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| njb35@cantab.net (Nick Bennett) wrote in message news:<d9e7522c.0408180843.2d09f356@posting.google.com>...
> j.umber@ac-nancy-metz.fr (Jean) wrote in message news:<5eb4d562.0408082142.494b850@posting.google.com>...
>
> It's true that a double-base substitution is required, but it's also
> clear that any and all mutations will exist at all sites in a mixture
> of HIV in vivo. ON average every genome will have at least mutation
> in it. The fact of the matter is though, that not all mutations have
> a selective advantage. Some will be disadvantageous, some will be
> neutral. You cannot expect a necessarily orderly progression,
But this is an assumption, where is the demonstration?
>
> No, they're saying that in addition to the OH group, there is room for
> 3 H2O molecules. As they say, ample room for an azido, presumeably
> through the loss of one or more water molecules.
Why presumeably? Still an assumption? We need certainties here !
Anyway, I read not the same things as you.
> and in the
>
> Why can't the azide group replace the water OH bonding? H-bonds are
> stronger than some, but they are non-covelant. They are changing all
> the time: if they weren't water wouldn't be a liquid at room
> temperature! I see no problem with H-bonds being replaced, altered,
> swapped out, unused....they're dynamic bonds by their very nature.
I see a big problem.
Here are the physical properties of hydrazoic acid :
http://www.osha-slc.gov/dts/sltc/me...d211/id211.html
Synonym name Hydrogen azide
Chemical formula HN3
Structural formula H-N=NN
Formula weight 43.03
Freezing point -80°C
Boiling point 37°C
For water, we have :
Formula weight 18
Freezing point 0°C
Boiling point 100°C
It is very obvious that hydrogen bonding is much more strong between O
and H then between NNN and H. You can say that we have two
possibilities for hydrogen bonding in water. But methanol has these
properties :
Formula weight 32
Boiling point 65°C
For instance, you can also look to this synthesis :
http://www.rhodium.ws/chemistry/eleusis/mda.html
and see that hydrazoic acid is soluble in benzene. What for a polar
component !
> It makes sense that with AZT versus 3TC, the mutations are in an area
> which interacts with the modified bit of the nucleotide found in AZT
> but not 3TC. All this supports the proposed mechanism of viral
> resistance.
>
>
> Not quite so clearly - at least to me. I can see no difference
> between a hydrogen bond formed between hydroxyl groups and azide
> groups: it's all just a matter of dipoles after all and electron
> clouds.
I have given reference above, which prove the contrary without
ambiguity
In certain situations (taking into account all the other
> bonds being formed and steric conformation alterations due to bonding)
> I can see no reason why a classically "less favoured" reaction cannot
> occur. After all, glucose can be converted to starch can it not,
> under the right conditions, even though that is energticaly
> unvavourable. That's part of the difference between biology and
> chemistry, in my mind.
Once more, chemistry is the basis of biology, and biology cannot
escape from the chemical rules.
Where have you seen that the conversion of glucose to starch is
thermodynamicaly unfavourable ?
I read (in Principles of biochemystry, Lehninger, p 740) :
Starch(n) + glucose 1-phosphate + ATP -> starch(n+1) + ADP + 2Pi
deltaG = - 50 kJ/mol
friendly
Jean
> Cheers
>
> Bennett
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