Life without water

Anhydrobiosis, or life without water is commonly demonstrated by a number of plants and animals. These organisms have the capacity to loose all body water, remain dry for various periods, and then be revived by rehydration. While in the anhydrobiotic state, these organisms become highly resistant to several environmental stresses such as extremely low temperatures, elevated temperatures, ionizing radiation, and high vacuum. Since water is commonly thought to be essential for life, survival of anhydrobiotic organisms with an almost total loss of water is examined. A search of literature reveal that many anhydrobiotic organisms make large quantities of trehalose or other carbohydrates. Laboratory experiments have shown that trehalose is able to stabilize and preserve microsomes of sarcoplasmic reticulum and artificial liposomes. It was demonstrated that trehalose and other disaccharides can interact directly with phosopipid headgroups and maintain membranes in their native configuration by replacing water in the headgroup region. Recent studies show that trehalose is an effective stabilizer of proteins during drying and that it does so by direct interaction with groups on the protein. If life that is able to withstand environmental extremes has ever developed on Mars, it is expected that such life would have developed some protective compounds which can stabilize macromolecular structure in the absence of water and at cold temperatures. On Earth, that role appears to be filled by carbohydrates that can stabilize both membrane and protein stuctures during freezing and drying. By analog with terrestrial systems, such life forms might develop resistance either during some reproductive stage or at any time during adult existence. If the resistant form is a developmental stage, the life cycle of the organism must be completed with a reasonable time period relative to time when environmental conditions are favorable. This would suggest that simple organisms with a short life cycle might be most sucessful

Is vitrification involved in depression of the phase transition temperature in dry phospholipids?

AbstractRecent literature has suggested that the depression of the phase transition temperature (Tm) in dry phospholipids by sugars may be ascribed to vitrification of the stabilizing solute, rather than by the direct interaction between sugar and phospholipid we have proposed. Koster et al. ((1994) Biochim. Biophys. Acta 1193, 14–150) claim that the only necessity is that the glass transition (Tg) for the sugar exceed Tm for the lipid. Evidence is presented in the present paper that this is not sufficient. Based on the vitrification hypothesis of Koster et al., the predicted order of effectiveness in depressing Tm in dry dipalmitoylphosphatidylcholine (DPPC) is dextran ≥ hydroxyethyl starch > stachyose > raffinose > trehalose > sucrose > glucose. In fact, the opposite order was seen. The effect of raffinose, sucrose, or trehalose on Tm in dry DPPC depends on the thermal history of the sample, as we have reported previously. When DPPC dried with trehalose is heated for the first time, Tm is about 55°C, but on the second and subsequent heating scans Tm falls to about 25°C. Koster et al. suggest that this effect is due to heating the sample above Tg rather than to melting the hydrocarbon chains. We present evidence here that all that is required is for the chains to be melted. Further, we show that retention of residual water by DPPC dried with trehalose depends on the drying temperature, but is independent of drying temperature with glucose, a finding that is consistent with direct interaction. We conclude that vitrification is not in itself sufficient to depress Tm in dry phospholipids

A tribute to Dr. Serge N. Timasheff, our mentor

63 p.-6 fig.Dr. Serge N. Timasheff, our mentor and friend, passed away in 2019. This article is a collection of tributes from his postdoctoral fellows, friends, and daughter, who all have been associated with or influenced by him or his research. Dr. Timasheff is a pioneer of research on thermodynamic linkage between ligand interaction and macromolecular reaction. We all learned a great deal from Dr. Timasheff, not only about science but also about life.Peer reviewe

