Seasonal changes of fatty acid composition and thermotropic behavior of polar lipids from marine macrophytes

Major glyco- and phospholipids as well as betaine lipid 1,2-diacylglycero-O-4'-(N,N,N-tri-methyl)-homoserine (DGTS) were isolated from five species of marine macrophytes harvested in the Sea of Japan in summer and winter at seawater temperatures of 20-23 and 3 degrees C, respectively. GC and DSC analysis of lipids revealed a common increase of ratio between n-3 and n-6 polyunsaturated fatty acids (PUFAs) of polar lipids from summer to winter despite their chemotaxonomically different fatty acid (FA) composition. Especially, high level of different n-3 PUFAs was observed in galactolipids in winter. However, the rise in FA unsaturation did not result in the lowering of peak maximum temperature of phase transition of photosynthetic lipids (glycolipids and phosphatidylglycerol (PG)) in contrast to non-photosynthetic ones [phosphatidylcholine (PC) and phosphatidylethanolamine (PE)]. Different thermotropic behavior of these lipid groups was accompanied by higher content of n-6 PUFAs from the sum of n-6 and n-3 PUFAs in PC and PE compared with glycolipids and PG in both seasons. Seasonal changes of DSC transitions and FA composition of DGTS studied for the first time were similar to PC and PE. Thermograms of all polar lipids were characterized by complex profiles and located in a wide temperature range between -130 and 80 degrees C, while the most evident phase separation occurred in PGs in both seasons. Polarizing microscopy combined with DSC has shown that the liquid crystal - isotropic melt transitions of polar lipids from marine macrophytes began from 10 to 30 degrees C mostly, which can cause the thermal sensitivity of plants to superoptimal temperatures in their environment.     

Seasonal changes of lipid content in the leaves of some ferns

Seasonal distribution of total lipids, of total and individual phospholipids as well as of one betaine lipid, diacylglyceryl-N,N,N-trimethylhomoserine (DGTS), found in the leaves of Dryopteris carthusiana, Dryopteris filix-mas, Matteuccia struthiopteris and Pteridium aquilinum was studied. Using thin-layer chromatography it was shown that lipid composition was different in these species and changed substantially throughout the development of scrolls (unrolled young leaves) to vegetatively mature leaves. The maximum concentration of DGTS for all the examined species was found in scrolls. DGTS then decreased to its minimum level or entirely disappeared to reappear at later stages of leaf development. This may indicate a specific role of DGTS in the plant membrane.     

Seasonal variability of lipids and fatty acids in the tree-growing lichen Xanthoria parientina L.

The composition of lipids, PLs and FAs in the treegrowing lichenXanthoria parientina, collected during the period from Marchto May, was studied. The major polar lipids found, includingphospholipids, were DGTS, PC, PE, and PG. Polar and PL contentswere also identified, and certain trends in the changing proportionsof PC (increasing from 17.8 to 50.1%) and DGTS (decreasing from27.1 to 12.6%) were determined. The fatty acid composition wasexamined using capillary GC-MS in the neutral, glyco- and PLfractions. Hydroxy acids were detected only in the glycolipidfraction; their seasonal dynamics were also studied. The seasonalchanges occurring in lipid composition due to the temperaturefactor were identified. It was found that X. parientina hada characteristic temperature-based lipid pattern, increasingin its neutral lipid content from 40.6% in March to 52.7% inMay but decreasing in glycolipid from 39.0% in March to 27.0%in May. Key words: Xanthoria, lipids, DGTS, fatty acids, lichen     

