Pauli O. Ripatti

The flexibility of natural hydrocarbon chains with non-methylene-interrupted double bonds

Abstract The question of a possible functional role of acyls with non-methylene-interrupted double bonds in biomembranes is discussed. Comparative analysis was made of the flexibility of hydrocarbon chains with 18 carbon atoms containing 1–5 isolated cis double bonds, between which 1 10 CH2 groups are located. The results are obtained by computer simulation of the conformational behaviour of molecules at 298 K. The inter-arrangement of double bonds and their localization in a chain is of a great importance for definition of its flexibility: in the case of non-methylene-interrupted double bonds a growth of their number in a chain does not always result in increased flexibility of the molecule.

The effect of environmental conditions on the dynamics of fatty acids in juveniles of the Atlantic salmon (Salmo salar L.)

The dynamics of fatty acid composition have been studied in differently aged salmon juveniles (0+, 1+, 2+ parrs and 3+ smolts) inhabiting two biotopes of the Varzuga River (the White Sea basin) differing in ecological conditions. Differences in the levels of linoleic (18:2n-6), linolenic (18:3n-3), and oleic (18:1n-9) acids have been revealed. It has also been shown that 3+ smolts have an increased content of long-chain fatty acids—arachidonic (20:4n-6), eicosapentaenoic (20:5n-3), and docosahexaenoic (22:6n-3)—characteristic of the composition of marine-type lipids.

Lipid Status of the Two High Latitude Fish Species, Leptoclinus maculatus and Lumpenus fabricii

A comparative study of the lipid status (i.e., the total lipid and phospholipid concentrations and the percentage of fatty acids of the total lipids) of adult specimens of daubed shanny (Leptoclinus maculatus) from Svalbard waters (Isfjord) and slender eel blenny (Lumpenus fabricii) from the White Sea (Onega Bay and Tersky shore) was performed to study the metabolism and functions of lipids of these fishes in ontogeny and under various ecological conditions. Slender eel blenny from both areas of the White Sea were distinguished by a high level of sphingomyelin compared with the daubed shanny from Svalbard, and the amount of total phospholipids was higher in slender eel blenny from Onega Bay than in slender eel blenny from the Tersky shore. The extent of saturation and the signature of polyenic fatty acids varied according to the specific species of the Stichaeidae family under study. These results demonstrate the differences in the trophoecological and hydrobiological conditions of habitations of these species and highlighted the importance of considering certain trends in the lipid profiles of these fishes as specific features of the organization of the ecological and biochemical mechanisms of adaptation.

Comparative investigation of lipid membrane systems

Molecular dynamics (MC) simulations of bilayers consisted of (1) phosphatidylcholines (PC) and (2) diacylglycerolipids (DG), and lattice-based molecular-level self-consistent field (SCF) calculations of the model lipid bilayers were carried out. Lipid molecules with acyl chains of 18:0/18:0, 18:0/18:1(omega) 9cis, 18:0/18:2(omega) 6cis, 18:0/18:3(omega) 3cis, 18:0/20:4(omega) 6cis, 18:0/22:6(omega) 3cis were investigated. The C-H and C-C bond order parameter (-SCH, SCC) profiles of the hydrocarbon tails, the bond orientation distribution functions, the root-mean-square values of the positional fluctuations of the lipid chain carbons were calculated. The theoretical results are compared with the available experimental data. The main qualitatively characteristic features of the properties of bilayer with lipid chains of a given chemical structure show up in both the MD and in the SCF results. The key physical properties of lipid bilayers that are composed of unsaturated lipids are discussed from a theoretical perspective.

Molecular Dynamics Investigation of Bond Ordering of Unsaturated Lipids in Monolayers

Molecular dynamics simulations of three model lipid monolayers of 2,3-diacyl-D-glycerolipids, that contained stearoyl (18:0) in the position 3 and oleoyl (18:ω9cis), linoleoyl (18:2ω6cis), or linolenoyl (18:3ω3cis) in the position 2, have been carried out. The simulation systems consisted of 24 lipid molecules arranged in a rectangular simulation cell, with periodic boundary conditions in the surface plane. 1 nanosecond simulations were performed at T = 295 K. C-C and C-H bond order parameter profiles and the bond orientation distributions about the monolayer normal have been calculated. The relation of the distributions to the order parameters was analyzed in terms of maxima and widths of the distributions. The cis double bond order parameter is found to be higher than those of adjacent single C-C bonds. The widths of the two distributions of C-H bonds of the cis double bond segment in di- and triunsaturated molecules are much smaller than that obtained for methylene group located between the double bonds. The bond orientation distribution function widths depend on both the segment location in the chain and the segment chemical structure.

Lipid status of larvae and adults of the White Sea herring Clupea pallasii marisalbi Berg (Clupeiformes, Clupeidae)

37 The population of the White Sea herring Clupea pallasii marisalbi Berg (Clupeiformes, Clupeidae) is one of the closest forms of the Pacific herring and one of the most important commercially valuable fishes of the White Sea. The growth of the herring stock in recent years is due to its gradual recovery (after the death in the early 1960s) of the White Sea eelgrass, whose thickets serve as spawning and development sites of eggs as well as foraging and growth sites of her ring larvae and fries [1]. Biochemical studies on the White Sea herring are practically absent. However, such studies could help answer the question as to whether different groups of herring are characterized by biochemical heterogeneity. It is known that lipids play an important role in the formation of the bio chemical status of organisms. They are essential struc tural components of biological membranes, are involved in energy processes in cells and in the regula tion of biochemical reactions and physiological pro cesses, are the precursors of the biosynthesis of steroid hormones, etc. [2, 7].

