Sex-ratio optimization with helpers at the nest

In many cooperatively breeding animals, offspring produced earlier in life assist their parents in raising subsequent broods. Such helping behaviour is often confined to offspring of one sex. Sex-allocation theory predicts that parents overproduce offspring of the helping sex, but the expected degree of sex-ratio bias was thought to depend on specific details of female and male life histories, hampering empirical tests of the theory. Here we demonstrate the following two theories. (i) If all parents produce the same sex ratio, the evolutionarily stable sex ratio obeys a very simple rule that is valid for a general class of life histories. The rule predicts that the expected sex-ratio bias depends on the product of only two parameters which are relatively easily measured: the average number of helping offspring per nest and the relative contribution to offspring production per helper. (ii) If the benefit of helping varies between parents, and parents facultatively adjust the sex ratio accordingly, then the population sex ratio is not necessarily biased towards the helping sex. For example, in line with empirical evidence, if helpers are produced under favourable conditions and parents do not adjust their clutch size to the number of helpers, then a surplus of the non-helping sex is expected.     

Voting at Home Is Associated with Lower Cortisol than Voting at the Polls

Previous research finds that voting is a socially stressful activity associated with increases in cortisol levels. Here we extend this research by investigating whether different voting modalities have differential effects on the stress response to voting. Results from a field experiment conducted during the 2012 presidential elections strongly suggest that traditional “at the polls” voting is more stressful, as measured by increases in cortisol levels, than voting at home by mail-in ballot or engaging in comparable non-political social activities. These findings imply that increased low-stress voting options such as mail-in ballots may increase political participation among individuals who are sensitive to social stressors.     

Therapy with saffron and the goddess at Thera

This paper presents a new interpretation of a unique Bronze Age (c. 3000-1100 BCE) Aegean wall painting in the building of Xeste 3 at Akrotiri,Thera. Crocus carturightianus and its active principle, saffron, are the primary subjects at Xeste 3. Several lines of evidence suggest that the meaning of these frescoes concerns saffron and healing: (1) the unusual degree of visual attention given to the crocus, including the variety of methods for display of the stigmas; (2) the painted depiction of the line of saffron production from plucking blooms to the collection of stigmas; and (3) the sheer number (ninety) of medical indications for which saffron has been used from the Bronze Age to the present.The Xeste 3 frescoes appear to portray a divinity of healing associated with her phytotherapy, saffron. Cultural and commercial interconnections between the Therans, the Aegean world, and their neighboring civilizations in the early 2nd millennium BCE indicate a close network of thematic exchange, but there is no evidence that Akrotiri borrowed any of these medicinal (or iconographic) representations. The complex production line, the monumental illustration of a goddess of medicine with her saffron attribute, and this earliest botanically accurate image of an herbal medication are all Theran innovations.     

Interactions of selenium with metal ions at the cellular level

In a supplementation study in which organic selenium asl-selenomethionine was administered in low doses during 1 yr, alterations in the concentrations of metal ions in the erythrocytes and the neutrophil granulocytes were observed. In the erythrocytes, altered concentrations of zinc were parallel with selenium. The concentrations of magnesium, calcium, manganese, copper, and sulfur were not significantly altered. However, altered concentrations of iron and zinc were observed in the neutrophils. The concentrations of magnesium, calcium, manganese, copper, and sulfur were not significantly altered. The accumulation of selenium in individual blood cells was different from that obtained with supplementation of inorganic selenium. When organic selenium was supplemented, the thrombocytes accumulated more selenium than the erythrocytes and the neutrophil granulocytes. The observations indicate that selenium interacts with metal ions at the cellular level when supplemented in low doses. The chemical form of selenium might be important in nutrition and therapy in view of the interaction and distribution pattern at the cellular level.     