Fatty acid composition of individual polar lipid classes from marine macrophytes

Major glycolipids [monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacylglycerol (SQDG)) and phospholipids (phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylglycerol (PG)] as well as betaine lipid 1,2-diacylglycero-O-4'-(N,N,N-tri-methyl)-homoserine (DGTS) were isolated from Anfeltia tobuchiensis (Rhodophyta), Laminaria japonica, Sargassum pallidum (Phaeophyta), Ulva fenestrata (Chlorophyta) and Zostera marina (Embriophyta), harvested in the Sea of Japan. GC analysis of their fatty acid (FA) composition revealed that the n-6 polyunsaturated FAs (PUFAs) shared the most part of the sum of n-6 and n-3 PUFAs in PC and PE compared with glycolipids and PG. In algae, it was related to the prevalence of 20:4n-6 over 20:5n-3 in non-photosynthetic lipids. Percentage of n-6 PUFAs as well as the sum of n-3 and n-6 PUFAs decreased in the following sequence: PC-->PE-->PG. The saturation increased in the lines of MGDG-->DGDG-->SQDG and PC-->PE-->PG. PG was close to SQDG by the level of saturation. Distribution of C(18) and C(20) PUFAs in polar lipids depended on taxonomic position of macrophytes. Balance between C(18) and C(20) PUFAs was preferably shifted to the side of C(20) PUFAs in PC and PE that was observed in contrast to glycolipids and PG from L. japonica containing both series of FAs. The set of major FAs of polar lipid classes can essentially differ from each other and from total lipids of macrophytes. For example, MGDG was found to accumulate characteristic fatty acids 16:4n-3, 16:3n-3, 18:3n-6 and 18:4n-3, 20:3n-6 in U. fenestrata, Z. marina, L. japonica and S. pallidum, respectively.     

The modulating effects of lipids on purified rat liver Golgi galactosyltransferase

Galactosyltransferase was purified from rat liver Golgi membranes. The Triton X-100, used to solubilize the enzyme was removed immediately prior to the lipid interaction studies. In lipid vesicles, prepared from a variety of phosphatidylcholines (PCs), including egg PC, DOPC, DMPC, DPPC and DSPC, the ability of the lipids to stimulate the enzyme decreased in the order egg PC greater than DOPC greater than DMPC greater than DPPC greater than DSPC, i.e. the lower the transition temperature (Tc) the greater the stimulation of the enzyme. A second, neutral lipid, phosphatidylethanolamine was used to permit a comparison of the effect of a different head group of the same net charge at neutral pH. The PEs included, egg PE, soy PE, Pl-PE, PE(PC) and DPPE in order of increasing Tc. The effect of the PEs was opposite to that of the PCs, i.e. the higher the Tc, the greater the stimulation of the enzyme. In fact egg PE and soy PE which have the lowest Tc values were inhibitory. Thus the modulation of the Golgi membrane galactosyltransferase by these lipids was different from that reported earlier for the bovine milk galactosyltransferase. The effects of two acidic lipids, egg phosphatidic acid (PA) and egg phosphatidylglycerol (PG) were studied also. Both totally inhibited the enzyme even at low concentrations of lipid, however, the PA was more effective than PG. In mixtures of neutral lipid (PC) and acidic lipid (PA or PG), the effect of the acidic lipid dominated. Even in the presence of excess PC, total inhibition of the enzyme was observed. It was concluded that the enzyme bound the acidic lipid preferentially to itself. The choice of the lipids allowed us to make several direct comparisons concerning the effect of the nature of the lipid head group on the activity of the enzyme. For example PE(PC), egg PA and egg PG would have fatty acid chains identical to egg PC since these three lipids are all prepared by modification of egg PC. As well, DPPE differs from DPPC only by nature of the head group. These comparisons indicated that not only the net charge but also chemical nature of the head group were important in the lipid modulation of Golgi galactosyltransferase.     

Lipid and fatty acids composition of photoautotrophically and heterotrophically grownChlamydomonas reinhardtii

Monogalactosyl diacylglycerol (MGDG), digalactosyl diacylglycerol (DGDG), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), phosphatidylinositol (PI) and sulfoquinovosyl diacylglycerol (SQDG) are the most abundant lipid classes present in both the autotrophically and heterotrophically grownChlamydomonas reinhardtii. However, phosphatidylcholine (PC) and diacylglycerol (N,N,N-trimethyl)-homoserine (DGTS) were absent in both alga types. The polyne index B was higher in heterotrophic than photoautotrophic algae, but the unsaturation index was higher in photoautotrophic algae PI, PE and DGDG. The proportion of linolenic acid decreased under heterotrophy with compensatory increases in hexadecadienoic (16 : 3), oleic (18 : 1) and linoleic (18 : 3) acids.     

