[The effect of fixed water molecules on fractal properties of globular protein surfaces]

On the base of the technique developed by the authors together with Schmidt the fractal properties of the 17 globular proteins have been analysed using the crystal structure data at high resolution. For all the proteins there are the coordinates of fixed water molecules in the protein data bank. For each protein the fractal dimension of its surface D has been calculated with and without taking into account the fixed water molecules located inside a 3-Angstrom hydrated layer. Small but systematic decrease of the DS values for the proteins with the fixed water molecules has been demonstrated. It means that the fixed water molecules tend to fill gaps on the protein surfaces and in that way to smooth the surfaces. The volumes and the molecular surfaces of the proteins have been also calculated on the base of the cube technique. The molecular surfaces of the proteins with the fixed water molecules prove to decrease. This fact can be considered as the indirect evidence that the protein surfaces become to be smoother.