Acid-base Catalysis in the Mechanism of Thioredoxin Reductase from Drosophila melanogaster.

Thioredoxin reductase (TrxR) catalyses the reduction of thioredoxin (Trx) by NADPH. Like other members of the pyridine nucleotide-disulfide family, TrxR is a homodimer. The catalytically active unit in the enzyme from Drosophila melanogaster (DmTrxR) consists of three redox centers: FAD and an N-terminal Cys-57/Cys-62 redox-active disulfide from one monomer, and a Cys-489’/Cys-490’ C-terminal redox-active disulfide from the second monomer. Because dipteran insects such as D. melanogaster lack glutathione reductase, glutathione disulfide must be reduced by Trx, making DmTrxR particularly important in this organism. DmTrxR is used as a model for the enzyme from a malaria vector, Anopheles gambiae. Based on the structures and mechanisms of other family members, a dyad of His-464’ and Glu-469’ acts as the acid-base catalyst of the dithiol-disulfide interchange reactions required in the catalysis of DmTrxR. The functions of His-464’ and Glu-469’ in the catalytic mechanism of DmTrxR were investigated. His-464’ was shown to be critical to catalysis by DmTrxR; thus, H464’Q retains only 2% of the wild-type activity. The pH dependence of Vmax for wild-type DmTrxR has apparent pKa values of 6.4 and 9.3, whereas H464’Q DmTrxR has an observable pKa only at 6.4, indicating that the pKa at pH 9.3 is contributed by His-464’. The macroscopic pKa at pH 6.4 has been assigned to Cys-57 and Cys-490’; the thiolate of Cys-57 is the nucleophile in the internal dithiol-disulfide interchange reaction and the thiolate of Cys-490’ is the nucleophile in the reduction of Trx. The rates of both the reductive and oxidative half reactions are markedly smaller in H464’Q DmTrxR than those of wild-type enzyme, indicating that His-464’ is involved in both half reactions. The pH dependence of the steady-state kinetics shows that the basicity of His-464’ decreases in the glutamate variants, as predicted. The reductive half-reactions of two glutamate variants are slower than those of wild-type enzyme. Malaria causes serious public health problems in the world. It is hoped that differences among TrxRs from human, Plasmodium falciparum (the causative agent) and Diptera (the vector) will be useful for developing differential inhibitors, useful as prophylactics.Ph.D.ToxicologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/58421/1/huanghh_1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/58421/2/huanghh_2.pd

Machine Learning-based Indoor Positioning Systems Using Multi-Channel Information

The received signal strength indicator (RSSI) is a metric of the power measured by a sensor in a receiver. Many indoor positioning technologies use RSSI to locate objects in indoor environments. Their positioning accuracy is significantly affected by reflection and absorption from walls, and by non-stationary objects such as doors and people. Therefore, it is necessary to increase transceivers in the environment to reduce positioning errors. This paper proposes an indoor positioning technology that uses the machine learning algorithm of channel state information (CSI) combined with fingerprinting. The experimental results showed that the proposed method outperformed traditional RSSI-based localization systems in terms of average positioning accuracy up to 6.13% and 54.79% for random forest (RF) and back propagation neural networks (BPNN), respectively

Machine Learning-based Indoor Positioning Systems Using Multi-Channel Information

The received signal strength indicator (RSSI) is a metric of the power measured by a sensor in a receiver. Many indoor positioning technologies use RSSI to locate objects in indoor environments. Their positioning accuracy is significantly affected by reflection and absorption from walls, and by non-stationary objects such as doors and people. Therefore, it is necessary to increase transceivers in the environment to reduce positioning errors. This paper proposes an indoor positioning technology that uses the machine learning algorithm of channel state information (CSI) combined with fingerprinting. The experimental results showed that the proposed method outperformed traditional RSSI-based localization systems in terms of average positioning accuracy up to 6.13% and 54.79% for random forest (RF) and back propagation neural networks (BPNN), respectively

Primary Pulmonary Synovial Sarcoma: A Case Report

We report a rare case of primary synovial sarcoma of the lung. A 57-year-old man had a well-defined tumor in the right middle lobe seen on chest computed tomography, and underwent lobectomy. Grossly, the nonencapsulated tumor measured 4.5 cm in greatest diameter, with a solid and tan-white cut surface. Histologically, the tumor was mainly composed of a dense proliferation of spindle cells. Immunohistochemical studies were focally positive for epithelial membrane antigen, and diffusely positive for CD99 and Bcl-2. Cytokeratin, S-100 protein, desmin, smooth muscle actin, and CD34 were absent. SYT-SSX1 gene fusion transcript was detected by reverse transcription-polymerase chain reaction, which is diagnostic of primary synovial sarcoma of the lung. We also review the literature with regard to the clinicopathologic, immunohisto-chemical, and molecular studies of primary pulmonary synovial sarcoma

In vitro propagation of Gentiana scabra Bunge – an important medicinal plant in the Chinese system of medicines

Background: Gentiana scabra Bunge commonly known as `Long dan cao\u27 in China has been used in traditional Chinese medicines for more than 2000 years. Dry roots and rhizome of the herb have been used for the treatment of inflammation, anorexia, indigestion and gastric infections. Iridoids and secoiridoids are the main bioactive compounds which attribute to the pharmacological properties of this plant. The species is difficult to mass propagate by seed due to the low percentage of germination and limited dormancy period. Wild populations in some locations are considered to be in the endangered category due to over exploitation. Results: In the present study, we report an efficient micropropagation system. Shoot apices of six weeks old in vitro grown G. scabra plants were used as explants for the in vitro propagation. Induction of multiple shoots (9.1/explant) was achieved on the culture of shoot apices on half strength Murashige and Skoog\u27s basal medium (MSBM) containing 2.0 mg/L 1 6-benzylaminopurine (BA), 3% sucrose and 0.9% Difco agar. In vitro shoots induced profuse rooting on half strength of MSBM supplemented with 0.1 mg/L 1 1-naphthaleneacetic acid (NAA), 3% sucrose and 0.3% gelrite. A two-stage ventilation closure procedure during the in vitro culture, and transparent sachet technique enhanced the survival rate of G. scabra plantlets to 96% in the greenhouse. Tissue culture plants flowered after 5 months of transfer to pots. Conclusions: A simple and an efficient in vitro propagation protocol of Gentiana scabra Bunge by optimizing the medium composition and ventilation closure treatments has been developed. The protocol can be very useful in germplasm conservation and commercial cultivation of G. scabra plants