Investigation of ring transformations of diaryl-β-lactams condensed with 1,3-benzothiazines

Reactions of derivatives of the isoquinoline analog trans-2,2a-diaryl-2,2a-dihydro-5,6-dimethoxy-1H,8H-azeto[2,1-b][1,3]benzothiazin-1-one were studied under basic conditions. Their treatment with sodium methoxide in methanol resulted first in alcoholysis of the beta-lactam ring, followed by opening of the thiazine ring and oxidation of the thiol moiety to disulfide. Thus, the corresponding beta-amino acid derivatives, disulfides of N-(ortho-mercaptobenzyl)substituted diaryl-3-aminoacrylic acid methyl esters, were obtained in good yields. The structures of the new molecules were proved by means of NMR and IR spectroscopy. Geometric isomerism investigations indicated the presence of the Z forms of the acrylic acid moiety

Detection of plasmin based on specific peptide substrate using acoustic transducer

© 2015 Elsevier B.V. All rights reserved. In this work we report the detection of plasmin protease by means of the thickness shear mode (TSM) acoustic method. The biorecognition element consists of a peptide substrate (PS) specific to plasmin immobilized on a piezoelectric quartz crystal electrode. After enzymatic reaction with plasmin, it cleaves a short fragment of the peptide causing increase in the resonance frequency of the piezo crystal. Plasmin was detected in the range of concentrations 1-20 nM, a target interval in which its presence presumably affects the quality of milk. The PS exhibited negligible response against to similar protease trypsin. This has been confirmed also by electrochemical detection method. Limit of detection of this acoustic transducer was found to be 0.65 nM. Formation of the sensing surface and kinetic effect of plasmin on the peptide substrate was studied by atomic force microscopy (AFM). The PS response was also validated in pretreated milk samples spiked by known concentrations of plasmin achieving an average recovery of 63 ± 0.6%

Highly substrate selective nucleophilic amination of nitro-substituted 4-(2-hydroxyethylamino)phthalazin-1(2H)-ones

An unexpected selectivity was observed in the aromatic displacement reaction of 4-(2-hydroxyethylamino)phthalazinones 1-3 and 7, 8 differently substituted with the leaving nitro group on the condensed benzene ring. On treatment with a series of amine and hydrazine nucleophiles, the 8-nitro isomers 1-3 were readily transformed into the corresponding aromatic amine (4-6), while the substrates carrying the nitro group at position 6 or 7 (7 and 8) remained unchanged on prolonged treatment with any of the reagents used. Application of pyridine or DMF as a solvent proved to be indispensable to successful conversions even of the 8-nitro derivatives 1-3

Detection of plasmin based on specific peptide substrate using acoustic transducer

© 2015 Elsevier B.V. All rights reserved. In this work we report the detection of plasmin protease by means of the thickness shear mode (TSM) acoustic method. The biorecognition element consists of a peptide substrate (PS) specific to plasmin immobilized on a piezoelectric quartz crystal electrode. After enzymatic reaction with plasmin, it cleaves a short fragment of the peptide causing increase in the resonance frequency of the piezo crystal. Plasmin was detected in the range of concentrations 1-20 nM, a target interval in which its presence presumably affects the quality of milk. The PS exhibited negligible response against to similar protease trypsin. This has been confirmed also by electrochemical detection method. Limit of detection of this acoustic transducer was found to be 0.65 nM. Formation of the sensing surface and kinetic effect of plasmin on the peptide substrate was studied by atomic force microscopy (AFM). The PS response was also validated in pretreated milk samples spiked by known concentrations of plasmin achieving an average recovery of 63 ± 0.6%

Detection of plasmin based on specific peptide substrate using acoustic transducer

© 2015 Elsevier B.V. All rights reserved. In this work we report the detection of plasmin protease by means of the thickness shear mode (TSM) acoustic method. The biorecognition element consists of a peptide substrate (PS) specific to plasmin immobilized on a piezoelectric quartz crystal electrode. After enzymatic reaction with plasmin, it cleaves a short fragment of the peptide causing increase in the resonance frequency of the piezo crystal. Plasmin was detected in the range of concentrations 1-20 nM, a target interval in which its presence presumably affects the quality of milk. The PS exhibited negligible response against to similar protease trypsin. This has been confirmed also by electrochemical detection method. Limit of detection of this acoustic transducer was found to be 0.65 nM. Formation of the sensing surface and kinetic effect of plasmin on the peptide substrate was studied by atomic force microscopy (AFM). The PS response was also validated in pretreated milk samples spiked by known concentrations of plasmin achieving an average recovery of 63 ± 0.6%