A mechanism for phosphoglyceride and Ca2+ transbilayer movement

The ionophoretic capabilities of phosphoglycerides (PL) have been examined by measuring their translocation via cations from aqueous dispersions into linear and cyclic hydrocarbons. The PL surveyed were phosphatidic acid (PA), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), phosphatidylcholine (PC) and phosphatidylinositol (PI). Only PA displayed ionophoretic activity in single lipid dispersions with a cation selectivity order of Mn greater than Ca. PG, PE and PC, but not PI, had a synergistic affect of PA induced translocation. These PL, inactive individually or in any combination, became strong Ca2+ ionophores of variable activity in association with PA. A dimeric structure proposed for the ionophoretic species forms the basis of a mechanism for transbilayer movement of PA, PG, PE and PC which would establish an asymmetric distribution of these lipids in the two faces of the bilayer by equilibrium processes.     

The effect of salt on the lipid composition of Ectothiorhodospira

Major components of polar lipids of halophilic phototrophic Ectothiorhodospira species were PG, CL, PC and PE. PA was only present in minor amounts. According to ¹⁴C-incorporation, polar lipids approximated to 75%–93% of the total lipid carbon. With increasing salinity, a strong increase in the portion of PG and a decrease in that of PE (especially in Ectothiorhodospira mobilis BN 9903) and CL (especially in E. halophila strains) were observed. Moreover, there was a significant increase in the excess negative charges of phospholipids upon increasing medium salinity. This increase was most dramatic in the slightly halophilic E. mobilis BN 9903, but quantitatively less important in both strains of E. halophila which had, however, a higher percentage of negative charges of their lipids. During salt-shift experiments, E. halophila BN 9630 responded to suddenly increased salinity by promoting the biosynthesis of PG and decreasing that of PC, CL and PE. Upon dilution stress, responses were reversed and resulted in a strong increase in PE biosynthesis. The effects of lipid charges and bilayer forming forces in stabilizing the membranes of Ectothiorhodospira species during salt stress are discussed.Abbreviations PC phosphatidylcholine - PG, PG-1, PG-2 phosphatidylglycerol - CL, CL-1, Cl-2 cardiolipin - PE phosphatidylethanol-amine - PA phosphatidic acid - NL nonpolar lipids - ori origin - TLC thin layer chromatography     

Betaine lipids in chlorarachniophytes

Evolving from the endosymbiosis of a green algal cell by a filose amoeba or amoeboflagellate, the chimearic chlorarachniophytes combine unique features retained from both of their ancestral units. They have preserved from the endosymbiont only the nucleomorph and chloroplast. Four strains from three genera of this algal class were studied to identify a set of non‐phosphorous‐containing polar lipids and their associated fatty acids using the techniques of positive‐ion electrospray ionization/mass spectrometry (ESI/MS) and electrospray ionization/mass spectrometry/mass spectrometry (ESI/MS/MS). Fourteen non‐phosphorous‐containing polar lipids, classified as betaine lipids were primarily identified as forms of diacylglyceryl‐N,N,N‐trimethylhomoserine (DGTS) and its structural isomer diaclyglycerylhydroxymethyl‐N,N,N‐trimethyl‐β‐alanine (DGTA). Though the number of forms of DGTA and DGTA were roughly equal, DGTS composed more of the polar lipid portion present in three of the strains tested, while the fourth, Lotharella globosa, was dominated by forms of DGTA. In addition, a lipid tentatively identified as diacylglycerylcarboxyhydroxymethylcholine (DGCC) was observed twice in minor amounts. The polar lipid‐associated fatty acids of the aforementioned algal strains generally included dodecanoic acid (12:0), tetradecanoic acid (14:0), hexadecanoic acid (16:0), octadecanoic acid (18:0), octadecenoic acid (18:1), and eicosapentaenoic acid [20:5(n‐3)]. The differences in betaine lipid content among the species studied may allow for further conclusions to be drawn regarding the taxonomy of chlorarachniophytes.     

