PubMed · 4797005
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K Kurachi. 1973. [Cerebral amines and sexual function].. https://pubmed.ncbi.nlm.nih.gov/4797005/
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Electrochemical principle of ion-selective electrodes (ISEs) based on the ion-transfer reactions across a polarizable organic or oil/aqueous or water interface is described; the amperometric ISE and the potentiometric ISE are addressed. Electrochemical sensors and biosensors based on amperometric ISEs are discussed in some details. Amperometric sensors for monitoring ammonia (and other volatile amines) can be constructed on the basis of amperometric ammonium-ISE, where the pulse amperometric technique can successfully be employed. Urea and creatinine biosensors can also be fabricated by immobilizing urease or creatinine deiminase, respectively, on the surface of the amperometric ammonia sensor. Some favored characteristics of amperometric ISE-based sensors and biosensors are discussed with reference to the sensors and biosensors described.
A new method for the simultaneous determination of hemoglobin adducts from aromatic amines and tobacco-specific nitrosamines (TSNA) is described. After mild base-catalysed hydrolysis releasing aromatic amines and the TSNA adduct 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB), the extraction, cleanup, and concentration are performed by a one-step procedure using C18 cartridges. Determination in the picograms per gram of hemoglobin range by gas chromatography-mass spectrometry with negative chemical ionization requires a separate derivatization procedure with pentafluoropropionic anhydride and pentafluorobenzoylchloride for aromatic amines and HPB, respectively. The method is shown to be quantitative, reproducible, and applicable to the determination of hemoglobin adducts from monocyclic and bicyclic aromatic amines as well as TSNA in smokers and nonsmokers.
Pepper (Capsicum annuum) beta-cyclohexenyl xanthophyll epoxidase cDNA was cloned and the corresponding enzyme overexpressed and purified from Escherichia coli, for investigation of its catalytic activity. The recombinant protein did not directly accept NADPH for epoxidation of cyclohexenyl carotenoids, nor did it operate according to a peroxygenase-based mechanism. Instead, the reducing power of NADPH was transferred to the epoxidase via reduced ferredoxin as shown by reconstitution of epoxidase activity in the presence of NADPH, ferredoxin oxidoreductase, and ferredoxin. Bacterial rubredoxin could be substituted for ferredoxin. The pepper epoxidase acted specifically on the beta-ring of xanthophylls such as beta-cryptoxanthin, zeaxanthin, and antheraxanthin. The proposed reaction mechanism for epoxidation involves the formation of a transient carbocation. This characteristic allows selective inhibition of the epoxidase activity by different nucleophilic diethylamine derivatives, p-dimethylaminobenzenediazonium fluoroborate and N,N-dimethyl-2-phenylaziridinium. It was also shown that the epoxidase gene was up-regulated during oxidative stress and when chloroplasts undergo differentiation into chromoplasts in pepper fruit.