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On the existence of two states in liquid water [pdf]

polymer.bu.edu

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Re: On the existence of two states in liquid water [pdf]

#21

Post by schiffern »

kmonad wrote: post #19

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…

> 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

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

Re: On the existence of two states in liquid water [pdf]

#22

Post by dave_sullivan »

kmonad wrote: post #19

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…

Interestingly, geothermal vents--such as those found on Earth and possibly Europa--come out at about 60-460C. They are thought to be good origin of life candidates. Behavior of proteins in this state sounds pretty interesting in that light.

Re: On the existence of two states in liquid water [pdf]

#23

Post by lmm »

amelius wrote: post #20
lisper wrote: post #3

Earlier quoted context omitted.

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 criti…

> This is probably why sous vide temperature is around 60C. But why are sauna temperatures above this, being in the range of 70C-90C?

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

Re: On the existence of two states in liquid water [pdf]

#24

Post by marcosdumay »

schiffern wrote: post #21
kmonad wrote: post #19

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…

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

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.

Re: On the existence of two states in liquid water [pdf]

#25

Post by marcosdumay »

mirimir wrote: post #8
chadcmulligan wrote: post #5

Earlier quoted context omitted.

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, o…

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.

> Lower dipole moment means weaker hydrogen bonding

Wouldn't weaker hydrogen bounding imply on much lower surface tension?

There is some smaller tension, but the trend is really tiny.

Re: On the existence of two states in liquid water [pdf]

#26

Post by icegreentea »

lisper wrote: post #3
wyager wrote: post #2

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.

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 criti…

I wouldn't use 'probably' at all. The level of proof submitted is incredibly light - it only inspects two and a half proteins - and doesn't attempt to inspect the relationship between its proposed mechanism (change in hydration shell density) and protein denaturation.

They show two graphs of protein denaturation curves showing maximum rate change in 50-65 degree range, and a curve of a different protein's hydration shell density changing. At the very least, showing correspondence between hydration shell density and denature curves within a single protein would be significantly more convincing.

While protein folding and interaction is devilishy tricky to compute, the basic idea that injecting extra energy into a system thats held together only by weak hydrogen bonds will disrupt structure and function hardly requires invocation of additional forms of water.

This isn't to say that the claims may not be true. But I would not jump to "probably".

In fact, your quoted statement doesn't even say that proteins become less stable, what the quoted statement says is that a SINGLE protein (lysozyme) undergoes irreversible structural changes over 65 degrees.

We know of a variety of high temperature resistant proteins (Taq Polymerase for example). While is certainly true that most "ordinary" (ie non extremopile) proteins will probably suffer irreversible structural changes in about that temperature change, it's not super great proof.

Re: On the existence of two states in liquid water [pdf]

#27

Post by mhutter »

lmm wrote: post #23
amelius wrote: post #20

Earlier quoted context omitted.

> This is probably why sous vide temperature is around 60C. But why are sauna temperatures above this, being in the range of 70C-90C?

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

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

Re: On the existence of two states in liquid water [pdf]

#28

Post by icegreentea »

amelius wrote: post #20
lisper wrote: post #3

Earlier quoted context omitted.

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 criti…

> This is probably why sous vide temperature is around 60C. But why are sauna temperatures above this, being in the range of 70C-90C?

Thats because you have enough thermal mass and evaporative cooling capacity to withstand those temperatures for a short period of time - ie, very little of your body will experience drastically elevated temperatures for long - if at all. Remember that air (even humid air) is not a super great heat conductor - so while the air might be very hot, it's going to be pretty bad transferring that into your body, which in turn has a lot of mass to distrube heat over, and good conductivity to move heat away from contact areas. And that whole sweat thing works pretty well too (especially in a dry sauna).

Being submerged into a 90 degree water bath will probably rapidly hideously wound you and/or kill you.

Re: On the existence of two states in liquid water [pdf]

#29

Post by mirimir »

the8472 wrote: post #16
mirimir wrote: post #8

Earlier quoted context omitted.

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.

> 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.

Yes, I should have quoted those bits.

Re: On the existence of two states in liquid water [pdf]

#30

Post by mirimir »

kmonad wrote: post #19

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…

There's this:

> In addition, Raman scattering measurements, obtained using multivariate curve resolution (Raman-MCR) have been used to explore the hydrophobic hydration of linear alcohols from methanol to heptanol [25]. The authors conclude that below 60°C the hydration shells have a hydrophobic-enhanced water structure with a greater tetrahedral order and fewer weak hydrogen bonds than the surrounding bulk water. This configuration disappears above 60°C and is replaced by a structure with weaker bonds. These findings support the existence of two different hydration shells in liquid water with a crossover temperature of ≈60°C.

So it seems that proteins have evolved to stabilize the "ice-like" structure in hydration shells, and in turn depend on those hydration shells to stabilize their 3D structure. Above 50-60°C, that doesn't work. But there are some Archaea that do quite well at 100°C. Their proteins presumably do a better job of stabilizing the "ice-like" structure in hydration shells.

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