Adsorption of non-membrane proteins on the surface of model phospholipid membranes

1. Two new methods are proposed for enhancement of the binding of hydrophilic proteins by liposomes. 2. An alkylating derivative of phosphatidic acid has been obtained by its reaction with N,N,N′-tris(2-chloroethyl)-N′- (p-formylphenyl)propylene-1,3-diamine. The alkylating activity of this derivative is very low due to the electron-acceptor effect of the formyl residue. Phosphatidylcholine liposomes which contain this alkylating derivative in the lipid bilayer may be obtained. The compound residing in the outer monolayer may be reduced by NaBH₄. Upon reduction, the formyl residue is transformed into a hydroxymethyl residue. Therefore, the alkylating group of the compound is activated, and proteins may be attached covalently to the outer monolayer by alkylation with such chemically reactive liposomes. 3. Reaction of alkylating liposomes with myoglobin results in covalent binding of this hydrophilic protein. Complement-mediated leakage of such myoglobin-carrying liposomes may be induced by antibodies against myoglobin. 4. Modification of hydrophilic proteins with dansyl chloride results, even at small extents of modification, in a dramatic increase of the affinity of such proteins to phosphatidylcholine liposomes.     

Ammonia volatilization after injection of anhydrous ammonia into arable soils of different moisture levels

Laboratory experiments have shown appreciable losses of ammonia after injection of anhydrous ammonia into dry and wet soils. In this study losses of ammonia injected into a moist (tension 10 kPa), dry (tension 160 kPa) and a wet (tension 1.6 kPa) sandy loam were measured under field conditions using wind tunnels. Losses were insignificant from a moist soil. However losses from a dry and a wet soil were 20% and 50% of injected ammonia, respectively. From the dry soil, losses of gaseous ammonia took place within the first hours after injection, which indicates a rapid transport through cracks and voids. From the wet soil, 20% of the injected ammonia was lost more gradually between 6 h and 6 d. This indicates that upward movement of water due to evaporation may be the cause of these ammonia losses which proceeded for longer periods.     

Carbon isotope discrimination at vegetative stage as an indicator of yield and water use efficiency of spring wheat (Triticum turgidum L. var. durum)

A field experiment was conducted to investigate if carbon isotope (¹³C) discrimination () measured at the vegetative stage of spring wheat (Triticum turgidum L. var. durum) is related with the yield and water use efficiency (WUE) at ripening. A line source sprinkler irrigation system exposed the wheat genotypes to different watering regimes, from rainfed to full irrigation and thereby increased the range in yield and WUE attainable in the four genotypes studied. The results indicated that values measured at the late stem elongation stage 60 days after planting (DAP), showed strong positive correlation with total dry matter yield (r=0.732^***), and a highly significant negative correlation with WUE (r=–0.755^***) measured at ripening 105 DAP. The data suggest that the imprints of measured at vegetative growth stage persists throughout the entire growth period, until maturity. Subject to confirmation from additional studies in other crops and locations, early measurements of may prove a useful tool for rapid and early screening of cultivars, for high yield and high WUE.     

Low hydration phase properties of phospholipid mixtures

An experimental investigation of the low hydration phase properties of phospholipid mixtures is described. ²H (D₂O) NMR, X-ray diffraction and differential scanning calorimetry have been used to elucidate the phase properties of mixtures of the mixed chain phospholipids palmitoyloleoylphosphatidylcholine (POPC) and palmitoyloleoylphosphatidylethanolamine (POPE). At 10% hydration pure POPE exhibited a H_II phase above 330 K, a fluid lamellar phase below 315 K, and a minimally hydrated crystalline phase below 300 K. For the 1:1 mixture, the samples exhibited only gel or fluid phases between 270 K and 360 K for hydrations in the range 15% to 30%. Below 15% hydration the mixture exhibited two fluid phases with different repeat spacings, as predicted previously.     

First record of Crustacea Malacostraca from fresh waters in the Canary Islands

Crustacea Malacostraca were hitherto unknown from fresh waters of the Canary Islands. A new species of Amphipoda, Rhipidogammarus rheophilus, has recently been discovered in springs and spring brooks in Tenerife.

