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9. Cellular effects of monohydrochloride of l-arginine, N α-lauroyl ethylester (LAE) on exposure to Salmonella typhimurium and Staphylococcus aureus.

Author

Rodríguez, E., Seguer, J., Rocabayera, X., and Manresa, A.

Subjects
*LAURIC acid, *ARGININE, *LAURIC acid diethanolamide, *AMINO acids, *SALMONELLA typhimurium, *SALMONELLA, *FLOW cytometry
Abstract

e. rodríguez, j. seguer, x. rocabayera and a. manresa. 2004. Here we study the effect of monohydrochloride of l-arginine, N α-lauroyl ethylester (LAE), a cationic preservative derived from lauric acid and arginine, on the cell envelopes of Salmonella typhimurium and Staphylococcus aureus at sub-lethal concentration such as their respective minimal inhibitory concentrations, 32 and 8 μg ml−1, respectively. Bacterial populations were studied by using transmission electron and fluorescence microscopy (TEM and FM), flow cytometry (FC) and ion-flux across the cellular membrane. Cell integrity was altered mainly in the outer membrane of S. typhimurium, but there was no significant change in the cytoplasm. However, in Staph. aureus, clear zones, abnormal septation and mesosome-like structures were observed in the cytoplasm. Bacterial populations were double-stained with propidium iodide (PI) and SYTO-13 for FC analysis. In S. typhimurium the proportion of damaged cells after 24 h was 97% and in Staph. aureus 56·3%. LAE induced transmembrane ion flux, the increase of potassium leakage after 30 min of contact was 7·7 and 3·34 μg ml−1 for Staph. aureus and S. typhimurium, respectively. Membrane disruption was detected by measuring the proton flow across the membrane. Disturbance in membrane potential and structural changes was caused by LAE, although cells were not disrupted. This is the first time the cellular effects of LAE on bacterial cells were studied. [ABSTRACT FROM AUTHOR]

Published
2004
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10. Stereochemistry-Dependent Self-Assembly in Synthetic Glycolipid/Water Systems:  The Aqueous Phase Structure of 1,3-Di-O-dodecyl-2-(β-maltoheptaosyl)glycerol

Author

Hato, M., Minamikawa, H., and Seguer, J. B.

Abstract

We have investigated the temperature−concentration dependent phase diagram of an aqueous maltoheptaose-containing lipid, 1,3-di-O-dodecyl-2-(β-maltoheptaosyl)glycerol, Mal7(C12)2. In the region examined (25−90 °C and 0−65 wt % lipid), two liquid crystalline phases form:  a normal hexagonal phase (HI) above 40−45 wt % lipid and a second phase (most probably a lamellar phase Lα) at higher temperatures (>55 °C) and higher concentrations (>60 wt % lipid). From the dilute solution to about 30 wt % lipid, an optically isotropic solution region is found where normal micelles exist. The present results together with the phase behavior of MalN(C12)2/water systems with N = 1−5 (Hato, M.; Minamikawa, H. Langmuir 1996, 12, 1658) indicate that a preferred phase of the MalN(C12)2 where the headgroup is composed of N glucose residues linked via α-1,4-O-glycosidic bonds shifts from an HII to an HI via an Lα phase as N increases. The observed phase sequence makes a marked contrast to the CelN(C12)2/water systems where the headgroup is composed of N glucose residues linked via β-1,4-O-glycosidic bonds (Hato, M.; Minamikawa, H. Langmuir 1996, 12, 1658). The stereochemistry-dependent phase behavior can be interpreted in terms of different conformations of the headgroups, i.e., a “helical” conformation of the maltooligosaccharide headgroups, and an “extended” conformation of the cellooligosaccharide headgroups.

Published
1998

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