Excitation energy transfer kinetics and efficiency in phototrophic green sulfur bacteria

A series of spectroscopic measurements were performed on membrane fractions and detergent-solubilized complexes from the green sulfur bacterium (GSB) Chlorobaculum (Cba.) tepidum. The excitation migration through the entire GSB photosynthetic apparatus cannot be observed upon excitation of membranes in the chlorosome region at 77?K. In order to observe energy transfer from the Fenna-Matthews-Olson (FMO) protein to the reaction center (RC), FMO was directly excited at ~800?nm in transient absorption experiments. However, interpretation of the results is complicated by the spectral overlap between FMO and the RC. The availability of the Y16F FMO mutant, whose absorption spectrum is drastically different from that of the WT, has enabled the selection of spectral regions where either only FMO or the RC contributes. The application of a directed kinetic modeling approach, or target analysis, revealed the various decay and energy transfer pathways within the pigment-protein complexes. The calculated FMO-to-RC excitation energy transfer efficiencies are approximately 25% and 48% for the Y16F and WT samples, respectively.     

PCR primers for microsatellite loci in the desert tortoise (Gopherus agassizii,Testudinidae)

The desert tortoise, Gopherus agassizii, is a threatened species native to the North American desert southwest and is recognized as having distinct Mojave and Sonoran populations. We identified six polymorphic microsatellite loci in the desert tortoise. All six loci were polymorphic in Sonoran samples. Five of the loci were variable in Mojave samples with varying degrees of amplification success. Two of the loci exhibited low allelic variation (2–3 alleles) while four were highly variable (8–27 alleles).     

Regenerating cellulose from ionic liquids for an accelerated enzymatic hydrolysis

The efficient conversion of lignocellulosic materials into fuel ethanol has become a research priority in producing affordable and renewable energy. The pretreatment of lignocelluloses is known to be key to the fast enzymatic hydrolysis of cellulose. Recently, certain ionic liquids (ILs) were found capable of dissolving more than 10wt% cellulose. Preliminary investigations [Dadi, A.P., Varanasi, S., Schall, C.A., 2006. Enhancement of cellulose saccharification kinetics using an ionic liquid pretreatment step. Biotechnol. Bioeng. 95, 904-910; Liu, L., Chen, H., 2006. Enzymatic hydrolysis of cellulose materials treated with ionic liquid [BMIM]Cl. Chin. Sci. Bull. 51, 2432-2436; Dadi, A.P., Schall, C.A., Varanasi, S., 2007. Mitigation of cellulose recalcitrance to enzymatic hydrolysis by ionic liquid pretreatment. Appl. Biochem. Biotechnol. 137-140, 407-421] suggest that celluloses regenerated from IL solutions are subject to faster saccharification than untreated substrates. These encouraging results offer the possibility of using ILs as alternative and non-volatile solvents for cellulose pretreatment. However, these studies are limited to two chloride-based ILs: (a) 1-butyl-3-methylimidazolium chloride ([BMIM]Cl), which is a corrosive, toxic and extremely hygroscopic solid (m.p. approximately 70 degrees C), and (b) 1-allyl-3-methylimidazolium chloride ([AMIM]Cl), which is viscous and has a reactive side-chain. Therefore, more in-depth research involving other ILs is much needed to explore this promising pretreatment route. For this reason, we studied a number of chloride- and acetate-based ILs for cellulose regeneration, including several ILs newly developed in our laboratory. This will enable us to select inexpensive, efficient and environmentally benign solvents for processing cellulosic biomass. Our data confirm that all regenerated celluloses are less crystalline (58-75% lower) and more accessible to cellulase (>2 times) than untreated substrates. As a result, regenerated Avicel((R)) cellulose, filter paper and cotton were hydrolyzed 2-10 times faster than the respective untreated celluloses. A complete hydrolysis of Avicel((R)) cellulose could be achieved in 6h given the Trichoderma reesei cellulase/substrate ratio (w/w) of 3:20 at 50 degrees C. In addition, we observed that cellulase is more thermally stable (up to 60 degrees C) in the presence of regenerated cellulose. Furthermore, our systematic studies suggest that the presence of various ILs during the hydrolysis induced different degrees of cellulase inactivation. Therefore, a thorough removal of IL residues after cellulose regeneration is highly recommended, and a systematic investigation on this subject is much needed.     

Classification of hybrid and altered Vibrio cholerae strains by CTX prophage and RS1 element structure

Analysis of the CTX prophage and RS1 element in hybrid and altered Vibrio cholera O1 strains showed two classifiable groups. Group I strains contain a tandem repeat of classical CTX prophage on the small chromosome. Strains in this group either contain no element(s) or an additional CTX prophage or RS1 element(s) on the large chromosome. Group II strains harbor RS1 and CTX prophage, which has an E1 Tor type rstR and classical ctxB on the large chromosome.     

