A representation of proteins based on the geometry of space curves is described. This representation enables the application of continuum methods to the analysis of macromolecular structure and form that cannot be applied to the more familiar discrete atomic coordinate models. It is shown that the continuous modeling method defines the geometry of the protein fold very efficiently. An analytical solution for curve construction is employed from which both continuous and coordinate models can be obtained. The method is applied to five representative test proteins which are used to assess the accuracy and efficiency of the modeling procedure. (c) 2006 Elsevier Inc. All rights reserved.