Browsing by Author "Yip, Bak-Sau"

Now showing 1 - 5 of 5

Multiple Pleomorphic Tetramers of Thermostable Direct Hemolysin from Grimontia hollisae in Exerting Hemolysis and Membrane Binding
(2019-07-08)
Wang, Yu-Kuo
;
Huang, Sheng-Cih
;
Chang, Chin-Yuan
;
Huang, Wan-Ting
;
Liao, Man-Jun
Oligomerization of protein into specific quaternary structures plays important biological functions, including regulation of gene expression, enzymes activity, and cell-cell interactions. Here, we report the determination of two crystal structures of the Grimontia hollisae (formally described as Vibrio hollisae) thermostable direct hemolysin (Gh-TDH), a pore-forming toxin. The toxin crystalized in the same space group of P2(1)2(1)2, but with two different crystal packing patterns, each revealing three consistent tetrameric oligomerization forms called Oligomer-I, -II, and -III. A central pore with comparable depth of similar to 50 angstrom but differing in shape and size was observed in all determined toxin tetrameric oligomers. A common motif of a toxin dimer was found in all determined structures, suggesting a plausible minimum functional unit within the tetrameric structure in cell membrane binding and possible hemolytic activity. Our results show that bacterial toxins may form a single or highly symmetric oligomerization state when exerting their biological functions. The dynamic nature of multiple symmetric oligomers formed upon release of the toxin may open a niche for bacteria survival in harsh living environments.
Optimization of Nanobelt Field Effect Transistor with a Capacitive Extended Gate for Use as a Biosensor
(2018-01-01)
Chen, Chih-Wei
;
Yip, Bak-Sau
;
Pan, Fu-Ming
;
Sheu, Jeng-Tzong
;
交大名義發表
In this study, various types of extended gate field effect transistor (EGFET) biosensors were compared and then a model based on potential coupling between a disposable extended gate (EG) capacitor and the gate-source/drain capacitor of a nanobelt field effect transistor (NBFET) was developed and optimized for biosensor applications. Several parameters, including the dielectric thicknesses and the EG gate area coverage, the ionic strength of buffer solution, and the charge density of specific binding biomolecules, were included in the model. The potential coupling efficiency between the potential induced by surface charge on the EG and the gate voltage of the FET was analyzed and verified through pH detection. Biotin-streptavidin/avidin sensing was demonstrated with the optimized EG and NBFET. In addition, real-time measurements of the detection of botulinum neural toxin (BoNT) type-A were also performed using the EG NBFET, which could detect an extremely low concentration (20 fM) of BoNT type-A. Because the nanoelectronic field effect transistor does not need to be sacrificed after detection, the optimized EG NBFET biosensor has great potential for use in bio/chemical and point-of-care applications. (C) The Author(s) 2018. Published by ECS.
Potential antitumor therapeutic application of Grimontia hollisae thermostable direct hemolysin mutants
(2015-04-01)
Huang, Sheng-Cih
;
Wang, Yu-Kuo
;
Huang, Wan-Ting
;
Kuo, Tsam-Ming
;
Yip, Bak-Sau
We report on the preparation of a new type of immunotoxin by conjugation of an epidermal growth factor receptor (EGFR)-binding peptide and an R46E mutation of thermostable direct hemolysin from Grimontia hollisae, (Gh-TDHR46E/EB). The hybrid immunotoxin was purified to homogeneity and showed a single band with slight slower mobility than that of Gh-TDHR46E. Cytotoxicity assay of Gh-TDHR46E/EB on EGFR highly, moderately, low, and non-expressed cells, A431, MDA-MB-231, HeLa, and HEK293 cells, respectively, showed apparent cytotoxicity on A431 and MDA-MB-231 cells but not on HeLa or HEK293 cells. In contrast, no cytotoxicity was observed for these cells treated with either Gh-TDHR46E or EB alone, indicating enhanced cytotoxic efficacy of Gh-TDHR46E by the EGFR binding moiety. Further antitumor activity assay of Gh-TDHR46E/EB in a xenograft model of athymic nude mice showed obvious shrinkage of tumor size and degeneration, necrosis, and lesions of tumor tissues compared to the normal tissues. Therefore, the combination of Gh-TDHR46E with target affinity agents opens new possibilities for pharmacological treatment of cancers and potentiates the anticancer drug's effect.
Respiratory Feature Extraction in Emotion of Internet Addiction Abusers Using Complementary Ensemble Empirical Mode Decomposition
(2015-04-01)
Hsieh, Dai-Ling
;
Ji, Hong-Ming
;
Hsiao, Tzu-Chien
;
Yip, Bak-Sau
;
分子醫學與生物工程研究所
Background: Internet addiction can be generally conceptualized as excessive computer and Internet use which results in negative consequences in physical or mental functions. In recent years, Internet addiction is a growing problem around the world, and should be studied through scientific methods. Some studies indicated that Internet addiction was correlated to physical responses including heart rate, respiration, and psychological reactions including emotion, social interaction. This study assumed that emotion was one of significant roles in Internet addiction, and emotion can be observed by subjective self-report and objective autonomic nervous responses. Respiration can be a type of biofeedback to regulate respiratory rate and amplitude which affects autonomic nervous responses. The respiratory features in emotion states of Internet addiction abusers were investigated by Complementary Ensemble Empirical Mode Decomposition. Results: The results showed that the respiratory features of Internet addiction abusers differed from normal Internet users among different emotions. Such results could be expected to monitor or assist to treat Internet addiction.
The Thermostable Direct Hemolysin from Grimontia hollisae Causes Acute Hepatotoxicity In Vitro and In Vivo
(2013-02-21)
Lin, Yan-Ren
;
Chen, Yao-Li
;
Wang, Keh-Bin
;
Wu, Yi-Fang
;
Wang, Yu-Kuo
Background: G. hollisae thermostable direct hemolysin (Gh-TDH) is produced by most strains of G. hollisae. This toxin has been reported to be absorbed in the intestines in humans. Secondary liver injury might be caused by venous return of the toxin through the portal system. We aimed to firstly analyze the in vitro and in vivo hepatotoxicity of Gh-TDH. Methods: Liver cells (primary human non-cancer cell and FL83B mouse cells) were treated and mice (BALB/c) were fed with this toxin to investigate its hepatotoxicity. Morphological examination and cytotoxicity assays using liver cells were also performed. Fluorescein isothiocyanate-conjugated toxin was used to analyze the localization of this protein in liver cells. Mice were subjected to liver function measurements and liver biopsies following toxin treatment and wild-type bacterial infection. PET (positron emission tomography)/CT (computed tomography) images were taken to assess liver metabolism during acute injury and recovery. Results: The effect of hepatotoxicity was dose and time dependent. Cellular localization showed that the toxin was initially located around the cellular margins and subsequently entered the nucleus. Liver function measurements and liver biopsies of the mice following treatment with toxin or infection with wild-type Grimontia hollisae showed elevated levels of transaminases and damage to the periportal area, respectively. The PET/CT images revealed that the reconstruction of the liver continued for at least one week after exposure to a single dose of the toxin or bacterial infection. Conclusions: The hepatotoxicity of Gh-TDH was firstly demonstrated. The damage was located in the periportal area of the liver, and the liver became functionally insufficient.