Identification of MarvelD3 as a tight junction-associated transmembrane protein of the occludin family

Background

Protein translocation across the membrane of the Endoplasmic Reticulum (ER) is the first step in the biogenesis of secretory and membrane proteins. Proteins enter the ER by the Sec61 translocon, a proteinaceous channel composed of three subunits, α, β and γ. While it is known that Sec61α forms the actual channel, the function of the other two subunits remains to be characterized.

Results

In the present study we have investigated the function of Sec61β in Drosophila melanogaster. We describe its role in the plasma membrane traffic of Gurken, the ligand for the Epidermal Growth Factor (EGF) receptor in the oocyte. Germline clones of the mutant allele of Sec61β show normal translocation of Gurken into the ER and transport to the Golgi complex, but further traffic to the plasma membrane is impeded. The defect in plasma membrane traffic due to absence of Sec61β is specific for Gurken and is not due to a general trafficking defect.

Conclusion

Based on our study we conclude that Sec61β, which is part of the ER protein translocation channel affects a post-ER step during Gurken trafficking to the plasma membrane. We propose an additional role of Sec61β beyond protein translocation into the ER.     

Prophylactic and Therapeutic Efficacy of Avian Antibodies Against Influenza Virus H5N1 and H1N1 in Mice

Background

Pandemic influenza poses a serious threat to global health and the world economy. While vaccines are currently under development, passive immunization could offer an alternative strategy to prevent and treat influenza virus infection. Attempts to develop monoclonal antibodies (mAbs) have been made. However, passive immunization based on mAbs may require a cocktail of mAbs with broader specificity in order to provide full protection since mAbs are generally specific for single epitopes. Chicken immunoglobulins (IgY) found in egg yolk have been used mainly for treatment of infectious diseases of the gastrointestinal tract. Because the recent epidemic of highly pathogenic avian influenza virus (HPAIV) strain H5N1 has resulted in serious economic losses to the poultry industry, many countries including Vietnam have introduced mass vaccination of poultry with H5N1 virus vaccines. We reasoned that IgY from consumable eggs available in supermarkets in Vietnam could provide protection against infections with HPAIV H5N1.

Methods and Findings

We found that H5N1-specific IgY that are prepared from eggs available in supermarkets in Vietnam by a rapid and simple water dilution method cross-protect against infections with HPAIV H5N1 and related H5N2 strains in mice. When administered intranasally before or after lethal infection, the IgY prevent the infection or significantly reduce viral replication resulting in complete recovery from the disease, respectively. We further generated H1N1 virus-specific IgY by immunization of hens with inactivated H1N1 A/PR/8/34 as a model virus for the current pandemic H1N1/09 and found that such H1N1-specific IgY protect mice from lethal influenza virus infection.

Conclusions

The findings suggest that readily available H5N1-specific IgY offer an enormous source of valuable biological material to combat a potential H5N1 pandemic. In addition, our study provides a proof-of-concept for the approach using virus-specific IgY as affordable, safe, and effective alternative for the control of influenza outbreaks, including the current H1N1 pandemic.     

Isolation of a Cellodextrinase from Bacteroides succinogenes

An enzyme which released the cellobiose group from p-nitrophenyl cellobioside was isolated from the periplasmic space of Bacteroides succinogenes grown on Avicel crystalline cellulose in a continuous cultivation system and separated from endoglucanases by column chromatography. The molecular weight of the enzyme was approximately 40,000, as estimated by gel filtration. The enzyme has an isoelectric point of 4.9. The enzyme exhibited low hydrolytic activity on acid-swollen cellulose and practically no activity on carboxymethyl cellulose, Avicel cellulose, and cellobiose, but it hydrolyzed p-nitrophenyl lactoside and released cellobiose from cellotriose and from higher cello-oligosaccharides. These data demonstrate that the enzyme is a cellodextrinase with an exotype of function.     

Vegetative growth and frost hardiness of cloudberry (Rubus chamaemorus) as affected by temperature and photoperiod

The effect of photoperiod and temperature on growth and induction and development of frost hardiness in cloudberry ( Rubus chamaemorus L.) was examined in two experiments. The photoperiods were 8, 12 or 24 h and the temperatures were 18, 15, 12, 9, 4, 3, –3 or –4°C depending on the experiment. The level of hardiness was expressed as LT₆₆ or LT₅₀ (the lethal temperature for 66 or 50% of the plant material) for percentage of bud break and for the degree of coloring by triphenyltetrazolium chloride for rhizomes. The vegetative growth was clearly affected by daylength; petiole elongation, leaf growth, shoot dry weight and number of shoots per plant were all reduced under short days compared with long days. However, the photoperiod had no significant effect on hardening of buds or rhizomes. Hardening increased with successively decreasing temperatures. To get the maximum hardiness, plants had to be exposed to freezing temperatures.