Microalgal hydrogen production: prospects of an essential technology for a clean and sustainable energy economy

Modern energy production is required to undergo a dramatic transformation. It will have to replace fossil fuel use by a sustainable and clean energy economy while meeting the growing world energy needs. This review analyzes the current energy sector, available energy sources, and energy conversion technologies. Solar energy is the only energy source with the potential to fully replace fossil fuels, and hydrogen is a crucial energy carrier for ensuring energy availability across the globe. The importance of photosynthetic hydrogen production for a solar-powered hydrogen economy is highlighted and the development and potential of this technology are discussed. Much successful research for improved photosynthetic hydrogen production under laboratory conditions has been reported, and attempts are underway to develop upscale systems. We suggest that a process of integrating these achievements into one system to strive for efficient sustainable energy conversion is already justified. Pursuing this goal may lead to a mature technology for industrial deployment.     

Application of Nitrate Reductase for the Determination of Nitrate in Meat and Fishery Products

A rapid and specific method is described for the determination of nitrate in meat and fishery products.

Nitrate separated from foods by extraction with 1/50Ν sodium hydroxide and ultrafiltration was readily reduced to nitrite by the use of respiratory nitrate reductase (NR) from Escherichia coli K-12. The nitrite so obtained can be determined by the specific diazotation-coupling reaction method.

The use of an enzymatic reaction resulted in quantitative reduction of nitrate, and the method was relatively free of interferences. Recoveries of 10 and 100 ppm of nitrate from 5 samples of meat and fishery products ranged from 92.8 to 97.8% for 10 ppm and 97.8 to 99.4% for 100 ppm with a detection limit of 0.5 ppm.     

Muscle activation of patients suffering from asymmetric ankle osteoarthritis during isometric contractions and level walking – A time–frequency analysis

Asymmetric osteoarthritis (OA) is a common type of OA in the ankle joint. OA also influences the muscles surrounding a joint, however, little is known about the muscle activation in asymmetric ankle OA. Therefore, the aim of this study was to characterize the patients’ muscle activation during isometric ankle torque measurements and level walking. Surface electromyography (EMG) was measured of gastrocnemius medialis (GM) and lateralis (GL), soleus (SO), tibialis anterior (TA), and peroneus longus (PL) in 12 healthy subjects and 12 ankle OA patients. To obtain time and frequency components of the EMG power a wavelet transformation was performed. Furthermore, entropy was introduced to characterize the homogeneity of the wavelet patterns.Patients produced lower plantar- and dorsiflexion torques and their TA wavelet spectrum was shifted towards lower frequencies. While walking, the patients’ muscles were active with a lower intensity and over a broader time–frequency region. In contrast to controls and varus OA patients, maximal GM activity of valgus OA patients lagged behind the activity of GL and SO. In both tasks, PL of the valgus patients contained more low frequency power. The results of this study will help to assess whether surgical interventions of ankle OA can reestablish the muscle activation patterns.     

Topical Enzyme-Replacement Therapy Restores Transglutaminase 1 Activity and Corrects Architecture of Transglutaminase-1-Deficient Skin Grafts

Transglutaminase-1 (TG1)-deficient autosomal-recessive congenital ichthyosis (ARCI) is a rare and severe genetic skin disease caused by mutations in TGM1. It is characterized by collodion babies at birth, dramatically increased transepidermal water loss (TEWL), and lifelong pronounced scaling. The disease has a tremendous burden, including the problem of stigmatization. Currently, no therapy targeting the molecular cause is available, and the therapeutic situation is deplorable. In this study, we developed the basis for a causative therapy aiming at the delivery of the enzyme to the inner site of the keratinocytes’ plasma membrane. We prepared sterically stabilized liposomes with encapsulated recombinant human TG1 (rhTG1) and equipped with a highly cationic lipopeptide vector to mediate cellular uptake. The liposomes overcame the problems of insufficient cutaneous delivery and membrane penetration and provided excellent availability and activity of rhTG1 in primary keratinocytes. To demonstrate the general feasibility of this therapeutic approach in a humanized context, we used a skin-humanized mouse model. Treatment with rhTG1 liposomes resulted in considerable improvement of the ichthyosis phenotype and in normalization of the regenerated ARCI skin: in situ monitoring showed a restoration of TG1 activity, and cholesterol clefts vanished ultrastructurally. Measurement of TEWL revealed a restoration of epidermal barrier function. We regard this aspect as a major advance over available nonspecific approaches making use of, for example, retinoid creams. We conclude that this topical approach is a promising strategy for restoring epidermal integrity and barrier function and provides a causal cure for individuals with TG1 deficiency.     

