## Abstract Vitronectin (Vn) is an abundant glycoprotein present in plasma and the extracellular matrix of most tissue and is an important medium required for bone cells to attach and spread on biomaterial surfaces. Hence, Vn adsorption is an initial and key step in implantation. In this study, ads
Tapping mode atomic force microscopy of scleroglucan networks
β Scribed by Anil K. Vuppu; Antonio A. Garcia; Chad Vernia
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1997
- Tongue
- English
- Weight
- 304 KB
- Volume
- 42
- Category
- Article
- ISSN
- 0006-3525
No coin nor oath required. For personal study only.
β¦ Synopsis
Tapping mode Atomic Force Microscopy (TmAFM) has been used to study the fungal polysaccharide scleroglucan deposited from aqueous solution and dimethyl sulfoxide (DMSO) onto a mica surface. The solutions from which the microscope samples were produced were prepared by first dissolving the solid scleroglucan in 0.1M NaOH, then neutralizing the solution with HCl, followed by dilution to the required concentration in either water or DMSO. It was found that from the aqueous solution described above, scleroglucan forms networks. Based on a comparison of the denatured-renatured and aqueous solution samples, network formation is due to the imperfect registration between the chains forming the triple helices. The relatively large stiffness of the scleroglucan triple helix is also assumed to contribute to the formation of the extended networks. The triple helix diameter was measured to be 0.92 { 0.27 nm, which is in the same range as that obtained by other researchers using similar techniques. Denatured scleroglucan, deposited from DMSO onto mica, forms a web-like layer on top of which there are sphere-like structures. These morphologies are believed to be due to triple helix denaturation yielding highly flexible single chains in DMSO, which results in coiling and web-like dense packing of scleroglucan upon deposition onto mica. Most interestingly after addition of water to the samples deposited from DMSO, some of the chains can be renatured into short, stiff rod-like structures which are similar to the structures observed by other researchers. The imaging data for aqueous solution deposition can be analyzed by plotting maximum end-to-end distance versus the perimeter of the networks deposited onto mica. This yields a Flory-like exponent of 0.67, which is almost similar in value to that obtained by other researchers for linear structures of scleroglucan but less than that expected for a polymer chain following a self-avoiding walk (n Γ 0.75) model on a two-dimensional surface. The fractal dimension that can be used to characterize the networks was determined graphically to be 1.22 { 0.06.
π SIMILAR VOLUMES
The probe-sample force in tapping mode scanning force microscopy was evaluated using the phenomenon of sublimation of organic benzamide crystal and the assumption that the equal rate of sublimation in both tapping and contact modes is caused by the equal probe-sample force. Contact force was estimat