The Antibody Light-Chain Linker Regulates Domain Orientation and Amyloidogenicity

The antibody light chain (LC) consists of two domains and is essential for antigen binding in mature immunoglobulins. The two domains are connected by a highly conserved linker that comprises the structurally important Arg108 residue. In antibody light chain (AL) amyloidosis, a severe protein amyloid disease, the LC and its N-terminal variable domain (V_L) convert to fibrils deposited in the tissues causing organ failure. Understanding the factors shaping the architecture of the LC is important for basic science, biotechnology and for deciphering the principles that lead to fibril formation. In this study, we examined the structure and properties of LC variants with a mutated or extended linker. We show that under destabilizing conditions, the linker modulates the amyloidogenicity of the LC. The fibril formation propensity of LC linker variants and their susceptibility to proteolysis directly correlate implying an interplay between the two LC domains. Using NMR and residual dipolar coupling-based simulations, we found that the linker residue Arg108 is a key factor regulating the relative orientation of the V_L and C_L domains, keeping them in a bent and dense, but still flexible conformation. Thus, inter-domain contacts and the relative orientation of V_L and C_L to each other are of major importance for maintaining the structural integrity of the full-length LC.     

<Emphasis Type="Italic">Polytrichum commune</Emphasis> spores nucleate ice and associated microorganisms increase the temperature of ice nucleation activity onset

Moss spores disperse via wind and have been found previously in precipitation and air samples. Their presence in the atmosphere led to this study’s examining the potential of moss spores to contribute to ice nucleation, a process necessary for ice formation in clouds prior to precipitation. Ice nucleation assays were conducted using Polytrichum commune spores that were either associated with natural assemblages of microbes or extracted aseptically from capsules and subsequently confirmed to be free of culturable microbes. Liquid suspensions of capsule spores and non-sterile spores nucleated ice at temperatures as high as ?12 and ?7 °C, respectively. When capsule and non-sterile spores were heated at 95 °C for 10 min, which killed all culturable microbes on non-sterile spores, both nucleated ice from ?10 to ?13 °C. An additional non-sterile spore sample collected from partially opened capsules in a forested ecosystem (ID, USA) nucleated ice at temperatures as high as ?7 °C, similar to non-sterile P. commune spores. This is the first set of results to indicate that P. commune spores themselves are capable of nucleating ice at temperatures higher than many abiological particles such as mineral dust (≤?15 °C) and that natural assemblages of microbes can increase their ice nucleation efficiency. Future studies aimed at determining the abundance of moss spores in the atmosphere and the identity of ice-nucleating microbes associated with them will provide further insights into the ability of moss spores to impact precipitation patterns.     

Melting barriers to faunal exchange across ocean basins

Accelerated loss of sea ice in the Arctic is opening routes connecting the Atlantic and Pacific Oceans for longer periods each year. These changes may increase the ease and frequency with which marine birds and mammals move between the Pacific and Atlantic Ocean basins. Indeed, recent observations of birds and mammals suggest these movements have intensified in recent decades. Reconnection of the Pacific and Atlantic Ocean basins will present both challenges to marine ecosystem conservation and an unprecedented opportunity to examine the ecological and evolutionary consequences of interoceanic faunal exchange in real time. To understand these changes and implement effective conservation of marine ecosystems, we need to further develop modeling efforts to predict the rate of dispersal and consequences of faunal exchange. These predictions can be tested by closely monitoring wildlife dispersal through the Arctic Ocean and using modern methods to explore the ecological and evolutionary consequences of these movements.     

Can pollen match shoes to a previously visited indoor location?

This paper is part of an investigation dedicated to indoor pollen from a forensic point of view. Previous studies documented the ‘natural’ pollen content of a flat and how it was ‘artificially’ altered by ornamental plants. The present study investigated if this ‘artificial pollen trace’ can be transferred to shoes. Brand new sneakers were worn in the flat and afterwards examined for pollen on their soles. The results showed that the shoes gathered pollen and that some pollen types correlated to those found in the flat. Afterwards, some of these shoes were worn while walking through the city for approximately 1.8 km. On these shoes, flat pollen was also detectable, but in low abundances. This study shows that, from a palynological point of view, shoes are worth a look at when a crime is investigated. Uncommon pollen grains on shoes can point to an indoor location with the corresponding ornamental plants.     

Effects of resource pulses on nutrient availability,ecosystem productivity,and temporal variability following a stochastic disturbance in eutrophic glacial lakes

Tropical macrophytes sold in the live garden trade are perceived as unlikely to invade temperate regions owing to climate mismatches. Here we study two tropical macrophytes (Pistia stratiotes and Eichhornia crassipes) not previously considered an invasion risk but which were recently discovered in the Great Lakes, and determine mechanisms that may be responsible for their continued presence including human introduction, reproduction through viable seeds and tolerance of winter conditions. Surveys conducted in 2011 and 2012 revealed recurrent presence of one or both species at some sites. Macrophytes in in situ enclosures failed to survive winter conditions, with plant health declining progressively prior to mortality. Water hyacinth seeds were field-collected, identified using Sanger sequencing, and germinated at 28°C with or without scarification. Germination was highest for scarified versus non-scarified seeds. Human introduction was observed at two sites, one involving both species, the other only water hyacinth. These species likely persist through a combination of annual reintroduction (both species) and possibly by production of viable seed (water hyacinth). Macrophytes, particularly water hyacinth, that were not previously viewed as a threat to the Great Lakes owing to environmental incompatibility may need to be reassessed.     

Screening and identification of a microsatellite marker associated with sex in Wami tilapia, <Emphasis Type="Italic">Oreochromis urolepis hornorum</Emphasis>

In this study, primer pairs of 15 microsatellite markers associated with sex determination of tilapia were selected and amplified in Wami tilapia, Oreochromis urolepis hornorum. While one marker, UNH168, on linkage group 3 (LG3) was associated (P < 0.001) with the phenotypic sex in the experimental population, nine genotypes were detected in both sexes. Only 99-bp allele was detected in the female samples, while 141, 149 and 157-bp alleles were present in both male and female samples. UNH168 was localized by fluorescence in situ hybridization (FISH) on the long arm of the largest tilapia chromosome pair (chromosome 1, equivalent to LG3). This sex-linked microsatellite marker could potentially be used for marker-assisted selection in tilapia breeding programmes to produce monosex male tilapia.     

Revisiting Kadenbach: Electron flux rate through cytochrome c‐oxidase determines the ATP‐inhibitory effect and subsequent production of ROS

Mitochondrial respiration is the predominant source of ATP. Excessive rates of electron transport cause a higher production of harmful reactive oxygen species (ROS). There are two regulatory mechanisms known. The first, according to Mitchel, is dependent on the mitochondrial membrane potential that drives ATP synthase for ATP production, and the second, the Kadenbach mechanism, is focussed on the binding of ATP to Cytochrome c Oxidase (CytOx) at high ATP/ADP ratios, which results in an allosteric conformational change to CytOx, causing inhibition. In times of stress, ATP‐dependent inhibition is switched off and the activity of CytOx is exclusively determined by the membrane potential, leading to an increase in ROS production. The second mechanism for respiratory control depends on the quantity of electron transfer to the Heme aa3 of CytOx. When ATP is bound to CytOx the enzyme is inhibited, and ROS formation is decreased, although the mitochondrial membrane potential is increased.