PRIMARY MECHANISMS OF ERYTHROCYTE PHOTOLYSIS INDUCED BY BIOLOGICAL SENSITIZERS AND PHOTOTOXIC DRUGS

Abstract— The elucidation of the molecular mechanism of photosensitized hemolysis of red blood cells may give important clues to the primary events underlying the phototoxic reactions observed in pathological conditions such as porphyria and induced by photosensitizing drugs. Sensitizers effective in photo-hemolysis are porphyrins, the tryptophan metabolite kynurenic acid, and phototoxic drugs such as chlor-promazine and demethylchlortetracycline. Utilizing the singlet oxygen quenchers. jS-carotene and histi-dine and the large deuterium effect on the lifetime of singlet oxygen previously described by us, good evidence of the participation of this excited molecular species in the photohemolysis in the presence of kynurenic acid was obtained. Chlorpromazine and demethylchlortetracycline clearly act by a non-singlet oxygen pathway. The situation observed with haematoporphyrin is less clear and may represent a mixed Type I-Type II mechanism.     

Determination of dextropropoxyphene and norpropoxyphene in plasma by high-performance liquid chromatography.

A simple and sensitive procedure for the routine assay of the analgesic drug dextropropoxyphene and its main metabolite, norpropoxyphene, in plasma is described. After liquid-liquid extraction from alkalinized plasma and back-extraction into a small volume of an acidic aqueous phase, the aqueous phase was injected into a column packed with 3-microns octadecylsilica particles. Ultraviolet absorbance detection at 210 nm was used. Concentrations down to 2 nM could be determined for both compounds; at this level, the intra-assay coefficient of variation was 5%.     

Miniaturized dynamic liquid-liquid extraction of organophosphate triesters from blood plasma using the hollow fibre-based XT-tube extractor

A miniaturized liquid–liquid extractor for bioanalytical sample preparation is described. The extractor consists of a polypropylene hollow fibre mounted inside polytetrafluoroethylene (PTFE) tubing by means of a cross (X) connector and a tee (T) connector. All parts are commercially available, inexpensive, and easily assembled. The aqueous sample, injected into a carrier flow, is pumped along the outside of the fibre and the organic phase, which also wets the pores of the hollow fibre wall, is pumped inside. Eight organophosphate triester (OPE) plasticisers/flame retardants were extracted from 50 µL spiked blood plasma that had been mixed with 50 µL formic acid to denature plasma proteins. The organic phase was a mixture of hexane and methyl tert-butyl ether (MTBE). A high concentration of formic acid in the sample and of MTBE in the organic phase had positive effects on the recovery of some OPE. When investigating the recovery as a function of extraction time it was found that the extraction reached a maximum after 10 min, at a flow-rate of 15 µL min^–1. Recoveries varied between 40 and 80% with RSD around 4% for most compounds. The whole 150-µL extract was injected into a GC–MS system equipped with a programmed-temperature vaporization (PTV) injector. With the MS in selected-ion monitoring (SIM) mode, the LOD for triphenyl phosphate and 2-ethylhexyl diphenyl phosphate were 0.3 and 0.2 ng mL^–1, respectively. More than 40 plasma extractions were performed with the same fibre without any detectable change in extraction efficiency.     

Protein assembly by orthogonal chemical ligation methods

Chemical synthesis harbors the potential to provide ready access to natural proteins as well as to create nonnatural ones. The Staudinger ligation of a peptide containing a C-terminal phosphinothioester with a peptide containing an N-terminal azide gives an amide with no residual atoms. This method for amide bond formation is orthogonal and complementary to other ligation methods. Herein, we describe the first use of the Staudinger ligation to couple peptides on a solid support. The fragment thus produced is used to assemble functional ribonuclease A via native chemical ligation. The synthesis of a protein by this route expands the versatility of chemical approaches to protein production.     

Representations of the Lie algebra of vector fields on a sphere

For an affine algebraic variety X we study a category of modules that admit compatible actions of both the algebra A of functions on X and the Lie algebra of vector fields on X. In particular, for the case when X is the sphere ${\mathbb{S}}^2$, we construct a set of simple modules that are finitely generated over A. In addition, we prove that the monoidal category that these modules generate is equivalent to the category of finite-dimensional rational ${\mathrm{GL}}_2$-modules.     

An error model for evaluation and interpretation of proficiency testing

Data from proficiency testing can be used to increase our knowledge of the performance of populations of laboratories, individual laboratories and different measurement methods. To support the evaluation and interpretation of results from proficiency testing an error model containing different random and systematic components is presented. From a single round of a proficiency testing scheme the total variation in a population of laboratories can be estimated. With results from several rounds the random variation can be separated into a laboratory and time component and for individual laboratories it is then also possible to evaluate stability and bias in relation to the population mean. By comparing results from laboratories using different methods systematic differences between methods may be indicated. By using results from several rounds a systematic difference can be partitioned into two components: a common systematic difference, possibly depending on the level, and a sample-specific component. It is essential to distinguish between these two components as the former may be eliminated by a correction while the latter must be treated as a random component in the evaluation of uncertainty. Received: 20 November 2000 Accepted: 3 January 2001