Chemically functionalized AFM tips: easy way to resolution enhancement in single biomolecule visualization.
|Year of publication||2008|
|Type||Article in Proceedings|
|Conference||5th international interdisciplinary meeting on bioanalysis CECE 2008|
|MU Faculty or unit|
|Keywords||AFM microscope cantilever tip silanization hydrophobicity|
|Description||Atomic Force Microscopy (AFM) technique allows visualization of structures in a sub-nanometer scale, i.e. imaging of individual biomolecules. In principle AFM scanning probe, presented by ultra-sharp tip, is in close contact with surface and relief is visualized as 3D map (after conversion of a measured quantity, e.g. tip bending). Resolution of an AFM microscope is essentially affected by the tip curvature (sharpness), however other experimental conditions would affect this parameter, too. Only weak and medium forces are usually employed in the interaction between tip and surface in the relief visualization. Surfaces visualized in a non-controlled atmosphere are naturally coated with a very thin (1-5 nm) layer of adsorbed water. In some cases capillary forces originating from this layer can strongly affect visualization process, as those forces are much stronger comparing to other intermolecular forces (van derWaals, hydrogen, ionic forces, etc.). Formation of capillary forces can be effectively suppressed by chemical modification of tip (mostly by hydrophobization of the tip) surface. Various methods for tip surface modification are presented. Procedure always starts with the surface activation by a silanization. Subsequent coupling of either hydrophilic or hydrophobic molecules determines surface properties in this way. Impact of the tip surface modification on resolution of images of individual biomolecules (proteins, nucleic acids) are shown as examples (on the right: IgG molecule-hydrophilic tip, DNA-lipophilic tip).|