PubMed · 10503383
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S Ono. 1999. [Chloride].. https://pubmed.ncbi.nlm.nih.gov/10503383/
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A single-step procedure was developed for the incorporation of iodoazide into oleic acid, triolein, and phosphatidylcholine. Iodoazide was generated using [125I]iodomonochloride and sodium azide that was found to add stereospecifically in a variety of olefins. Photoreactive and radiolabeled triacylglycerol and phosphatidylcholine were synthesized with a moderate yield and high specific activity. The stability of both the radiolabel and the photoreactive group was studied under ultraviolet light under aqueous as well as anhydrous conditions. These synthesized analogs act as substrates in the dark, and as irreversible inhibitors under ultraviolet irradiation for the target hydrolytic enzymes. The synthesized radiolabeled photoprobes were subsequently used to label lipase and phospholipase A(2). The results highlighted the efficiency and rapidity of the method and its potential application in the study of lipid-metabolizing enzymes.
Fluorescent sensing microspheres based on perhaps the most selective and practically useful chloride ionophore known, the recently reported [9]mercuracarborand-3 (MC-3), have been prepared and optimized for physiological measurements. In initial work, this ionophore was shown to yield functional optical sensing films in combination with an electrically neutral chromoionophore, ETH 5418. Unfortunately, however, these optodes suffered from unacceptably high levels of sodium interference under physiological conditions. To better understand the sensing mechanism, optical and potentiometric binding experiments were used to characterize the stoichiometry and the complex formation constants for this ionophore. It was found that the preferred stoichiometry is 1:2, rather than 1:1 as assumed earlier. The 1:2 complex is extremely stable (logbeta2 = 13.4), but a relatively strong 1:1 complex also exists (log K1 = 9.9). These characteristics were used to fabricate chloride optodes that make use of the stepwise ion-ionophore decomplexation equilibrium, by adding a calculated amount of lipophilic anion exchanger to the polymer film. Such optodes showed dramatically reduced sodium interference while maintaining the excellent selectivity of the traditional formulation. The optimized composition also shifted the measuring range to physiological conditions, making them useful for the assessment of chloride in undiluted and 10-fold-diluted blood at pH 7.4. After necessary alterations of the particle preparation procedure and sensor formulation, the new insights were used to fabricate mass-produced optical sensing microspheres with characteristics essentially identical to those of the optode sensing films.
The principle of an on-line preconcentration method for capillary zone electrophoresis (CZE) named electrokinetic supercharging (EKS), is described and based on computer simulation the preconcentration behavior of the method is discussed. EKS is an electrokinetic injection method with transient isotachophoretic process, is a powerful preconcentration technique for the analysis of dilute samples. After filling the separation capillary with supporting electrolyte, an appropriate amount of a leading electrolyte was filled and the electrokinetic injection was started. After a while, terminating electrolyte was filled subsequently and migration current was applied. This procedure enabled the introduction of a large amount of sample components from a dilute sample without deteriorating separation. Computer simulation of the electrokinetic injection revealed that EKS was effective for the preconcentration of analytes with wide mobility ranges by proper choice of transient isotachophoresis (ITP) system and electroosmotic flow (EOF) should be suppressed to increase injectable amount of analytes under constant voltage mode. A test mixture of rare-earth chlorides was used to demonstrate the uses of EKS-CZE. When a 100 microL sample was used, the low limit of detectable concentration was 0.3 microg/L (1.8 nM for Er), which was comparable or even better than that of ion chromatography and inductively coupled plasma-atomic emission spectrometry (ICP-AES).