苜蓿根瘤菌17560细胞膜膜脂组成分析及DGTS合成基因克隆与表达

【目的】分析一株分离自黑龙江省的苜蓿根瘤菌在低磷胁迫及正常磷含量条件下细胞膜脂的组成,并从该菌中克隆和鉴定细胞膜无磷脂二酰基甘油三甲基高丝氨酸(DGTS)合成基因。【方法】分别在不同磷含量的Sherwood基本培养基中进行根瘤菌培养,采用Bligh-Dyer方法提取细胞膜脂,以文献报道Sinorhizobium meliloti(苜蓿中华根瘤菌)菌株1021的脂类图谱和磷脂PE、PG、PC标准品作为参照,利用薄层层析方法分析不同磷含量条件下培养菌株的细胞膜脂组成。根据GenBank中已发表的DGTS合成基因btaA和btaB序列设计引物,以产DGTS菌株基因组DNA为模板,扩增btaA和btaB同源基因,并在E.coil BL21(DE3)表达。同时检测表达菌株是否合成细胞膜无磷脂DGTS以验证基因功能。对菌株17560进行16S rRNA基因序列分析。【结果】分离自黑龙江省的苜蓿根瘤菌17560与Sinorhizobium meliloti的16S rRNA基因序列相似性高达99.8%,但其细胞膜脂组成明显不同于参比菌株Sinorhizobium meliloti 1021的膜脂组成。在低磷胁迫条件下,该菌株的细胞膜脂主要由OL和DGTS等无磷脂组成,但OL的组成明显不同,该菌株含有3种不同类型的鸟氨酸脂(OLs),而参比菌株Sinorhizobium meliloti 1021只含有一种类型的鸟氨酸脂(OL)。在正常磷含量条件下,该菌株的细胞膜脂主要由PE和一种未知的含氨基磷脂组成,PG与PC的含量均较少,而参比菌株Sinorhizobium meliloti 1021的细胞膜脂主要由PE、PG与PC组成。通过PCR扩增从产DGTS菌株17560中获得1 913 bpDNA片段,经序列分析发现其中有两个ORF与菌株Sinorhizobium meliloti 1021的btaA和btaB基因序列相似性均为99%。将该DNA片段克隆于pET-30a(+)得到重组质粒pLH01,转化宿主菌获得表达菌株E.coli BL21(DE3).pLH01,经IPTG诱导后产生相对分子量约为45 kD和25 kD的蛋白。薄层层析验证重组菌细胞膜脂组成,结果表明,表达菌株E.coliBL21(DE3).pLH01可以在IPTG诱导后合成无磷脂DGTS,而转入空载体pET-30a(+)的阴性对照菌株E.coli BL21(DE3).pET-30a(+)则不能合成。【结论】系统发育地位相同的苜蓿根瘤菌株的细胞膜脂组成明显不同;苜蓿根瘤菌的细胞膜组成随培养基中的磷含量不同而变化,低磷胁迫条件下其细胞膜脂主要由OL和DGTS等无磷脂组成;在Sinorhizobium膜脂中首次发现一种未知的氨基磷脂及3种不同类型的鸟氨酸脂(OLs);从菌株17560中克隆获得2个DGTS合成基因btaA和btaB,在大肠杆菌中成功表达,并证实了所表达基因的功能。     

Effects of Cadmium on Polar Lipid Composition and Unsaturation in Maize （Zea mays） in Hydroponic Culture

