RESUMO
Diaquacobinamide (H(2)O)(2)Cbi(2+) or its conjugate base hydroxyaquacobinamide (OH(H(2)O)Cbi(+))) can bind up to two cyanide ions, making dicyanocobinamide. This transition is accompanied by a significant change in color, previously exploited for cyanide determination. The reagent OH(H(2)O)Cbi(+) is used in excess; when trace amounts of cyanide are added, CN(H(2)O)Cbi(+) should be formed. But the spectral absorption of CN(H(2)O)Cbi(+) is virtually the same as that of OH(H(2)O)Cbi(+). It has been inexplicable how trace amounts of cyanide are sensitively measured by this reaction. It is shown here that even with excess OH(H(2)O)Cbi(+), (CN)(2)Cbi is formed first due to kinetic reasons; this only slowly forms CN(H(2)O)Cbi(+). This understanding implies that CN(H(2)O)Cbi(+) will itself be a better reagent. We describe a single valve merging zone flow analyzer that allows both sample and reagent economy. With a 50 cm liquid core waveguide (LCW) flow cell and an inexpensive fiber optic-charge coupled device array spectrometer, a S/N=3 limit of detection of 8 nM, a linear dynamic range to 6 µM, and excellent precision (RSD 0.49% and 1.07% at 50 and 100 nM, respectively, n=5 each) are formed. At 1% carryover, sample throughput is 40 h(-1). The setup is readily used to measure thiocyanate with different reagents. We demonstrate applicability to real samples by analyzing human saliva samples and hydrolyzed extracts of apple seeds, peach pits, and almonds.
Assuntos
Cobamidas/química , Cianetos/análise , Análise de Injeção de Fluxo/métodos , Saliva/química , Sementes/química , Humanos , Limite de Detecção , Malus/química , Prunus/química , Espectrofotometria/métodosRESUMO
"Base on"/"base off" coordination of the intramolecular bound benzimidazole nucleobase of vitamin B 12 allows the specific colorimetric detection of millimolar concentrations of cyanide in water. In various competition experiments, it was demonstrated that up to 12 different anions as well as a 1000-fold excess of Cl (-) over CN (-) do no interfere with the sensor. An 8-fold increased sensitivity in the "naked eye" detection of CN (-) was observed when water was replaced by MeOH/H 2O (5%) as a solvent.
Assuntos
Benzimidazóis/química , Cianetos/análise , Solventes/química , Vitamina B 12/análise , Ânions/química , Cloretos/química , Colorimetria/métodos , Metanol/química , Estrutura Molecular , Água/químicaRESUMO
A bifunctional Zn-salen modified cavitand, reminiscent of the enzyme phospholipase C, shows high efficiency and synergic effect in the binding of the phospholipid DOPC.
Assuntos
Etilenodiaminas/química , Compostos Organometálicos/química , Fosforilcolina/química , Zinco/química , Sítios de Ligação , Ésteres , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Estrutura Molecular , TermodinâmicaRESUMO
A Zn-salen-modified cavitand templates the catalytic formation of acetylcholine from choline and acetic anhydride.
Assuntos
Acetilcolina/metabolismo , Éteres Cíclicos/química , Etilenodiaminas/química , Resorcinóis/química , Zinco/química , Anidridos Acéticos/química , Anidridos Acéticos/metabolismo , Acetilcolina/química , Acilação , Catálise , Quelantes/química , Colina/química , Colina/metabolismo , Modelos Moleculares , Estrutura MolecularRESUMO
Catalytic release of carboxylates from their 8-hydroxyquinoline esters by Cu(II) complexes, both attached to peptide nucleic acid strands, is triggered by complementary DNA.
Assuntos
DNA/química , Metais/química , Ácidos Carboxílicos/química , Catálise , Cátions Bivalentes/química , Cobre/química , Ésteres/química , Metais/farmacologia , Modelos Químicos , Oxiquinolina/química , Ácidos Nucleicos Peptídicos/químicaRESUMO
A series of conjugates of peptide nucleic acids (PNA) and Zr(IV) complexes was prepared. Their ability to hydrolyze DNA was tested using MALDI-TOF mass spectrometry and HPLC. The most efficient artificial restriction enzyme found, PNA conjugate with Zr(IV) complex of tris(hydroxymethyl)-aminomethane, cleaves DNA targets sequence selectively in close proximity to the Zr(IV) complex. It was demonstrated that cleavage products are substrates of terminal transferase.