Marine mammal hotspots across the circumpolar Arctic

Aim: Identify hotspots and areas of high species richness for Arctic marine mammals. Location: Circumpolar Arctic. Methods: A total of 2115 biologging devices were deployed on marine mammals from 13 species in the Arctic from 2005 to 2019. Getis-Ord Gi* hotspots were calculated based on the number of individuals in grid cells for each species and for phyloge-netic groups (nine pinnipeds, three cetaceans, all species) and areas with high spe-cies richness were identified for summer (Jun-Nov), winter (Dec-May) and the entire year. Seasonal habitat differences among species’ hotspots were investigated using Principal Component Analysis. Results: Hotspots and areas with high species richness occurred within the Arctic continental-shelf seas and within the marginal ice zone, particularly in the “Arctic gateways” of the north Atlantic and Pacific oceans. Summer hotspots were generally found further north than winter hotspots, but there were exceptions to this pattern, including bowhead whales in the Greenland-Barents Seas and species with coastal distributions in Svalbard, Norway and East Greenland. Areas with high species rich-ness generally overlapped high-density hotspots. Large regional and seasonal dif-ferences in habitat features of hotspots were found among species but also within species from different regions. Gap analysis (discrepancy between hotspots and IUCN ranges) identified species and regions where more research is required. Main conclusions: This study identified important areas (and habitat types) for Arctic marine mammals using available biotelemetry data. The results herein serve as a benchmark to measure future distributional shifts. Expanded monitoring and teleme-try studies are needed on Arctic species to understand the impacts of climate change and concomitant ecosystem changes (synergistic effects of multiple stressors). While efforts should be made to fill knowledge gaps, including regional gaps and more com-plete sex and age coverage, hotspots identified herein can inform management ef-forts to mitigate the impacts of human activities and ecological changes, including creation of protected areas

Stability of the lipid component of trout sperm plasma membrane during freeze-thawing

5 graph.International audienceTrout spermatozoa are very sensitive to freeze-thawing, and the best cryoprotectants tested until now have a highly variable protective effect. It is not rare that only 10% of the frozen spermatozoa display an undamaged plasma membrane. The aim of this study was to determine whether membrane fragility of rainbow trout sperm (Oncorhynchus mykiss) is due to membrane lipid phase transitions, as postulated for other species, and to explore stabilization of membrane phospholipids by the components present in the freezing extender. Using Fourier transform infrared spectroscopy, we showed that the plasma membrane exhibited a steady decrease in fluidity as temperature decreased. A clear phase transition was observed only with purified membrane phospholipids. Stability of frozen-thawed liposomes made with trout plasma membrane phospholipids was assessed. Although dimethyl sulfoxide stabilized the liposomes better than glycerol, it showed negative interactions with other components added to the extender such as TES (N-tris[hydroxymethyl]methyl-2-aminoethanesulfonic acid) or phosphate. We propose that membrane phospholipid liposomes provide an interesting way to assess the compatibility between various molecules when testing a freezing extender

Membrane phase transitions are responsible for imbibitional damage in dry pollen

We have found that the most probable cause of the leakage seen when dry cells or organisms such as seeds, pollen, or yeast cells are plunged into water is a gel to liquid crystalline phase transition in membrane phospholipids accompanying rehydration. By using Fourier transform infrared spectroscopy we have recorded infrared spectra of CH(2) stretching vibrations in dry and partially hydrated intact pollen grains of Typha latifolia. The vibrational frequency changes abruptly as phospholipids pass through the gel to liquid crystalline phase transition. Below the apparent transition, viable pollen shows low germination and high leakage when placed in water, but above the transition germination increases and leakage decreases. The apparent transition temperature falls with increasing water content, much as in pure phospholipids. By using this phenomenon, it was possible to construct a hydration-dependent phase diagram for the intact pollen. This phase diagram has immediate applications since it has high predictive value for the viability of the pollen when it is placed in water

INTRACELLULAR pH DECREASES DURING THE IN VITRO INDUCTION OF THE ACROSOME REACTION IN THE SPERM OF SICYONIA INGENTIS

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Alterations in membrane surfaces induced by attachment of carbohydrates

We have examined the behavior of the dry phospholipid dipalmitoylphosphatidylcholine (DPPC) in the presence of several carbohydrate derivatives. These carbohydrate derivatives possess a hydrophobic portion which is incorporated directly into the DPPC membrane and a hydrophilic portion which places the carbohydrate structure at the membrane interface with the surrounding matrix. In the presence of these derivatives, the physical properties of the membrane are altered. These alterations are evident in changes observed in the phosphate and carbonyl vibrational modes of the phospholipid portion of the membrane. In addition, the phase transition behavior of the lipid is significantly altered as evidenced by a reduction in the gel to liquid-crystalline phase transition temperature. These results are consistent with those Previously reported for free carbohydrates interacting with membranes in which a water replacement hypothesis has been used to explain the behavior. The attachment of carbohydrates to the membrane enhances these effects by localizing the agent responsible for these alterations at the membrane interface