Nanoscale membrane activity of surfactins: Influence of geometry, charge and hydrophobicity

We used real-time atomic force microscopy (AFM) to visualize the interactions between supported lipid membranes and well-defined surfactin analogs, with the aim to understand the influence of geometry, charge and hydrophobicity. AFM images of mixed dioleoylphosphatidylcholine/dipalmitoylphosphatidylcholine (DOPC/DPPC) bilayers recorded after injection of cyclic surfactin at 1 mM, i.e. well-above the critical micelle concentration, revealed a complete solubilization of the bilayers within 30 min. A linear analog having the same charge and acyl chains was able to solubilize DOPC, but not DPPC, and to promote redeposition leading eventually to a new bilayer. Increasing the charge of the polar head or the length of the acyl chains of the analogs lead to the complete solubilization of both DOPC and DPPC, thus to a stronger membrane activity. Lastly, we found that at low surfactin concentrations (40 µM), DPPC domains were always resistant to solubilization. These data demonstrate the crucial role played by geometry, charge and hydrophobicity in modulating the membrane activity (solubilization, redeposition) of surfactin. Also, this study suggests that synthetic analogs are excellent candidates for developing new surfactants with tunable, well-defined properties for medical and biotechnological applications.     

Novel mutations in the adipose triglyceride lipase gene causing neutral lipid storage disease with myopathy

A subgroup of neutral lipid storage disease has been recently associated with myopathy (NLSDM) and attributed to mutations in the gene (PNPLA2) encoding an adipose triglyceride lipase involved in the degradation of intracellular triglycerides. Five NLSDM patients have been described thus far and we reported three additional patients. A 44-year old Iranian woman and two Italian brothers, aged 40 and 35, presented with exercise intolerance and proximal limb weakness, elevated CK levels, and Jordan’s anomaly. Muscle biopsies showed marked neutral lipid accumulation in all patients. The 10 exons and the intron-exon junctions of the PNPLA2 gene were sequenced. Two novel homozygous mutations in exon 5 of PNPLA2 gene were found (c.695delT and c.542delAC). Both mutations resulted in frameshifts leading to premature stop codons (p.L255X and p.I212X, respectively). These mutations predict a truncated PNPLA2 protein lacking the C-terminal hydrophobic domain. These findings indicate that NLSDM is rare, but genetically heterogeneous.     

Lipid transfer proteins from Rosaceae fruits share consensus epitopes responsible for their IgE-binding cross-reactivity

Four IgE-binding epitopes have been characterized that cover a large area (40%) of the molecular surface of lipid transfer protein allergens of Rosaceae (apple, peach, apricot, and plum). They mainly correspond to electropositively charged regions protruding on the molecular surface of the modeled apple (Mal d 3), apricot (Pru ar 3), and plum (Pru d 3) allergens. Two of these epitopes consist of consensus epitopes structurally conserved among the lipid transfer protein allergens from the Rosaceae. Their occurrence in different lipid transfer protein allergens presumably accounts for the IgE-binding cross-reactivity often observed among different Rosaceae fruits. In this respect, LTP consist of phylogenetically- and structurally-related pan allergens. However, the IgE-binding cross-reactivity due to fruit lipid transfer protein has varying degrees of clinical relevance and this cross-reactivity is not necessarily accompanied by a cross-allergenicity to the corresponding fruits.     

Structural diversity and endotoxic activity of the lipopolysaccharide of Yersinia pestis

The endotoxic activity of the lipopolysaccharides (LPS) with defined chemical structure from Yersinia pestis strains of various subspecies differing in their epidemic potential was studied. The LPS of two strains of Y. pestis ssp. caucasica and ssp. altaica, whose structures have not been studied earlier, were analyzed by high-resolution mass spectrometry. In addition to reported structural changes, an increase in the degree of LPS phosphorylation was observed when strain I-2377 (ssp. altaica) was cultivated at an elevated temperature. A high tumor necrosis factor alpha(TNF-alpha)-inducing activity observed for LPS samples from Y. pestis cultures grown at 25 degrees C correlated with an increased degree of lipid A acylation, particularly, with the presence of the hexaacyl form of lipid A, which was absent from the LPS when bacteria were cultivated at 37 degrees C. No correlation was found between the lethal toxicity of the LPS in vivo and its ability to induce TNF-alpha production in vitro.     

