Lipids of marine cold-water fishes

The study deals with the lipid and fatty acid compositions of the muscles, gills and liver of marine fishes inhabiting cold waters (0.5–6°C) and caught in Peter the Great Bay (3 species) and Vostok Bay (2 species), as well as with the fatty acid compositions of the main phospholipids in the muscle tissues of fish from Olyutorskii Bay (4 species). The average content of phosphatidylcholine was about 60% in muscles and in the liver and 53.8% of the sum of all phospholipids in gills. The phosphatidylethanolamine content was on the average 24.3, 25.1 and 22.3% in muscles, liver and gills, respectively. Increased contents of phosphatidylserine and sphingomyeline were recorded in the gills. The mean (S.D.) molar ratios of cholesterol/phospholipids were 0.20, 0.32, and 0.58 in the muscles, liver, and gills, respectively. It was established that phosphatidylcholine has a higher content of saturated fatty acids, whereas phosphatidylethanolamine was richer in monoenic acids and docosahexaenoic acid (DHA). It was noted that the level of polyenic fatty acids was increasing and the level of monoenic and saturated acids was decreasing in the series from gills-liver-muscles. The species with a more active mode of life were distinguished by an increased content of docosahexaenoic acid.     

Phospholipids of the organs and tissues of echinoderms and tunicates from peter the great bay (Sea of Japan)

The phospholipid compositions of organs and tissues were determined in representatives of two phyla of marine invertebrates: Echinodermata [Asteroidea: Aphelasterias japonica (Bell, 1881), Evasterias echinosoma Fisher, 1926, Distolasterias nipon (Doderlein, 1902), Asterias amurensis Lutken, 1871; Echinoidea: Strongylocentrotus intermedius (A. Agassiz, 1863); Holothurioidea: Cucumaria frondosa japonica (Semper, 1868), Eupentacta fraudatrix (Djakonov et Baranova, 1958), Apostichopus japonicus (Selenka, 1867)], and Tunicata [Ascidia: Halocynthia aurantium (Pallas, 1787), H. roretzi (Drasche, 1884), and Styela clava (Herdman, 1881)]. The specificity of phospholipid distribution was shown to be related to the taxonomic position of marine invertebrates and the functional properties of their organs and tissues. Ceramide aminoethylphosphonate was found only in the digestive organs of all holothurians and the starfishes D. nipon and A. amurensis, suggesting its exogenous origin. Phosphatidylglycerol was found in all organs and tissues of the holothurians C. frondosa japonica and E. fraudatrix, as well as in the gastrointestinal tract of ascidians; its origin is unclear.     

Thermotropic behaviour of membrane lipids from brown marine alga Laminaria japonica

Microcalorimetry was used to show that transition-temperature ranges of phospho- and glycolipids of the brown marine alga Laminaria japonica were similar (from -62 to -47 degrees C up to 62-65 degrees C), except for monogalactosyldiacylglycerol, the low-temperature limit of which was shifted to -78 degrees C. As was shown by polarizing microscopy, the low-enthalpy peaks at temperatures of approx. 30-45 degrees C corresponded to isotropic melting of galactolipids and coincided with the high-temperature limit for photosynthetic and mitochondrial activity of the algae. As a whole, a classical interrelation was observed between thermotropic behaviour and the fatty acid unsaturation of lipids.     

Location and volume of the active site of chymotrypsin

The active site of chymotrypsin molecule (approximated by a sphere with radius of 20 A) was taken as the largest cavity on the enzyme surface. The volume inside the approximating sphere is sufficient for placement of 95% of non-hydrogen atoms of the enzyme. The active site cavity is localized in a spherical sector with solid angle of 80 degrees whose axis passes through the CB-atom of the Ser195 residue. The volume of the active site cavity is about 2700 A(3) (8% of the volume of the approximating sphere) as computed by the Monte-Carlo method from known X-ray data. The size and shape of the active site cavity is sufficient for entrance of significantly large fragments (more than 60 non-hydrogen atoms) of the substrate molecule. At the active site cavity bottom, there is a narrow compartment adjacent to an oxy-anion hollow and accessible to water but not to substrate molecules. The water molecules inside this narrow compartment can take part in heat exchange with the external medium during different steps of the enzymatic process.     

