Formation of Inverted Hexagonal Phase in SDPE as Observed by Solid-State 31P NMR

Shaikh, Saame Raza; Brzustowicz, Michael R.; Stillwell, William; Wassall, Stephen R.

doi:10.1006/bbrc.2001.5454

Cited by 20 publications

(20 citation statements)

References 47 publications

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“…We intentionally designed the fluorophore to be localized to the head-group region rather than the terminal methyl end since we aimed to investigate the molecular motions of the acyl chains. One alternative possibility was to place the Bodipy on a phosphatidylethanolamine (PE) head-group; however, this probe could have been difficult to study since DHA-containing PEs can form inverted hexagonal phase [15]. Overall, our results were consistent with our previous study in which we showed another Bodipy probe could localize to the plasma membrane [18].…”

Section: Discussionsupporting

confidence: 90%

“…The rationale for using model membranes was that we wanted to determine if the probe could provide novel mechanistic information about DHA in highly disordered and ordered microdomains, which respectively model nonraft and raft-like membranes. Therefore, we used three different types of lipid vesicles that represented highly ordered (POPC/Chol), disordered (POPC) and highly disordered (SDPC) microdomains [15,16]. To verify that the probe was sensitive to membrane phase behavior, we measured the steady-state anisotropy in the fluid (37°C) and ordered (23°C) environments, similar to the cell culture studies (Fig.…”

Section: Resultsmentioning

confidence: 99%

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DHA-fluorescent probe is sensitive to membrane order and reveals molecular adaptation of DHA in ordered lipid microdomains

Teague

Ross

Harris

et al. 2013

The Journal of Nutritional Biochemistry

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Docosahexaenoic acid (DHA) disrupts the size and order of plasma membrane lipid microdomains in vitro and in vivo. However, it is unknown how the highly disordered structure of DHA mechanistically adapts to increase the order of tightly packed lipid microdomains. Therefore, we studied a novel DHA-Bodipy fluorescent probe to address this issue. We first determined if the DHA-Bodipy probe localized to the plasma membrane of primary B and immortal EL4 cells. Image analysis revealed that DHA-Bodipy localized into the plasma membrane of primary B cells more efficiently than EL4 cells. We then determined if the probe detected changes in plasma membrane order. Quantitative analysis of time-lapse movies established that DHA-Bodipy was sensitive to membrane molecular order. This allowed us to investigate how DHA-Bodipy physically adapted to ordered lipid microdomains. To accomplish this, we employed steady-state and time-resolved fluorescence anisotropy measurements in lipid vesicles of varying composition. Similar to cell culture studies, the probe was highly sensitive to membrane order in lipid vesicles. Moreover, these experiments revealed, relative to controls, that upon incorporation into highly ordered microdomains, DHA-Bodipy underwent an increase in its fluorescence lifetime and molecular order. In addition, the probe displayed a significant reduction in its rotational diffusion compared to controls. Altogether, DHA-Bodipy was highly sensitive to membrane order and revealed for the first time that DHA, despite its flexibility, could become ordered with less rotational motion inside ordered lipid microdomains. Mechanistically, this explains how DHA acyl chains can increase order upon formation of lipid microdomains in vivo.

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Section: Discussionsupporting

confidence: 90%

Section: Resultsmentioning

confidence: 99%

DHA-fluorescent probe is sensitive to membrane order and reveals molecular adaptation of DHA in ordered lipid microdomains

Teague

Ross

Harris

et al. 2013

The Journal of Nutritional Biochemistry

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“…An ever-expanding number of reports demonstrate that phospholipids containing DHA can have a tremendous impact upon membrane properties. Examples include increasing membrane permeability (Huster et al, 1997), driving the formation of inverted hexagonal (HII) phase (Shaikh et al, 2001), inducing negative curvature strain (Epand, 1998), increasing membrane fusion (Kafrawy et al, 1998) and vesicle formation (Williams et al, 1998), increasing phospholipid flipflop (Armstrong et al, 2003), increasing membrane inplane elasticity (Koenig et al, 1997;Smaby et al, 1997) and possibly promoting lateral segregation of lipids into domains . The extremely high degree of acyl chain flexibility conferred by polyunsaturation (Feller et al, 2002;Huber et al, 2002) is responsible.…”

Section: Membrane Structurementioning

confidence: 99%

Order from disorder, corralling cholesterol with chaotic lipids

Wassall

Brzustowicz

Shaikh

et al. 2004

Chemistry and Physics of Lipids

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“…An ensemble of many rapidly inter-converting conformations is the definitive picture that has subsequently emerged from a combination of NMR, X-ray diffraction and MD simulations (Eldho et al, 2003;Feller et al, 2002;Huber et al, 2002). This extreme flexibility of the PUFA chain accounts for the high "fluidity" (Holte et al, 1995;Salem and Niebylski, 1995), permeability (Huster et al, 1997), elasticity (Smaby et al, 1997), fusion (Ehringer et al, 1990;Kafrawy et al, 1998), enhanced flip-flop (Armstrong et al, 2003) and preference for non-lamellar phases (Gawrisch and Holte, 1996;Shaikh et al, 2001) associated with DHA in membranes. Therefore, DHA-rich regions in membranes are thin, have looser lipid packing, may prefer non-lamellar phases, can induce negative curvature strain to proteins (Slater et al, 1994) and are just more "dynamic" than the regions of membranes composed of other fatty acids.…”

Section: Introductionmentioning

confidence: 99%