The lactate dehydrogenase gene has a length of 20417 base pairs. There are sever

Question

The lactate dehydrogenase gene has a length of 20417 base pairs. There are several introns in the gene. The exons are as follows (from http://www.ncbi.nlm.nih.gov/nuccore/NG_008185.1):
Base pairs that form exons:
4955..5202
7385..7534
9997..10114
11403..11576
13406..13579
14260..14377
16015..16138
17683..18784
Moreover, on this sequence, the open reading frame spans from the position 7409 to 17847 on the DNA.
a. What is the length of the messenger RNA (excluding the poly(A) tail)? (2 marks)
b. What is the length of the polypeptide chain (number of amino acids prior to any posttranslational modifications)?

Explanation / Answer

The use of amino acid retention or hydrophobicity coefficients for the prediction of peptide retention time and/or the elution order on hydrophobic stationary phases is based on the premise that amino acid composition is the major factor affecting peptide retention in reversed-phase chromatography. Although this assumption generally agrees well for small peptides (up to ca. 15 residues), the retention times of increasingly larger peptides are less than expected from a simple summation of retention coefficients. In the present study, we report the synthesis of four series of peptide polymers which vary significantly in overall hydrophobicity and polypeptide chain length (5-50 amino acid residues, Ac = acetyl): Ac-(G-L-G-A-K-G-A-G-V-G)n-amide (n = 1-5), Ac-(G-K-G-L-G)n-amide (n = 1, 2, 4, 6, 8, 10), Ac-(L-G-L-K-A)n-amide (n = 1, 2, 4, 6, 8, 10) and Ac-(L-G-L-K-L)n-amide (n = 1, 2, 4). From the retention behaviour of these peptide polymers on C4, C8 and C18 stationary phases under gradient elution conditions, we have clearly established the effect of polypeptide chain length and hydrophobicity on peptide retention. This, in turn, has enabled us to extend the utility of retention time prediction for peptides containing up to 50 residues by introducing a peptide chain-length correction.

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.