Maximising survival requires animals to balance the competing demands of maintaining energy balance and avoiding predation. Here, quantitative modelling shows that optimising the daily timing of ...activity and rest based on the encountered environmental conditions enables small mammals to maximise survival. Our model shows that nocturnality is typically beneficial when predation risk is higher during the day than during the night, but this is reversed by the energetic benefit of diurnality when food becomes scarce. Empirical testing under semi‐natural conditions revealed that the daily timing of activity and rest in mice exposed to manipulations in energy availability and perceived predation risk is in line with the model’s predictions. Low food availability and decreased perceived daytime predation risk promote diurnal activity patterns. Overall, our results identify temporal niche switching in small mammals as a strategy to maximise survival in response to environmental changes in food availability and perceived predation risk.
Energetic cost of building a virus Mahmoudabadi, Gita; Milo, Ron; Phillips, Rob
Proceedings of the National Academy of Sciences - PNAS,
05/2017, Letnik:
114, Številka:
22
Journal Article
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Viruses are incapable of autonomous energy production. Although many experimental studies make it clear that viruses are parasitic entities that hijack the molecular resources of the host, a detailed ...estimate for the energetic cost of viral synthesis is largely lacking. To quantify the energetic cost of viruses to their hosts, we enumerated the costs associated with two very distinct but representative DNA and RNA viruses, namely, T4 and influenza. We found that, for these viruses, translation of viral proteins is the most energetically expensive process. Interestingly, the costs of building a T4 phage and a single influenza virus are nearly the same. Due to influenza’s higher burst size, however, the overall cost of a T4 phage infection is only 2–3% of the cost of an influenza infection. The costs of these infections relative to their host’s estimated energy budget during the infection reveal that a T4 infection consumes about a third of its host’s energy budget, whereas an influenza infection consumes only ≈ 1%. Building on our estimates for T4, we show how the energetic costs of double-stranded DNA phages scale with the capsid size, revealing that the dominant cost of building a virus can switch from translation to genome replication above a critical size. Last, using our predictions for the energetic cost of viruses, we provide estimates for the strengths of selection and genetic drift acting on newly incorporated genetic elements in viral genomes, under conditions of energy limitation.
Abstract
To understand the irradiation resistance and hydrogen (H) behavior in tungsten borides (W
x
B
y
) in a burning plasma fusion environment, the energetics of intrinsic point defects and H in ...six stable ground state W borides, including W
2
B, WB, WB
2
, W
2
B
5
, WB
3
and WB
4
, have been investigated using first-principles density functional theory calculations. The results show that the formation energies of interstitials and vacancies do not directly depend on the W and B content in W borides. However, the interaction between vacancies of a stoichiometric vacancy (SV) cluster in W
x
B
y
is related to the atomic ratio of B to W (
y
/
x
). The vacancies of a minimum-size SV cluster in W
x
B
y
are energetically repulsive for
y
/
x
⩽ 1, while the vacancies energetically bind together for
y
/
x
larger than 1. The formation energy of B Frenkel pairs in each W boride is lower than that of W Frenkel pairs. Among the six evaluated W
x
B
y
compositions, WB has the highest and the lowest formation energy of H interstitials and H-vacancy complexes, respectively; however, these two energies in WB
2
are in reverse order. The average H binding energies to single vacancies in WB and WB
4
are comparable with that in W, while this binding energy in WB
3
and WB
2
is obviously higher or lower than in W, respectively. The diffusion activation energy of H in W borides is anisotropic. One dimensional (1D) diffusion of H in W
2
B, as well as 1D/2D diffusion in WB, W
2
B
5
, WB
3
and WB
4
are preferred at relatively low temperatures; however, three-dimensional diffusion of H is predicted in WB
2
. The diffusion activation energy of H generally increases with B content in W borides due to the increasing local charge deficit caused by strong B–B covalent bonds. This study is useful for evaluating the performance of W borides in a fusion environment.
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•Solubilities of Glycine, dl-alanine and l-threonine in aqueous (NH4)2SO4 were determined.•Relative solubility and salting-in/out constant were measured.•The standard transfer Gibbs ...energies, enthalpy, entropy were calculated.•The chemical contributions of free energies and entropies of the amino acids were computed and explained.
In this article the equilibrium saturated solubility of glycine, dl-alanine and l-threonine in aqueous ammonium sulphate media at various temperatures were estimated. The standard transfer Gibbs free energies and different thermodynamic parameters were also estimated. Different interactions were analysed for the solvation of the amino acids in the experimental media to explain the mechanism of solvation. For dl-alanine and l-threonine, salting-in effect is observed at lower electrolyte concentration while at higher electrolyte concentration salting-out effect is observed at a particular temperature. The chemical stability of the amino acids in aqueous electrolyte mixture was explained to justify the experimental results.
Summary
The migration of humpback whales to and from their breeding grounds results in a short, critical time period during which neonatal calves must acquire sufficient energy via suckling from ...their fasting mothers to survive the long return journey.
Understanding neonate suckling behaviour is critical for understanding the energetics and evolution of humpback whale migratory behaviour and for informing conservation efforts, but despite its importance, very little is known about the details, rate and behavioural context of this critical energy transfer.
To address this pertinent data gap on calf suckling behaviour, we deployed multi‐sensor Dtags on eight humpback whale calves and two mothers allowing us to analyse detailed suckling and acoustic behaviour for a total of 68·8 h.
Suckling dives were performed 20·7 ± 7% of the total tagging time with the mothers either resting at the surface or at depth with the calves hanging motionless with roll and pitch angles close to zero.
