Identifying Membrane Lateral Organization by Contrast-Matched Small Angle Neutron Scattering

A Small-Angle Neutron Scattering, Calorimetry and Densitometry Study to Detect Phase Boundaries and Nanoscale Domain Structure in a Binary Lipid Mixture

“…Hence, when a mixture consisting of a deuterated lipid species (dDPPC) and a hydrogenated lipid species (DLPC) phase separates, the phase-separated regions acquire different SLDs because of the difference in lipid composition in each phase. To drastically highlight these differences in SLD between phases in the membrane, the solvent’s SLD is chosen to match the membrane’s mean SLD, typically obtained when the membrane’s lipids are fully mixed—in a single phase—above the miscibility transition [ 14 ]. At this contrast match condition (when ), the scattering becomes flat (equal to the background) and featureless (as shown by Equation (1)).…”

“…At 40.6 °C, which is above the miscibility transition for this mixture, the scattering signal is flat, confirming that the membrane’s SLD has been matched to the solvent’s SLD. Upon lowering the temperature, below the miscibility transition, phase separation into solidus and liquidus domains ensues, and their presence is clearly captured by a significant increase in the scattering intensity [ 14 ]. This emergent scattering, however, is not due to the vesicle form factor as it is contrast-matched to the solvent but due to the characteristics of the domains in the vesicles.…”

“…Thus, techniques that study membranes at the nanoscale have been heavily pursued. Small-angle neutron scattering (SANS) stands out as a technique to probe this length scale because even though it is considered to be a low-resolution structure technique, with the use of selective deuteration, it has exquisite sensitivity to the emergence of nanoscale heterogeneities in membranes [ 14 ] and, as a result, has helped advance the field both using membrane mimics [ 15 ] as well as living cells [ 16 ]. In addition, analysis of the structures formed by phase separation in model membranes has given insights into, for example, the role of membrane mismatch between domains and the surrounding membrane environment and the size of the domains [ 17 ].…”

Vitamin E Does Not Disturb Polyunsaturated Fatty Acid Lipid Domains

“…As per Heberle et al, suspending a contrast-matched composition in mixtures of D 2 O and H 2 O can mask scattering from structural features that would normally dominate the scattering form factor. 40,55,56 In this situation, an increase in scattering emanates from contrast provided by lateral clustering of deuterated saturated lipid into ordered domains.…”

“…For contrast-matched neutron scattering investigations of lateral lipid organization, the scattering length density of the system must be tuned to suppress scattering from nonlateral features. , In this study, samples were prepared using a combination of chain protiated and chain perdeuterated (d70) DSPC such that the average scattering length density of the hydrocarbon region of the bilayer is equal to the scattering length density of the phosphatidylcholine headgroups. As per Heberle et al, suspending a contrast-matched composition in mixtures of D 2 O and H 2 O can mask scattering from structural features that would normally dominate the scattering form factor. ,, In this situation, an increase in scattering emanates from contrast provided by lateral clustering of deuterated saturated lipid into ordered domains.…”