
On the existence of two states in liquid water [pdf] - anigbrowl
http://polymer.bu.edu/hes/articles/mmcjggjms16.pdf
======
mathgenius
John Baez has some interesting things to say about different structures that
appear in water:

[https://johncarlosbaez.wordpress.com/2013/11/29/water/](https://johncarlosbaez.wordpress.com/2013/11/29/water/)

And these things have a very strong temperature dependence. I wonder if it has
anything to do with the current discussion.

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wyager
Interesting that the low end of this phase transition range coincides with the
maximum safe temperature for mammals and birds. It could be that the delicate
biological mechanisms we've developed over the years are highly sensitive to
some of the bulk characteristics that change in this range.

~~~
lisper
The paper talks about this. It's not just mammals and birds, proteins in
general become less stable over 60C:

"This raises the question of whether temperature-driven structural changes in
water affect biological macromolecules in aqueous solutions and in particular
in proteins... It was found that the temperature stability range of the
protein is confined to the reversible interval 45–65°C. ... In all cases the
critical temperature of the protein denaturation is very close to the
crossover temperature T* observed in all the properties of liquid water
reviewed in this work."

This is probably why sous vide temperature is around 60C.

~~~
amelius
> This is probably why sous vide temperature is around 60C.

But why are sauna temperatures above this, being in the range of 70C-90C?

~~~
lmm
That small organisms cannot survive saunas, only large organisms with
temperature regulation ("warm-blooded"), is probably a design feature.

~~~
mhutter
This and because you don't stay in a Sauna for more than a few hours

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kmonad
I think it is cool that there is evidence for these two states in water. I
don't think, however, that the biological relevance was made particularly
clear. There is hardly any life on earth for which these temperatures (upwards
of 45C) play a role, and consequently, any effect on proteins would be 'out of
context' within which protein function was under selective pressure. Whether
or not protein stability is affected by these transitions of water states
could therefore be purely coincidental. Having said this, however, one could
perhaps learn more about how water affects protein function in 'normal'
temperature ranges by breaking function with the other water state (but I
don't understand this well enough to think of a way how to do this).

~~~
schiffern
> There is hardly any life on earth for which these temperatures (upwards of
> 45C) play a role, and consequently, any effect on proteins would be 'out of
> context'

It makes me wonder what the pressure dependence is for this phase change.
[http://www1.lsbu.ac.uk/water/water_phase_diagram.html](http://www1.lsbu.ac.uk/water/water_phase_diagram.html)

Pressures inside a particular piece of cellular machinery can be much higher
than 0.1 MPa (1 bar).

~~~
marcosdumay
There's nothing on the article about thermal expansion and heat coefficient.
So I'm assuming in both states they are the same.

If so, there is really no reason to expect this state change to be much
affected by pressure.

There also seems to be no latent heat absorbing¹, and from the widely varying
changing temperature, I imagine both states coexist on those ~20°C. Water is
really weird.

1 - Otherwise people would have discovered this long ago.

~~~
schiffern
I just realized you're forgetting a huge class of life -- soil organisms.
Compost heaps contain the most diversity of life when "cooked" between 55C and
65C.

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rosstex
ELI5 please?

~~~
chadcmulligan
the conclusion probably says it all?

"In conclusion, a review of the physical properties of water in the 0–100°C
temperature range reveals a bilinear behaviour that defines a crossover
temperature at 50 ± 10°C. This observation supports the hypothesis that there
are two states of liquid water. We find that these two states play an
important role in the thermal and optical properties of nanomedical systems.
Finally, our preliminary findings suggest that the structure of liquid water
strongly influences the thermal stability of proteins. More in-depth research
on the thermal stability of proteins dispersed in liquid water is needed."

~~~
mirimir
Yes, but just what _are_ those states? I see no explicit hypotheses. The
clearest hint that I see is that the calculated dipole moment is 2.3 Ds at
0–60°C, "which is close to the value for ice", and 1.8 Ds at 60–100°C, "which
is comparable to that reported for the vapour phase". Lower dipole moment
means weaker hydrogen bonding, and less tetrahedral structure.

~~~
the8472
> Yes, but just what are those states?

That's covered in the introduction.

> Despite these efforts, the structure of liquid water is still not fully
> understood.

> This suggests that there are of two states in bulk liquid water that differ
> in the amount of their dipole moment. Unfortunately, a correlation between
> the dipole moment and the microscopic structure of these two states has not
> yet been determined.

~~~
mirimir
Yes, I should have quoted those bits.

