HW3 key - BMEN 289 Engineering Biology Homework #3 Due...

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BMEN 289 Engineering Biology Homework #3 Due Sept. 20 th (Thursday) Carefully read each question. Provide answers which specifically address the questions and demonstrate your understanding of the class/textbook material. You must explain your answers to receive full credit. 1. Consider the forces that hold a DNA molecule together (15 pts) . a. What types of molecular interactions stabilize double stranded DNA? For each type of interaction indicate specifically where in the molecule it is acting on. Covalent bonds hold together individual strands together. Hydrogen bonds are responsible for base pairing. Wand der Waals and hydrophobic interactions are responsible for “stacking” of bases. b. The plot illustrates how the melting temperature of DNA varies as a function of the percentage of guanine- cytosine base pairs in a segment of double-stranded DNA. Explain why T m increases as the percentage of guanine- cytosine base pairs increases in a segment of double-stranded DNA. G-C pairing involves 3 H-bonds, while A-T pairing involves only 2, hence the more G-C base pairs the stronger the bonding between DNA strands and hence the higher the value for Tm. 2. A peptide has been isolated with the following amino acid sequence: NH 3 + -Val-His-Asp-Gly-Phe-Arg-COO - Using the attached list of pK a values, calculate the net charge for this peptide when placed in a buffer with the following values for pH:
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This note was uploaded on 08/30/2008 for the course BMEN 289 taught by Professor Kaunas during the Spring '07 term at Texas A&M.

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HW3 key - BMEN 289 Engineering Biology Homework #3 Due...

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