Change in electron and spin density upon electron transfer to haem

Haems are the cofactors of cytochromes and important catalysts of biological electron transfer. They are composed of a planar porphyrin structure with iron coordinated at the centre. It is known from spectroscopy that ferric low-spin haem has one unpaired electron at the iron, and that this spin is paired as the haem receives an electron upon reduction (I. Bertini, C. Luchinat, NMR of Paramagnetic Molecules in Biological Systems, Benjamin/Cummins Publ. Co., Menlo Park, CA, 1986, pp. 165-170; H.M. Goff, in: A.B.P. Lever, H.B. Gray (Eds.), Iron Porphyrins, Part I, Addison-Wesley Publ. Co., Reading, MA, 1983, pp. 237-281; G. Palmer, in: A.B.P. Lever, H.B. Gray (Eds.), Iron Porphyrins, Part II, Addison-Wesley Publ. Co., Reading, MA, 1983, pp. 43-88). Here we show by quantum chemical calculations on a haem a model that upon reduction the spin pairing at the iron is accompanied by effective delocalisation of electrons from the iron towards the periphery of the porphyrin ring, including its substituents. The change of charge of the iron atom is only approx. 0.1 electrons, despite the unit difference in formal oxidation state. Extensive charge delocalisation on reduction is important in order for the haem to be accommodated in the low dielectric of a protein, and may have impact on the distance dependence of the rates of electron transfer. The lost individuality of the electron added to the haem on reduction is another example of the importance of quantum mechanical effects in biological systems.     

The effect of the cassava green mite Mononychellus tanajoa on the growth and yield of cassava Manihot esculenta in a seasonally dry area in Kenya

The effect of the cassava green mite Mononychellus tanajoa on the growth and yield of cassava Manihot esculenta was studied over a 10-month period in two field trials near Lake Victoria in Kenya. One plot was maintained free of mites by means of acaricide, while the other was artificially infested.The highest population density of M. tanajoa occurred during the dry season. A maximum leaf area index (LAI) of about 2 was reached at the onset of the dry season. The total leaf area of mite infested plants was reduced compared with uninfested plants during the dry spell. During the following rainy season infested plants recovered and attained the same leaf area as uninfested plants. A multiple regression model predicting the leaf area showed that 58% of the seasonal variation could be explained by plant age, soil water, and leaf injury.The net growth rate of infested plants was lower than that of uninfested plants. Maximum values of 21 (infested plants) and 49 (uninfested plants) g m^-2 week^-1 were attained at the onset of the second rainy season. No difference was found between uninfested and infested plants with respect to net assimilation rates per unit leaf area during the dry season. The net assimilation rates reached a maximum almost at the same time as the growth rates, but the infested plants peaked slightly earlier and at a lower level than the uninfested plants. M. tanajoa did not affect the relative allocation of dry matter into stems and storage roots, but the absolute allocation of dry matter declined with increasing mite injury. Thus, after 10 months the dry matter of infested plants was reduced by 29% and 21% for storage roots and stems, respectively, compared with the uninfested plants.     

Structural and immunochemical identification of Leb glycolipids in the plasma of a group O Le(a-b-) secretor

Total non-acid glycosphingolipids were isolated from the plasma of a healthy red blood cell group O Le(a-b-) salivary ABH secretor individual. Glycolipids were fractionated by HPLC and combined into eight fractions based on chromatographic and immunoreactive properties. These glycolipid fractions were analysed by thin-layer chromatography and tested for Lewis activity with antibodies reactive to the type 1 precursor (Le^c), H type 1 (Le^d), Le^a and Le^b epitopes. Fractions were structurally characterized by mass spectrometry (EI-MS and LSIMS) and proton NMR spectroscopy. Expected blood group glycolipids, such as H type 1, (Fuc1-2Gal1-3GlcNAc1-3Gal1-4Glc1-1Cer) were immunochemically and structurally identified. Inconsistent with the red cell phenotype and for the first time, small quantities of Le^b blood group glycolipids (Fuc1-2Gal1-3(Fuc1-4)GlcNAc1-3Gal1-4Glc1-1Cer) were immunochemically and structurally identified in the plasma of a Lewis-negative individual. These findings confirm recent immunological evidence suggesting the production of small amounts of Lewis antigens by Lewis negative individuals. Abbreviations: HPLC, high performance liquid chromatography; TLC, (high performance) thin layer chromatography; EI-MS, electron impact ionisation mass spectrometry; LSIMS, liquid secondary ion mass spectrometry; NMR, nuclear magnetic resonance spectroscopy. The sugar types are abbreviated to Hex for hexose, HexNAc forN-acetylhexosamine and dHex for deoxyhexose (fucose). The ceramide types are abbreviated to d for dihydroxy and t for trihydroxy base, n for non-hydroxy and h for hydroxy fatty acids; LCB, long chain base.     

