Distinct Binding Interactions of α5ß1-Integrin and Proteoglycans with Fibronectin.

Dynamic single-molecule force spectroscopy was performed to monitor the unbinding of fibronectin with the proteoglycans syndecan-4 (SDC4) and decorin and to compare this with the unbinding characteristics of α5ß1-integrin. A single energy barrier was sufficient to describe the unbinding of both SDC4 and decorin from fibronectin, whereas two barriers were observed for the dissociation of α5ß1-integrin from fibronectin. The outer (high-affinity) barriers in the interactions of fibronectin with α5ß1-integrin and SDC4 are characterized by larger barrier heights and widths and slower dissociation rates than those of the inner (low-affinity) barriers in the interactions of fibronectin with α5ß1-integrin and decorin. These results indicate that SDC4 and (ultimately) α5ß1-integrin have the ability to withstand deformation in their interactions with fibronectin, whereas the decorin-fibronectin interaction is considerably more brittle.

Reduced curvilinear velocity of boar sperm on substrates with increased hydrophobicity.

The curvilinear velocity (VCL) of boar spermatozoa between standard microscopy glassware decreases when the slides are coated with the hydrophobic polymer polystyrene (PS) compared with the less hydrophobic poly(methyl methacrylate) (PMMA) coating. Sperm from three boars were observed and analyzed using particle tracking software. The VCL did not differ significantly between coatings of different thickness, indicating no penetration of the sperm into the coating and that only the surface layer of the polymer film interacts with the sperm and buffer medium. The VCL of sperm between PS-coated surfaces was significantly reduced compared with PMMA surfaces (P < 0.0001), and this was attributed to a stronger hydrophobic effect between PS and water. The size of this effect varied between different boars, perhaps as a consequence of variations in hydrophobicity of sperm from different boars or different ejaculates. The modification of surface properties in this way may improve our understanding of sperm behavior and may provide improvements to assisted conception techniques as animal or human sperm used in assisted conception are frequently manipulated in laboratory plastics as part of diagnostic procedures (e.g., semen analysis) or before injection into an oocyte or during the co-incubation with the oocyte in IVF. Controlling the velocity of sperm using the interaction properties of inert polymer coatings could lead to new sperm selection procedures for clinical use or the development of model systems to better understand sperm-surface interactions.