This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.104.048876v1 88/5/3545    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Maulucci, G. Articles by Briganti, G. Search for Related Content PubMed PubMed Citation Articles by Maulucci, G. Articles by Briganti, G.

Particle Size Distribution in DMPC Vesicles Solutions Undergoing Different Sonication Times

Giuseppe Maulucci ^*, Marco De Spirito ^*, Giuseppe Arcovito ^*, Federico Boffi , Agostina Congiu Castellano  and Giuseppe Briganti 

^* Istituto di Fisica, Universitá Cattolica S. Cuore "A. Gemelli", Rome, Italy; and INFM-CRS, Centro Ricerca Sviluppo-Soft, Dipartimento di Fisica, Universitá di Roma "La Sapienza", Rome, Italy

Correspondence: Address reprint requests to Marco De Spirito, Istituto di Fisica, Università Cattolica S. Cuore "A. Gemelli", 00168 Rome, Italy. Tel.: 39-06-30154265; E-mail: m.despirito{at}rm.unicatt.it.

Size distribution of dimyristoylphosphatidylcholine liposome suspensions was investigated by dynamic-light scattering (DLS) as a function of the sonication time (t_s). Cumulant expansion (second- and third-order) and regularized Laplace inversion (CONTIN) of dynamic single-angle laser light-scattering data were performed. With both methods, the intensity-weighted mean hydrodynamic radius r_I depended on the investigated lengthscale. The number-weighted mean hydrodynamic radius (r_N), obtained from CONTIN by modeling dimyristoylphosphatidylcholine vesicles as thin-walled hollow spheres, resulted as independent on the lengthscale. However, the r_N value obtained from cumulant expansions remained lengthscale-dependent. Therefore, the number-weighted radius distribution function is highly asymmetric. The number-weighted mean radius, the standard deviation, and the number-weighted radius at the peak all decreased to a plateau when increasing sonication time. At t_s longer than 1 h, the compares well with the radius of unilamellar vesicles in equilibrium with monomers predicted on a thermodynamic basis. The reliability of our analysis is proved by the comparison of experimental Rayleigh ratios with simulated ones, using the normalized number-weighted radius distribution function p_N(r) determined by DLS data. A perfect agreement was obtained at longer sonication times, and the average aggregation number was determined. At lower t_s values, simulations did not match experimental data, and this discrepancy was ascribed to the presence of large and floppy unilamellar vesicles with ellipsoidal shapes. Our investigation shows that, from single-angle DLS data, the radius distribution function of the vesicles can only be obtained if p_N(r) is known.

This article has been cited by other articles:

				M. De Spirito, R. Brunelli, G. Mei, F. R. Bertani, G. Ciasca, G. Greco, M. Papi, G. Arcovito, F. Ursini, and T. Parasassi Low Density Lipoprotein Aged in Plasma Forms Clusters Resembling Subendothelial Droplets: Aggregation via Surface Sites Biophys. J., June 1, 2006; 90(11): 4239 - 4247. [Abstract] [Full Text] [PDF]

				K. T. Samiee, J. M. Moran-Mirabal, Y. K. Cheung, and H. G. Craighead Zero Mode Waveguides for Single-Molecule Spectroscopy on Lipid Membranes Biophys. J., May 1, 2006; 90(9): 3288 - 3299. [Abstract] [Full Text] [PDF]