Scanning Force Microscopy Characterization of Biopolymer Films: Gelatin on Mica
Scanning force microscopy of thin gelatin films on mica reveals two distinct film components with characteristic frictional, morphological and stability signatures. A high-friction continuous film 1–4 nm thick strongly adheres to mica, while a low-friction component is adsorbed as porous islands on top of or small domains within, the high-friction layer and is more easily perturbed by the scanning process. A high-force scanning procedure remarkably transforms the molecularly rough high-friction film into the molecularly smooth low-friction component if a sufficient amount of water is present in or on the film. The nanostructure of both the high- and low-friction components is imaged using a nanometer-scale asperity of gelatin attached to the SFM tip. The anticipated network structure of gelatin is observed on the high-friction layer. The low-friction material is interpreted as moieties of intramolecularly folded gelatin, with thickness (1.5±0.2 nm) equal to the diameter of the collagen-fold triple helix, containing substantial structural water.
KeywordsFrictional Force Gelatin Film Scan Force Microscopy Gelatin Molecule Friction Force Microscopy
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