Thermoadaptation and fatty acid composition of main phospholipids of the small-scaled redfin <Emphasis Type="Italic">Tribolodon brandti</Emphasis> under natural and experimental conditions

The fatty acid (FA) composition of the main membrane phospholipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE), was investigated in the muscle, gills, and liver of the small-scaled redfin Tribolodon brandti (Dybowskii, 1872) at different temperatures under natural and experimental conditions. It was established that a water temperature decrease in the natural habitat was accompanied by an increase in polyunsaturated fatty acid contents and the unsaturation index, mainly at the expense of FAs of the ω3 series (20:5ω3 and 22:6ω3), and by a decrease in saturated fatty acid levels in PC and PE. A similar, but less pronounced tendency was revealed in experiments with a rapid lowering of water temperature. These findings suggest the weak adaptation ability of the small-scaled redfin to a drastic shift of environmental temperature. Temperature changes produced the greatest alterations in the FA composition of phospholipids in the liver and the smallest changes occurred in muscle tissue.     

The thermotropic behavior and major molecular species composition of the phospholipids of echinoderms

This study examines the molecular species composition and heat-induced crystalline-liquid crystalline phase transitions of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) from the muscle tissues of six species of echinoderms that were collected during the summer: the starfishes Distolasterias nipon and Asterias amurensis, the sea urchin Strongylocentrotus intermedius, and the holothurians Eupentacta fraudatrix, Cucumaria frondosa japonica, and Apostichopus japonicus. Phospholipids (PLs) were in the liquid crystalline state, which is optimal for the functioning of the cell membranes. The use of data on the molecular species composition of PLs for the interpretation of their thermotropic behavior indicated that homeoviscous adaptation is achieved by various rearrangements in the composition of the aliphatic groups of PLs. The phase transitions of PC and PE of echinoderms (except holothurians) were symbatic. The presence of a high-temperature peak on the PC thermograms of C. frondosa japonica and A. japonicus is attributable to the melting of the phospholipid domain, which is composed of molecular species with saturated aliphatic groups. Such domains are responsible for a significant shift in the temperature ranges of the phase transitions of phospholipids of holothurians and sea urchin towards temperatures above 0°C.     

Changes in the lipid composition of mussel (<Emphasis Type="Italic">Mytilus trossulus</Emphasis>) embryo cells during cryopreservation

The survival and the lipid composition of mussel (Mytilus trossulus) larval cells was analyzed before and after cryopreservation in two protective media. Cell survival and functional recovery were greatly improved when the conventional DMSO + trehalose were supplemented with a lipid extract from mature mollusks (Crenomytilus grayanus) + vitamins E and C. These additives also markedly influenced the fatty acid composition of the cells upon thawing, particularly as regards the share of monoenic acids and the unsaturation index. The probable causes of these effects are discussed.     

Thermal Adaptation and Fatty Acid Composition of Major Phospholipids in the Plain Sculpin <Emphasis Type="Italic">Myoxocephalus jaok</Emphasis> at Different Temperatures of Natural Habitat

The composition of phospholipids (PLs), fatty acids (FAs), molecular species of major membrane lipids phosphatidylcholine (PC) and phosphatidylethanolamine (PE) as well as the cholesterol (CL) level in the gills and liver of the plain sculpin Myxocephalus jaok were analyzed at different habitat temperatures (18, 9, 0°C). Polar lipids and cholesterol were shown to be actively involved in adaptation of the plain sculpin to changes in environmental temperature. A decrease in temperature evoked multidirectional changes in the level of monoenoic (MUFA) and polyenoic (PUFA) FAs, ω-3 PUFA, etheric PLs, and in the unsaturation index (UI) of FAs in PC and PE of th e plain sculpin organs. Changes in the composition of PL molecular forms were unidirectional in all organs but showed some organ specificity. Thus, PC showed an increase in the total percentage of SFA/PUFA and MUFA/PUFA containing predominantly 20:5, 22:5 and 22:6 of PUFA and a decrease in the percentage of SFA/MUFA and PUFA/PUFA as well as in the level of alkylacyl forms of PC. PE showed an increase in the percentage of MUFA/PUFA and a decrease in that of SFA/PUFA and PUFA/PUFA as well as in the level of alkenylacyl forms of PE. Despite a close FA composition of PC and PE, the repertoire of their molecular forms differed in an organ- and temperature-dependent manner. Molecular mechanisms of thermal adaptation in the plain sculpin organs were traced more distinctly at the level of PC and PE molecular forms rather than in their FA spectrum.     

