scholarly journals Chemically synthesized Gb3 glycosphingolipids: tools to access their function in lipid membranes

2020 ◽  
Author(s):  
Jeremias Sibold ◽  
Somayeh Ahadi ◽  
Daniel B. Werz ◽  
Claudia Steinem
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Protein Binding ◽  
Shiga Toxin ◽  
Lipid Membranes ◽  
Phase Behaviour ◽  
Head Group ◽  
Force Microscopy ◽  
Toxin Binding ◽  
Liquid Ordered

Abstract Gb3 glycosphingolipids are the specific receptors for bacterial Shiga toxin. Whereas the trisaccharidic head group of Gb3 defines the specificity of Shiga toxin binding, the lipophilic part composed of sphingosine and different fatty acids is suggested to determine its localization within membranes impacting membrane organisation and protein binding eventually leading to protein internalisation. While most studies use Gb3 extracts, chemical synthesis provides a unique tool to access different tailor-made Gb3 glycosphingolipids. In this review, strategies to synthesize these complex glycosphingolipids are presented. Special emphasis is put on the preparation of Gb3 molecules differing only in their fatty acid part (saturated, unsaturated, α-hydroxylated and both, unsaturated and α-hydroxylated). With these molecules in hand, it became possible to investigate the phase behaviour of liquid ordered/liquid disordered supported membranes doped with the Gb3 species by means of fluorescence and atomic force microscopy. The results clearly highlight the influence of the different fatty acids of the Gb3 sphingolipids on the phase behaviour and the binding properties of Shiga toxin B subunits, even though the membranes were only doped with 5 mol% of the receptor lipid. To obtain fluorescent Gb3 derivatives, either fatty acid labelled Gb3 molecules or head group labelled ones were synthesized. These molecules enabled us to address the question, where the Gb3 sphingolipids are localized prior protein binding by means of fluorescence microscopy on giant unilamellar vesicles. The results again demonstrate that the fatty acid of Gb3 plays a pivotal role for the overall membrane organisation.

scholarly journals Shiga Toxin (Stx)-Binding Glycosphingolipids of Primary Human Renal Cortical Epithelial Cells (pHRCEpiCs) and Stx-Mediated Cytotoxicity

Toxins ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 139
Author(s):  
Johanna Detzner ◽  
Elisabeth Krojnewski ◽  
Gottfried Pohlentz ◽  
Daniel Steil ◽  
Hans-Ulrich Humpf ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Epithelial Cells ◽  
Shiga Toxin ◽  
Saturated Fatty Acids ◽  
Human Kidney ◽  
Enterohemorrhagic Escherichia Coli ◽  
Highly Sensitive ◽  
Liquid Ordered ◽  
Uremic Syndrome

Human kidney epithelial cells are supposed to be directly involved in the pathogenesis of the hemolytic–uremic syndrome (HUS) caused by Shiga toxin (Stx)-producing enterohemorrhagic Escherichia coli (EHEC). The characterization of the major and minor Stx-binding glycosphingolipids (GSLs) globotriaosylceramide (Gb3Cer) and globotetraosylceramide (Gb4Cer), respectively, of primary human renal cortical epithelial cells (pHRCEpiCs) revealed GSLs with Cer (d18:1, C16:0), Cer (d18:1, C22:0), and Cer (d18:1, C24:1/C24:0) as the dominant lipoforms. Using detergent-resistant membranes (DRMs) and non-DRMs, Gb3Cer and Gb4Cer prevailed in the DRM fractions, suggesting their association with microdomains in the liquid-ordered membrane phase. A preference of Gb3Cer and Gb4Cer endowed with C24:0 fatty acid accompanied by minor monounsaturated C24:1-harboring counterparts was observed in DRMs, whereas the C24:1 fatty acid increased in relation to the saturated equivalents in non-DRMs. A shift of the dominant phospholipid phosphatidylcholine with saturated fatty acids in the DRM to unsaturated species in the non-DRM fractions correlated with the GSL distribution. Cytotoxicity assays gave a moderate susceptibility of pHRCEpiCs to the Stx1a and Stx2a subtypes when compared to highly sensitive Vero-B4 cells. The results indicate that presence of Stx-binding GSLs per se and preferred occurrence in microdomains do not necessarily lead to a high cellular susceptibility towards Stx.

scholarly journals 2-Hydroxy Fatty Acid Enantiomers of Gb 3 Impact Shiga Toxin Binding and Membrane Organization