Natural Variation in Maize Aphid Resistance Is Associated with 2,4-Dihydroxy-7-Methoxy-1,4-Benzoxazin-3-One Glucoside Methyltransferase Activity

Plants differ greatly in their susceptibility to insect herbivory, suggesting both local adaptation and resistance tradeoffs. We used maize (Zea mays) recombinant inbred lines to map a quantitative trait locus (QTL) for the maize leaf aphid (Rhopalosiphum maidis) susceptibility to maize Chromosome 1. Phytochemical analysis revealed that the same locus was also associated with high levels of 2-hydroxy-4,7-dimethoxy-1,4-benzoxazin-3-one glucoside (HDMBOA-Glc) and low levels of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one glucoside (DIMBOA-Glc). In vitro enzyme assays with candidate genes from the region of the QTL identified three O-methyltransferases (Bx10a-c) that convert DIMBOA-Glc to HDMBOA-Glc. Variation in HDMBOA-Glc production was attributed to a natural CACTA family transposon insertion that inactivates Bx10c in maize lines with low HDMBOA-Glc accumulation. When tested with a population of 26 diverse maize inbred lines, R. maidis produced more progeny on those with high HDMBOA-Glc and low DIMBOA-Glc. Although HDMBOA-Glc was more toxic to R. maidis than DIMBOA-Glc in vitro, BX10c activity and the resulting decline of DIMBOA-Glc upon methylation to HDMBOA-Glc were associated with reduced callose deposition as an aphid defense response in vivo. Thus, a natural transposon insertion appears to mediate an ecologically relevant trade-off between the direct toxicity and defense-inducing properties of maize benzoxazinoids.     

Environmental and Kinetic Parameters for Cr(VI) Bioreduction by a Bacterial Monoculture Purified from Cr(VI)-Resistant Consortium

Hexavalent chromium, Cr(VI), is toxic to living systems. Widespread contamination of water and soil by Cr(VI) present a serious public health problem. Chromium-resistant bacteria can reduce and detoxify Cr(VI). Twelve bacteria resistant to high concentrations of Cr(VI) were isolated from soil enrichment cultures. Environmental parameters and kinetic parameters of Cr(VI) bioreduction by one monoculture isolate, identified by 16S rRNA gene sequence as Bacillus sp. PB2, were studied. The optimal temperature for growth and Cr(VI) reduction was 35 degrees C. The isolate grew luxuriantly and substantially reduced Cr(VI) at initial pH 7.5 to 9. Maximal Cr(VI) bioreduction occurred at initial pH 8.0. Substantial Cr(VI) bioreduction was observed in salt media, but removal efficiency was inversely related to salt concentration (1-9%). Michaelis-Menten hyperbolic equation and the Lineweaver-Burk double reciprocal plot were comparatively employed to determine the k (m) and V (max) of Cr(VI) bioreduction. A k (m) of 82.5 microg mL(-1) and V (max) of 7.78 microg mL(-1) h(-1) were calculated by nonlinear regression analysis of the hyperbola curve. Linear regression analysis of the double reciprocal plot revealed k (m) and V (max) of 80.9 microg mL(-1) and 10.6 microg mL(-1) h(-1), respectively. Time course studies displayed about 90% reduction of Cr(VI) at an initial concentration of 8,000 microg L(-1) in 8 h, with an estimated t (1/2) of 4 h. Data from time course analysis of the rate of Cr(VI) bioreduction fitted zero-order model, and the kinetic constant k was calculated to be 840 microg L(-1) h(-1). The monoculture isolate, Bacillus sp. PB2, strongly reduces Cr(VI) and could be used for bioremediation of Cr(VI)-contaminated aquatic and terrestrial environments.     

