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The extreme ultraviolet absorption of vanadium dioxide is probed with attosecond transient absorption during a photoinduced phase transition. Measurements reveal an ultrafast rearrangement in the density of states suggestive of electron correlation and Mott physics.

Currently, there is a high demand for amaranth due to its ability to withstand harsh climatic conditions, making it an ideal crop in the changing climate. There is also increased awareness and education on its nutritional and overall health benefits, and the availability of improved recipes. However, the presence of hazards can hinder the commercialisation of amaranth, which is in most cases traded informally. Food safety issues along the amaranth value chain should, therefore, be addressed to cope with both production and safety demands. The objective of this study, therefore, was to develop a Hazard Analysis and Critical Control Point (HACCP) plan for hazards in the amaranth value chain in Uganda. The seven principles outlined by Codex Alimentarius were followed to develop the HACCP plan. A tree diagram was further used to identify each potential hazard at each processing stage and Critical Control Points (CCPs) along the chain. For the CCPs identified, reliable control mechanisms and corrective actions were established to fulfil the requirements set by the critical limits to guarantee the safety of the products. Verification and records systems were proposed to determine the effectiveness and traceability of the HACCP plan. For each of the identified CCPs, samples were collected purposively and analysed for chemical and microbial contaminants. From the analysis, fifteen processing stages, starting from the land section to cooking and serving, were identified. Out of these, eight stages were defined as CCPs. These were site selection, land and seedbed preparation, irrigation, market display/humidity control, washing before preparation, chopping, cooking, and holding time and serving. At CCP 1, soils were contaminated with lead and cadmium, mercury and aflatoxins but at considerably low levels. At CCP 2, organic fertilisers were only contaminated with E. coli. At CCP3, E. coli was present in irrigation water. Heavy metals were also present in the irrigation water but were below the critical limits. At CCP4, E. coli was absent in water and display surfaces. E. coli was, however, present on raw amaranth. S. aureus was detected on vendors' hands. At CCP5, water was not contaminated with E. coli. At CCP6, only personnel hands were infected with S. aureus and Enterobacteriaceae. No contamination was detected in CCP7 and CCP8. Strict control of E. coli in manure and water and S. aureus and Enterobacteriaceae on personnel hands is required to ensure the amaranth value chain attains good food safety output. Key words: Amaranth, food safety, prerequisite programs, HACCP plan, hazards, Uganda, INTRODUCTION Due to the rise of overnutrition and its health consequences in developing countries, there has been an increased public health awareness on proper nutrition. These efforts have led to [...]

An often limiting factor for studying protein folding by single-molecule fluorescence resonance energy transfer (FRET) is the ability to site-specifically introduce a photostable organic FRET donor (D) and a complementary acceptor (A) into a polypeptide chain. Using alternating-laser excitation and chymotrypsin inhibitor 2 as a model, we show that chemical labeling of a unique cysteine, followed by enzymatic modification of a reactive glutamine in an N-terminally appended substrate sequence recognition tag for transglutaminase (TGase) affords stoichiometrically D-/A-labeled protein suitable for single-molecule FRET experiments. Thermodynamic data indicate that neither the presence of the TGase tag nor D/A labeling perturbs protein stability. As the N terminus in proteins is typically solvent accessible, a TGase tag can (in principle) be appended to any protein of interest by genetic engineering. Two-step chemical/enzymatic labeling may thus represent a simple, low-cost, and widely available strategy for DIA labeling of proteins for FRET-based single-molecule protein folding studies, even for non-protein-experts laboratories.

We study protein and nucleic acid structure and dynamics using single-molecule FRET and alternating-laser excitation. Freely diffusing molecules are sorted into subpopulations based on single-molecule signals detected within 100 mu s to 1 ms. Distance distributions caused by fluctuations faster than 100 mu s are studied within these subpopulations by using time-correlated single-photon counting. Measured distance distributions for dsDNA can be accounted for by considering fluorophore linkers and fluorophore rotational diffusion, except that we find smaller fluctuations for internally labeled dsDNA than DNA with one of the fluorophores positioned at a terminal site. We find that the electrostatic portion of the persistence length of short single-stranded poly(dT) varies approximately as the ionic strength (l) to the -1/2 power (l(-1/2)), and that the average contribution to the contour length per base is 0.40-0.45 nm. We study unfolded chymotrypsin inhibitor 2 (02) and unfolded acyl-CoA binding protein (ACBP) even under conditions where folded and unfolded subpopulations coexist (contributions from folded proteins are excluded by using alternating-laser excitation). At lower denaturant concentrations, unfolded C12 and ACBP are more compact and display larger fluctuations than at higher denaturant concentrations where only unfolded proteins are present. The experimentally measured fluctuations are larger than the fluctuations predicted from a Gaussian chain model or a wormlike chain model. We propose that the larger fluctuations may indicate transient residual structure in the unfolded state.

