Abstract: TSG101 is a tumor susceptibility gene exhibits multiple biological function, including the regulation of cell progression, intracellular protein sorting and membrane trafficking, and transcription activity of nuclear recptor such as estrogen recptor. TSG101 contains an UBC domain which is homologous to that in ubiquitin conjugating E2 enzyme. However, it lacks an essential cysteine residue, which is essential for catalytic activity. Cellular protein ubiquitination serves as a signal for protein degradation or sorting into multivesicular body. UBC domain of TSG101 was proved to contain amino acid residues that are important for its interaction with ubquitin (residues V43, N46, D46 and F88) and PTAP sequence found in the late domain of HIV gag protein (residues Y63, M95, V141). SUMO is an ubquitin-like modifier which can modify cellular protein harbors £ZKXE amino acid sequence, thereby change its subcellular localization and biological activities. TSG101 protein contains K98, K243, K264 and K269 residues that localize in potential SUMO modification site. Our preliminary data indicated that TSG101 colocalize with SUMO in nucleus. It is interesting to know whether TSG101 is sumoylated, and its functional significance. In this thesis, a series of site-directed mutageneic mutant HA and GFP-tagged expression plasmids which contain mutation of the above mentioned functional related amino acid residues were constructed for future TSG101 functional studies.

Dissolved inorganic carbon (DIC), titration alkalinity (TA), and nitrate + nitrite (N+N) are measured from seasonal cruises at the time-series site SEATS in the northern South China Sea (18¢XN 116¢XE) between March 2002 and November 2004. The most distinctive feature of the annual nDIC (DIC normalized to a constant salinity of 33.8) cycle is an increase in wintertime and a decrease in summertime (March¡VAugust). The nDIC drawdown (-3.15 ¡Ó 2.23 mmol m-2 day-1) at summertime is mainly attributed to biological uptake of DIC. The other terms in the DIC budget calculation, i.e. the carbon fluxes of air-sea CO2 gas exchange, horizontal advection and vertical diffusion, are estimated to be -0.48 ¡Ó 0.31, -0.70 ¡Ó 0.86, and 2.50 ¡Ó 0.59 mmol m-2 day-1, respectively. Accordingly, results from the DIC budget calculation reveals a net community production (NCP) of -4.47 ¡Ó 1.98 mmol m-2 day-1. This calculated NCP from our data is in good agreement with the export and new production previously reported in the South China Sea. The consistency demonstrates that carbon system is almost in a steady state during summertime at SEATS. According to the Refield C : N ratio of 106 : 16, a flux of 0.67 ¡Ó 0.30 mmol m-2 day-1 of bioavailable nitrogen (Nbio) is needed to sustain the calculated NCP. The source terms in the Nbio budget calculation, i.e. the nitrogen fluxes of vertical diffusion, wet deposition, dry deposition and the contribution from the putative nitrogen-fixing cyanobacteria Trichodesmium and Richelia intra., are estimated to be 0.20 ¡Ó 0.04, 0.03 ¡Ó 0.01, 0.04 ~ 0.08, and 0.02 ~ 0.13 mmol m-2 day-1, respectively. It thus seems that all the source terms can only collectively account for 50 ~ 70% Nbio needed to support the estimated NCP. With this regard, unicellular cyanobacteria, which have been reported as an important N2-fixer in the subtropical North Pacific and identified by the nitrogenase genes (nifH) in the small size (less than 10

The researches of this thesis are divided into two parts. One is to investigate the applicability of ANSI C63.5 in high frequencies of 1 GHz to 6 GHz. In general, the Standard Site Method (SSM) of C63.5 is usually used to calculate the antenna factors for the calibration of broadband antennas. Through the theoretical calculations, the numerical simulations and measurements, we found that the discrepancies between the calibrated results of horizontal and vertical polarization related to the un-dipole-like pattern in higher frequencies. Furthermore, we analyzed the relations of the antenna factors, the heights of receive antennas and the radiation patterns. We also found that the predicted calibration results can be close to the practical ones by including the effects of radiation patterns. The other research is to study the issue about the ground plane size of a test site. The ground plane size of a qualified test site must be larger than the minimum size defined by C63.7. For this reason, we provide a method which combines the tilted antennas measurement with a trapezoid shape ground. By using this method in the smaller ground size, we can obtain the measured results close to those obtained in the larger ground size. This method can effectively reduce the required ground size and then decrease the installation cost of a test site. Meanwhile, this method can be applied for both of the horizontal and vertical polarizations.

The periplasmic nuclease of Vibrio vulnificus, Vvn, has been purified to homogeneity by a one step purification procedure using chromatography on a SP Sepharose column. The purified enzyme showed different mobilities on reducing and non-reducing SDS-PAGE, suggesting that disulfide bonds are involved in the maintenance of a stable tertiary conformation of the protein. Vvn randomly cleaved single and double stranded DNA and RNA, and possessed endonucleolytic activity. The enzyme exhibited an optimal activity between pH 8.0 and pH 10.0, and the optimal temperatures for the DNase and RNase activity were 40 oC ¡V 60 oC and 40 oC ¡V 50 oC, respectively. The enzymatic activity was inhibited by EDTA and EGTA, indicating that Vvn was a metalloenzyme. The DNase and RNase activity of Vvn had different requirements for divalent cations. Chemical modification studies on Vvn revealed the involvement of lysine, arginine, tryptophan and carboxylate residues in the catalytic activity of the enzyme. The extents of inactivation of the DNase and RNase activity of Vvn by modification of the carboxylate group with EDC were different. Substrate DNA and RNA protected the DNase and RNase activity of Vvn from inactivation by PLP, PGO, NBS and EDC which modified lysine, arginine, tryptophan and the carboxylate group. Mg2+ could not protect the DNase and RNase activity of Vvn against the inactivation by PLP and PGO. Whereas Mg2+ protection was observed in NBS- and EDC-mediated inactivation of the DNase but not the RNase activity of Vvn . From these results, it is postulate that there may be two distinct but overlapping active sites, for the DNase and RNase activity, respectively.

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Texte remanié de: Diss.--Fachbereich für Orientalistik--Universität Hamburg, 1998. / Bibliogr. p. [335]-356. Index.

Diss.--Evangelisch-theologische Fakultät--Tübingen--Eberhard-Karls-Universität, Wintersemester 1998/1999. / Résumés en anglais et en arabe. Bibliogr. p. 203-222. Index.

Texte remanié de: Diss.--Geschichts- und Kulturwissenschaft. N°: Freie Universität Berlin, 1999. / Textes en allemand, résumés en anglais et allemand, sommaire en grec. Notes bibliogr.

Thesis--Faculty of arts and sciences--University of Pittsburgh, 1999. / Bibliogr. p. 220-241.

Dissertation--Stanford university, 1997. / Bibliogr. p. 235-255.