Interfacial properties and critical micelle concentration of lysophospholipids

Abstract

The critical micelle concentration (cmc) of several lysophospholipids and of a lysophospholipid analogue was determined from surface tension measurements using the maximum bubble pressure method and/or 31P NMR. The use of the maximum bubble pressure method has now been extended to micromolar concentrations of surfactant, and the experimental parameters that effect its use have been explored. Surface activity was found to vary with changes in the chain length and in the headgroup polarity of the lysophospholipid. The cmc's for 1-decanoyl-, 1-dodecanoyl-, 1-tetradecanoyl-, and 1-hexadecanoyl-sn-glycero-3-phosphocholine are 7.0, 0.70, 0.070, and 0.007 mM, respectively. The cmc's for 1-decanoyl- and 1-dodecanoyl-sn-glycero-3-phosphoethanolamine are 4.4 and 0.33 mM, respectively. The cmc for dodecylphosphocholine, a lysophospholipid analogue, was found to be 1.1 mM. The cmc's for 1-tetradecanoyl- and 1-hexadecanoyl-sn-glycero-3-phosphoglycerol were found to be 3.0 and 0.60 mM, respectively, in pure water. In 0.1 M Tris-HCl (pH = 8.0), their cmc's are 0.16 and 0.018 mM, respectively. Surface tension and adsorption density values determined at the cmc are reported for each compound. The relationship of dynamic surface tension and lipid purity is discussed. These studies provide information about the micellization and interfacial properties of several biologically important lysophospholipids.

Lysophospholipids of Different Classes Mobilize Neutrophil Secretory Vesicles and Induce Redundant Signaling through G2A

“…Appropriately, plasma lyso-PLs are not stimulating: although present at concentrations of 100 M or more (all lyso-PC species combined) (20), the lyso-PLs are protein-bound, mostly to albumin, which mitigates against stimulation and cell damage (26 -28, 62, 63). Of note, G2A signaling by lyso-PLs in neutrophils required 10 M, approaching critical micelle concentrations (51,52), and introduction on albumin at substantially lower concentrations than that found in plasma. However, calcium flux was still seen at albumin concentrations up to 1%, approximately onequarter of that present in plasma (4%) (Fig.…”

“…In the current experiments, lyso-PE (even at concentrations of up to 50 M) gave clearly blunted responses in comparison with lyso-PC and lyso-PS for both calcium flux and G2A mobilization. Lyso-PE is considerably less polar and hydrated than lyso-PC and less membrane perturbing (51). Furthermore, lyso-PA was unable to induce calcium flux, suggesting that the presence of a bulky head group is a requirement for G2A signaling (see below).…”

Determining the Membrane Topology of Peptides by Fluorescence Quenching

“…Third, lyso-phospholipids can strongly adsorb to vesicles, while having at the same time the ability to exchange readily between vesicles. Furthermore, because they also form micellar dispersions in water (22), solubility problems associated with diacyl phospholipids can be circumvented. Finally, their transbilayer exchange rate (flip-flop) in diacyl phospholipid vesicles is low [t 1/2 ∼ days (23,24)].…”

Interhelical Packing in Detergent Micelles

“…EMRs were measured for TM 3-4 constructs dissolved in lauroyl-PG (LPG), myristoyl-PG (MPG), palmitoyl-PG (PPG), and stearoyl-PG (SPG) as well as octanoyl-PC (OPC), nonanoyl-PC (NPC), capryl-PC (CPC), lauroyl-PC (LPC), myristoyl-PC (MPC), and palmitoyl-PC (PPC). All lyso-lipids were at a concentration of 20 mM, except OPC, which was at a concentration of 100 mM to account for its critical micellar concentration, which may be as high as 70 mM (27). The pyrene fluorescence emission spectra in these various detergents are shown in Fig.…”

“…Thus, optimal interaction occurs in detergents with acyl chains of eight or nine carbons (in the case of lyso-PC) and decreases as the length of the acyl chain increases. We did not test the effect of lyso-PC detergents of fewer than 8 carbons or more than 16 carbons due to the high critical micellar concentration values of short chain lyso-PCs and the low water solubility of long chain lyso-PCs (27,35).…”