Vocalisations between mother and calf, which included very weak tonal and grunting sounds, were produced more frequently during active dives than suckling dives, suggesting that mechanical stimuli rather than acoustic cues are used to initiate nursing.
Use of mechanical cues for initiating suckling and low level vocalisations with an active space of <100 m indicate a strong selection pressure for acoustic crypsis.
Such inconspicuous behaviour likely reduces the risk of exposure to eavesdropping predators and male humpback whale escorts that may disrupt the high proportion of time spent nursing and resting, and hence ultimately compromise calf fitness.
The small active space of the weak calls between mother and calf is very sensitive to increases in ambient noise from human encroachment thereby increasing the risk of mother–calf separation.
A lay summary is available for this article.
Lay Summary
Sampling and genomic efforts over the past decade have revealed an enormous quantity and diversity of life in Earth's extreme environments. This new knowledge of life on Earth poses the challenge of ...understandingits molecular basis in such inhospitable conditions, given that such conditions lead to loss of structure and of function in biomolecules from mesophiles. In this review, we discuss the physicochemical properties of extreme environments. We present the state of recent progress in extreme environmental genomics. We then present an overview of our current understanding of the biomolecular adaptation to extreme conditions. As our current and future understanding of biomolecular structure-function relationships in extremophiles requires methodologies adapted to extremes of pressure, temperature, and chemical composition, advances in instrumentation for probing biophysical properties under extreme conditions are presented. Finally, we briefly discuss possible future directions in extreme biophysics.
A complete understanding of the mechanisms by which high explosives (HEs) are shock initiated, especially at the particle scale, is still in demand. One approach to explain shock initiation ...phenomenon is hot spot theory, which suggests that distributed energy in energetic material is localized due to shock or impact to generate the high temperatures for ignition. This study focuses on the impact response of a HE polycrystalline particle, specifically HMX, in a polymer matrix. This represents a simplified analog of a traditional polymer‐bonded explosive (PBX) formulation. A light gas gun, together with high‐speed x‐ray phase contrast imaging (PCI), was used to study the impact response of a single particle of production‐grade HMX in a Sylgard‐184® matrix. The high‐speed x‐ray PCI allows for real‐time visualization of HE particle behavior. The experiments revealed that, at impact velocities of ∼200 m s−1, the energetic particle was cracked and crushed. When the impact velocity was increased to 445 m s−1, a significant volume expansion of the particle was observed. This volume expansion is considered to be the result of chemical reaction within the HE particle.
OPA1 is a dynamin-related GTPase that controls mitochondrial dynamics, cristae integrity, energetics and mtDNA maintenance. The exceptional complexity of this protein is determined by the presence, ...in humans, of eight different isoforms that, in turn, are proteolytically cleaved into combinations of membrane-anchored long forms and soluble short forms. Recent advances highlight how each OPA1 isoform is able to fulfill “essential” mitochondrial functions, whereas only some variants carry out “specialized” features. Long forms determine fusion, long or short forms alone build cristae, whereas long and short forms together tune mitochondrial morphology. These findings offer novel challenging therapeutic potential to gene therapy.
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•“mtDNA content, cristae, energetics” are the core functions sustained by each isoform.•Long forms support mitochondrial fusion and short forms energetics.•The multiplicity of the eight OPA1 isoforms fine tunes the mitochondrial dynamics.
The present research focuses on the seasonal changes in the energy content and metabolic patterns of red porgy (Pagrus pagrus) sampled in a fish farm in North Evoikos Gulf (Greece). The study was ...designed in an effort to evaluate the influence of seasonality in several physiological feauteres of high commercial importance that may affect feed intake and growth. We determined glycogen, lipids and proteins levels, and cellular energy allocation (CEA) as a valuable marker of exposure to stress, which integrates available energy (Ea) and energy consumption (Ec). Metabolic patterns and aerobic oxidation potential were based on the determination of glucose transporter (GLU), carnitine transporter (CTP), L-lactate dehydrogenase (L-LDH), citrate synthase (CS), cytochrome C oxidase subunit IV isoform 1 (COX1) and 3-hydroxyacyl CoA dehydrogenase (HOAD) relative gene expression. To integrate metabolic patterns and gene expression, L-LDH, CS, COX and HOAD activities were also determined. For further estimation of biological stores oxidized during seasonal acclimatization, we determined the blood levels of glucose, lipids and lactate. The results indicated seasonal changes in energy content, different patterns in gene expression and reorganization of metabolic patterns during cool acclimatization with increased lipid oxidation. During warm acclimatization, however, energy consumption was mostly based on carbohydrates oxidation. The decrease of Ec and COX1 activity in the warm exposed heart seem to be consistent with the OCLTT hypothesis, suggesting that the heart may be one of the first organs to be limited during seasonal warming. Overall, this study has profiled changes in energetics and metabolic patterns occurring at annual temperatures at which P. pagrus is currently farmed, suggesting that this species is living at the upper edge of their thermal window, at least during summer.
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•Pagrus pagrus growth is strongly dependent on sea-water temperature.•Lower feed intake and growth rate were observed in P. pagrus during cold acclimatization.•Protein mobilization in metabolism and energy provision was also observed in winter.•Optimal temperatures for P. pagrus physiological processes are 20oC–22 °C.•White muscle energy after winter recovery is associated with carbohydrate stores.
In the last two decades, neuroscience studies have suggested that various psychological phenomena are produced by predictive processes in the brain. When considered together, these studies form a ...coherent, neurobiologically inspired program for guiding psychological research about the mind and behavior. In this article, we consider the common assumptions and hypotheses that unify an emerging framework and discuss the ramifications of such a framework, both for improving the replicability and robustness of psychological research and for renewing psychological theory by suggesting an alternative ontology of the human mind.
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