Probing structures and dynamics within biomolecules using ensemble and single-molecule fluorescence resonance energy transfer requires the conjugation of fluorophores to proteins in a site-specific and thermodynamically nonperturbative fashion. Using single-molecule fluorescence-aided molecular sorting and the chymotrypsin inhibitor 2-subtilisin BPN' complex as an example, we demonstrate that protein-protein interactions can be exploited to afford site-specific labeling of a recombinant double-cysteine variant of CI2 without the need for extensive and time-consuming chromatography. The use of protein protein interactions for site-specific labeling of proteins is compatible with and complementary to existing chemistries for selective labeling of N-terminal cysteines, and could be extended to label multiple positions within a given polypeptide chain.

Common beans (Phaseolus vulgaris L) may be contaminated with heavy metals and aflatoxins. Cooked beans may also be contaminated with micro-organisms due to poor hygiene and sanitation practices. Hazard Analysis and Critical Control Point (HACCP), which is a globally recognised food safety program, was proposed as a suitable program to minimise/eliminate the risk of contamination. Therefore, the objective of this study was to develop a HACCP plan for dry common beans in Uganda and an accompanying food safety toolkit. The seven principles of HACCP as outlined by Codex Alimentarius were followed to develop a HACCP plan for the dry common beans value chain in Uganda. A decision tree diagram was further used to identify each potential hazard at each processing stage and Critical Control Points (CCPs) along the chain. The identification of the CCPs was further supported by an evaluation of the actual risk and severity of the hazard. For the CCP identified, reliable control mechanism and corrective actions were established to fulfill the requirements set by the critical limits to guarantee the safety of the products. Verification and records systems were proposed to determine the effectiveness and traceability of the HACCP plan. For identified CCPs, a co-creation methodology was used to develop the food safety toolkit. This was carried out in four sessions that included a background of the chain actors' ambitions to determine the suitability of the toolkit, assessment of CCPs, expert advice on the CCP and an exercise to develop concepts for each CCP. From the analysis, fourteen processing stages starting from land selection to cooking and serving were identified. Out of these, four stages were CCPs. These were land selection and preparation, storage, post-harvest drying, and cooking and serving. Hazards at the CCPs included heavy metals, mycotoxins, and micro-organisms such as S. aureus, E. coli, and Salmonella spp. A combination of good hygiene and sanitation practices and good agricultural practices were recommended as control measures against the hazards. To further equip the value chain actors with mitigation strategies, a food safety toolkit whose usefulness is to give the actors a systematic means to control identified CCPs was developed. In this regard, the toolkit and HACCP plan will complement each other. From the study results, implementation of the toolkit, followed by an assessment of its uptake and impact on livelihoods and food safety risks is recommended.Key words: Common beans, food safety toolkit, prerequisite programs, HACCP plan, hazards, Uganda, INTRODUCTIONFood safety is an essential condition for food quality, which implies the absence or occurrence, within acceptable limits, of hazards that may create risks for human health [1]. Hazards are [...]

A survey was sent to 33 managers at units and centres involved in Higher Education student-to-student support services in the form of peer help programmes. The survey focused on managers' perspectives on peer help programme demographics, management, planning and resourcing, on intra-institutional and other linkages, as well as on institutional commitment to peer helping. It also requested their views on challenges experienced in these areas, concluding with challenges related to peer programme sustainability. Thirty managers from a wide variety of settings such as student counselling, academic support and student health responded. Their responses articulated the strategic alignment of their programmes with institutional top priorities, functional linkages and partnerships with other institutional support structures and the dedication of staff and students involved in peer helping. Securing sufficient financial, human and physical resources appeared to form the core of their challenges in terms of peer programme management and sustainability.