Differentially oriented populations of actin filaments generated in lamellipodia collaborate in pushing and pausing at the cell front

Eukaryotic cells advance in phases of protrusion, pause and withdrawal. Protrusion occurs in lamellipodia, which are composed of diagonal networks of actin filaments, and withdrawal terminates with the formation of actin bundles parallel to the cell edge. Using correlated live-cell imaging and electron microscopy, we have shown that actin filaments in protruding lamellipodia subtend angles from 15-90 degrees to the front, and that transitions from protrusion to pause are associated with a proportional increase in filaments oriented more parallel to the cell edge. Microspike bundles of actin filaments also showed a wide angular distribution and correspondingly variable bilateral polymerization rates along the cell front. We propose that the angular shift of filaments in lamellipodia serves in adapting to slower protrusion rates while maintaining the filament densities required for structural support; further, we suggest that single filaments and microspike bundles contribute to the construction of the lamella behind and to the formation of the cell edge when protrusion ceases. Our findings provide an explanation for the variable turnover dynamics of actin filaments in lamellipodia observed by fluorescence speckle microscopy and are inconsistent with a current model of lamellipodia structure that features actin filaments branching at 70 degrees in a dendritic array.     

A high molecular weight glutamyl endopeptidase and its endogenous inhibitors from cucumber leaves

We purified a glutamyl endopeptidase that is a major foliar endopeptidase in cucumber. The endopeptidase had a molecular mass of 400 kDa, consisted of four subunits of 97 kDa, and was inactivated by SH-modifying reagents. Its optimum pH and optimum temperature were 8.0 and 30-37 degrees C, respectively. An internal amino acid sequence of the endopeptidase was highly homologous to a partial sequence of unidentified proteins deduced from genetic information for Arabidopsis thaliana, soybean and rice, but not to the sequences of bacterial glutamyl endopeptidases or animal proteases. Therefore, the unidentified proteins might be glutamyl endopeptidases and be widely distributed only among plant species. The activity of the cucumber glutamyl endopeptidase was inhibited by at least three inhibitors existing in cucumber leaves. One of the inhibitors was a competitive inhibitor of 25 kDa, which did not significantly inhibit commercial endopeptidases derived from animals and microorganisms. This suggests that the cucumber glutamyl endopeptidase might be controlled by endogenous inhibitors in vivo.     

Role of small GTP binding proteins in the growth-promoting and antiapoptotic actions of gastrin

G17 has growth promoting and antiapoptotic effects on the AR4-2J pancreatic acinar cell line. We previously reported that whereas MAPK regulates G17-stimulation of AR4-2J cell proliferation, Akt mediates the antiapoptotic action of G17. We examined the signal-transduction pathways mediating G17 stimulation of AR4-2J cell growth and survival. G17 activated the small GTP binding proteins Ras, Rac, Rho, and Cdc42. Transduction of the cells with adenoviral vectors expressing dominant negative Akt, Ras, Rho, and Cdc42 but not dominant negative Rac inhibited AR4-2J cell proliferation and survival. Both exoenzyme C3 from Clostridium botulinum (C3), a toxin known to inactivate Rho, and PD98059, a MAPK inhibitor, reversed G17 inhibition of AR4-2J cell apoptosis. G17 induction of Akt activation was reduced by >60% by both dominant negative Ras and Rho and by 30% by dominant negative Cdc42. In contrast, G17-stimulated MAPK activation was blocked by >80% by dominant negative Ras but not by dominant negative Rho and Cdc42. Similar results were observed in the presence of C3. Dominant negative Rac failed to affect G17 induction of both Akt and MAPK, whereas it inhibited sorbitol by almost 50% but not G17-stimulated activation of p38 kinase. Thus G17 promotes AR4-2J cell growth and survival through the activation of multiple GTP binding proteins, which, in turn, regulate different protein kinase cascades. Whereas Ras activates Akt and MAPK, Rho and Cdc42 appear to regulate Akt and possibly other as yet unidentified kinases mediating the growth-stimulatory actions of G17.