Leucine-enkephalin, determination

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 receptors 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 pain killers. 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. 

The structure of the pentapeptide leucine enkephalin shown as (a) a structural drawing and (b) as a molecular model. The shape of the molecular model was determined by X-ray crystallography. Hydrogens have been omitted for clarity. 

Copper oxide-covered electrodes in alkaline media have been anployed for detection of peptides in both HPLC [112,114] and CE [116]. Peptides that have been determined include small peptides such as Gly-Gly-amide [112,116], Gly-Gly [112,116], tri-, tetra-, penta-, and hexaglycine [114,116], aspartame [116] cyclic Leu-Trp-Asp-Pro-Val [116], cycfic Leu-Tyr-Asp-Pro-Val [116], and des-Tyr-leucine enkephalin [114]. Detection limits (withont on-column preconcentration) are poor, typically in the 5-100 pM range [114,116]. 

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