Alteration of membrane lipid biophysical properties and resistance of human lung adenocarcinoma A_(549) cells to cisplatin

Alterations of membrane lipid biophysical properties of sensitive A549 and resistant A549/DDP cells to the Cis-dichlorodiammine platinum (Cisplatin) were performed by measurements of fluorescence and flow cytometry approaches using fluorescence dyes of DPH, N-AS and Mero-cyanine 540 (MC 540) respectively. Fatty acids of membrane lipid of the two cell lines were analyzed by gas chromatography. The results indicated clearly that fluorescence polarization (P) of the DPH probe is 0.169 for the sensitive A549 cell and 0.194 for the resistant A549/DDP cells. Statistical analysis showed significant difference between the two cell lines. The polarizations of 2-AS and 7-AS which reflect the fluidity of surface and middle of lipid bilayer are 0.134 and 0.144 for the sensitive A549 cells as well as 0.171 and 0.178 for the resistant A549/DDP cells respectively, but there is no significant difference of the polarization of 12-AS between the two cell lines. This shows that alterations of the membrane fluidity of both     

芝麻素散剂调血脂作用研究

目的：观察芝麻素散剂对实验性高脂血症大鼠血脂的影响。方法：在给大鼠喂以高脂饲料的同时灌胃芝麻素散剂14天后测定血清总胆固醇（TC）、甘油三酯（TG）和高密度脂蛋白胆固醇（LDL－C）水平。结果：芝麻素散剂明显抑制TC、LDL－C的升高。结论：芝麻素散剂对大鼠实验性高脂血症有显著的预防作用。     

豌豆根瘤脂质体的分布及形态特征

豌豆根瘤中有大量的脂质体,广泛分布于非侵染细胞和侵染细胞内,它既可以存在细胞质中,也可位于液泡里面。有时单个存在,有时又多个聚集在一起。非侵染细胞与侵染细胞相比,前者中的脂质体明显多于后者。这些脂质体近似圆形或椭圆形,表面无膜,电子密度较高,内部无固定的结构,常有一些细胞器位于它的附近。讨论了脂质体的细胞发育及细胞种类的关系。     

基因工程改良作物营养品质的研究

综述了近10年来采用基因工程技术改良作物蛋白质、糖类、脂类营养成分研究的最新发展,尤其对作物蛋白质含量及氨基酸组分改良方面进行了详细描述;并简要介绍了基因工程食品可能存在的不安全性问题及解决的办法。     

Reddening of Cotton (Gossypium Hirsutum L.) Leaves

Reddening of leaves is a physiological disorder in cotton induced by different abiotic stresses. Dramatic biochemical changes occurred in reddening leaves: strong accumulation of anthocyanins and drop of chlorophyll content, important increase of proline content and peroxidase activity. The lipid peroxide content indicative of membrane fragmentation was decreased. In this way a multicomponent system encompassing anthocyanins, proline, and peroxidase may act coordinately to overcome abiotic stress in cotton.     

Dynamics and orientation of transmembrane peptide from bacteriorhodopsin incorporated into lipid bilayer as revealed by solid state (31)P and (13)C NMR spectroscopy.

13C and (31)P NMR spectra of a transmembrane peptide, [1-(13)C]Ala(14)-labeled A(6-34), of bacteriorhodopsin incorporated into dimyristoylphosphatidylcholine (DMPC) bilayer were recorded to clarify its dynamics and orientation in the lipid bilayer. This peptide is shown to take an alpha-helical form both in liquid crystalline and gel phases, as viewed from the conformation dependent (13)C chemical shifts. In addition, this peptide undergoes rapid rigid-body rotation about the helical axis at ambient temperature as viewed from the axially symmetric (13)C chemical shift anisotropy, whereas this symmetric anisotropy is changed to an asymmetric pattern at temperatures below 10 degrees C. We further incorporated the peptide into the spontaneously aligned DMPC bilayer to applied magnetic field, induced by dynorphin (dynorphin:DMPC =1:10), a heptadeca-opioid peptide with very high affinity to opioid receptor, in order to gain insight into its orientation in the bilayer. This magnetically aligned system turned out to be persistent even at 0 degrees C as viewed from (31)P NMR spectra of the lipid bilayer, after this peptide was incorporated into this system [A(6-34): dynorphin: DMPC = 4:10:100]. It was found from the (13)C NMR spectra of [1-(13)C]Ala(14) A(6-34) that the helical axis of A(6-34) is oriented parallel to the bilayer normal irrespective of the presence or absence of reorientation motion about the helical axis at a temperature above the lowered gel to liquid crystalline phase transition.