Using heterozygosity–fitness correlations to study inbreeding depression in an isolated population of white‐tailed deer founded by few individuals

A heterozygosity–fitness correlations (HFCs) may reflect inbreeding depression, but the extent to which they do so is debated. HFCs are particularly likely to occur after demographic disturbances such as population bottleneck or admixture. We here study HFC in an introduced and isolated ungulate population of white‐tailed deer Odocoileus virginianus in Finland founded in 1934 by four individuals. A total of 422 ≥ 1‐year‐old white‐tailed deer were collected in the 2012 hunting season in southern Finland and genotyped for 14 microsatellite loci. We find significant identity disequilibrium as estimated by g₂. Heterozygosity was positively associated with size‐ and age‐corrected body mass, but not with jaw size or (in males) antler score. Because of the relatively high identity disequilibrium, heterozygosity of the marker panel explained 51% of variation in inbreeding. Inbreeding explained approximately 4% of the variation in body mass and is thus a minor, although significant source of variation in body mass in this population. The study of HFC is attractive for game‐ and conservation‐oriented wildlife management because it presents an affordable and readily used approach for genetic monitoring that allowing identification of fitness costs associated with genetic substructuring in what may seem like a homogeneous population.     

Habitat-specific clutch size and cost of incubation in eiders reconsidered

The energetic incubation constraint hypothesis (EICH) for clutch size states that birds breeding in poor habitat may free up resources for future reproduction by laying a smaller clutch. The eider (Somateria mollissima) is considered a candidate for supporting this hypothesis. Clutch size is smaller in exposed nests, presumably because of faster heat loss and higher incubation cost, and, hence, smaller optimal clutch size. However, an alternative explanation is partial predation: the first egg(s) are left unattended and vulnerable to predation, which may disproportionately affect exposed nests, so clutch size may be underestimated. We experimentally investigated whether predation on first-laid eggs in eiders depends on nest cover. We then re-evaluated how nesting habitat affects clutch size and incubation costs based on long-term data, accounting for confounding effects between habitat and individual quality. We also experimentally assessed adult survival costs of nesting in sheltered nests. The risk of egg predation in experimental nests decreased with cover. Confounding between individual and habitat quality is unlikely, as clutch size was also smaller in open nests within individuals, and early and late breeders had similar nest cover characteristics. A trade-off between clutch and female safety may explain nest cover variation, as the risk of female capture by us, mimicking predation on adults, increased with nest cover. Nest habitat had no effect on female hatching weight or weight loss, while lower temperature during incubation had an unanticipated positive relationship with hatching weight. There were no indications of elevated costs of incubating larger clutches, while clutch size and colony size were positively correlated, a pattern not predicted by the ‘energetic incubation constraint’ hypothesis. Differential partial clutch predation thus offers the more parsimonious explanation for clutch size variation among habitats in eiders, highlighting the need for caution when analysing fecundity and associated life-history parameters when habitat-specific rates of clutch predation occur.     

Epizoochorous seed dispersal in relation to seed availability – an experiment with a red fox dummy

Questions: Is the red fox a potential vector for epizoochorous seed dispersal? Can seed attachment and retention be predicted from plant and seed traits? Location: Grasslands in southern Norway. Methods: Epizoochorous seed attachment on the red fox was studied by walking a dummy fox through the vegetation and comparing seeds found on the dummy with the estimated seed availability in the vegetation. Seed retention, i.e. the ability of different seeds to stay on the fox, was estimated in a separate experiment. Seed attachment and retention were related to plant and seed traits using statistical models that account for heteroscedasticity and zero‐inflated data. Results: The majority of seeds attached to the fox originated from a few species, but also species without specific seed traits that are supposed to enhance epizoochory attached at least some seeds to the fox. The probability of seed attachment was positively related to plant height, bristle and hooked seed appendages, and negatively related to winged appendages, seed mass, and seed sphericity. Seed retention was positively related to the seed traits bristles, hooks and pappus. For several species, the results indicate a high potential for dispersal over long distances. Conclusions: In modern agricultural landscapes, large herbivores are often restricted in their mobility or are found at low densities, and other animal vectors may therefore be important for seed dispersal. In our study, a range of plant species were able to disperse by attaching seeds to, and having their seeds retained in, the fox fur some distance. We suggest that the red fox may be an important vector for epizoochorous seed dispersal in the agricultural landscape.     

