This web-server presents the Complex Informational Spectrum Analysis for Protein Sequences (CISAPS). As recent studies show, only the use of the absolute spectrum in the analysis of protein sequences using the informational spectrum analysis is proven to be insufficient. Therefore, CISAPS is developed to consider and provide results in three forms including absolute, real and imaginary spectrum. Biologically related features to the analysis of influenza A subtypes as presented as a case study in this study, can also appear individually either in the real or imaginary spectrum. As the results presented, protein classes can present similarities or differences according to the features extracted from CISAPS webserver. These associations are probable to be related with the protein feature that the specific amino acid index represents. In addition, various technical issues such as zero-padding and windowing that may affect the analysis are also addressed.

CISAPS uses an expanded list of 611 unique amino acid indices where each one represents a different property to perform the analysis. This web-based server enables researchers with little knowledge of signal processing methods to apply and include complex informational spectrum analysis to their work. CISAPS web server is available at

If you find the method and webserver useful in your research, please cite the following papers