Stability and State of Aggregation of Aqueous Fibrinogen and Dipalmitoylphosphatidylcholine Lipid Vesicles

Abstract

The stability and state of aggregation of aqueous fibrinogen (FB) and dipalmitoylphosphatidylcholine (DPPC) vesicles in water or buffer at 25 degrees C were studied with dynamic light scattering (DLS), UV-vis spectroturbidimetry (ST), and cryo-transmission electron microscopy (cryo-TEM). In water, when 1000 ppm (0.10 wt %) DPPC dispersions were prepared with a protocol including extensive sonication, they contained mostly vesicles and were quite clear, transparent, and stable for at least 30 days. FB mixtures with water (0.075 wt %) were quite unstable and biphasic. They formed large aggregates which eventually precipitated. The addition of DPPC vesicles into these unstable FB dispersions reversed FB aggregation and precipitation and produced stable translucent microdispersions. The inferred lipid/protein aggregates were limited in size, with average diameters ranging from 200 to 300 nm. In buffer, DPPC dispersions were also clear and quite stable, with average dispersed particles diameter of ca. 90 nm. FB dissolved in aqueous buffer and formed transparent and stable solutions. Adding salt to an aggregated FB dispersion in water reversed the aggregation. FB aggregated and redissolved in the presence of the citrate and after the citrate was removed. There was no effect of citrate (present in FB initially) in the FB aggregation or redissolution. FB molecules in buffer form dimers or higher aggregates. Their average aggregation number is 2, determined with Rayleigh scattering analysis of turbidity data. The average hydrodynamic diameter of FB solutions from DLS was 30 nm. Mixing a stable FB solution in buffer and a stable DPPC dispersion in buffer produced highly unstable mixtures, in which large aggregates precipitated. These results have implications in understanding the interactions of lipids and proteins in many biological applications and food processing applications.

Colloidal dispersion stability of unilamellar DPPC vesicles in aqueous electrolyte solutions and comparisons to predictions of the DLVO theory

“…(7). technique, provided evidence that mostly vesicles are present in such dispersions [9,10]. The images here show that the diameters of the vesicles ranged from 20 to 100 nm when observed 12 h after the dispersions were prepared, or from 30 to 200 nm 50 days later.…”

“…This preparation protocol method was originally described in Refs. [6][7][8][9][10] and is designed to produce dispersions containing primarily fluid vesicles (unilamellar particles). The effect of sonication time was also examined.…”

“…With water DPPC forms fluid multi-lamellar liposomes or unilamellar vesicles above T c = 41°C, the chain melting transition temperature [2][3][4][5]. DPPC vesicular dispersions in water form only after extensive sonication above 41°C [6][7][8][9][10]. When these dispersions are cooled to 25 or 37°C, the vesicles become ''frozen", and the chains are in a solid-like state.…”

Identification of Human Plasma Proteins as Major Clients for the Extracellular Chaperone Clusterin

“…Many examples of such interactions are known; for example, lactoferrin (36), protein C (37), and myeloperoxidase (38) interact with CERU; at least 11 proteins are known to interact with FGN including vitronectin (39), histidine-rich glycoprotein (40), and apolipoprotein(a) (41); and over 60 different proteins are believed to interact with HSA (42). Self-aggregation, which has been reported for both FGN (43) and HSA (44), may also account for the detection of these proteins as larger species. Corresponding analyses of stressed plasma strongly detected CLU and each of the three client proteins CERU, FGN, and HSA in fractions representing still larger species approaching (or at) the exclusion limit of the SEC column (4 ϫ 10 7 Da; Fig.…”

Interactions of KLVFF‐PEG Peptide Conjugate with Fibrinogen in Neutral Aqueous Solutions

“…[24] In this work we report R H ¼ 252 Å for c Fbg ¼ 0.5 wt.-% (D ¼ 0). It is possible that our results are affected by c Fbg , since it has been shown that R H increases with c Fbg , [25] probably due to glycoprotein aggregation.…”