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Ning Chen

Publications and source records attributed to Ning Chen.

43 records · Page 3Linked to original sources
PubMed2003

Quantitative structure-biodegradation relationships for ortho-substituted biphenyl compounds oxidized by Methylosinus trichosporium OB3b.

Methanotrophs, bacteria that thrive in the presence of stable methane and oxygen concentrations, can cometabolically oxidize ortho-substituted biphenyls to yield a variety of hydroxylated products. Despite awareness of the susceptibility of ortho-substituted biphenyls and other aromatic compounds to methanotrophic oxidation, the molecular properties relevant for predicting rates of methanotrophic oxidation are unknown. To this end, we have developed quantitative structure-biodegradation relationships using oxygen uptake activity by the type 2 methanotroph. Methylosinus trichosporium OB3b, expressing the soluble form of methane monooxygenase and in the presence of nine ortho-substituted biphenyls. Multivariate analysis yielded the strongest correlations using the initial slope of the oxygen uptake rate versus substrate concentration curve as the dependent variable. Quantum mechanical descriptors, including the sum of carbon charges on the substituted ring, the charge on the substituted carbon, and the width of compound calculated using computationally derived bond lengths and dihedral angles, correlated more strongly with oxygen uptake activity than did empirically derived electronic descriptors. The resulting models suggest a significant influence of substituent electronic nature and size and the involvement of the substituted carbon site in the oxidation of these compounds by M. trichosporium OB3b.

Biodegradation, Environmental↗
PubMed2003

[Metabolic flux analysis of L-Tryptophan biosynthesis].

The metabolic flux balance model of L-Try synthesis by Corynebacterium glutamicum was constructed in this paper. Using this model, the metabolic flux distribution during the middle and late period were determined and the optimal flux distribution were calculated by linear program of MATLAB software. The analysis results indicate that 24.85% metabolic flux entered the HMP pathway and 75.15% entered the EMP cycle. But comparing to the optimal flux distributions, the production of L-Try should be improved from the genetic manipulation and fermentation control through reducing byproduct of amino acid and decreasing the metabolic flux of TCA and EMP.

Biosynthetic Pathways↗
PubMed2002

Sensitive and efficient detection of RB1 gene mutations enhances care for families with retinoblastoma.

Timely molecular diagnosis of RB1 mutations enables earlier treatment, lower risk, and better health outcomes for patients with retinoblastoma; empowers families to make informed family-planning decisions; and costs less than conventional surveillance. However, complexity has hindered clinical implementation of molecular diagnosis. The majority of RB1 mutations are unique and distributed throughout the RB1 gene, with no real hot spots. We devised a sensitive and efficient strategy to identify RB1 mutations that combines quantitative multiplex polymerase chain reaction (QM-PCR), double-exon sequencing, and promoter-targeted methylation-sensitive PCR. Optimization of test order by stochastic dynamic programming and the development of allele-specific PCR for four recurrent point mutations decreased the estimated turnaround time to <3 wk and decreased direct costs by one-third. The multistep method reported here detected 89% (199/224) of mutations in bilaterally affected probands and both mutant alleles in 84% (112/134) of tumors from unilaterally affected probands. For 23 of 27 exons and the promoter region, QM-PCR was a highly accurate measure of deletions and insertions (accuracy 95%). By revealing those family members who did not carry the mutation found in the related proband, molecular analysis enabled 97 at-risk children from 20 representative families to avoid 313 surveillance examinations under anesthetic and 852 clinic visits. The average savings in direct costs from clinical examinations avoided by children in these families substantially exceeded the cost of molecular testing. Moreover, health care savings continue to accrue, as children in succeeding generations avoid unnecessary repeated anaesthetics and examinations.

Algorithms↗
PubMed2002

Identification and cross-species comparisons of CYP2F subfamily genes in mammals.

The cytochrome P450 2F (CYP2F) subfamily genes are currently known only from cDNA sequences in human, mouse, rat and goat. Compared to other divisions of the CYP2 gene family, the CYP2F subfamily is unusual in having few genes per species and in being selectively expressed in lung tissues. Sequencing genomic DNAs from human and gorilla has allowed us to determine the number of CYP2F subfamily loci in these species, the sources of known human transcripts, and the functional status of CYP2F loci in both primates. This information will make accurate genotyping of the functional and medically significant CYP2F1 gene possible in humans. Comparisons across multiple species show that the sequences of CYP2F subfamily genes are very conserved in mammals for intronic as well as exonic DNA.

Animals↗