Use of UV absorbance To monitor furans in dilute acid hydrolysates of biomass

A simple method based on UV spectra was developed for the estimation of total furans (furfural and hydroxymethylfurfural) in hemicellulose hydrolysates. UV spectra of hemicellulose hydrolysate contained a single dominant peak at around 278 nm. Approximately two-thirds of this peak can be attributed to furan absorbance (furfural and hydroxymethylfurfural). At 284 nm, both furfural and hydroxymethylfurfural have equal absorbance on a weight basis. A comparison of HPLC determinations for different samples of hydrolysate was used to develop a simple equation that allows the accurate prediction of total furans based on the difference in absorbance at 284 and 320 nm. This method may prove useful for quality control applications during the production of biomass syrups using a dilute acid hydrolysis process and during treatments for the amelioration of toxins. Although furans represent only a portion of the toxins present in hemicellulose hydrolysates, the abundance of furans appears to serve as a useful marker to predict relative toxicity.     

The auxilin-like phosphoprotein Swa2p is required for clathrin function in yeast

BACKGROUND: In eukaryotic cells, clathrin-coated vesicles transport specific cargo from the plasma membrane and trans-Golgi network to the endosomal system. Removal of the clathrin coat in vitro requires the uncoating ATPase Hsc70 and its DnaJ cofactor auxilin. To date, a requirement for auxilin and Hsc70 in clathrin function in vivo has not been demonstrated. RESULTS: The Saccharomyces cerevisiae SWA2 gene, previously identified in a synthetic lethal screen with arf1, was cloned and found to encode a protein with a carboxy-terminal DnaJ domain which is homologous to that of auxilin. Like auxilin, Swa2p has a clathrin-binding domain and is able to stimulate the ATPase activity of Hsc70. The swa2-1 allele recovered from the original screen carries a point mutation in its tetratricopeptide repeat (TPR) domain, a motif not found in auxilin but known in other proteins to mediate interaction with heat-shock proteins. Swa2p fractionates in the cytosol and appears to be heavily phosphorylated. Disruption of SWA2 causes slow growth and several phenotypes that are very similar to those exhibited by clathrin mutants. Furthermore, the swa2Delta mutant exhibits a significant increase in membrane- associated or -assembled clathrin relative to a wild-type strain. CONCLUSIONS: These results indicate that Swa2p is a clathrin-binding protein required for normal clathrin function in vivo. They suggest that Swa2p is the yeast ortholog of auxilin and has a role in disassembling clathrin, not only in uncoating clathrin-coated vesicles but perhaps in preventing unproductive clathrin assembly in vivo.     

A dual-luciferase reporter system for studying recoding signals.

A new reporter system has been developed for measuring translation coupling efficiency of recoding mechanisms such as frameshifting or readthrough. A recoding test sequence is cloned in between the renilla and firefly luciferase reporter genes and the two luciferase activities are subsequently measured in the same tube. The normalized ratio of the two activities is proportional to the efficiency with which the ribosome "reads" the recoding signal making the transition from one open reading frame to the next. The internal control from measuring both activities provides a convenient and reliable assay of efficiency. This is the first enzymatic dual reporter assay suitable for in vitro translation. Translation signals can be tested in vivo and in vitro from a single construct, which allows an intimate comparison between the two systems. The assay is applicable for high throughput screening procedures. The dual-luciferase reporter system has been applied to in vivo and in vitro recoding of HIV-1 gag-pol, MMTV gag-pro, MuLV gag-pol, and human antizyme.     

Effects of process errors on the production of ethanol by Escherichia coli KO11

Escherichia coli KO11 was previously constructed for the production of ethanol from both hexose and pentose sugars in hemicellulose hydrolysates by inserting the Zymomonas mobilis genes encoding pyruvate decarboxylase (pdc) and alcohol dehydrogenase (adhB). This biocatalyst appears relatively resistant to potential process errors during fermentation. Antibiotics were not required to maintain the maximum catabolic activity of KO11 even after deliberate contamination with up to 10% soil. Fermentations exposed to extremes of temperature (2 h at 5°C or 50°C) or pH (2 h at pH 3 or pH 10) recovered after re-adjustment to optimal fermentation conditions (35°C, pH6) although longer times were required for completion in most cases. Ethanol yields were not altered by exposure to extremes in temperature but were reduced by exposure to extremes in pH. Re-inoculation with 5% (by volume) from control fermentors reduced this delay after exposure to pH extremes. Received 24 July 1997/ Accepted in revised form 16 April 1998     

Widespread positive but weak assortative mating by diet within stickleback populations

Assortative mating – correlation between male and female traits – is common within populations and has the potential to promote genetic diversity and in some cases speciation. Despite its importance, few studies have sought to explain variation in the extent of assortativeness across populations. Here, we measure assortative mating based on an ecologically important trait, diet as inferred from stable isotopes, in 16 unmanipulated lake populations of three‐spine stickleback. As predicted, we find a tendency toward positive assortment on the littoral–pelagic axis, although the magnitude is consistently weak. These populations vary relatively little in the strength of assortativeness, and what variation occurs is not explained by hypothesized drivers including habitat cosegregation, the potential for disruptive selection, costs to choosiness, and the strength of the relationship between diet and body size. Our results support recent findings that most assortative mating is positive, while suggesting that new approaches may be required to identify the environmental variables that drive the evolution of nonrandom mating within populations.     

Comparing plasma and faecal measures of steroid hormones in Adelie penguins Pygoscelis adeliae

Physiological measurements of both stress and sex hormones are often used to estimate the consequences of natural or human-induced change in ecological studies of various animals. Different methods of hormone measurement exist, potentially explaining variation in results across studies; methods should be cross-validated to ensure that they correlate. We directly compared faecal and plasma hormone measurements for the first time in a wild free-living species, the Adelie penguin (Pygoscelis adeliae). Blood and faecal samples were simultaneously collected from individual penguins for comparison and assayed for testosterone and corticosterone (or their metabolites). Sex differences and variability within each measure, and correlation of values across measures were compared. For both hormones, plasma samples showed greater variation than faecal samples. Males had higher mean corticosterone concentrations than females, but the difference was only statistically significant in faecal samples. Plasma testosterone, but not faecal testosterone, was significantly higher in males than females. Correlation between sample types was poor overall, and weaker in females than in males, perhaps because measures from plasma represent hormones that are both free and bound to globulins, whereas measures from faeces represent only the free portion. Faecal samples also represent a cumulative measure of hormones over time, as opposed to a plasma ‘snapshot’ concentration. Our data indicate that faecal sampling appears more suitable for assessing baseline hormone concentrations, whilst plasma sampling may best define immediate responses to environmental events. Consequently, future studies should ensure that they select the most appropriate matrix and method of hormone measurement to answer their research questions.     

Patient-orientated longitudinal study of multiple sclerosis in south west England (The South West Impact of Multiple Sclerosis Project,SWIMS) 1: protocol and baseline characteristics of cohort

Background  

There is a need for greater understanding of the impact of multiple sclerosis (MS) from the perspective of individuals with the condition. The South West Impact of MS Project (SWIMS) has been designed to improve understanding of disease impact using a patient-centred approach. The purpose is to (1) develop improved measurement instruments for clinical trials, (2) evaluate longitudinal performance of a variety of patient-reported outcome measures, (3) develop prognostic predictors for use in individualising drug treatment for patients, particularly early on in the disease course.