Ultrasensitive high-performance liquid chromatography determination of tetracycline antibiotics and their 4-epimer derivatives based on dual effect of methanesulfonic acid.

In reversed-phase liquid chromatography, tetracycline antibiotics yield broad and asymmetrical peaks, as a result of their ionic interaction with the anionic free silanol groups and metal ion present in the silica-based stationary phases (commonly derivatized with C18 groups). These frequently encountered difficulties were absolutely eliminated based on dual effect when methanesulfonic acid was employed as an eluent additive. The study revealed that the performance of methanesulfonic acid to minimize the "silanol effect" is mainly explained by both direct neutralization of the anionic silanol sites and electrostatic attraction with analytes. Based on these dual action mechanisms, an ultrasensitive method has been successfully developed for the simultaneous determination of tetracycline antibiotics and their derivatives (minocycline, oxytetracycline, tetracycline, chlortetracycline, metacycline, doxycycline, 4-epitetracycline, and 4-epichlortetracycline) in bovine milk with convenient ultraviolet detection within 15 min. Under the optimal conditions, the calibration curves showed good linearity (r2  > 0.999) for all analytes in the range of 1∼200 ng/mL with the instrument limits of detection as low as 0.3 ng/mL. The study sheds new light on suitable additives to analyze basic compounds with the advantage of good compatibility with MS detection.

Selective and sensitive determination of tetracyclines by HPLC with chemiluminescence detection based on a cerium(IV)-methoxylated cypridina luciferin analogue system.

A novel approach for the simultaneous and selective analysis of chlortetracycline, doxycycline, 4-epichlortetracycline, oxytetracycline, metacycline, and tetracycline by high-performance liquid chromatography coupled with sensitive post-column chemiluminescence reaction was set up. Six tetracyclines were separated through a simple and effective isocratic procedure using a mixture of acetonitrile and 3.5 mM methanesulfonic acid. After that, intensive chemiluminescence signals were produced by the reaction between cerium(IV) and methoxylated cypridina luciferin analogues system in the presence of tetracyclines. Under the appropriate experimental conditions, the developed method was evaluated by testing of linearity, limits of detection, precision, and accuracy. The limit of detection was from 2 to 10 nM and relative standard deviation of intraday precision was below 9%. The developed high-performance liquid chromatography with chemiluminescence method has been performed for the with trace analysis of tetracycline antibiotic residues in milk samples with satisfactory results.

Learning linear discriminant projections for dimensionality reduction of image descriptors.

In this paper, we present Linear Discriminant Projections (LDP) for reducing dimensionality and improving discriminability of local image descriptors. We place LDP into the context of state-of-the-art discriminant projections and analyze its properties. LDP requires a large set of training data with point-to-point correspondence ground truth. We demonstrate that training data produced by a simulation of image transformations leads to nearly the same results as the real data with correspondence ground truth. This makes it possible to apply LDP as well as other discriminant projection approaches to the problems where the correspondence ground truth is not available, such as image categorization. We perform an extensive experimental evaluation on standard data sets in the context of image matching and categorization. We demonstrate that LDP enables significant dimensionality reduction of local descriptors and performance increases in different applications. The results improve upon the state-of-the-art recognition performance with simultaneous dimensionality reduction from 128 to 30.

Genetic variation in the Fat10 gene is associated with risk of hepatocellular carcinoma in a Chinese population.

BACKGROUND AND OBJECTIVES: This study examined whether variation in exonic and flanking sequences of the human HLA-F adjacent transcript 10 (FAT10) gene might be associated with susceptibility and clinicopathological development of hapatocellular carcinoma (HCC). METHODS: A total of 522 subjects, including 268 healthy controls and 254 patients with HCC, were recruited. Genotyping was accomplished using DNA sequencing. Haplotypes were determined through genotypic and disequilibrium analysis of identified single nucleotide polymorphisms (SNPs). RESULTS: Ten SNPs in FAT10 were identified, namely -143 A/G (rs362535), -121 A/G (rs2272991), +3446 C/T, +3476 T/C (rs2076484), +3527 T/C (rs2076485), +3607 T/C (rs2076486), +3620 C/G (rs2076487), +3803 C/G (rs8337), +3809 G/T (rs7757931), +3833 G/C (rs444013). +3446 C/T is a novel polymorphism. The -143 A/G, -121 A/G, +3476 T/C, +3607 T/C, +3620 C/G and +3809 G/T genotypes were associated with a decreased risk for HCC (all P-values <0.05). No SNPs were associated with disease clinicopathology (all P-values>0.05). Furthermore, under the analysis of haplotype, GGCTCGT and AGCTCGT were related to reduced HCC risk (OR=0.41, 95%CI=0.24, 0.70, P<0.05 and OR=0.43, 95% CI=0.22, 0.983, P<0.05, respectively), while AATTTCG was associated with an increased risk (OR=1.64, 95% CI=1.24-2.17, P<0.05). 10-million permutation testing also indicated the AATTTCG and GGCTCGT haplotypes to be associated with HCC susceptibility (both P-values<0.05). Patients carrying AATTTCG were in higher tumor and clinical stages (P<0.05), while GGCTCGT appeared protective in this context (P<0.05). CONCLUSION: This study provides first evidence that FAT10 gene genetic variants may be involved in the susceptibility and clinicopathological development of HCC in the Chinese Han population.