Re: Chuck...Could you please explain...?

[Guest guest]

,

You wrote:

>

> Could you explain why these 'look' different?

The text book version is the way the molecule looks in water. The Synthroid is

the way it looks as a dry sodium salt. The position of the NH2 (above or below)

does not matter, since that part can rotate. When the dry version is dropped

into water, a hydrogen H from the water replaces the sodium Na+ ion which then

wanders off into solution with the other attached H2O.

Note the statement two sentences before the Synthroid structure:

" Synthetic T4 is identical to that produced in the human thyroid gland. "

Chuck

[Guest guest]

Hi Chuck,

Thanks! I'm still trying to work this out in my head...so, now, it is

my understanding that T3 and rT3 (reverse T3) are identical, but the

structure is reverse (IIRC, I read 'mirror image')--so looking at the

diagrams (of the natural) for T3 & rT3 (just below T4), since you say

they can rotate and that doesn't matter, could you explain the

differences here, please? Also, are the vertical dashes (of the

diagrams themselves) representative of the ions attached to the

molecules? If not, what do they represent? And when you refer to

'they can rotate', but that doesn't matter...do you mean horizontally,

vertically, or either?

Thanks again...hope I'm not being a PITA,

> >

> > Could you explain why these 'look' different?

>

> The text book version is the way the molecule looks in water. The

Synthroid is the way it looks as a dry sodium salt. The position of

the NH2 (above or below) does not matter, since that part can rotate.

When the dry version is dropped into water, a hydrogen H from the

water replaces the sodium Na+ ion which then wanders off into solution

with the other attached H2O.

>

> Note the statement two sentences before the Synthroid structure:

> " Synthetic T4 is identical to that produced in the human thyroid

gland. "

>

> Chuck

>

[Guest guest]

,

You wrote:

> ... it is

> my understanding that T3 and rT3 (reverse T3) are identical, but the

> structure is reverse (IIRC, I read 'mirror image')...

No. The iodine atoms are attached differently. In T3, there are two on

the inner ring, at positions 3 and 5. There is a single iodine on the

outer ring, at the 3' position.

In RT3, there is only one atom on the inner ring, at the 3 position. The

outer ring has two, at 3' and 5'.

Those are very different structures, which is why they have very

different activities.

I don't know what you mean by vertical dashes. Those could either be

covalent bonds (two shared electrons), or they could be the letter I for

iodine.

The part that I said could " rotate " was the second carbon in the chain

from the inner ring. That had an NH2 on one side and an H on the other.

Those could be drawn with either up or down, and it would be the same

structure. That was one of the " differences " I thought you might be

seeing between the diagrams. They are actually the same.

This is like drawing methyl chloride with the Cl on the left side, right

side, top, or bottom. They are all still the same molecule.

Chuck

[Guest guest]

Thanks Chuck! This is the part I wasn't sure about...and related to

what I was asking about rotating, etc. :-) The vertical dashes I was

referring to were part of the labeling... i.e. left top, etc.

....

> This is like drawing methyl chloride with the Cl on the left side,

right

> side, top, or bottom. They are all still the same molecule.

>

> Chuck

>

[Guest guest]

,

You wrote:

>

>

> Thanks Chuck! This is the part I wasn't sure about...and related to

> what I was asking about rotating, etc.

There is another sense of rotation, the levo- and dextro- stereoisomers.

These refer to the direction of spiral of the chain attached to the

proximal ring. Levo means left handed, and dextro means right handed.

All the thyroid hormones spiral to the left, or they don't work. Both

synthetic and natural molecules are levo-.

Chuck