What is Chameleon sequence?

The secondary structure prediction methods were generated after determining the role of the primary amino acid sequence in folded native protein structure in 1950. Based on this finding, researchers subsequently began to develop methods to answer one of the most important biological challenges: prediction of protein structure from its primary sequence.
Chou Fasman's method was one of the first available method computed the propensities of amino acids to adopt secondary structures: Helix, Extended and Coil, based on the observation of their location in protein structures determined by X-ray diffraction.
Detecting the regions that under different conditions, different structures tend to take,is very important because they are responsible for amyloid and aggregation formation in proteins.These regions are called Chameleon sequences. Therefore, we have created the ChamFinder website, using propensities, calculated from a data base containing 37,000 proteins, which identifies and collects fragments susceptible to form amyloid fibrils.
The size of window:

The calculations are based on the sliding-window averaging technique: a sliding window of a given length (3, 5 or 7 residues) is chosen and the program calculates the average of window and assigns it to the central residue of the window. Among the numbers obtained, the Chameleon amino acids are found and finally reported.