Effect of Trehalose on the Nonbond Associative Interactions between Small Unilamellar Vesicles and Human Serum Albumin and on the Aging Process

Abstract

The effect of trehalose on the interaction of human serum albumin (HSA) with neutral and negatively charged small unilamellar vesicles (SUVs) composed of 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) or of mixtures of DMPC (19:1 w/w) with 1,2-dimyristoyl-sn-glycero-3-phosphatidylglycerol (DMPG) was studied by time-resolved fluorescence and dynamic light scattering measurements. The results are interpreted with supporting nonbond calculations describing the nonbond domains most likely to be involved in the protein-SUV interaction. In the absence of trehalose, lifetime measurements of the single Trp of HSA are indicative of two different SUV-HSA associative mechanisms depending on the [lipid]/[HSA] concentration ratios. At low ratios, depletion of phospholipid molecules from vesicles by HSA occurs independently of the lipid composition of the vesicles via favorable hydrophobic contacts. At higher ratios, vesicle-HSA assocation is favored by electrostatic interactions for the negatively charged SUVs. For neutral SUVs, hydrophobically driven penetration of HSA is proposed. All association mechanisms are damped in the presence of trehalose, due to its capacity to coat the interacting surfaces. The results of dynamic light scattering experiments clearly show that the aging of the liposomes is dependent on the lipid composition. The aging of DMPC vesicles is faster and not affected by the presence of either HSA or trehalose. The aging of DMPC/DMPG liposomes is more pronounced in the presence of HSA. These SUVs are stabilized by trehalose through different mechanisms depending on whether they are covered by HSA or not.

Solvation dynamics in DMPC vesicle in the presence of a protein

“…Then the translational diffusion coefficient (D T ) is calculated using the relation D T ¼ ðr 2 M =6s D Þ where for DMPC, r M % 15 nm [24].…”

“…In a lipid vesicle, an aqueous volume (Ôwater poolÕ) is enclosed by a surfactant bilayer [24][25][26][27][28]. When many protein molecules are confined in one lipid vesicle, the system closely resembles a biological cell.…”

“…HSA is an ellipsoidal molecule of dimensions 8 nm  8 nm  3 nm [25,29]. Considering the area of the head group of the lipid molecules is 0.48 nm 2 at a lipid:protein weight ratio of 1:1, the entire lipid surface is covered by the HSA molecules and there are about 80 HSA molecules per vesicle [24,25]. Incorporation of HSA within DMPC vesicles results in a marginal change in the radius of the vesicle (%15 nm) [24].…”

Photophysics of a β-carboline based non-ionic probe in anionic and zwitterionic liposome membranes

“…In the present study, fluorescence technique has been advantageously exploited to monitor the interaction behavior of this probe with two well-known vesicles, DMPG and DMPC, differing in their surface charge characteristics. The average radii of these systems are reported to be ∼15 nm (Bárdos-Nagy et al, 2003). The photophysics of AODIQ have been studied in DMPG and DMPC environments intending to assess the location of the probe, micropolarity around the probe and to see the effect of surface charge.…”

On the origin of the anomalous ultraslow solvation dynamics in heterogeneous environments

“…The radius (r h ) of a DMPC vesicle is about 15 nm. 44 Thus, the volume of the vesicle is about 140 times than that of a single HSA molecule. From (9), τ m is 3500 ns for the lipid vesicle.…”