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Quasi-elastic and electrophoretic light scattering studies of the reorganization of dioleoylphosphatidylcholine vesicle membranes by poly(2-ethylacrylic acid)

Eum, Ki Min and Langley, Kenneth H. and Tirrell, David A. (1989) Quasi-elastic and electrophoretic light scattering studies of the reorganization of dioleoylphosphatidylcholine vesicle membranes by poly(2-ethylacrylic acid). Macromolecules, 22 (6). pp. 2755-2760. ISSN 0024-9297. http://resolver.caltech.edu/CaltechAUTHORS:EUMm1989

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Abstract

Quasi-elastic light scattering (QELS) and electrophoretic light scattering (ELS) measurements have been used to investigate the pH-dependent structural reorganization of phospholipid vesicles suspended in aqueous solutions of poly(2-ethylacrylic acid) (PEAA). The average radius of dioleoylphosphatidylcholine (DOPC) vesicles suspended in aqueous PEAA was reduced within 1 h from approximately 600 to 60 nm upon acidification. Size distribution analysis revealed narrow single peaks far from the pH at which the reorganization occurs but bimodal distributions in the transition region. The transition pH was shifted from 7.0 to 6.5 as the ionic strength of the sample solutions was increased from 50 to 500 mM. The conformational transition of PEAA from an expanded form at high pH to a relatively compact coil in acidic solutions was also observed by QELS. ELS measurements showed that, as the pH is lowered from 8.0 to 5.5 in the presence of PEAA, the electrophoretic mobility of DOPC vesicles passes through a minimum at the transition pH. At pH lower than that of the transition, vesicle mobility is greater in PEAA solutions than in simple buffers. We believe the increase in mobility is due to adsorption of PEAA on the vesicle surface. We infer that as the pH is lowered, the collapsed PEAA chain provides a hydrophobic site for solubilization of the phospholipid hydrocarbon tails and in so doing disrupts the structural organization characteristic of the pure phospholipid.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/ma00196a038DOIArticle
http://pubs.acs.org/doi/abs/10.1021/ma00196a038PublisherArticle
ORCID:
AuthorORCID
Tirrell, David A.0000-0003-3175-4596
Additional Information:© 1989 American Chemical Society. Received May 2, 1988; Revised Manuscript Received December 16, 1988. This work was supported by an NSF Presidential Young Investigator Award to D. A. Tirrell and by Army Research Office Grant DAAL03-88-K-0038 to D. A. Tirrell and K. H. Langley. We thank Langley Ford Instruments Division of Coulter Electronics, Inc., for the use of DELSA electrophoretic light scattering apparatus. Polymer molecular weights were determined for us by Dr. U. K. O. Schroder. The fluorescence results presented in Figure 1 were provided by K. A. Borden. Registry No. PEAA, 62607-09-4; DOPC, 10015-85-7.
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Funding AgencyGrant Number
NSFUNSPECIFIED
Army Research Office (ARO)DAAL-03-88-K-0038
Record Number:CaltechAUTHORS:EUMm1989
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:EUMm1989
Official Citation:Quasi-elastic and electrophoretic light scattering studies of the reorganization of dioleoylphosphatidylcholine vesicle membranes by poly(2-ethylacrylic acid) Ki Min Eum, Kenneth H. Langley, and David A. Tirrell Macromolecules 1989 22 (6), 2755-2760
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ID Code:53531
Collection:CaltechAUTHORS
Deposited By: Anne Hormann
Deposited On:11 Jan 2015 03:47
Last Modified:11 Jan 2015 03:47

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