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Resumen Crustacea Malacostraca era hasta ahora desconocida de las aguas dulces de las Islas Canarias. Una nueva especie de anfípodo, Rhipidogammarus rheophilus, ha sido recientemente descubierto de fuentes y manantiales de Tenerife.

     

A form-function analysis of photon capture for seaweeds

A large material of planktonic and semiplanktonic micro-crustaceans from various type of waters in south and central Sweden was computerized. The more frequent species were listed according to pH-preference and relation to humic content measured as mg Pt/l. Species indicating oligotrophy have their optima just below the neutral point, eurytopic ones around this level, while the eutrophic species Daphnia cucullata and D. magna were closely correlated with higher pH-levels. No really extreme pH-preference was observed. There is no link between trophic indication and the ranking list for humic content. Most planktic species occur at lower humic contents and semiplankters at higher.     

The phosphorus economy of a hypertrophic seepage lake in Scania,south Sweden groundwater influence

The phosphorus dynamics and economy of Lake Bysjön, a hypertrophic seepage lake in Scania, southern Sweden, were investigated during 1973–1977. The mean dissolved inorganic phosphorus concentration (1973–1977) was 580 µg · l^–1. There were no correlations between dissolved inorganic P, total organic P, dissolved organic P, particulate P and phytoplankton biomass. Groundwater inflow and lake water outflow through the ground are the most important factors for maintaining a constant water volume. Groundwater seepage is also important for water quality. Groundwater inflow, together with planktonic activity, keeps the P concentration high in the lake water.     

Occurrence,properties and biological implications of the active uptake of water vapour from the atmosphere in Psocoptera

Water vapour absorption is shown to occur in 22 species of Psocoptera inhabiting diverse environments and representing all major groups of this insect order. Evidently the faculty is a common feature of the whole order and it seems not to be related to specific environmental conditions. For the first time water vapour uptake could be demonstrated in fully winged and flying insects. The critical equilibrium humidities vary considerably among different species ranging from 58 to 85% r.h. Marked interspecific differences are also observed in water loss and uptake rates but no clear correlation with habitat or systematic group is recognizable. The uptake rates of Psocoptera are among the highest of all arthropods investigated so far. From weight recordings with a sensitive microbalance it could be seen that continuous operation of the uptake mechanism is restricted to limited periods of time of less than 1 hr regardless of the water status of the animals. Initiation and termination of the uptake process are abrupt and continuous uptake proceeds at a constant rate at a given relative humidity. Uptake rates are humidity-dependent decreasing with falling relative humidity whereas the adjustment of the equilibrium level of body water is independent of ambient humidity. Equilibrium is maintained by intermittent operation of the uptake mechanism within ca. 3% of body water mass. The uptake mechanism exhibits marked sensitivity to starvation in most members of the Psocomorpha. Some features of the uptake process of Psocoptera are in close agreement with those of Mallophaga reflecting the close relationship between the two groups.     

The induction of sensitivity to gibberellin in aleurone tissue of developing wheat grains

Aleurone tissue from undried immature developing wheat grains (Triticum aestivum L. cv. Sappo), normally insensitive to gibberellic acid, can be made to respond to the hormone by a series of temperature treatments. Incubation of the de-embryoed grains at temperatures above 27° C for at least 8 h causes the tissue to become sensitive. Prolonged incubation at temperatures below 27° C does not effect a change in sensitivity. In addition to the requirement for exposure to an elevated temperature for a period of several hours the tissue must also subsequently be subjected to a period at a lower temperature for just a few seconds for the response to be observed. Once sensitized, the tissue remains responsive to gibberellic acid for substantial periods of time. Exposure of the tissue to temperatures which induce sensitivity to gibberellic acid also results in an increased leakage of amino acids. It is suggested that the increase in sensitivity to gibberellin requires two separate processes to take place. One could be a homeoviscous adaptation of the cell membranes in response to elevated temperature, the other a subsequent, permanent change in conformation of membrane components.