2015 ◽  
Vol 108 (12) ◽  
pp. 2775-2778 ◽  
Author(s):  
Ole M. Schütte ◽  
Lukas J. Patalag ◽  
Lucas M.C. Weber ◽  
Annika Ries ◽  
Winfried Römer ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Shiga Toxin ◽  
Hydroxy Fatty Acid ◽  
Membrane Organization ◽  
Toxin Binding

Formation of modulated phases and domain rigidification in fatty acid-containing lipid membranes

2017 ◽  
Vol 19 (20) ◽  
pp. 13252-13263 ◽  
Author(s):  
Naofumi Shimokawa ◽  
Rieko Mukai ◽  
Mariko Nagata ◽  
Masahiro Takagi
Keyword(s):  
Oleic Acid ◽  
Fatty Acid ◽  
Palmitic Acid ◽  
Elaidic Acid ◽  
Lipid Membranes ◽  
Phytanic Acid ◽  
Domain Boundary ◽  
Line Tension ◽  
Modulated Phases ◽  
Liquid Ordered

A liquid-ordered domain is transformed into a solid-ordered domain by the addition of palmitic acid or elaidic acid. Oleic acid and phytanic acid reduce the line tension at the liquid domain boundary and consequently modulated phases appear.

Modulation of BKCa channel activity by fatty acids: structural requirements and mechanism of action

2002 ◽  
Vol 283 (5) ◽  
pp. C1441-C1453 ◽  
Author(s):  
Alison L. Clarke ◽  
Steven Petrou ◽  
John V. Walsh ◽  
Joshua J. Singer
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Membrane Surface ◽  
Direct Interaction ◽  
Carbon Chain ◽  
Structural Features ◽  
Head Group ◽  
Bkca Channel ◽  
Channel Activity ◽  
Excised Patches

To determine the mechanism of fatty acid modulation of rabbit pulmonary artery large-conductance Ca2+-activated K+(BKCa) channel activity, we studied effects of fatty acids and other lipids on channel activity in excised patches with patch-clamp techniques. The structural features of the fatty acid required to increase BKCa channel activity (or average number of open channels, NP o) were identified to be the negatively charged head group and a sufficiently long (C > 8) carbon chain. Positively charged lipids like sphingosine, which have a sufficiently long alkyl chain (C ≥ 8), produced a decrease in NP o. Neutral and short-chain lipids did not alter NP o. Screening of membrane surface charge with high-ionic-strength bathing solutions (330 mM K+ or 130 mM K+, 300 mM Na+) did not alter the modulation of the BKCa channel NP oby fatty acids and other charged lipids, indicating that channel modulation is unlikely to be due to an alteration of the membrane electric field or the attraction of local counterions to the channel. Fatty acids and other negatively charged lipids were able to modulate BKCa channel activity in bathing solutions containing 0 mM Ca2+, 20 mM EGTA, suggesting that calcium is not required for this modulation. Together, these results indicate that modulation of BKCa channels by fatty acids and other charged lipids most likely occurs by their direct interaction with the channel protein itself or with some other channel-associated component.

Interference of fatty acids in the competitive protein-binding assay for serum thyroxine.

1976 ◽  
Vol 22 (5) ◽  
pp. 673-678 ◽  
Author(s):  
W Shaw ◽  
I L Hubert ◽  
F W Spierto
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Protein Binding ◽  
Unsaturated Fatty Acids ◽  
Binding Assay ◽  
Nonesterified Fatty Acids ◽  
Serum Thyroxine ◽  
Protein Binding Assay ◽  
Competitive Protein Binding Assay ◽  
Competitive Protein Binding

Abstract An increase in apparent thyroxine values obtained by competitive protein-binding assay on storage of sera is well documented. We find that the major source of this positive bias is probably the unsaturated nonesterified fatty acids. Nonesterified fatty acids cause a positive basis in the competitive protein-binding assay for serum thyroxine because they inhibit the binding of radioactive thyroxine by the serum-binding reagent (probably thyroxine-binding globulin). This inhibition by fatty acids may be due to the formation of a fatty acid/thyroxine complex. The degree of inhibition caused by the fatty acids depends on the length of the carbon chain of the fatty acid and the degree of saturation. Short-chain fatty acids are more potent inhibitors of thyroxine binding than those with a longer chain, and unsaturated fatty acids are more potent inhibitors of thyroxine binding than are saturated fatty acids. The polyunsaturated fatty acid, arachidonic acid, was the most potent inhibitor of all the fatty acids tested. Triglycerides (triacylglycerols) insignificantly inhibit thyroxine binding in this assay.

