A bifunctional luminogenic substrate for two luminescent enzymes: firefly luciferase and horseradish peroxidase

A highly selective chemiluminescent probe for the detection of chromium(VI)

In present work, rhodamine B hydrazide and rhodamine 6G hydrazide were synthesized and the chemiluminescence performance has been investigated. Based on the chemiluminescence of rhodamine 6G hydrazide‑chromium(VI), a selective and sensitive method for the direct detection of chromium(VI) was developed. The chemiluminescence intensity was linearly related to the concentration of chromium(VI) in the range of 2.60×10^-8-8.00×10^-6mol/L with a correlation coefficient of r=0.998 and a detection limit of 1.4×10^-8mol/L (S/N=3). The results indicated rhodamine 6G hydrazide was an excellent chemiluminescent probe for chromium(VI) without reduction of chromium(VI) to chromium(III). A possible mechanism of CL emission was also suggested.

Proficiency testing for the detection of anti-citrullinated protein antibody in China

BACKGROUND

Anti-citrullinated protein antibodies (ACPAs) are important for the detection of rheumatoid arthritis (RA). There are many laboratories to detect it in their routine work, but their performance is not displayed in China. To examine the performance of ACPA assays from all laboratories, it is necessary to organize a laboratory proficiency test (PT).

METHODS

A panel of 5 samples, including 4 positive and 1 negative, was produced by the National Center for Clinical Laboratories, using serum derived from patients, then distributed to 271 clinical laboratories. Quantitative and qualitative results reported by the participating laboratories were compared.

RESULTS

Overall, 80.97% (200/247) of the laboratories had eligible PT scores. Of the kits used, most ELISA and chemiluminescence kits had a high sensitivity and specificity. Regarding intra-assay discrepancy, the Roche and Abbott kit had a better variable coefficient. The ratios of the quantitative results to the kit-specific cut-off values were similar.

CONCLUSION

Performance varied between laboratories. Reagents and methods are the most important factors. Other factors may affect the intra-assay discrepancy. The similar mean of ratios of the quantitative results to the kit-assigned cut-offs suggests that a national criterion is requisite. It is necessary to organize a PT to identify performances of different laboratories.

Firefly luciferase: an adenylate-forming enzyme for multicatalytic functions

Firefly luciferase is a member of the acyl-adenylate/thioester-forming superfamily of enzymes and catalyzes the oxidation of firefly luciferin with molecular oxygen to emit light. Knowledge of the luminescence mechanism catalyzed by firefly luciferase has been gathered, leading to the discovery of a novel catalytic function of luciferase. Recently, we demonstrated that firefly luciferase has a catalytic function of fatty acyl-CoA synthesis from fatty acids in the presence of ATP, Mg(2+) and coenzyme A. Based on identification of fatty acyl-CoA genes in firefly, Drosophila, and non-luminous click beetles, we then proposed that the evolutionary origin of firefly luciferase is a fatty acyl-CoA synthetase in insects. Further, we succeeded in converting the fatty acyl-CoA synthetase of non-luminous insects into functional luciferase showing luminescence activity by site-directed mutagenesis.

Luminol-type chemiluminescence derivatization reagents for liquid chromatography and capillary electrophoresis

The present paper provides the principles for chemiluminescence of luminol-type compounds and their wide and powerful application to the detection system in liquid chromatography and capillary electrophoresis as derivatization reagents. The reagents can be classified into two types, chemiluminescence labeling and chemiluminogenic reagents. The former reagents are highly chemiluminescent themselves and used for tagging their intense chemiluminophores to analytes, whereas the latter are weakly chemiluminescent but generate intense chemiluminescence by reaction with analytes. The liquid chromatographic methods utilizing chemiluminescence derivatizing reactions with luminol-type reagents allow the analytes to be detected at pmol-sub-fmol levels. Furthermore, the chemiluminogenic reactions show high selectivity owing to their selective reaction against the analytes permitting facile and reproducible detection.

Functional expression and stabilization of horseradish peroxidase by directed evolution in Saccharomyces cerevisiae

Biotechnology applications of horseradish peroxidase (HRP) would benefit from access to tailor-made variants with greater specific activity, lower K(m) for peroxide, and higher thermostability. Starting with a mutant that is functionally expressed in Saccharomyces cerevisiae, we used random mutagenesis, recombination, and screening to identify HRP-C mutants that are more active and stable to incubation in hydrogen peroxide at 50 degrees C. A single mutation (N175S) in the HRP active site was found to improve thermal stability. Introducing this mutation into an HRP variant evolved for higher activity yielded HRP 13A7-N175S, whose half-life at 60 degrees C and pH 7.0 is three times that of wild-type (recombinant) HRP and a commercially available HRP preparation from Sigma (St. Louis, MO). The variant is also more stable in the presence of H(2)O(2), SDS, salts (NaCl and urea), and at different pH values. Furthermore, this variant is more active towards a variety of small organic substrates frequently used in diagnostic applications. Site-directed mutagenesis to replace each of the four methionine residues in HRP (M83, M181, M281, M284) with isoleucine revealed no mutation that significantly increased the enzyme's stability to hydrogen peroxide.