Two-Dimensional Polymerization of Lipid Bilayers:Degree of Polymerization of Sorbyl Lipids

Lamparski, Henry; O’Brien, David F.

doi:10.1021/ma00110a010

Cited by 48 publications

(146 citation statements)

References 15 publications

(17 reference statements)

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“…Acryl/DenPC 16,16 exhibited a broad main transition endotherm, which could be either a function of the lipid-phase behavior or due to the presence of isomer impurities. A phase transition was not observed between 6 and 60°C for Acryl/ DenPC 16,14 . Sorb/DenPC 18,21 did not have a phase transition above 5°C, presumably because of the cis double bond at the center of the sn-1 chain, which substantially lowers T m values.…”

Section: Resultsmentioning

confidence: 81%

“…12 The reactive groups were selected to yield one series of monomeric lipids with groups having similar reactivity, i.e., Sorb/Den, and a second series where the reactivity of the groups differ significantly, i.e., Acryl/Den. 13,14 These variations in molecular structure may result in differences in the rate and degree of polymerization. This report focuses on the effect of monomer structure on the architecture (linear or crosslinked) of the polymers formed.…”

Section: Resultsmentioning

confidence: 99%

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Synthesis and Polymerization of Heterobifunctional Amphiphiles to Cross-Link Supramolecular Assemblies

2000

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The cross-linking of supramolecular assemblies of hydrated amphiphiles is an effective method to stabilize the assembly. A well-known strategy for cross-linking of lipids in lyotropic phases is the inclusion of identical reactive groups in each hydrophobic tail of the lipids. An alternative approach is to incorporate two similar but distinct groups into different locations within a single hydrophobic tail of the amphiphile. In principle, these heterobifunctional amphiphiles could react to form ladderlike polymers or cross-linked polymers. This report describes the synthesis, characterization, and polymerization in lipid vesicles of two series of heterobifunctional phosphatidylcholine (PC) lipids with different separation distances between the two reactive groups. One of the groups, i.e., dienoyl (Den), is attached to the secondary oxygen of the glycerol backbone of the lipid, and the other is either an acryloyl (Acryl) or sorbyl (Sorb) functional group located at the sn-2 chain terminus. Polymerization of both reactive groups in the Acryl/DenPC or the Sorb/DenPC was achieved by either redox polymerization or direct photoirradiation. The degree of polymerization depends on the initiation chemistry. Photoirradiation yields oligomers that are insufficient to cross-link the vesicles, whereas redox-initiated radical polymerization affords cross-linked polymeric vesicles. Under radical polymerization conditions a spacer length of seven or more atoms between the two reactive groups was long enough to ensure that each reactive group can follow an independent reaction path.

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Section: Resultsmentioning

confidence: 81%

Section: Resultsmentioning

confidence: 99%

Synthesis and Polymerization of Heterobifunctional Amphiphiles to Cross-Link Supramolecular Assemblies

2000

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“…Because of the possibility that this second photoreaction could lead to uncontrolled cross-linking of the sorbyl lipids, precautions were taken against this occurrence by both the use of short photolysis times (13.0 min) and the attenuation of short wavelength light incident on the samples with a 230 nm high-pass filter. Recently, the photoactivated polymerization of LUV composed of monoSorbPC was shown to produce oligomers and no high molecular weight polymers (Lamparski & O'Brien, 1995). The size of the bis-SorbPC polymers is not known, but their greater insolubility in organic solvents than the polymers from mono-SorbPC implies that considerable cross-linking occurs with the bis-SorbPC at short photolysis times.…”

Section: Resultsmentioning

confidence: 99%

“…Radical-initiated polymerization of mono-SorbPC or bis-SorbPC liposomes proceeds via a chain reaction and produces high molecular weight polymers having repeat units numbering from 50 to 600 (Lamparski & O'Brien, 1995). Hence, radical chain polymerization of either DOPEhis-SorbPC or DOPE/mono-SorbPC LUV should effect more dramatic changes in the membrane properties than photoactivated polymerization.…”

Section: Biochemistrymentioning

confidence: 99%

Photoactivated Enhancement of Liposome Fusion

Bennett¹,

O’Brien²

1995

Biochemistry

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The photopolymerization of two-component large unilamellar liposomes (LUV) composed of 3:1 dioleoylphosphatidylethanolamine (DOPE) and either 1,2-bis[10-(2'-hexadienoyloxy)decanoyl]-sn-glycero-3-phosphatidylc holine (bis-SorbPC) or 1-palmitoyl-2-[10-(2'-hexadienoyloxy)decanoyl]-sn- glycero-3-phosphatidylcholine (mono-SorbPC) facilitated liposome fusion. Fusion was characterized by fluorescent assays for lipid mixing, aqueous contents mixing, and aqueous contents leakage. The rate and extent of the liposome fusion was dependent on the extent of photopolymerization, temperature, and the fusion initiation conditions, including the pH and the presence of Mg2+ ions. Examination of the temperature dependence of fusion for unpolymerized and polymerized liposomes showed that an enhancement of the rate of fusion occurred in the temperature range delta TI, which previous NMR studies have identified as the initial appearance of precursors to the formation of the inverted cubic phase [Barry, J. A., et al. (1992) Biochemistry 31, 10114]. The phase behavior and fusion characteristics of the DOPE/bis-SorbPC (3:1) membranes provide unequivocal evidence that liposome fusion is mediated via intermediates associated with the lamellar to QII phase transition rather than the HII phase. Photopolymerization of SorbPC-containing liposomes forms poly-SorbPC, which enhances the lateral separation of the liposome components. The formation of enriched domains of polymorphic lipids, e.g., DOPE, causes isothermal induction of fusion by lowering the critical fusion temperature of the membranes.

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“…The 1 H NMR spectra of the transesterified polymers indicated the structures were 1,4-polymers. 70 The numberaverage degree of polymerization (X n ) ranged from 50 to nearly 600 and was inversely proportional to the concentration of the initiator, [I]. These results, which suggest that chain termination at high conversion of SorbPC to polymer is dominated by primary termination, are similar to the behavior of acryloyl-substituted lipids in bilayers.…”

Section: B Dienoyl Sorbyl and Diene Monomersmentioning

confidence: 93%

Supramolecular Materials via Polymerization of Mesophases of Hydrated Amphiphiles

2002

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Two-Dimensional Polymerization of Lipid Bilayers:Degree of Polymerization of Sorbyl Lipids

Cited by 48 publications

References 15 publications

Synthesis and Polymerization of Heterobifunctional Amphiphiles to Cross-Link Supramolecular Assemblies

Synthesis and Polymerization of Heterobifunctional Amphiphiles to Cross-Link Supramolecular Assemblies

Photoactivated Enhancement of Liposome Fusion

Supramolecular Materials via Polymerization of Mesophases of Hydrated Amphiphiles

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