6. The 20 standard amino acids we have looked at are all -amino acids, with the

Question

6. The 20 standard amino acids we have looked at are all -amino acids, with the amino group attached to the carbon next to the carboxylic acid group. B-amino acids have the amino group attached two carbons away from the carboxylic acid group: C-amino acid B-amino acid CH CH CH It should be possible to make peptides from ß-amino acids. Would you expect such peptides to more or less conformational flexibility in their backbones than peptides made from a-amino acids? Explain your reasoning 7. Now let us turn to dragons. Before he disappeared 30 years ago, the celebrated chemist and dragonologist Merlin von Camelot had managed to obtain a small sample of dragon blood and had begun to analyze its contents. He had run a 2-D gel on the blood serum proteins and the dried gel was found in his lab after his disappearance. You are working in a lab that studies the evolutionary relationships between various vertebrate species using serum albumen, a major protein found in blood, and you have been given the task of determining the relationship between dragons and their closest apparent relatives, alligators and birds. What information would you need to obtain to perform this analysis and how would you go about getting that information using the protein spots in the gel? Note that this gel is the sole authentic biological sample currently available from dragons; in particular, no dragon DNA is available and the sequence of the dragon genome is utterly unknown

Explanation / Answer

Yes, it is possible to make peptide from amino acids but -peptides in general do not appear in nature. Two main types of -peptides exist: those with the organic residue (R) next to the amine are called 3-peptides and those with position next to the carbonyl group are called 2-peptides. Generally speaking, -peptides form a more stable helix than -peptides

Compared to -peptides, -peptides have the advantage of increased conformational stability in an aqueous environment. The -peptide backbone compared to natural peptides is resistant to protease degradation and has the potential for a great variety of substitution patterns. In addition, -peptides form more stable helices in solution compared to -peptides; -peptides can form secondary structures with as few as four to six residues in solution, compared to over 30 residues needed for stability of the natural analogs. The stability of -peptides, important for biological activity, makes them good candidates for useful drugs.

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