[Show abstract][Hide abstract] ABSTRACT: Urease thin films were produced by Matrix Assisted Pulsed Laser Evaporation (MAPLE) and Pulsed Laser Deposition from two types of targets: frozen water solutions of urease with different concentrations (1–10% m/v) and pure urease pellets. The fluence of the ablating KrF excimer laser was varied between 300 and 2200 mJ/cm2. Fourier transform infrared spectra of the deposited films showed no difference as compared to the original urease. Morphologic studies proved that the films consist of a smooth “base” layer with embedded micrometer-sized droplets. Absorption-coefficient measurements contradicted the traditional “absorptive matrix” model for MAPLE deposition. The laser energy was absorbed by urease clusters leading to a local heating-up and evaporation of the frozen matrix from the uppermost layer accompanied by the release of dissolved urease molecules. Significant enzymatic activity of urease was preserved only during matrix assisted transfer.
[Show abstract][Hide abstract] ABSTRACT: The coupling of dimethyl acetonedicarboxylate 1 with a variety of aryldiazonium salts 2a-i produces the hydrazones 3a-i which can be cyclized in boiling dichlorobenzene to yield the pyridazone esters 4a-i, or in sodium hydroxide solution to give the pyridazone acids 5a-f,h,i, which can be decarboxylated at elevated temperatures. The hydroxy group in 4a,d can be acylated, sulfonated or alkylated yielding compounds 8a-n. Condensation of 4a,d with magic malonates 9a-d produces the pyronopyridazinones 10a-f. The reaction of 4a with hydrazine yields the hydrazide 12via the salt 11, and with ammonia the amide 14.
[Show abstract][Hide abstract] ABSTRACT: The nucleophilic introduction of chloro- (2), azido- (4), (substituted) amino (3, 6), mercapto (10) and hydrazino-groups (13) into 2-aryl-5-hydroxypyridazin-3(2H)-ones  is described. The 5-aminopyridazin-3(2H)-one (6) also reacts with activated malonates 8  to give pyrido[2,3-d]pyridazines 9. Hydrazino compounds 13 can be treated with aldehydes to yield compounds 14. Iodine can be introduced into position 4 of 5-amino-(15) and 5-hydroxypyridazin-3(2H)-ones (17) by electrophilic substitution to afford compounds 18.
[Show abstract][Hide abstract] ABSTRACT: Urease thin films have been immobilized using matrix-assisted pulsed laser evaporation for biosensor applications in clinical diagnostics. The targets exposed to laser radiation were made of frozen composites that had been manufactured by dissolving urease in distilled water. An UV KrF* (lambda = 248 nm, tauFWHM congruent with 30 ns, nu = 10 Hz) excimer source was used for the multipulse laser irradiation of the targets that were cooled down to solidification using Peltier elements. The incident laser fluence was set at 0.4 J/cm2. The surface morphology and chemical bonding states of the laser immobilized urease thin films were investigated by atomic force microscopy and Fourier transform infrared spectroscopy. The enzymatic activity and kinetics of the immobilized urease were assayed by the Worthington method, which monitors urea hydrolysis by coupling ammonia production to a glutamate dehydrogenase reaction. Decreased absorbance was found at 340 nm and correlated with the enzymatic activity of urease.
Journal of Biomedical Materials Research Part A 05/2008; 89(1):186-91. · 2.83 Impact Factor