The dynamics of bax channel formation: influence of ionic strength

Mitochondrial outer membrane permeabilization (MOMP) is a complex multistep process. Studies of MOMP in vivo are limited by the stochastic variability of MOMP between cells and rapid completion of IMS protein release within single cells. In vitro models have provided useful insights into MOMP. We have investigated the dynamics of Bax-mediated MOMP in isolated mitochondria using ionic strength as a tool to control the rate of MOMP. We find that Bax can induce both transient permeabilization, detected by protein release, and more substantial long-lasting permeabilization, measured by the rate of oxidation of added cytochrome c. We found that higher ionic strength causes Bax to form small channels quickly but the expansion of these early channels is impeded. This inhibitory effect of ionic strength is independent of tBid. Channels formed under low ionic strength are not destabilized by raising the ionic strength. Increase in ionic strength also increases the ability of Bcl-xL to inhibit Bax-mediated MOMP. Ionic strength does not affect Bax insertion into mitochondria. Thus, ionic strength influences the assembly of Bax molecules already in membrane into channels. Ionic strength can be used as an effective biophysical tool to study Bax-mediated channel formation.     

Predicting protein structural class by SVM with class-wise optimized features and decision probabilities

Determination of protein structural class solely from sequence information is a challenging task. Several attempts to solve this problem using various methods can be found in literature. We present support vector machine (SVM) approach where probability-based decision is used along with class-wise optimized feature sets. This approach has two distinguishing characteristics from earlier attempts: (1) it uses class-wise optimized features and (2) decisions of different SVM classifiers are coupled with probability estimates to make the final prediction. The algorithm was tested on three datasets, containing 498 domains, 1092 domains and 5261 domains. Ten-fold external cross-validation was performed to assess the performance of the algorithm. Significantly high accuracy of 92.89% was obtained for the 498-dataset. We achieved 54.67% accuracy for the dataset with 1092 domains, which is better than the previously reported best accuracy of 53.8%. We obtained 59.43% prediction accuracy for the larger and less redundant 5261-dataset. We also investigated the advantage of using class-wise features over union of these features (conventional approach) in one-vs.-all SVM framework. Our results clearly show the advantage of using class-wise optimized features. Brief analysis of the selected class-wise features indicates their biological significance.     

Pervasiveness of UVC254-resistant Geobacillus strains in extreme environments

Applied Microbiology and Biotechnology - We have characterized a broad collection of extremophilic bacterial isolates from a deep subsurface mine, compost dumping sites, and several hot spring...     

Acute toxicity of prostaglandins E2,F2α and 15 (s) 15 methyl prostaglandin E2 methyl ester in the baboon

The cardiovascular, uterine stimulant and gastrointestinal effects of prostaglandins E₂, F_2α and 15 (S) 15 methyl PGE₂ methyl ester in the East African Baboon (P. Anubis) have been studied. In these three parameters the baboon responds both qualitatively and quantitatively in a similar manner to man. The lethal doses of the prostaglandins given by bolus intravenous injelctions have been determined and the human lethal doses estimated.     

STUDIES ON THE MARINE ALGAL FLORA OF VENEZUELA. V. PSEUDOGLOIOPHLOEA HALLIAE1,2

Details of structure and reproduction, particularly pre- and postfertilization development, are given for the first time in Pseudogloiophloea halliae. In general, the author's observations agree with what is known for most species of the genus. Some remarks on the identity of 3 species of Pseudogloiophloea in the tropical and subtropical American Atlantic shores are also included.     

Physiologic determinants of radiation resistance in Deinococcus radiodurans

Immense volumes of radioactive wastes, which were generated during nuclear weapons production, were disposed of directly in the ground during the Cold War, a period when national security priorities often surmounted concerns over the environment. The bacterium Deinococcus radiodurans is the most radiation-resistant organism known and is currently being engineered for remediation of the toxic metal and organic components of these environmental wastes. Understanding the biotic potential of D. radiodurans and its global physiological integrity in nutritionally restricted radioactive environments is important in development of this organism for in situ bioremediation. We have previously shown that D. radiodurans can grow on rich medium in the presence of continuous radiation (6,000 rads/h) without lethality. In this study we developed a chemically defined minimal medium that can be used to analyze growth of this organism in the presence and in the absence of continuous radiation; whereas cell growth was not affected in the absence of radiation, cells did not grow and were killed in the presence of continuous radiation. Under nutrient-limiting conditions, DNA repair was found to be limited by the metabolic capabilities of D. radiodurans and not by any nutritionally induced defect in genetic repair. The results of our growth studies and analysis of the complete D. radiodurans genomic sequence support the hypothesis that there are several defects in D. radiodurans global metabolic regulation that limit carbon, nitrogen, and DNA metabolism. We identified key nutritional constituents that restore growth of D. radiodurans in nutritionally limiting radioactive environments.     

Neoxanthin prevents H2O2-induced cytotoxicity in HepG2 cells by activating endogenous antioxidant signals and suppressing apoptosis signals

Molecular Biology Reports - The liver has a solid inbuilt antioxidant defense system to regulate oxidative stress. However, exposure to an excessive level of ROS causes liver injury. This study...