Size-dependent ultrafast structural dynamics inside phospholipid vesicle bilayers measured with 2D IR vibrational echoes

Abstract

The ultrafast structural dynamics inside the bilayers of dilauroylphosphatidylcholine (DLPC) and dipalmitoylphosphatidylcholine vesicles with 70, 90, and 125 nm diameters were directly measured with 2D IR vibrational echo spectroscopy. The antisymmetric CO stretch of tungsten hexacarbonyl was used as a vibrational probe and provided information on spectral diffusion (structural dynamics) in the alkyl region of the bilayers. Although the CO stretch absorption spectra remain the same, the interior structural dynamics become faster as the size of the vesicles decrease, with the size dependence greater for dipalmitoylphosphatidylcholine than for DLPC. As DLPC vesicles become larger, the interior dynamics approach those of the planar bilayer.vesicle bilayer dynamics | vesicle size dependent dynamics | vesicles chainlength dependent dynamics T he plasma membrane provides a boundary between a living cell and its surroundings and between cellular compartments, providing organizational control of proteins and small molecules that are critical for achieving the complexity of biological systems. In addition to a permeability barrier, the second role of the plasma membrane is serving as the solvent for membrane proteins and other biomolecules. The lipid environment of membrane proteins can influence their function (1-5), and so impact cell signaling, metabolism, growth, defense, and a myriad of other biological functions.Membranes have a bilayer structure where the nonpolar chains of the lipids form the interior of bilayer, with zwitterionic or ionic head groups at the interfaces with water. Artificial lipid bilayers are frequently used as models of cell membranes for investigation of membrane properties and in studies of transmembrane proteins. Although a good deal is known about the structure of artificial membranes (6-12) and orientational and translational diffusion of lipids and other molecules (7, 13-16), much less is known about the fast interior structural dynamics of the bilayers, which serve as the dynamic bath modes that can impact membrane processes.Unilamellar vesicles (ULVs) of different sizes, as well as multilamellar vesicles (MLVs), are used as model membranes owing to their ease of preparation and handling. It has been shown that their properties depend on the curvature (size) (8,9,13,(17)(18)(19)(20). Aligned planar multi-bilayers (21) are membrane models that do not have curvature, yet they are less attractive for routine use because they are substantially more difficult to prepare than vesicles.Numerous experiments have been performed to determine which type of model bilayers most closely represents the properties of the plasma membrane. However, no consensus exists because the results obtained by different methods and groups are not in agreement. Some small-angle X-ray scattering and small-angle neutron scattering (SANS) experiments indicate that the structural properties of ULVs and MLVs are curvature independent, the overall bilayer thickness does not dependent on vesicle size, and the thicknesses of...

Phosphatidylinositol-(4,5)-Bisphosphate Acyl Chains Differentiate Membrane Binding of HIV-1 Gag from That of the Phospholipase Cδ1 Pleckstrin Homology Domain

“…This experimental system allowed us to study interactions within a membrane that is largely flat and thus mimics the natural membrane curvature encountered by cytoplasmic proteins in cells. Curvature effects could also impact acyl chain dynamics, which have been observed in model systems through two different approaches (26,27). Also, the use of GUVs, which are easily visualized by fluorescence microscopy, enabled us to probe Gag binding to membranes containing multiple phases of lipids in different physical states.…”

The Influence of Cholesterol on Fast Dynamics Inside of Vesicle and Planar Phospholipid Bilayers Measured with 2D IR Spectroscopy

“…33 The vesicle dynamics approached those of planar bilayers as the size of the vesicle was increased. 33 Here, regardless of the cholesterol concentration, the dynamics in the vesicle bilayers are faster than in the planar bilayers. In contrast to the planar bilayers, the first addition of cholesterol to the vesicle bilayers leaves the fast component of the dynamics unchanged and the slow component speeds up outside of the error bars.…”

“…33 The lipid/cholesterol/W(CO) 6 mixture was first dissolved in dichloromethane, the dichloromethane was evaporated, and the lipid was rehydrated in D 2 O. The concentration of W(CO) 6 in the vesicle bilayers was 1 per 100 lipids.…”

“…The orientational relaxation times are all ∼6 ps. 14,33 The orientational relaxation contributes ∼0.6 cm −1 to the homogeneous line width. This is a small contribution that does not vary systematically with sample.…”

Thin and ordered hydrogel films deposited through electrospinning technique; a simple and efficient support for organic bilayers

“…3b show a micrograph with certain surface homogeneity, probably related to technique used for DPPC bilayer deposition (Langmuir-Blodgett). However, on layer surface it was possible to observe small rounded aggregates structures with a diameter that rounds 0.6-0.8 µm, identified as vesicles (closed bilayer upon itself containing water in their interior), these structures were formed probably due to the moist environment and, also, to hydrogel ability of absorb water and release it to the system [35].…”