Lipid Librations at the Interface with the Na,K-ATPase

Transitions between conformational substates of membrane proteins can be driven by torsional librations in the protein that may be coupled to librational fluctuations of the lipid chains. Here, librational motion of spin-labeled lipid chains in membranous Na,K-ATPase is investigated by spin-echo electron paramagnetic resonance. Lipids at the protein interface are targeted by using negatively charged spin-labeled fatty acids that display selectivity of interaction with the Na,K-ATPase. Echo-detected electron paramagnetic resonance spectra from native membranes are corrected for the contribution from the bilayer regions of the membrane by using spectra from dispersions of the extracted membrane lipids. Lipid librations at the protein interface have a flat profile with chain position, whereas librational fluctuations of the bilayer lipids increase pronouncedly from C-9 onward, then flatten off toward the terminal methyl end of the chains. This difference is accounted for by increased torsional amplitude at the chain ends in bilayers, while the amplitude remains restricted throughout the chain at the protein interface with a limited lengthening in correlation time. The temperature dependence of chain librations at the protein interface strongly resembles that of the spin-labeled protein side chains, suggesting solvent-mediated transitions in the protein are driven by fluctuations in the lipid environment.     

Membrane Biogenesis: Networking at the ER with Atlastin

The peripheral endoplasmic reticulum forms a dynamic network of interconnected membrane tubules. Although some determinants of this striking architecture are known, the mechanism underlying fusion of individual tubules has remained elusive. Two studies now identify atlastin proteins as key mediators of homotypic fusion of endoplasmic reticulum membranes.     

Huntingtin associates with acidic phospholipids at the plasma membrane

We have identified a domain in the N terminus of huntingtin that binds to membranes. A three-dimensional homology model of the structure of the binding domain predicts helical HEAT repeats, which emanate a positive electrostatic potential, consistent with a charge-based mechanism for membrane association. An amphipathic helix capable of inserting into pure lipid bilayers may serve to anchor huntingtin to the membrane. In cells, N-terminal huntingtin fragments targeted to regions of plasma membrane enriched in phosphatidylinositol 4,5-bisphosphate, receptor bound-transferrin, and endogenous huntingtin. N-terminal huntingtin fragments with an expanded polyglutamine tract aberrantly localized to intracellular regions instead of plasma membrane. Our data support a new model in which huntingtin directly binds membranes through electrostatic interactions with acidic phospholipids.     

Peptidyl-prolyl-tRNA at the ribosomal P-site reacts poorly with puromycin

Despite remarkable recent progress in our chemical and structural understanding of the mechanisms of peptide bond formation by the ribosome, only very limited information is available about whether amino acid side chains affect the rate of peptide bond formation. Here, we generated a series of peptidyl-tRNAs that end with different tRNA-attached amino acids in the P-site of the Escherichia coli ribosome and compared their reactivity with puromycin, a rapidly A-site-accessing analog of aminoacyl-tRNAs. Among the 20 amino acids examined, proline was found to receive exceptionally slow peptidyl transfer to puromycin. These results raise a possibility that the peptidyl transferase activity of the ribosome may have some specificity with regard to the P-site amino acids.     

Feeling the heat at the millennium: Thermosensors playing with fire

An outstanding question regards the ability of organisms to sense their environments and respond in a suitable way. Pathogenic bacteria in particular exploit host-temperature sensing as a cue for triggering virulence gene expression. This micro-review does not attempt to fully cover the field of bacterial thermosensors and in detail describe each identified case. Instead, the review focus on the time-period at the end of the 1990's and beginning of the 2000's when several key discoveries were made, identifying protein, DNA and RNA as potential thermosensors controlling gene expression in several different bacterial pathogens in general and on the prfA thermosensor of Listeria monocytogenes in particular.     

