At 08:15 PM 5/2/97 -0400, you wrote:
>Chemistry: (This won't add the slightest bit of help or info about
>PD, just a little fun to share with the technically minded.) From
>time to time I wondered about the loose and interchangeable use of
>the terms DOPA, L-DOPA, Levodopa, and Dopamine- so I decided to look
>up the definitions. The books don't all agree exactly, but I think I
>have a handle on it that is adequate for my degree of interest.
>Names of compounds are often chosen to tell a little about the
>chemcal's composition. DOPA is an acronym, or shorthand, for
>DihydrOxyPhenylAlanine, as depicted below. The diagrams are another
>kind of shorthand, where chemists can recognize familiar groups and
>see how they go together. You need to recall from freshman chemistry
>how compound molecules are made of atoms connected by something
>called valence bonds, of which each element has a characteristic
>number: Hydrogen 1, Oxygen 2, Nitrogen (usually) 3, and Carbon 4.
>In DOPA, the hydroxyl group is water, H2O, minus a hydrogen. The
>phenyl is based on the benzene hexagon, C6H6, and Alanine, itself
>an amino acid when complete, is the group on the right. DOPA
>becomes Dopamine when the C-O-OH part of the alanine group is
>replaced by a single hydrogen atom. Levodopa refers to the fact that
>the DOPA molecule isn't flat like its diagram, but has a three=
>dimensional aspect that permits more than one shape. When you look
>at a solution of DOPA through a Polaroid filter, you find that one
>of its forms twists the polarization to the left, or "levo". The
>Different forms of a compound may have identical composition but
>quite distinct chemical properties. The best analog I can think of
>for right- or left-handedness is in a pair of dice. If you obey the
>convention that marks on opposite sides of each cube must add up to
>7, and look at a corner so you can see 1, 2, and 3, there are two
>possible arrangements: clockwise and counterclockwise. Something
>like that happens in many chemical compounds.
>
> H H H H
> | | | /
> H C H H---C---C---N---H
> \ // \ / | |
> C C H C--O--H
> | || \\
> C C O
> / \\ / \
> H C H Alanine
> |
> H
>
> Benzene
>
> H H
> | |
> H--O C H H H H--O C H H H
> \ // \ | | / \ // \ | | /
> C C---C---C---N--H C C---C---C---N--H
> | || | | | || | |
> C C H C--O--H C C H H
> / \\ / \ \\ / \\ / \
> H--O C H O H--O C H
>(Dihydroxy) | (Alanine) |
> H H
> (Phenyl) (Carboxyl)
>
> DOPA = DihydrOxyPhenylAlanine Dopamine
> (Levodopa)
>
>
>
>
>J. R. Bruman (818) 789-3694
>3527 Cody Road
>Sherman Oaks CA 91403
>
J.R.
For an interesting look at the problem, see William S. Knowles 'ASYMMETRIC
HYDROGENATION'in the Accounts of Chemical Research [1983] 16,106-112. It's
tough reading but on topic. Knowles is or was an aggie chem researcher with
Monsanto. I don't know him. He got his PhD at Columba in 1942...and that's a
long time back for a graduate degree.
Will
And here's to long "ons" and short "offs"
WILL JOHNSTON 4049 OAKLAND SCHOOL ROAD
SALISBURY, MD 21804-2716
410-543-0110
Pres A.P.D.A. DelMarVa Chapter
