Subject total signal

The main apohpoprotein of LDL (P-lipopro-tein) is apohpoprotein B (B-lOO) and is found also in VLDL. Chylomicrons contain a truncated form of apo B (B-48) that is synthesized in the intestine, while B-lOO is synthesized in the hver. Apo B-lOO is one of the longest single polypeptide chains known, having 4536 amino acids and a molecular mass of 550,000 Da. Apo B-48 (48% of B-lOO) is formed from the same mRNA as apo B-lOO after the introduction of a stop signal by an RNA editing enzyme. Apo C-1, C-11, and C-111 are smaller polypeptides (molecular mass 7000— 9000 Da) freely transferable between several different hpoproteins. Apo E is foimd in VLDL, HDL, chylomicrons, and chylomicron remnants it accounts for 5— 10% of total VLDL apohpoproteins in normal subjects. 

Recently, there has been an explosion in our understanding about the nudeocytoplasmic transport systems that import proteins into the nucleus and export them from there. The emerging picture is more complex than expected, maybe too complicated to directly apply this knowledge to the interpretation of localization signals at this time. This section briefly describes the total picture and then summarizes the various signals involved. As there are so many references on this subject, most of the original references were not cited. 

In threshold measuring situations small signals are presented and at times when the internal noise is low, the total impact of the noise plus signal may be lower than that of the strongest noise alone. In such a case the subject may say no to a presentation containing the signal (a miss) and yes to a presentation in which only the strong noise was present (a false alarm). 

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