Hart

A Novel Route to Prepare Highly Reactive and Versatile Chromatographic Monoliths

The copolymer poly(isocyanatoethyl methacrylate-co-methyl methacrylate-co-ethylene glycol dimethacrylate) (poly(IEM-co-MMA-co-EGDMA)) was developed as a novel, facile, highly reactive and versatile monolithic matrix, which was amenable to surface functionalization with a variety of nucleophilic modifiers based on the reactive isocyanate group, producing monoliths of various chemistries suitable for chromatography. The specific surface area, pore size distribution, porosity and morphology of the monolithic matrix were characterized using a mercury intrusion porosimeter and scanning electron microscopy (SEM), respectively. Thermal analysis results revealed that the monolith was thermally stable up to 307 °C. The success of the chemical modification of the monolithic matrix was confirmed by FT-IR, solid state (13) C NMR and XPS elemental analysis, showing the high ligand density of the modified monoliths. A ligand density of up to 2.33 mmol·mL(-1) was obtained for the 1-octanol modified monolith (M1) with an isocyanate group conversion of 96.9%, indicating a high efficiency of the modification reaction. The potential application of the monoliths was demonstrated by the separation of a series of compounds. The novel monolithic columns exhibited high mechanical stability, column efficiency and good repeatability and reproducibility.

Biocompatibility and modification of the protein‐based adhesive secreted by the Australian frog Notaden bennetti

When provoked, Notaden bennetti frogs secrete a proteinaceous exudate, which rapidly forms a tacky and elastic glue. This material has potential in biomedical applications. Cultured cells attached and proliferated well on glue-coated tissue culture polystyrene, but migrated somewhat slower than on uncoated surfaces. In organ culture, dissolved glue successfully adhered collagen-coated perfluoropolyether lenses to debrided bovine corneas and supported epithelial regrowth. Small pellets of glue implanted subcutaneously into mice were resorbed by surrounding tissues, and all of the animals made a full recovery. An initial but transient skin necrosis at the implant site was probably caused by some of the potentially toxic metabolites present in the frog secretion; these include sterols and carotenoids, as well as fatty alcohols, aldehydes, ketones, acids, and aromatic compounds. Removal of the carotenoid pigments did not significantly alter the glues material properties. In contrast, peroxidase treatment of dissolved glue introduced unnatural crosslinks between molecules of the major protein (Nb-1R) and resulted in the formation of a soft hydrogel, which was very different to the original material.

A comparison of the pulmonary toxicity produced by metal-free and copper-complexed analogs of bleomycin and phleomycin

Abstract Previous studies from this laboratory indicated that the terminal amine groups adjacent to the thiazole rings of bleomycins are important determinants of pulmonary toxicity. The present study examines the relation between pulmonary toxicity and molecular sites other than the terminal amine. Phleomycins differ from bleomycins in having a thiazoline instead of a thiazole ring. The contribution of the thiazole rings and also the metal binding sites were assessed by studying the pulmonary toxicity produced by metal-free and copper-complexed bleomycins and phleomycins bearing identical terminal amines. Bleomycin and phleomycin CHP; bleomycin B6, bleomycin B6 Cu, phleomycin G, phleomycin G Cu, bleomycin PEPP, bleomycin PEPP Cu, and phleomycin PEPP Cu (1 and 10 nmol) were administered to DBA 2J mice by the endotracheal route. The abilities of these analogs to produce pulmonary fibrosis and metaplasia were evaluated by histopathologic criteria and compared to the activity of a mixture of bleomycins (Blenoxane). Bleomycin B6 and phleomycin G tended to be more toxic than the other analogs, while the toxicities of bleomycin and phleomycin CHP and PEPP were comparable to Blenoxane. Analogous bleomycins and phleomycins with identical terminal amine groups were equally toxic. Copper-complexed analogs retained the toxicity of the respective metal-free bleomycin or phleomycin. These studies indicated that neither administration as a copperchelate nor substitution of a 4,5-dihydrothiazole ring for a thiazole ring affected pulmonary toxicity. These results are consistent with the importance of the variable bleomycin terminal amine groups in the production of lung injury.

Total Synthesis of Methotrexate-γ-TRIS-Fatty Acid Conjugates

Several routes for the regiospecific synthesis of lipophilic γ-conjugates of methotrexate are described. Coupling of methotrexate-α-tert-butyl ester with glycyl-TRIS-(mono-/di-/tri-)palmitate followed by trifluoroacetic acid cleavage of the α-protection afforded the target methotrexate-γ-glycyl-TRIS-(mono-/di-/tri-)palmitate derivatives. Methotrexate-α-benzyl-γ-glycyl-TRIS-tripalmitate was prepared but no method was found to selectively cleave the α-ester. A method where the diaminopteridinylmethyl moiety was attached last was successful, but was low yielding in the final step. Coupling of 4-amino-4-deoxy-N10-methylpteroic acid with glutamoyl-γ-glycyl-TRIS-palmitate derivatives efficiently afforded the desired conjugates.