The effect of light availability on the photosynthetic activity and productivity of outdoor cultures of Arthrospira platensis (Spirulina)

The basic requirement for establishing economically viable large-scale production of algal biomass, be it for food, feed, high-value product, or energy, is the ability to produce the biomass at a low price. To achieve this goal, an efficient production protocol is needed that ensures that the potential productivity is obtained at any given time. When productivity is defined by the ability to utilize the available solar radiation that drives photosynthesis, the production protocol must be optimized to meet this requirement. In the current study, we demonstrate that by modifying the light available to Arthrospira platensis cells cultured outdoors by a variety of options like modifying the standing biomass concentration, changing the mixing rate, or shading can change the potential photosynthetic activity and apparent activity. By optimizing the light available to algae cells under outdoor conditions, productivity can be increased by approximately 50 %, from 15.6 g m^?2 day^?1 in a culture that suffers from overexposure to light to 22.4 g m^?2 day^?1 in a culture in which light downregulation is minimized. Therefore, by using a variety of methodologies to estimate photosynthetic activity, we demonstrate that overexposing the cells to light may result in downregulation of the photosynthetic activity leading to photoinhibition and lower biomass productivity.     

Molecular Modeling for a Comparative Analysis of Interactions Between 2LTRZFP and 2-LTR-Circle Junctions

In eukaryotes, one of the most often noticed DNA-binding motifs are Cys2His2 zinc finger proteins which have been extensively utilized as a framework for designing novel DNA-binding proteins. In this study, the conformational change, and binding stability, affinity and interactions of the 2LTRZFP–HIV-1 2-LTR-circle junction complexes were successfully reproduced with MD simulations, MM-PBSA/GBSA and binding mode analyses. The binding free energies were obtained, and it was found that the calculated binding free energy of Zif1 is lower than Zif2 and together with pharmacophore modeling, these binding results indicate strong affinity of 2LTRZFP for the DNA. Mutants of 2LTRZFP were analyzed. The computed energies provided proof for a relationship between the binding free energy and total electrostatic interaction energy. The mutation in a key amino acid (Glu81Tyr) of the finger 3 in position 6 showed increased binding energy to the DNA. The result agrees with our previous study which showed that the HIV-1 IN may be hindered by the 2LTRZFP. The obtained results may assist in the design of ZFPs depended on the 2-LTR-circle junctions inhibition mechanism.

     

Travelers' malaria among foreigners at the Hospital for Tropical Diseases, Bangkok, Thailand - a 6-year review (2000-2005)

We retrospectively examined the charts of travelers admitted to the Hospital for Tropical Diseases, Bangkok, Thailand, with malaria during the years 2000-2005. Twenty-one cases of malaria were identified, of which 12 (57%) were Plasmodium vivax infections and 9 (43%) were P. falciparum infections. There was one mixed case with vivax and falciparum infection. Only 1 P. falciparum case had complications. All cases were successfully treated with standard antimalarial drugs. Only 3 of the 21 cases were thought to be acquired in Thailand, the rest were regarded to be imported.     

Human monoclonal antibodies to neutralize all dengue virus serotypes using lymphocytes from patients at acute phase of the secondary infection

The global spread of the four dengue virus serotypes (DENV-1 to -4) has made this virus a major and growing public health concern. Generally, pre-existing neutralizing antibodies derived from primary infection play a significant role in protecting against subsequent infection with the same serotype. By contrast, these pre-existing antibodies are believed to mediate a non-protective response to subsequent heterotypic DENV infections, leading to the onset of dengue illness. In this study, we prepared hybridomas producing human monoclonal antibodies (HuMAbs) against DENV using peripheral blood mononuclear cells (PBMCs) from patients in the acute phase (around 1 week after the onset of illness) or the convalescent phase (around 2weeks after the onset of illness) of secondary infection. Interestingly, a larger number of hybridoma clones was obtained from patients in the acute phase than from those in the convalescent phase. Most HuMAbs from acute-phase infections were cross-reactive with all four DENV serotypes and showed significant neutralization activity to all four DENV serotypes. Thus, secondary DENV infection plays a significant role in stimulating memory cells to transiently increase the number of antibody-secreting plasma cells in patients in the early phase after the secondary infection. These HuMAbs will enable us to better understand the protective and pathogenic effects of DENV infection, which could vary greatly among secondarily-infected individuals.     

Investigation of the Skin Anti-photoaging Potential of Swertia chirayita Secoiridoids Through the AP-1/Matrix Metalloproteinase Pathway by Molecular Modeling

International Journal of Peptide Research and Therapeutics - Secoiridoids are bioactive compounds, which are present in plants and exhibit anti-inflammatory activity. In this work, to understand...     