Interaction of chitosan with cell membrane models at the air-water interface

In this paper we employed phospholipid Langmuir monolayers as membrane models to probe interactions with chitosan. Using a combination of surface pressure--area and surface potential--area isotherms and rheological measurements with the pendent drop technique, we observed that chitosan interacts with phospholipid molecules at the air-water interface. We propose a model in which chitosan interacts with the phospholipids mainly through electrostatic interactions, but also including H-bonding and hydrophobic forces, depending on the phospholipid packing density. At large areas per molecule, chitosan in the subphase adsorbs onto the monolayer, expanding it. At small areas per molecule, chitosan is located in the subsurface. Indeed, a mixed chitosan-phospholipid monolayer can be transferred onto solid supports, even at high surface pressures. The effects of chitosan on the viscoelastic properties of phospholipid monolayers may be taken as evidence for the ability of chitosan to disrupt cell membranes.     

Hemoglobin of mice with radiation-induced mutations at the hemoglobin loci.

Chemical analyses were done on the abnormal hemoglobins of five (101 × SEC)F₁ offspring of X-irradiated adult SEC mice to determine which hemoglobin genes were expressed in each hemoglobin variant. Three offspring of irradiated SEC males did not express either of the two kinds of α-chains normally found in all SEC mice. The deficient α-chain synthesis caused these mice to exhibit an α-thalassemia similar to human α-thalassemia. Scanning electron microscopy was used to show that many erythrocytes of mice with α-thalassemia have bizarre shapes; e.g. many erthrocytes appeared flattened or had thorny projections (acanthocytes). One mutant with a tandem duplication of a segment of chromosome 7 (site of locus determining β-chain structure) produced twice as much SEC as 101 β-chain polypeptides. One mutant that probably arose by non-disjunction of chromosome 7's in its unirradiated 101 mother and loss of chromosome 7 from the gamete of its irradiated SEC father did not express the SEC β-chain gene.     

Chemical probing of RNA with the hydroxyl radical at single-atom resolution

While hydroxyl radical cleavage is widely used to map RNA tertiary structure, lack of mechanistic understanding of strand break formation limits the degree of structural insight that can be obtained from this experiment. Here, we determine how individual ribose hydrogens of sarcin/ricin loop RNA participate in strand cleavage. We find that substituting deuterium for hydrogen at a ribose 5′-carbon produces a kinetic isotope effect on cleavage; the major cleavage product is an RNA strand terminated by a 5′-aldehyde. We conclude that hydroxyl radical abstracts a 5′-hydrogen atom, leading to RNA strand cleavage. We used this approach to obtain structural information for a GUA base triple, a common tertiary structural feature of RNA. Cleavage at U exhibits a large 5′ deuterium kinetic isotope effect, a potential signature of a base triple. Others had noted a ribose-phosphate hydrogen bond involving the G 2′-OH and the U phosphate of the GUA triple, and suggested that this hydrogen bond contributes to backbone rigidity. Substituting deoxyguanosine for G, to eliminate this hydrogen bond, results in a substantial decrease in cleavage at G and U of the triple. We conclude that this hydrogen bond is a linchpin of backbone structure around the triple.     

Bacterial patterning at the three-phase line of contact with microtextured alkanes

Aliphatic crystallites, characteristic of the eicosane and docosane components of naturally occurring lipids, were found to form microtextures that were structured by specific interactions with ordered graphite (HOPG) used as the underlying substratum, as confirmed by scanning electron microscopy (SEM) and fast Fourier transform (FFT) analysis. Confocal scanning laser microscopy (CLSM) showed highly directed bacterial alignment for two bacterial species (spherical and rod-shaped), reflecting the preferential orientation of the crystallite–air–water interfaces to give linear and triangular bacterial patterning. The mechanisms of bacterial attachment are demonstrated in terms of the balance between effective radial adhesional forces and the capillary forces resulting from the water contact angle of the bacteria at the three-phase line (TPL) of the lipid surface. It is suggested that these microtextured surfaces, which exhibit the ability to limit bacterial adhesion to a precise patterning at the lipid TPL, could be used as a means of controlling bacterial colonization.