PubMed · 4718391
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S P Benjamin, C E Willis, S Tytko, P Miklich. 1973. The coma profile.. https://doi.org/10.3949/ccjm.40.2.57
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On-line micellar electrokinetic chromatography (MEKC)-electrospray ionization mass spectrometry (ESIMS) is demonstrated for the analysis of chlorotriazine herbicides and barbiturates. In this study, the micellar velocity is directly manipulated by the adjustment of electroosmosis rather than the electrophoretic velocity of the micelle. The electroosmotic flow is adjusted against the electrophoretic velocity of the micelle by changing the solution pH in MEKC. The elimination of MEKC surfactant introduction into ESIMS is achieved with an anodically migrating micelle, moving away from the electrospray interface. The effects of moving surfactant boundary in the MEKC capillary on separation efficiency and resolution of triazine herbicides and barbiturates are investigated. The mass detection of herbicides and barbiturates sequentially eluted from the MEKC capillary is acquired using the positive and negative electrospray modes, respectively.
A mechanism is proposed to explain the activity of orotidine 5'-monophosphate decarboxylase (ODCase). This enzyme is the one of the most proficient known, with a catalytic proficiency (kcat/Km)/knon = 10(23) M-1. Quantum mechanical calculations predict a mechanism involving a stabilized carbene intermediate, which represents a previously unrecognized mode of enzymatic activity for ODCase. The proposed mechanism involves proton transfer from a weak acid (pKa = 7, where Ka is the acid constant) concerted with decarboxylation, in a nonpolar enzyme environment. Such a mechanism makes possible different approaches to the design of ODCase inhibitors. Furthermore, the prediction that general acid catalysis may only be effective in low dielectric media is of general significance for understanding the activity of many enzymes.
A personal computer based program (DDAPD1) was developed for calculating or determining the apparent distribution function of a drug to a possibly heterogeneous biophase, the mean transit time of a drug at the biophase, the ratio of distribution clearance to biophase volume of distribution, the drug concentration-time function at the biophase (Cb(t)), and a function which reflects the relationship between the pharmacodynamic response and Cb(t) of the drug. This program uses an approach based on disposition decomposition analysis and the hysteresis minimization principle. The application of the program is demonstrated using published data for heptabarbital.