Vacuolar H+-ATPase is involved in preventing heavy metal-induced oxidative stress in Saccharomyces cerevisiae

In Saccharomyces cerevisiae, vacuolar H⁺-ATPase (V-ATPase) involved in the regulation of intracellular pH homeostasis has been shown to be important for tolerances to cadmium, cobalt and nickel. However, the molecular mechanism underlying the protective role of V-ATPase against these metals remains unclear. In this study, we show that cadmium, cobalt and nickel disturbed intracellular pH balance by triggering cytosolic acidification and vacuolar alkalinization, likely via their membrane permeabilizing effects. Since V-ATPase plays a crucial role in pumping excessive cytosolic protons into the vacuole, the metal-sensitive phenotypes of the Δvma2 and Δvma3 mutants lacking V-ATPase activity were supposed to result from highly acidified cytosol. However, we found that the metal-sensitive phenotypes of these mutants were caused by increased production of reactive oxygen species, likely as a result of decreased expression and activities of manganese superoxide dismutase and catalase. In addition, the loss of V-ATPase function led to aberrant vacuolar morphology and defective endocytic trafficking. Furthermore, the sensitivities of the Δvma mutants to other chemical compounds (i.e. acetic acid, H₂O₂, menadione, tunicamycin and cycloheximide) were a consequence of increased endogenous oxidative stress. These findings, therefore, suggest the important role of V-ATPase in preventing endogenous oxidative stress induced by metals and other chemical compounds.     

Designed zinc finger protein interacting with the HIV‐1 integrase recognition sequence at 2‐LTR‐circle junctions

Integration of HIV‐1 cDNA into the host genome is a crucial step for viral propagation. Two nucleotides, cytosine and adenine (CA), conserved at the 3′ end of the viral cDNA genome, are cleaved by the viral integrase (IN) enzyme. As IN plays a crucial role in the early stages of the HIV‐1 life cycle, substrate blockage of IN is an attractive strategy for therapeutic interference. In this study, we used the 2‐LTR‐circle junctions of HIV‐1 DNA as a model to design zinc finger protein (ZFP) targeting at the end terminal portion of HIV‐1 LTR. A six‐contiguous ZFP, namely 2LTRZFP was designed using zinc finger tools. The designed motif was expressed and purified from E. coli to determine its binding properties. Surface plasmon resonance (SPR) was used to determine the binding affinity of 2LTRZFP to its target DNA. The level of dissociation constant (K_d) was 12.0 nM. The competitive SPR confirmed that 2LTRZFP specifically interacted with its target DNA. The qualitative binding activity was subsequently determined by EMSA and demonstrated the aforementioned correlation. In addition, molecular modeling and binding energy analyses were carried out to provide structural insight into the binding of 2LTRZFP to the specific and nonspecific DNA target. It is suggested that hydrogen‐bonding interactions play a key role in the DNA recognition mechanisms of the designed ZFP. Our study suggested an alternative HIV therapeutic strategy using ZFP interference of the HIV integration process.     

Decolorization of synthetic melanoidins-containing wastewater by a bacterial consortium

The presence of melanoidins in molasses wastewater leads to water pollution both due to its dark brown color and its COD contents. In this study, a bacterial consortium isolated from waterfall sediment was tested for its decolorization. The identification of culturable bacteria by 16S rDNA based approach showed that the consortium composed of Klebsiella oxytoca, Serratia mercescens, Citrobacter sp. and unknown bacterium. In the context of academic study, prevention on the difficulties of providing effluent as well as its variations in compositions, several synthetic media prepared with respect to color and COD contents based on analysis of molasses wastewater, i.e., Viandox sauce (13.5% v/v), caramel (30% w/v), beet molasses wastewater (41.5% v/v) and sugarcane molasses wastewater (20% v/v) were used for decolorization using consortium with color removal 9.5, 1.13, 8.02 and 17.5%, respectively, within 2 days. However, Viandox sauce was retained for further study. The effect of initial pH and Viandox concentration on decolorization and growth of bacterial consortium were further determined. The highest decolorization of 18.3% was achieved at pH 4 after 2 day of incubation. Experiments on fresh or used medium and used or fresh bacterial cells, led to conclusion that the limitation of decolorization was due to nutritional deficiency. The effect of aeration on decolorization was also carried out in 2 L laboratory-scale suspended cell bioreactor. The maximum decolorization was 19.3% with aeration at KLa = 2.5836 h⁻¹ (0.1 vvm).