n 1817 James Parkinson described \"Parkinson\'s Disease\". It has since been det
ID: 3165602 • Letter: N
Question
n 1817 James Parkinson described "Parkinson's Disease". It has since been determined that this condition is due to a lower than required level of DOPA in the brain. There are cell membrane receptors for DOPA in brain cells which must have a certain level of DOPA for the cells to function correctly. CH2-CH2-NH2 DOPA In order to better understand the structural and conformational requirements of DOPA, the dopamine agonist NPA, has been studied (a) In what way(s) structurally is NPA an analogue of DOPA? (2 marks) QUESTION 2 CONT'D (b) What do you think is the key conformational difference between DOPA and NPA that might give you a better map of the DOPA receptor? (2 marks) C3H7 ?? NPA ?? (c) Even though NPA turns out to be an agonist for DOPA receptors, what general feature of its structure would suggest that it could have just as easily have turned out to be an antagonist? Explain briefly. (2 marks)Explanation / Answer
a. NPA is an analogue of dopa because both dopa and NPA has a common catechol nucleus and a nitrogen atom separated by 2 carbon atom. This structural similarity make NPA the analogue of dopa.
b. In the structure of dopa, the open chain branch containg nitrogen atom is not rigid as the chain is open; no cyclic structure is there. It means this branch can rotate freely while the chain containing nitrogen atom in NPA is attached with cyclic structure which restrict the free rotation of this chain and make the structure rigid. This structural difference can give a better map of DOPA receptor.
c. The structure of NPA shows isomerism. The S-isomer of NPA is agoinst while the R-form of NPA may have antidopaminergic activity thus, by isomerization an NPA molecule can easily convert into antagonist of dopamine receptor from agonistic activity.
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