This study proposes a basic molecular formula for all
proteins. A total of 10,739 proteins belonging to 9 different protein
groups classified on the basis of their functions were selected
randomly. They included enzymes, storage proteins, hormones,
signalling proteins, structural proteins, transport proteins,
immunoglobulins or antibodies, motor proteins and receptor proteins.
After obtaining the protein molecular formula using the ProtParam
tool, the H/C, N/C, O/C, and S/C ratios were determined for each
randomly selected sample. In this case, H, N, O, and S coefficients
were specified per carbon atom. Surprisingly, the results
demonstrated that H, N, O, and S coefficients for all 10,739 proteins
are similar and highly correlated. This study demonstrates that
despite differences in the structure and function, all known proteins
have a similar basic molecular formula CnH1.58 ± 0.015nN0.28 ± 0.005nO0.30
± 0.007nS0.01 ± 0.002n. The total correlation between all coefficients was
found to be 0.9999.
 L. Jin, W. Fang, "On A comment on ÔÇÿPrediction of protein structural
classes by a new measure of information discrepancy," Comput. Biol.
Chem., vol. 33, no. 6, pp. 469-470,December. 2009.
 L. Palopoli, S. E. Rombo, G. Terracina, G. Tradigo, P. Veltri,
"Improving protein secondary structure predictions by prediction
fusion," Info. Fusion., vol. 10, no. 3, pp. 217-232, July. 2009.
 C.A. Ouzounis, R.M.R. Coulson, A.J. Enright, V. Kunin, J.B. Pereira-
Leal, "Classification schemes for protein structure and function," Nat.
Rev. Genet., vol. 4, no. 7, pp. 508-519, July. 2003.
 S.C. Rison, T.C. Hodgman, J.M. Thornton, "Comparison of functional
annotation schemes for genomes," Funct. Integr. Genomics., vol. 1, no.
1, pp. 56-69, May. 2000.