Molecular dynamics investigation of polar diacylglycerolipid monolayers: bond ordering properties

Molecular dynamics simulations of six monolayers composed of the molecules 2,3-diacyl-D-glycerolipids that contained stearoyl in the position 3 and stearoyl, oleoyl, linoleoyl, linolenoyl, arachidonoyl or docosahexaenoyl in the position 2 have been carried out; 1.5 nanosecond simulations were performed at T equals 303 K for the monolayers of unsaturated molecules and at T equals 326 K for saturated one. The average areas per lipid molecule over the simulations were 65.6 angstroms2 in 18:0/18:0-monolayer, 66.2 angstroms2 in 18:0/18:1(omega) 9cis-monolayer, 66.1 angstroms2 in 18:0/18:2(omega) 6cis-, 67.4 angstroms2 in 18:0/18:3(omega) 3cis-, 70.6 angstroms2 in 18:0/20:4(omega) 6cis- and 71.4 angstroms2 in 18:0/22:6(omega) 3cis-monolayer. The C-H bond orientation distributions and C-H bond order parameters profiles about the monolayer normals have been calculated. The bond orientation distribution function widths turned out to be depended on both the segment location in the chain and the segment chemical structure. The computer simulation data indicated the widths of the distributions of CH2-groups located between the double bonds of polyunsaturated chains to be much greater than that of C-H bonds of double bond carbons (broadening effect).

Heterogeneity of lipids and fatty acids of fingerlings of Atlantic salmon Salmo salar L. different in weight and size

Lipid and fatty acid spectra have been investigated in fingerlings of Atlantic salmon distinguished by weight and length characteristics and degree of fatness. Heterogeneity in terms of fatty acids in the studied groups of fingerlings is shown which indicates the differences in the rates of biochemical reactions of synthesis and modification of lipids and fatty acids caused by phenotypic diversity. Specificities of the metabolic processes in the studied groups of salmon fingerlings are related to the qualitative variety of nutrition spectra and the availability of food in the biotope.

Lipids in the daubed shanny (Teleostei: Leptoclinus maculatus) in Svalbard waters

The daubed shanny, Leptoclinus maculatus, is a common fish species in Arctic and North Atlantic waters and has an important role in high-latitude ecosystems as a link between lower trophic levels and many fish, marine mammal and seabird species. Its biology and ecology have, however, remained largely unstudied. The primary aim of this study was to increase the knowledge about the daubed shanny by analysing total lipids, lipid-classes and the fatty acid composition of liver, muscle and female gonads in adults from the high Arctic archipelago of Svalbard. In female gonads, the triacylglycerols and wax esters in addition to cholesterol esters were dominant among the stored lipids. Triacylglycerols dominated in the liver, whereas structural lipids, such as phospholipids and cholesterols, were the most important lipids in muscles. Phosphatidylcholine and phosphatidylethanolamine were major phospholipids in all organs studied. The fatty acid spectrum of the investigated organs was characterized by a high amount of monounsaturated fatty acids, particularly in the liver. Polyunsaturated fatty acids, particularly 22:6(n-3) and 20:4(n-6), were prevalent in muscle tissues. The lipid and fatty acid spectra in the organs during this period of life are tightly connected with the activation of the liver metabolism and the storage of lipids in the developed female gonads. Lipid accumulation and distribution in gonads are transferred to optimal development of embryos and larvae in Arctic waters.

Molecular dynamics study of phosphatidylcholine and diacylglycerolipid bilayers in the liquid crystal phase

Molecular dynamics (MD) simulations were carried out for (i) hydrated bilayers of phosphatidylcholines (PCs): 1,2 stearoyl-sn-glycero-3-PC (18:0/18:0 PC), 1-stearoyl-2-oleoyl-sn-glycero-3-PC (18:0/18:1ω9cis PC), 1-stearoyl-2-linoleoyl-sn-glycero-3-PC (18:0/18:2ω6cis PC), 1-stearoyl-2-lineolenoyl-sn-glycero-3-PC (18:0/18:3ω3cis PC), 1-stearoyl-2-arachidonoyl-sn-glycero-3-PC (18:0/20:4ω6cis PC), 1-stearoyl-2-docosahexaenoyl-sn-glycero-3-PC (18:0/22:66ω3cis PC), and (ii) bilayers of diacylglycerolipid (DG) molecules with the acyl composition identical to that for PCs. The simulation boxes of the PC bilayers consisted of 96 PC molecules and 2304 water molecules (48 lipid molecules per layer and 24 H2) molecules per lipid). The water was modeled by explicit TIP3P water molecules. The head group of the DG molecules was treated as an effective sphere. The interfaces of each DG bilayer were modeled by flat surfaces; no water molecules were present explicitly in the DG bilayer MD simulation boxes consisted of 96 DG molecules. Mass density profiles along the PC and DG bilayer normal for different groups of atoms were calculated. The computer simulation results are compared to one another, to the available experimental data and to other computer investigations of saturated and unstaturated lipid bilayers.