A peptide-amphiphile (C-12-A beta(11-17)) was constructed with a key fragment of amyloid beta-peptide (A beta(11-17)) attached to dodecanoic acid through an amide bond. The self-assembly behavior of C-12-A beta(11-17) in aqueous solution is studied at 25 degrees C and at pH 3.0 and 10.0. A beta(11-17) cannot form ordered self-assemblies. But C-12-A beta(11-17) exhibits a very strong ability to form ordered nanofibrils, and the specific fine structure of the nanofibrils can be modulated simply by adjusting the concentration or pH. The critical micelle concentration of C-12-A beta(11-17) was determined as 0.063 and 0.11 mM at pH 3.0 and 10.0, respectively, indicating a stronger assembling ability of C-12-A beta(11-17) at acidic pH. In 0.47 mM C-12-A beta(11-17) solution at pH 3.0, rodlike fibrils with a diameter of similar to 5 nm and varying length of hundreds of nanometers are observed. When the C-12-A beta(11-17) concentration increases to 1.87 mM at pH 3.0, the above rodlike fibrils pack in parallel and form tapelike fibrils through lateral association. In 1.87 mM C-12-A beta(11-17) solution at pH.10.0, twisted fibrils with regular periodicity of similar to 200 nm are formed by the twisting of similar to 20 nm wide and similar to 11 nm thick nanoribbons. The hydrophobic moiety is necessary in fibril formation, whereas the beta-sheet secondary structure of the peptide moiety plays an essential role in the twisting morphology. This work helps to understand the possible mechanism in amyloid fibrillogenesis and provides an approach to inscribe biological signals in self-assemblies with potential application in biomaterial fabrication.