This study aimed to evaluate the effect of Cd exposure （100 μmol/L） on polar lipid composition, and to examine the level of fatty acid unsaturation in maize （Zea mays L.）. In roots, the level of 16：0 and monounsaturated fatty acids （16：1 ＋ 18：1） decreased in phosphatidylcholine （PC） and phosphatidylethanolamine （PE）. In contrast, the proportion of unsaturated 18-C fatty acid species showed an opposite response to Cd. The content, on the other hand, of PC, PE, digalactosyldiacylglycerol （DGDG）, and steryl lipids increased in roots （2.9-, 1.6-, 5.3-, and 1.7-fold increase, respectively）. These results suggest that a more unsaturated fatty acid composition than found in control plants with a concomitant increase in polar lipids may favor seedling growth during Cd exposure. However, the observed increase in the steryl lipid （SL） ： phospholipid （PL） ratio （twofold）, the decrease in monogalactosyldiacylglycerol （MGDG） ： DGDG ratio, as well as the induction of lipid peroxidation in roots may represent symptoms of membrane injury. In shoots, the unsaturation level was markedly decreased in PC and phosphatidylglycerol （PG） after Cd exposure, but showed a significant increase in sulfoquinovosyldiacylglycerol （SQDG）, MGDG and DGDG. The content of PG and MGDG was decreased by about 65%, while PC accumulated to higher levels （4.4-fold increase）. Taken together, these changes in the polar lipid unsaturation and composition are likely to be due to alterations in the glycerolipid pathway. These results also support the idea that the increase in overall unsaturation plays some role in enabling the plant to withstand the metal exposure.     

The characterisation and cyclic production of a highly unsaturated homoserine lipid in Chlorella minutissima

The marine alga Chlorella minutissima contains DGTS (diacylglyceryl-N,N,N-trimethylhomoserine) as a major component (up to 44% of total lipids). This lipid is absent from other members of the Chlorococcales, except for C. fusca, which contains DGTS as 1.3% of total lipids. Contrary to expectation, the DGTS is accompanied by PC (phosphatidylcholine) as the major phospholipid. DGTS is normally highly saturated in the C-1 position of glycerol, but in C. minutissima, both C-1 and C-2 are acylated with EPA (eicosapentaenoic acid, 20:5) in the major molecular species (over 90% of total). The DGTS level shows a marked rhythmic fluctuation with time which is inversely correlated with the level of MGDG (monogalactosyldiacylglycerol), the other major lipid. Improved NMR data and the first electrospray MS data on this lipid are presented.     

The effect of phosphate starvation on the lipid and fatty acid composition of the fresh water eustigmatophyte Monodus subterraneus

Phosphate limitation caused significant changes in the fatty acid and lipid composition of Monodus subterraneus. With decreasing phosphate availability from 175 to 52.5, 17.5 and 0 microM (K2HPO4), the proportion of the major VLC-PUFA, eicosapentaenoic acid (EPA), gradually decreased from 28.2 to 20.8, 19.4 and 15.5 mol% (of total fatty acids), respectively. The cellular total lipid content of starved cells increased, mainly due to the dramatic increase in triacylglycerols (TAG) levels. Among polar lipids, cellular contents of digalactosyldiacylglycerol (DGDG) and diacylglyceroltrimethylhomoserine (DGTS) increased sharply from 0.29 and 0.19 to 0.60 and 0.38 fg cell(-1), respectively, while that of monogalactosyldiacylglycerol (MGDG) was not significantly changed. In the absence of phosphate, the proportion of phospholipids was significantly reduced from 8.3% to 1.4% of total lipids, and the proportion of triacylglycerols (TAG) increased from 6.5% up to 39.3% of total lipids. The share of MGDG was substantially reduced, from 35.7% to 13.3%, while that of DGDG and DGTS reduced less from 18.3% to 15.1%, and 12.2% to 8.6%, respectively. The most distinctive change in the fatty acid composition was noted in that of DGDG, where the proportion of EPA, located exclusively at the sn-1 position, increased from 11.3% to 21.5% at the expense of 16:0, 16:1 and 18:1. In MGDG, however, the proportion of EPA did not change appreciably. In contrast to higher plants, DGDG accumulated under P-deprivation in M. subterraneus, did not resemble PC and the positional distribution of its fatty acids was not altered, preserving the C20/C16 structure of its molecular species. We suggest that under phosphate starvation DGTS is a likely source of C20 acyl groups that can be exported to the sn-1 position of DGDG and can partially compensate for the decrease in PE, the apparent source of C20 acyl-containing diacylglycerols in this alga. Moreover, accumulation of non-esterified 18:0 indicates that no polar lipid can replace PC, which appears to be the only lipid capable of C18 desaturation in this alga.     