scholarly journals Preparation and Characterization of PEGylated C18 Fatty Acids/Anti-SNAP25 Antibody-Targeted Liposomes

2019 ◽  
Vol 13 (2) ◽  
pp. 129-139
Author(s):  
Lai Ti Gew ◽  
Vicit Rizal Eh Suk ◽  
Misni Misran
Keyword(s):  
Fatty Acids ◽  
Particle Size ◽  
Fatty Acid ◽  
Zeta Potential ◽  
Unsaturated Fatty Acids ◽  
Membrane Surface ◽  
Good Choice ◽  
Head Group ◽  
Transmission Electron ◽  
Membrane Bound

Background: Unsaturated C18 fatty acids, such as oleic acid (L1), linoleic acid (L2), and linolenic acid (L3), are a good choice of lipids to prepare liposomes. They are inexpensive, biocompatible, nontoxic, and readily available compared with phospholipids. Moreover, cis-double bonds of unsaturated fatty acids prevent the packing of molecules which increases membrane fluidity in liposomes making them a good choice of starting materials to prepare liposomes. Objective: Unsaturated C18 fatty acid liposomes, as well as their PEGylated and non- PEGylated antibody-targeted liposomes, were prepared and characterized. Methods: The particle size and zeta potential of the prepared liposomes (1 mM, pH = 7.4) for 28 and 14 days, respectively, were monitored and characterized. Membrane-bound antibodies Anti-SNAP25 (AS25) and DOPE PEG2000 (DP) were conjugated to pure C18 fatty acid liposomes to achieve stable fatty acid formulations. Results: The mean particle sizes of pure L1, L2, and L3 liposome solutions were 125, 129, and 122 nm respectively, while their polydispersity index values were 0.28, 0.21, and 0.40 respectively. A large negative zeta potential value of 45 mV was observed due to anionic carboxylate head-group of pure liposomes. The incorporation of AS25 into L1/DP, L2/DP, and L3/DP liposome solutions stabilized their mean particle size and zeta potential measurements over 28 and 14 days, respectively. Conclusion: L1/DP/AS25 was found to be the most stable PEGylated antibody-targeted liposome system because its particle size remained between 90 and 125 nm in 28 days. Transmission electron microscopy observations also supported the incorporation of AS25 and DP on the membrane surface as predicted.

Increased concentrations of serum free fatty acids falsely increase serum thyroxine as determined by competitive protein-binding.

1977 ◽  
Vol 23 (6) ◽  
pp. 990-993 ◽  
Author(s):  
P R Pannall ◽  
E Swanepoel ◽  
J M Bennett ◽  
F H Pauw
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Free Fatty Acid ◽  
Protein Binding ◽  
Free Fatty Acids ◽  
Close Association ◽  
Serum Thyroxine ◽  
Single Subjects ◽  
Competitive Protein Binding ◽  
Selection Of

Abstract Markedly increased concentrations of free fatty acids after a fatty meal and heparin injection already have been shown to falsely increase thyroxine values measured by competitive protein-binding techniques, where ethanol extraction in used. We report here the effect of lesser increases. In 10 patients receiving heparin during hemodialysis we found significant increases in serum thyroxine by competitive protein-binding (mean, 20 nmol/l) and in free fatty acid concentrations (164 micronmol/l). Thyroxine measured as iodine did not change significantly. In seven subjects who had fasted for 27 h, we also noted significant increases in thyroxine by competitive protein-binding (mean 63 nmol/l) and in free fatty acid concentrations (624 micronmol/l). In a single subjects, serial measurements showed a close association of the two variables and the overall correlation between the increases was good. This artefact limits the value of many currently used thyroxine methods because it imposes restrictions on transport of samples and selection of patients.

scholarly journals Adsorption Behavior and Wettability of Rhodochrosite Surface: Effect of C18 Fatty Acid Unsaturation

Minerals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 905
Author(s):  
Zhihui Shen ◽  
Qin Zhang ◽  
Xianbo Li ◽  
Qianlin Chen
Keyword(s):  
Fatty Acids ◽  
Contact Angle ◽  
Fatty Acid ◽  
Unsaturated Fatty Acids ◽  
Surface Effect ◽  
Surface Heterogeneity ◽  
Bond Number ◽  
Adsorption Behavior ◽  
Force Microscopy ◽  
Air Interface

