3. Sequence Determination of the Brain Peptide Leucine Enkephalin A group of peptides that influence nerve transmission in certain parts of the brain has been isolated from normal brain tissue. These peptides are known as opioids because they bind to specific recepton that also bind opiate drugs, such as morphine and naloxone. Opioids thus mimic some of the properties of opiates. Some researchers consider these peptides to be the brain's own painkiller Using the information below, determine the amino acid sequence of the opioid leucine enkephalin. Explain how your structure is consistent with each piece of information. (a) Complete hydrolysis by 6 M HCI at 110 _C followed by amino acid analysis indicated the presence of Gly, Leu, Phe, and Tyr in a 2:1:1:1 molar ratio. (b) Treatment of the peptide with 1-fluoro-2,4-dinitrobenzene, which reacts with free amines, followed by complete hydrolysis and chromatography indicated the presence of the 2,4- dinitrophenyl derivative of tyrosine. No free tyrosine could be found. (c) Complete digestion of the peptide with chymotrypsin followed by chromatography yielded fre tyrosine and leucine, plus a tripeptide containing Phe and Gly in a 1:2 ratio.

3. Sequence Determination of the Brain Peptide Leucine Enkephalin A group of peptides that influence nerve transmission in certain parts of the brain has been isolated from normal brain tissue. These peptides are known as opioids because they bind to specific recepton that also bind opiate drugs, such as morphine and naloxone. Opioids thus mimic some of the properties of opiates. Some researchers consider these peptides to be the brain's own painkiller Using the information below, determine the amino acid sequence of the opioid leucine enkephalin. Explain how your structure is consistent with each piece of information. (a) Complete hydrolysis by 6 M HCI at 110 _C followed by amino acid analysis indicated the presence of Gly, Leu, Phe, and Tyr in a 2:1:1:1 molar ratio. (b) Treatment of the peptide with 1-fluoro-2,4-dinitrobenzene, which reacts with free amines, followed by complete hydrolysis and chromatography indicated the presence of the 2,4- dinitrophenyl derivative of tyrosine. No free tyrosine could be found. (c) Complete digestion of the peptide with chymotrypsin followed by chromatography yielded fre tyrosine and leucine, plus a tripeptide containing Phe and Gly in a 1:2 ratio.

Biology: The Dynamic Science (MindTap Course List)

4th Edition

ISBN:9781305389892

Author:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Publisher:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Chapter56: Animal Behavior

Section: Chapter Questions

Problem 16TYK

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