Distribution of a Betaine Lipid O-(1,2-Diacylglycero)-4′-(N,N,N-Trimethyl)homoserine in Tissues of Some Lycopodiophyta Species

The distribution of O-(1,2-diacylglycero)-4-(N,N,N-trimethyl)homoserine (DGTS), a betaine lipid, in ten samples of plants belonging to the division Lycopodiophyta collected in various habitats was studied. Homogeneous plant tissues (vegetative shoots and spikelets) and mixed tissues (shoots with spikelets) were analyzed. A particular attention was paid to the DGTS-synthesizing ability of various club mosses, various tissue types forming an organ in a single plant species, as well as the ratio between DGTS and other glycerolipid classes.     

Betaine Lipids in Lower Plants. Biosynthesis of DGTS and DGTA in Ochromonas danica (Chrysophyceae) and the Possible Role of DGTS in Lipid Metabolism

Membrane lipids and fatty acids of Ochromonas danica were analyzed.Of the two betaine lipids, the homoserine lipid DGTS mainlycontains 14:0 and 18:2 fatty acids, while the alanine lipidDGTA is enriched in 18:0, 18:2 and 22:5 fatty acids. Of thepolar moiety of DGTA, improved NMR data are presented. On incubationof cells with [3,4-¹⁴C]methionine, DGTS as well as DGTA werelabelled. With [1-¹⁴C]methionine as a substrate, the label appearedin DGTS only. If double labelled [³H](glycerol)/[¹⁴C](polarpart)DGTS was used as a precursor, radioactivity was incorporatedspecifically into DGTA in which the isotope ratio was unchangedcompared to the precursor. Thus, the glyceryltrimethylhomoserinepart of DGTS acts as the precursor of the polar group of DGTA.Labelling of cells with [1-¹⁴C]oleate in a pulse-chase mannerand subsequent analysis of the label in the fatty acids andmolecular species of different lipids including DGTS and DGTA,suggested a clearly different role of the two betaine lipids:DGTS acts as a i) primary acceptor for exogenous C₁₈ monoeneacid, ii) substrate for the desaturation of 18:1 to 18:2 acid,and iii) donor of mainly 18:2 fatty acid to be distributed amongPE and other membrane lipids. Into DGTA, in contrast, fattyacids are introduced only after elongation and desaturation.As a result, the biosynthesis of DGTA from DGTS involves a decarboxylationand recarboxylation of the polar part and a simultaneous deacylationand reacylation of the glycerol moiety. (Received January 28, 1992; Accepted March 11, 1992)     

Seasonal changes in polar lipids in fronds of the ferns Dryopteris filix-mas and Matteuccia struthiopteris

The distribution pattern of total lipids, glyco- and phospholipids, and one betaine lipid (DGTS) in the fronds of the ferns Dryopteris filix-mas and Matteuccia struthiopteris was studied. The lipid composition of the embryo leaflets forming a bud, or treble clef, and that of fully opened leaves changed throughout the growth season. The maximum amount of DGTS in clefs and mature leaves was detected at the beginning of the season. By midsummer, the DGTS content decreased, dropping to zero in the fully opened leaves, and then increased again. The amount of DGTS in the clefs collected in October versus those collected in May was somewhat higher in the case of Dryopteris filix-mas and almost twofold lower in the case of Matteuccia struthiopteris. The ratio between polar lipids contained in the clefs and mature leaves throughout the growth season was determined.     

Profiling membrane lipids in plant stress responses. Role of phospholipase D alpha in freezing-induced lipid changes in Arabidopsis

A sensitive approach based on electrospray ionization tandem mass spectrometry has been employed to profile membrane lipid molecular species in Arabidopsis undergoing cold and freezing stresses. Freezing at a sublethal temperature induced a decline in many molecular species of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylglycerol (PG) but induced an increase in phosphatidic acid (PA) and lysophospholipids. To probe the metabolic steps generating these changes, lipids of Arabidopsis deficient in the most abundant phospholipase D, PLD alpha, were analyzed. The PC content dropped only half as much, and PA levels rose only half as high in the PLD alpha-deficient plants as in wild-type plants. In contrast, neither PE nor PG levels decreased significantly more in wild-type plants than in PLD alpha-deficient plants. These data suggest that PC, rather than PE and PG, is the major in vivo substrate of PLD alpha. The action of PLD alpha during freezing is of special interest because Arabidopsis plants that are deficient in PLD alpha have improved tolerance to freezing. The greater loss of PC and increase in PA in wild-type plants as compared with PLD alpha-deficient plants may be responsible for destabilizing membrane bilayer structure, resulting in a greater propensity toward membrane fusion and cell death in wild-type plants.     

