Computerized helical

After numerous complete genomic DNA sequences had been established and after these had been interpreted to a great extent in terms of protein sequences, it became evident that about 20% of all proteins are located in membranes (Liu and Rost, 2001). This number was derived from a search for transmembrane a-helices with a computerized prediction system, the results of which are known to come with a high confidence level. Such helices can be recognized from a continuous stretch of 20 to 30 nonpolar residues with a predominance of aliphatic side chains at the center and aromatic residues at both ends (Sipos and von Heijne, 1993). The number of transmembrane a-helices per protein is broadly distributed and averages around six. 

Seltzer MA, Barbaric Z, Belldegrun A, Naitoh J, Dorey F, Phelps ME, Gambhir SS, Hoh CK. Comparison of helical computerized tomography, position emission tomography and monoclonal antibody scans for evaluation of lymph node metastases in patients with prostate specific antigen relapse after treatment for localized prostate cancer. J Urol 1999 162 1322-1328. 

Table 12.3. Superiority of magnetic resonance (MR) angiography with respect to helical computerized tomography (CT) for detection of early hepatocellular carcinoma prior to liver transplantation...

---