A novel potentiometric biosensor for selective l-cysteine determination using l-cysteine-desulfhydrase producing Trichosporon jirovecii yeast cells coupled with sulfide electrode

ملخص البحث

Trichosporon jirovecii yeast cells are used for the first time as a source of l-cysteine desulfhydrase enzyme (EC and incorporated in a biosensor for determining l-cysteine. The cells are grown under cadmium stress conditions to increase the expression level of the enzyme. The intact cells are immobilized on the membrane of a solid-state Ag2S electrode to provide a simple l-cysteine responsive biosensor. Upon immersion of the sensor in lcysteine containing solutions, l-cysteine undergoes enzymatic hydrolysis into pyruvate, ammonia and sulfide ion. The rate of sulfide ion formation is potentiometrically measured as a function of l-cysteine concentration. Under optimized conditions (phosphate buffer pH 7, temperature 37±1 ◦C and actual weight of immobilized yeast cells 100 mg), a linear relationship between l-cysteine concentration and the initial rate of sulfide liberation (dE/dt) is obtained. The sensor response covers the concentration range of 0.2–150mgL−1 (1.7–1250mol L−1) l-cysteine. Validation of the assay method according to the quality control/ quality assurance standards (precision, accuracy, between-day variability, within-day reproducibility, range of measurements and lower limit of detection) reveals remarkable performance characteristics of the proposed biosensor. The sensor is satisfactorily utilized for determination of l-cysteine in some pharmaceutical formulations. The lower limit of detection is ∼1mol L−1 and the accuracy and precision of the method are 97.5% and ±1.1%, respectively. Structurally similar sulfur containing compounds such as glutathione, cystine, methionine, and d-cysteine do no interfere.

مكان النشر:

analytica chimica acta 6 0 2 ( 2 0 0 7 ) 108–113، العدد 6 0 2 108–113.

تاريخ البحث:

7 00 2

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