Interaction of Heparins and Dextran Sulfates with a Mesoscopic Protein Nanopore

Abstract

A mechanism of how polyanions influence the channel formed by Staphylococcus aureus alpha-hemolysin is described. We demonstrate that the probability of several types of polyanions to block the ion channel depends on the presence of divalent cations and the polyanion molecular weight and concentration. For heparins, a 10-fold increase in molecular weight decreases the half-maximal inhibitory concentration, IC(50), nearly 10(4)-fold. Dextran sulfates were less effective at blocking the channel. The polyanions are significantly more effective at reducing the conductance when added to the trans side of this channel. Lastly, the effectiveness of heparins on the channel conductance correlated with their influence on the zeta-potential of liposomes. A model that includes the binding of polyanions to the channel-membrane complex via Ca(2+)-bridges and the asymmetry of the channel structure describes the data adequately. Analysis of the single channel current noise of wild-type and site-directed mutant versions of alpha-hemolysin channels suggests that a single polyanion enters the pore due to electrostatic forces and physically blocks the ion conduction path. The results might be of interest for pharmacology, biomedicine, and research aiming to design mesoscopic pore blockers.

Morphological and growth responses of vascular smooth muscle and endothelial cells cultured on immobilized heparin and dextran sulfate surfaces

“…Previous studies indicate that dextran sulfate has a branched polymer architecture with a larger negative charge in comparison to the linear architecture of heparin. 27 In fact, previous examination of this phenomenon with other GAGs showed large differences between various natural GAGs in the binding of fibronectin and vitronectin, two well-known adhesion-promoting serum proteins. 35 Vitronectin has been shown to promote cell adhesion and spreading, as well as SMC migration, 26,36 while fibronectin was closely associated with arterial SMC ability to detect and react to mechanical forces via integrin receptors.…”

“…Extracellular matrix is a complex arrangement of fibrous proteins, associated with glycoproteins inserted in a hydrated ground substance of glycoaminoglycans and proteoglycans . Glycosaminoglycans contribute to a wide range of physiological processes including recognition and adhesion, and are essential for maintaining the structural organization of the extracellular matrix . In addition, the extracellular matrix provides the structural and mechanical properties required for vessel function and plays a vital role in the regulation of gene expression by interacting with specific matrix receptors on cells and by binding and storing growth factors that influence cellular function .…”

“…Given the major architectural differences between CMDS and heparin, it is reasonable to assume differences in the composition of bound serum proteins on the two polymers. Previous studies indicate that dextran sulfate has a branched polymer architecture with a larger negative charge in comparison to the linear architecture of heparin …”

“…26 Glycosaminoglycans contribute to a wide range of physiological processes including recognition and adhesion, and are essential for maintaining the structural organization of the extracellular matrix. 27 In addition, the extracellular matrix provides the structural and mechanical properties required for vessel function and plays a vital role in the regulation of gene expression by interacting with specific matrix receptors on cells and by binding and storing growth factors that influence cellular function. 28 At the same time, the collagenous structure of the extracellular matrix functions as an inert scaffold for cell attachment and can recognize and bind specific glycosaminoglycans, 29 which play significant roles in the organization of the matrix.…”

Molecular structure of dextran sulphate sodium in aqueous environment

“…Size of DSS Nanopore size Comment MMFF modelling Mr. 5000 Da; __ __ length 4.1 nm; diameter 2.1 nm; band width 1.1 nm; Teixeira et al [70] Mr. 5000-500,000 Da; Lengthz10 nm; diameterz2.6 nm.…”