Absorption of x-radiation by single crystals of proteins containing labile metal components: the determination of the number of iron atoms within the central core of ferritin

The number of metal atoms contained within a displaceable inorganic component of a metalloprotein was determined by considering X-ray absorption by single crystal samples of holo- and apo-proteins. Since this method is non-destructive, it can be used to determine the number of metal atoms associated with the molecules forming the crystal actually used for X-ray diffraction data collection and subsequent structure solution. The method has been applied to the iron storage protein ferritin, isolated from horse spleen, to give a reliable estimate of the average iron content of the ferritin molecules within the crystal. This value, of around 2000 iron atoms per molecule is consistent with that found for a typical ferritin preparation in solution and suggests non-selectivity of the crystallisation process for ferritin in terms of molecular iron content.     

Properties of a new crystal form of the complex of concanavalin A with methyl alpha-D-glucopyranoside

The complex of concanavalin A with methyl alpha-D-glucopyranoside crystallizes as regular rhombic dodecahedra containing 35% protein by weight. The crystal is of space group I23 with a = 167.8 A (1 A = 0.1 nm) and contains one concanavalin A dimer per asymmetric unit. It diffracts to a resolution of 1.9 A and is suitable for crystallographic investigation of the structure of the saccharide-binding site.     

Vegetation establishment on chalk marl spoil: the role of nurse grass species and fertiliser application

Abstract. The Channel Tunnel workings on the UK side have yielded nearly 4 million m³ of chalk-marl spoil which now forms a 36 ha landscaped reclamation platform. To establish vegetation of amenity and conservation interest on the spoil, seed mixtures of native wild flowers and grasses were sown with Lolium perenne (perennial rye grass) as a nurse species. Potentially, L. perenne is a suitable nurse species for grassland creation on infertile substrates as it provides rapid initial cover and stability, but it is non-persistent and declines in vigour with time, allowing wild flower species sown alongside to expand their cover and spread in the longer term. On very low fertility substrates like chalk marl, an initial application of fertilizer is needed to encourage plant growth. Results are reported of a fertilizer experiment on Channel Tunnel spoil to determine appropriate levels of fertilizer for establishment of species-rich grassland vegetation. An area hydroseeded with L. perenne and wild flowers in autumn 1992 was subjected to factorial treatment of four levels each of N and P in spring 1993. The results the following summer showed significant positive effects of nitrogen and phosphorus on L. perenne biomass and a negative impact of nitrogen on densities of wild flower species, especially legumes, establishing in the L. perenne sward. In general, low fertilizer applications encouraged low productivity and maximal species richness in the vegetation. Conversely high applications encouraged high productivity and competitive exclusion of sown wild flower species. Fertilizer applications must therefore balance encouragement of the stabilising nurse grass sward, while preventing competitive exclusion of wild flowers by the nurse grass.     

Effects of X-Ray Dose On Rhizosphere Studies Using X-Ray Computed Tomography

X-ray Computed Tomography (CT) is a non-destructive imaging technique originally designed for diagnostic medicine, which was adopted for rhizosphere and soil science applications in the early 1980s. X-ray CT enables researchers to simultaneously visualise and quantify the heterogeneous soil matrix of mineral grains, organic matter, air-filled pores and water-filled pores. Additionally, X-ray CT allows visualisation of plant roots in situ without the need for traditional invasive methods such as root washing. However, one routinely unreported aspect of X-ray CT is the potential effect of X-ray dose on the soil-borne microorganisms and plants in rhizosphere investigations. Here we aimed to i) highlight the need for more consistent reporting of X-ray CT parameters for dose to sample, ii) to provide an overview of previously reported impacts of X-rays on soil microorganisms and plant roots and iii) present new data investigating the response of plant roots and microbial communities to X-ray exposure. Fewer than 5% of the 126 publications included in the literature review contained sufficient information to calculate dose and only 2.4% of the publications explicitly state an estimate of dose received by each sample. We conducted a study involving rice roots growing in soil, observing no significant difference between the numbers of root tips, root volume and total root length in scanned versus unscanned samples. In parallel, a soil microbe experiment scanning samples over a total of 24 weeks observed no significant difference between the scanned and unscanned microbial biomass values. We conclude from the literature review and our own experiments that X-ray CT does not impact plant growth or soil microbial populations when employing a low level of dose (<30 Gy). However, the call for higher throughput X-ray CT means that doses that biological samples receive are likely to increase and thus should be closely monitored.     

Repeated oral administration of capsaicin increases anxiety-like behaviours with prolonged stress-response in rats

This study was conducted to examine the psycho-emotional effects of repeated oral exposure to capsaicin, the principal active component of chili peppers. Each rat received 1 mL of 0.02% capsaicin into its oral cavity daily, and was subjected to behavioural tests following 10 daily administrations of capsaicin. Stereotypy counts and rostral grooming were significantly increased, and caudal grooming decreased, in capsaicin-treated rats during the ambulatory activity test. In elevated plus maze test, not only the time spent in open arms but also the percent arm entry into open arms was reduced in capsaicin-treated rats compared with control rats. In forced swim test, although swimming duration was decreased, struggling increased in the capsaicin group, immobility duration did not differ between the groups. Repeated oral capsaicin did not affect the basal levels of plasma corticosterone; however, the stress-induced elevation of plasma corticosterone was prolonged in capsaicin treated rats. Oral capsaicin exposure significantly increased c-Fos expression not only in the nucleus tractus of solitarius but also in the paraventricular nucleus. Results suggest that repeated oral exposure to capsaicin increases anxiety-like behaviours in rats, and dysfunction of the hypothalamic-pituitary-adrenal axis may play a role in its pathophysiology.     

Alternative Mechanisms for Fast Na+/Ca2+ Signaling in Eukaryotes via a Novel Class of Single-Domain Voltage-Gated Channels

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