In the new model hydrogen bonds are formed by NH-group of glycine residue in the first polypeptide chain and CO-group of second residue in the tripeptide in the second chain and by NH-group of second residue in the second chain and CO-group of second residue in the first chain etc., i. e. one and the same CO-group serves as acceptor for two NH-groups belonging to other chains. CPK-model was built and then conformational computations for (Gly-Ala-Hyp)n and (Gly-Ala-Ala)n were performed. The resulting optimal structures have unit twist angle t = 52 degrees and 75 degrees. The two-bonded structure may coexist with Rich and Circk type one-bonded structure for any sequence of tripeptides. This suggests the uniform 7/2 helical symmetry for collagen molecule. The model is favourable for hydration and helps to interpret the physico-chemical characteristics of collagen.