Mineral surface wettability and its regulation by the adsorption of collectors have an important influence on the flotation performance. The adsorption behavior of C18 fatty acid with different unsaturation and its effect on rhodochrosite wettability was investigated with surface tension, contact angle, and atomic force microscopy (AFM) measurements. The results indicated that rhodochrosite hydrophobicity increased with the increasing concentration of fatty acid, along with the maximum contact angle (θmax) between hemimicelle concentration (HMC) and critical micelle concentration (CMC). Oleic acid (OA), linoleic acid (LA), and α-linolenic acid (ALA) had a higher θmax than stearic acid (SA), but the value decreased with the increase of C=C bond number. Besides, preferential adsorption of unsaturated fatty acids on the liquid-air interface can be attributed to the molecule’s steric hindrance resulting from C=C double bond, and the θ kept almost invariant with a higher value of ΓLG than ΓSL until HMC. The oriented monolayer and bilayer structure of fatty acids formed gradually on rhodochrosite surface with increasing concentration. However, the θmax may not necessarily correspond to the beginning of bilayer formation. Cylindrical monolayer and bilayer micelles of SA molecules were observed on rhodochrosite surface at HMC and CMC, respectively. While bilayer structures of unsaturated fatty acids formed before complete coverage of monolayer on rhodochrosite surface because of surface heterogeneity. This work provided a good understanding on the adsorption mechanism of fatty acid on rhodochrosite for flotation.

Platelet Aggregation in Finnish Men and Its Relation to Fatty Acids in Platelets, Plasma and Adipose Tissue

1985 ◽  
Vol 54 (03) ◽  
pp. 563-569 ◽  
Author(s):  
M K Salo ◽  
E Vartiainen ◽  
P Puska ◽  
T Nikkari
Keyword(s):  
Fatty Acids ◽  
Adipose Tissue ◽  
Fatty Acid Composition ◽  
Fatty Acid ◽  
Platelet Aggregation ◽  
Acid Composition ◽  
Saturated Fatty Acids ◽  
Free Living ◽  
Ω3 Fatty Acids ◽  
Induced Aggregation

SummaryPlatelet aggregation and its relation to fatty acid composition of platelets, plasma and adipose tissue was determined in 196 randomly selected, free-living, 40-49-year-old men in two regions of Finland (east and southwest) with a nearly twofold difference in the IHD rate.There were no significant east-southwest differences in platelet aggregation induced with ADP, thrombin or epinephrine. ADP-induced platelet secondary aggregation showed significant negative associations with all C20-C22 ω3-fatty acids in platelets (r = -0.26 - -0.40) and with the platelet 20: 5ω3/20: 4ω 6 and ω3/ ω6 ratios, but significant positive correlations with the contents of 18:2 in adipose tissue (r = 0.20) and plasma triglycerides (TG) (r = 0.29). Epinephrine-induced aggregation correlated negatively with 20: 5ω 3 in plasma cholesteryl esters (CE) (r = -0.23) and TG (r = -0.29), and positively with the total percentage of saturated fatty acids in platelets (r = 0.33), but had no significant correlations with any of the ω6-fatty acids. Thrombin-induced aggregation correlated negatively with the ω3/6ω ratio in adipose tissue (r = -0.25) and the 20: 3ω6/20: 4ω 6 ratio in plasma CE (r = -0.27) and free fatty acids (FFA) (r = -0.23), and positively with adipose tissue 18:2 (r = 0.23) and 20:4ω6 (r = 0.22) in plasma phospholipids (PL).The percentages of prostanoid precursors in platelet lipids, i. e. 20: 3ω 6, 20: 4ω 6 and 20 :5ω 3, correlated best with the same fatty acids in plasma CE (r = 0.32 - 0.77) and PL (r = 0.28 - 0.74). Platelet 20: 5ω 3 had highly significant negative correlations with the percentage of 18:2 in adipose tissue and all plasma lipid fractions (r = -0.35 - -0.44).These results suggest that, among a free-living population, relatively small changes in the fatty acid composition of plasma and platelets may be reflected in significant differences in platelet aggregation, and that an increase in linoleate-rich vegetable fat in the diet may not affect platelet function favourably unless it is accompanied by an adequate supply of ω3 fatty acids.

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