Water Suddenly Becomes Mysterious

An anonymous reader writes "Logical to assume that scientists know the structure of water. But wrong. A study in April by Anders Nilsson from the Stanford Linear Accelerator Center concluded the molecular bonds are looser than thought. Now a new study by Richard Saykally's group at UC Berkeley appears to debunk the April results. So a new debate is born. Both scientists agree on one thing: They don't fully understand how water molecules interact."

Comments

Hmm...

[Canar]

Considering that even fluid dynamics has a hard time making water behave in a way that looks realistic, why is this surprising?

Re:Hmm...

[Mark of THE CITY]

Different scale, for one thing...

Spectroscopists use ultrafast experiments for the same reason photographers use fast flashlamps: to capture the action, unblurred. But the motion of water, one of the most labile molecules around, is too fast, and there is argument (at least there was in the mid-90s, when I was going to seminars) about how meaningful the ball-and-stick models of water clusters were. Was it a real geometry, or an average over the time of the laser pulse? Apparently, arguments continue over this.

There are other systems where the molecules in a cluster can't move much, due to a higher degree of mutual interference than is the case with water. So the cluster models are more believable.

Re:Hmm...

[hankwang]

But the motion of water, one of the most labile molecules around, is too fast, and there is argument (at least there was in the mid-90s, when I was going to seminars) about how meaningful the ball-and-stick models of water clusters were.

Well, I did my Ph.D. on ultrafast infrared spectroscopy of water between 1997 and 2001 and things have changed since the mid-90s. The dynamics of the hydrogen-bond network in liquid water happens mainly on a timescale of a few picoseconds, which is actually in agreement with estimates based on NMR measurements several decades ago.

I'm not sure what you mean by "ball-and-stick models". The structure of the hydrogen-bond network changes continuously and rapidly, but it is quite reasonable to visualize the structure at a particular moment with balls and sticks. However, I am skeptical of theories that water molecules form persistant clusters such as 6-rings in liquid water, since one can measure in a number of different ways how fast individual molecules change their orientation. If the molecule were locked in a cluster, this reorientation ought to be much slower because of thermodynamic reasons---it is easier to turn a single molecule than six at the same time.

By the way, it is funny to see what happens when one publishes those kinds of measurements on the memory in the structure of the hydrogen bond network in water and water surrounding other molecules. Somehow, the homeopathy believers use this as a "scientific proof" that water has a memory for dissolved substances, conveniently forgetting that this memory lasts far less than one billionth of a second.

Why so mysterious? Drink it, take a shower, ...

[CodeMonkey4Hire]

Some of the programmers I work with don't understand that water (when used with soap) can help remove that small that follows them around. I wonder if some of these scientists have the same problem.

Vodka

[Shadow_139]

Somebody much of swapped the "control" test with Vodka......

"NIPPLES!! I HAVE NO NIPPLES!!!" -Happy Noodle Boy

water is weird

[rritterson]

among common substances, water is perhaps the weirdest. Here is why:

-the solid is less dense than the liquid (ice floats). This is key for life, as otherwise lakes would freeze from the bottom up and freeze solid. The ice that forms on top now acts as an insulator.

-there are 12 known varieties of ice, depending on pressure and temperature conditiions. Not all of them have a hexagonal crystal strucuture.

-for it's size, water boils at a very high temperature. This is due to the organization of the liquid into hexagonal rings of 6 molecules, preventing any from evaporating.

-it's one of the few common substances that we see in all 3 phases. (i.e. you don't see solid vodka around, nor gaseous iron, etc)

-it's the best known solvent in existance (i.e. it dissolves the most stuff).

The list goes on and on. Water is actually fairly miraculous.

Re:water is weird

[anothergene]

-it's one of the few common substances that we see in all 3 phases. (i.e. you don't see solid vodka around, nor gaseous iron, etc)

I didn't know vodka was an element now.

Re:water is weird

[Anonymous Coward]

I didn't know water was an element now.

Re:water is weird

[Anonymous Coward]

of course it is... the other three are earth, wind, and fire.

Re:water is weird

[cortana]

You forgot Heart!

I'm skeptic

[hankwang]

A claim that seems to disagree with everything else that is known should have solid evidence. It is of course possible that these guys are right and that the bookshelves full of other experimental data all are flawed. However, it might also be that the way they measured and modelled ignored some important effect.

From my background, I can mention that the infrared absorptions of the two OH bonds are at a wavenumber of 3650 and 3750 cm-1 (around 2.7 micrometers wavelength). In liquid water, these absorptions shift to a band around 3400 cm-1 (2.95 micron). It is a widely accepted fact that this shift of the OH vibration frequency occurs as a result of the hydrogen bond forming between the H of the OH and the O of the next water molecule:

H-OH ... OH2

There is hardly any absorption in liquid water at 3650 and 3750 cm-1, which would strongly suggest that nearly all water molecules have both of their hydrogen atoms bonded to other water molecules (that means four H-bonds per molecule). If the claim in the article were true, half of the OH groups would be free and absorb at a higher wavenumber.

The idea that the OH absorption wavelength depends on whether it has a hydrogen bond is in agreement with a large number of studies in which for example clusters of two, three, four water molecules embedded in another material or in vacuum have different infrared absorptions. They are also in agreement with calculations on what happens with an OH bond when you let it form a hydrogen bond, and with fully quantum-mechanical so-called ab initio calculations of how water molecules should behave, although with the latter, one might object that computers still are not powerful enough to do these calculations with more than a couple of ten molecules at a time.

bit of perspective

[Anonymous Coward]

I think most people don't realize that even before these results we didn't have a good grasp of water. This controversy dumps a whole load of new fuel into the large fire. The following issues are more simulation and protein related, but maybe they give brief insight into how much we don't know:

None of the (molecular dynamics, "MD") computer models of water are currently sufficient to reproduce all of the experimentally observered properties of water. This is a relatively big point of contention when simulating proteins as water needs to be accounted for. There are experimentalists that chide the theorists, even saying that they won't fully believe MD results until a decent model of water has been built. :)

We also don't quite know what the first hydration shell around a protein looks like. Imagine this is being the closest "coat" of water around a protein. This ordering of water could be a key component to understanding the properties/behavior of protein surfaces in binding to other molecules.

In addition, water mediated interactions between proteins is almost a completely open question. As far as I know, we don't really know how to approach the problem in an elegant manner and there have been no studies that reasonably address this at a detailed molecular level (partially due to the above two issues) even in a heuristic sense.

There is a huge literature on water. A good deal of work has been done on the above three issues and other big open issues with water that I won't go into depth on. Needless to say water has been and will continue to be a mystery for quite a while.

Masaru Emoto

[shpoffo]

...and if there isn't some consideration taken for the work of Masaru Emoto then any study is liable to be missing a few hints. He's suggesting that consciousness has a measure effect upon water. In most of the science world, that's Weird Shit, as we can only relate such phenomena to quantum mechanics.

.
-shpoffo

MOD Parent Up

[exp(pi*sqrt(163))]

Hear, hear! Molecular dynamics of large molecules like proteins is complete voodoo, but the emperor isn't listening, nobody wants to believe this. Given the difficulty modeling water any attempt to model a protein (likely surrounded by water) is like trying to fly a jet before you can crawl. I spent a couple of years working with computational chemists. It was astonishing how many tweakable parameters simulations had. There is only one set of laws of physics - there should be nothing to tweak. But computational 'chemists' would tweak and tweak all day. And after the x-ray crystallography results came in they'd say "see, the modeling worked, on the 23rd of last month the sim I ran at 3pm used these parameters and they came out just like these results." The whole area is a joke.