Effect of lipid composition on buforin II structure and membrane entry

Buforin II is a 21-amino acid polycationic antimicrobial peptide derived from a peptide originally isolated from the stomach tissue of the Asian toad Bufo bufo gargarizans. It is hypothesized to target a wide range of bacteria by translocating into cells without membrane permeabilization and binding to nucleic acids. Previous research found that the structure and membrane interactions of buforin II are related to lipid composition. In this study, we used molecular dynamics (MD) simulations along with lipid vesicle experiments to gain insight into how buforin II interacts differently with phosphatidylcholine (PC), phosphatidylglycerol (PG), and phosphatidylethanolamine (PE) lipids. Fluorescent spectroscopic measurements agreed with the previous assertion that buforin II does not interact with pure PC vesicles. Nonetheless, the reduced entry of the peptide into anionic PG membranes versus neutral PC membranes during simulations correlates with the experimentally observed reduction in BF2 translocation through pure PG membranes. Simulations showing membrane entry into PC also provide insight into how buforin II may initially penetrate cell membranes. Our MD simulations also allowed us to consider how neutral PE lipids affect the peptide differently than PC. In particular, the peptide had a more helical secondary structure in simulations with PE lipids. A change in structure was also apparent in circular dichroism measurements. PE also reduced membrane entry in simulations, which correlates with decreased translocation in the presence of PE observed in previous studies. Together, these results provide molecular-level insight into how lipid composition can affect buforin II structure and function and will be useful in efforts to design peptides with desired antimicrobial and cell-penetrating properties.     

Seasonal variations of diacylglyceryl-N,N,N-trimethylhomoserine content in Polypodiophyta

Diacylglyceryl-N,N,N-trimethylhomoserine (DGTS) belongs to a family of three known betaine lipids. It is synthesized by a number of bacteria, fungi, brown, red and green algae, in addition to lichens, and is also found in higher plants Bryophyta, Equisetophyta and Polydiophyta. It has been determined that DGTS plants can be DGTS-positive or DGTS-negative. The purpose of the present study was to examine the leaves of the ferns Drytopteris filix-mas (L.) Tod. and Pteridium aquilinum (L.) Kuhn, collected at different time periods during a single vegetation season for their DGTS contents. The results obtained show that amounts of DGTS in all of the species examined varies relative to the time periods in which they were collected.     

Interaction of a polymeric biguanide biocide with phospholipid membranes

Differential scanning calorimetry (DSC) and fluorescence polarization methods have been used to study the interactions between phospholipid membranes and a polymeric biocide, poly(hexamethylene biguanide hydrochloride) (PHMB). It was found that PHMB had very little effect on neutral lipids such as phosphatidylcholine (PC) and phosphatidylethanolamine (PE), whereas it greatly reduced the phase transition temperature of phosphatidylglycerol (PG), an acidic lipid found in bacteria. Although the corresponding monomeric biocide had a similar effect on the PG bilayer, the behaviour towards mixed lipid bilayers of PC and PG has been shown to be completely different for the polymeric and monomeric biocides: viz. the former can induce isothermal phase separation into a PHMB-PG complex domain and a PC-enriched domain, whilst the latter cannot. This may account for the great difference in bactericidal activity between them. It is suggested that PHMB interacts primarily with negatively charged species in the membranes, inducing aggregation of acidic lipids in the vicinity of the adsorption site, where higher fluidity and higher permeability are expected. The results have shown that two factors might be crucial in the cidal activity of such types of cationic disinfectants as biguanides: phase separation and interaction with the hydrocarbon interior of the membranes. Polymeric biocides could be particularly effective by virtue of their ability to combine hydrophobic character and multiple charges within a single molecule.