A 2nd Generation Linkage Map of Heterobasidion annosum s.l. Based on In Silico Anchoring of AFLP Markers

In this study, we present a 2^nd generation genetic linkage map of a cross between the North American species Heterobasidion irregulare and H. occidentale, based on the alignment of the previously published 1^st generation map to the parental genomes. We anchored 216 of the original 308 AFLP markers to their respective restriction sites using an in silico-approach. The map resolution was improved by adding 146 sequence-tagged microsatellite markers and 39 sequenced gene markers. The new markers confirmed the positions of the anchored AFLP markers, fused the original 39 linkage groups together into 17, and fully expanded 12 of these to single groups covering entire chromosomes. Map coverage of the genome increased from 55.3% to 92.8%, with 96.3% of 430 markers collinearly aligned with the genome sequence. The anchored map also improved the H. irregulare assembly considerably. It identified several errors in scaffold arrangements and assisted in reducing the total number of major scaffolds from 18 to 15. This denser, more comprehensive map allowed sequence-based mapping of three intersterility loci and one mating type locus. This demonstrates the possibility to utilize an in silico procedure to convert anonymous markers into sequence-tagged ones, as well as the power of a sequence-anchored linkage map and its usefulness in the assembly of a whole genome sequence.     

The relationship between anthropometric indexes of adiposity and vascular function in the FATE cohort

Objective:

Numerous indexes of adiposity have been proposed and are currently in use in clinical practice and research. However, the correlation of these indexes with measures of vascular health remain poorly defined. This study investigated which measure of adiposity is most strongly associated with endothelial function.

Design and Methods:

Data from the Firefighters And Their Endothelium (FATE) study was used. The relationships between three measures of vascular function: flow‐mediated dilation (FMD), hyperemic velocity time integral (VTI), and hyperemic shear stress (HSS), and five measures of adiposity: BMI, waist circumference (WC), waist‐to‐hip ratio (WHR), waist‐to‐height ratio (WHtR), and body adiposity index (BAI) were tested. Univariate comparisons were made, and subsequently models adjusted for traditional risk factors were constructed.

Results:

A total of 1,462 male firefighters (mean age 49 ± 9) without cardiovascular disease comprised the study population. No measure of adiposity correlated with FMD; all five measures of adiposity were negatively correlated with VTI and HSS (P values <0.0001), with WHtR most strongly correlated with VTI, and WC most strongly correlated with HSS (both P < 0.05). In models including all five measures of obesity simultaneously, BMI, WC, and WHtR were all predictive of HSS (all P values <0.05), and BMI and WHR were both predictive of VTI (P values <0.05).

Conclusions:

Anthropometric measures of adiposity may help refine estimations of atherosclerotic burden. BMI was most consistently associated with endothelial dysfunction, but measures of adiposity that reflect distribution of mass were additive.     

Bioturbation as Driver of Zooplankton Recruitment,Biodiversity and Community Composition in Aquatic Ecosystems

In an experimental study we assessed if benthic bioturbating invertebrates affect the recruitment (hatching) of zooplankton from the sediment, and if this effect persists as differences in the zooplankton community in the water column, that is, if bioturbation quantitatively stimulates benthic–pelagic coupling. We investigated the effects of four different benthic invertebrates (Asellus aquaticus, Chironomus plumosus, Tubifex tubifex in the presence or absence of the predator Sialis lutaria). In total, 45 zooplankton taxa hatched from the sediment and the hatching success of some of these was dependent on the species identity of the bioturbating invertebrate. The predator Sialis reduced the abundance of all three invertebrate species, but tended to positively influence the zooplankton recruitment rates, possibly through increasing the activity of the bioturbating invertebrates. The most striking effect of bioturbation on the hatching and pelagic zooplankton community properties was that, on average, 11% more species hatched in the Asellus treatment than in any other treatment. This was also mirrored in the zooplankton water column community where, on average, 7% more species established a viable population in treatments with Asellus as bioturbator. In a complementary field survey, Asellus was more common in littoral than in profundal sediments. Because Asellus strongly affected recruitment of zooplankton in our experiment, we argue that bioturbation may partly explain why recruitment of resting stages of both phyto- and zooplankton is generally higher in littoral than in profundal areas.