Elaboration of immune stimulating lipid-saponin subunit antigen carrier based on glycolipid monogalactosyldiacylglycerol from sea macrophytes and triterpene glycosides from Cucumaria japonica

The ability of some triterpene glycosides of holothurians: holotoxin A₁ from Apostichopus japonicus and a mixture of monosulfated triterpene glycosides from Cucumaria japonica called cucumarioside (CD) to form supramolecular complexes with cholesterol (Chol) and monogalactosyldiacylglycerol (MGDG) or phosphatidylcholine (PC) was studied. A transmission electron microscopy method was used to observe supramolecular lipid-saponin complexes formed by holotoxin A1 and CD with cholesterol in the presence of membrane lipids. The observed supramolecular complexes are tubular nanoparticles with a length of 100–300 nm, an external diameter of 10–16 nm and an internal diameter of 2–6 nm. The formation of tubular nanoparticles was more effective in the presence of MGDG than with PC. Nanoparticles forming in the presence of MGDG are shaped as a tubule, have a constant diameter and a strongly pronounced internal channel. In contrast, PC has no such properties; this lipid is unable to fully integrate in tubular nanoparticles. Based on electron-microscopy data the range of weight ratio of MGDG-Chol-CD was determined as a 1–10: 2: 3 that provided most effective formation of tubular nanoparticles. Different methods of incorporation of model antigens in complex MGDG-Chol-CD were studied. Influenza hemagglutinin and neuraminidase from commercial vaccine “Influvac” and pore forming protein YompF from Yersinia pseudotuberculosis were used as model antigens. From 54 to 72% of protein of “Influvac” vaccine and 88–92% of YompF were incorporated in supramolecular complexes depending on the method of incorporation. The loss of functional activity of hemagglutinin of vaccine “Influvac” was the result of applying ultrasonic disintegration for incorporation of this protein in complex MGDG-Chol-CD. YompF incorporation in MGDG-Chol-CD complex led to the increased diameter of tubular particles, in the same time incorporation of vaccine “Influvac” antigens produced the “cap” formation at the end of tubules. The possibility of a described supramolecular complex MGDG-Chol-CD to be a carrier for subunit bacterial and viral antigens is shown.     

The Effect of Seasonal Shifts in Temperature on the Lipid Composition of Marine Macrophytes

The comparative study of lipid composition was carried out in four species of marine algae, Ahnfeltia tobuchiensis, Laminaria japonica, Sargassum pallidum, and Ulva fenestrata, as well as a higher plant grass wrack (Zostera marina). Plants were collected in the Japan Sea in spring at 2.9 and 5.5°C and in summer at 23°C. The main lipid components of membranes were determined, and the general patterns of the ratio of phospholipids (PL), glycolipids (GL), betaine (BL), and neutral (NL) lipids were discerned. The relative content of NL in all species (except A. tobuchiensis) was higher in summer. The level of triacylglycerols was as high as 18–37%. The content of individual classes of PL and GL varied between the spring and summer samples, the relative content of PL being higher in spring. In most species, the ratio of PL to GL decreased in summer. The content of free sterols did not depend on the season. The molar ratios of phosphatidylcholine and diacylglycerol-o-(hydroxymethyl)-(N,N,N-trimethyl)homoserine to free sterols varied from 0.9 to 1.7. The seasonal changes of lipid composition were apparently related to macrophyte adaptation to water temperature and to biology of their development.