One step for Legionella pneumophila detection in environmental samples by DNA-gold nanoparticle probe.

AIMS: To develop and evaluate a DNA-gold nanoparticle (DNA-AuNP) probe assay to detect Legionella pneumophila, which causes Legionnaires' disease, compared with the gold standard culture method. METHODS AND RESULTS: Gold nanoparticles (AuNPs) were conjugated with DNA probes to detect the mip gene of L. pneumophila. The DNA-AuNP probe assay was evaluated for its specificity, sensitivity and stability. The results showed that only L. pneumophila mixed with this probe resulted in a red solution that was easily detected by the naked eye, and the colour was stable when 10 mmol l-1 MgSO4 was added. The 100 Legionella isolates and 10 other bacteria led to 100% specificity. Compared with the culture method, our method showed a 100% negative predictive value, 100% sensitivity (kappa = 0·87), and a detection limit of 4·5 ng DNA µl-1 with a 6-min response time for the 124 colonies suspected of being Legionella. The DNA-AuNP probe reagents were stable for more than 6 months. CONCLUSIONS: The developed DNA-AuNP probe assay has good negative predictive value, sensitivity, rapidity and ease of use, which is helpful for ruling out negative samples. SIGNIFICANCE AND IMPACT OF THE STUDY: The DNA-AuNP probe assay can detect the mip gene of L. pneumophila. Therefore, it may be an alternative method for screening colonies suspected of being L. pneumophila.

Antioxidant activities of polyphenolic compounds isolated from Antidesma thwaitesianum Müll. Arg. seeds and marcs.

Antidesma thwaitesianum Müll. Arg. or mao is widely used as commercial products of juice and wine in Thailand. As a result, waste products from the mao plant, such as mao seeds (MS) and mao marcs (MM), are plentiful. We aimed to purify and analyze polyphenolic content in both MS and MM and to investigate the radical scavenging activities of these polyphenolics against 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and 2,2'-Azinobis (3-ethylbenzothiazoline 6-sulphonate) (ABTS) radicals and thiobarbituric acid reactive products (TBARP). The results showed MS and MM to be an abundant source of polyphenols (97.32 to 130 mg gallic acid equivalents [GAE]/g) and proanthocyanidins. The radical scavenging activities of MS/MM against DPPH and ABTS radicals (IC(50) of 0.85 to 1.21 microg/mL) were significantly higher (P < 0.05) than that of standard trolox (IC(50) of 5.05 microg/mL). Activity of MS/MM extracts were 3.74 and 3.80 microg/mL trolox eq/g f.w. for the DPPH and ABTS assays, respectively. The oxidation of erythrocyte membranes using 2-thiobarbituric acid demonstrated that the protective effect of MS/MM on lipid peroxidation is as strong as grape seed proanthocyanidin extract. These findings suggest that polyphenolic compounds and proanthocyanidins isolated from these mao extracts had much higher antioxidant activities than those of standard trolox and exhibited similar antioxidant potential to grape seed proanthocyanidin extract. These findings may also increase value of mao waste products and allow development of commercial health products.

Isolectins from seeds of Artocarpus lakoocha.

Two isolectins (ALA-I and ALA-II), were isolated from seed extracts of Artocarpus lakoocha by anion exchange chromatography on Q-Sepharose fast flow columns at pH 8.5 and 8.0 ALA-I was unbound to the column at pH 8.5 and moved towards the cathode in non-denaturing polyacrylamide gel electrophoresis, whereas ALA-II possessed opposite properties. The two A. lakoocha agglutinins appeared to be composed of two dissimilar subunits (alpha and beta of M(r) 14,000 and 17,200) bound non-covalently. The isolectins possessed several similar properties including: blood type agglutination; pH optimum; pH and temp stability; as well as binding specificity towards asialomucins.