Blood Protein Used to Split Water

brian0918 writes "The Imperial College in London is reporting that genetically-engineered blood protein can be used to split water into oxygen and hydrogen. The abstract can be viewed for free from the Journal of the American Chemical Society." From the article: "Scientists have combined two molecules that occur naturally in blood to engineer a molecular complex that uses solar energy to split water into hydrogen and oxygen. This molecular complex can use energy from the sun to create hydrogen gas, providing an alternative to electrolysis, the method typically used to split water into its constituent parts. The breakthrough may pave the way for the development of novel ways of creating hydrogen gas for use as fuel in the future."

efficiency

[drDugan]

The mention efficiency many times in the article, but do not mention the most important efficiency number - that is total energy in/out.

So, a quick calculation of efficiency:

FTA

Light in:
6 hours, 450 W light = 2.7 kWh

H energy out:
0.044 mL H ... at 4.7 MJ/L (Wikipedia) * 1/1000 (L/mL) * 1/3.6e6 (kWh/J) * 1e6 (J/MJ) =

= 5.7 e -5 kWh

Disclaimer:

This probably has an error, please help me correct it.

It has been a really long time since I did physics or dimensional analysis.

I could not find in the paper the pressure for the 0.044 ml of generated hydrogen, nor it's weight, so I made a gross assumption the energy density listed in Wikipedia (at 700 bar) was close enough.

Regardless, if you put in 2.7 units of energy and get out 0.000057 units... that seems really (s)low.

Re:We really don't want to do that.

[CorSci81]

It has, it's called photosynthesis [wikipedia.org]. Granted, here you're not liberating free hydrogen. But to counter the GP argument of using up all water on earth... can you imagine how incredibly unstable the local environment would become for one of these organisms in the wild? They'd be very liable to kill themselves off either through pH changes or simply setting their environment on fire if they reproduced unchecked. That combined with the fact you could never split all the water on earth faster than it will recombine if sunlight is your only energy input.

Re:We really don't want to do that.

[SquareOfS]

Umm . . . we already do this? Check it out [wikipedia.org].

Net loss of 1 H2O molecule in the Krebs Cycle. And plenty of other places as well, I assume.

It's impossible, one presumes, for any standard cellular organism to destroy all water in its environment, because then no biochemical processes could occur and it would be dead.

I presume the way this works is that they isolate the protein, rather than adding the organism to the water. And proteins don't self-replicate.

Re:Energy output = input?

[radtea]

Actually they say it far surpasses the current method of separation and assuming this is a passive process

They say nothing of the kind. Quote from the abstract, "The efficiency of the photoproduction of H2 was greater than that of the system using the well-known organic chromophore, tetrakis(1-methylpyridinium-4-yl)porphinatozinc(II ) (ZnTMPyP4+), under the same conditions."

Note the complete lack of superlatives.

Re:We really don't want to do that.

[Coryoth]

I think we (collectively) need to reevaluate the risk factors here; such an organism in the wild could very well turn our planet into a dustbowl in such a shockingly short time we wouldn't even have time to lynch the scientists who created it (think: hours - the mathematics of unchecked reproduction are truly alarming).

Who said anything about reproduction, let alone unchecked reproduction? The article says it is a molecular complex, not a living organism capable of reproduction. I expect it is just an enzyme to catalyse the reaction, so I wouldn't worry about this any more than you would be inclined to worry about naturally occuring cellulase [wikipedia.org] suddenly going rampant and destroying all plant life on earth in a matter of hours. Generally being somewhat informed is a prerequisite critical analysis of risks and any ensuing scaremongering (okay, that's not true, i just think it should be a prerequisite!).

Re:Energy output = input?

[Pedrito]

Though it doesn't specify, it's highly unlikely that albumin or porphyrin is used up in the reaction. Instead, it likely cleaves the water molecules (the substrate). Not quite physically tearing it apart, but that probably isn't an entirely inaccurate description either. Many proteins perform functions like this on other molecules. They'll attach to part of the substrate and remove, say an -OH hydroxyl group, or some other piece of the molecule. This is how liver enzymes breaks down certain drugs so that the byproducts (called metabolites) can be removed from the blood by the kidneys. As someone else mentioned catalase from yeast, it works in a similar way and removes an oxygen molecule off of hydrogen peroxide, leaving water and oxygen, but the catalase isn't "used up" in the process.

That said, proteins don't usually last forever and how long they last largely depends on how hostile their environment is, and what constitutes a hostile environment for a protein varies from protein to protein.

Re:Problem with large scale use?

[Anonymous Coward]

Right on the money, it's hard to believe the Journal of the American CHEMICAL Society would publish this as is. First, water is not reduced; protons are reduced. If they had added a little acid, they could have claimed "photosensitized reduction of acid X" just as well. Second, as you mentioned, triethanolamine is a sacrificial reductant. So, the Slashdot title is misleading--water is not being split (which in the scientific jargon means reversing combustion of hydrogen, i.e. net reaction 2H2O --> 2H2 + O2, no sacrifical reductants allowed). Their work leaves the oxygen in its reduced state. Third, they require a platinum catalyst. There are already means to use expensive Pt catalysts or electrodes wired into a circuit with a photovoltaic module. What they've accomplished is light-driven oxidation of TEA to H2. From an industrial-scale energy conversion standpoint, this work doesn't seem terrifically relevant.

It is a neat use of HSA to solubilize Zn protoporphyrin IX and prevent collisional self-quenching of the excited triplet state, though. And, they achieved a greater efficiency in this non-water-splitting reaction than another known catalyst, so that's worth knowing too, I suppose.

Re:Energy output = input?

[sillybilly]

Yes, but most biological matter is easily degraded by UV radiation, plus infection - bacteria would love to feast on your new solar cells.
As a sidenote, to quote the artilce: "Dr Stephen Curry Opens in new window, a structural biologist from Imperial College London's Division of Cell and Molecular Biology who participated in the research explains: "This work has shown that it is possible to manipulate molecules and proteins that occur naturally in the human body by changing one small detail of their make-up, such as the type of metal at the heart of a porphyrin molecule, as we did in this study.
Naturally occur in a human? I was hoping they'd be talking about cow-derived materials, unless they are interested in genetically engineering photosynthetic human beings? Maybe one of our great great grand children will be engineered enough to be vacuum resistant and fully photosynthetic, then he can fly around in outer space while living off of sunshine.

Re:We really don't want to do that.

[Qzukk]

(The molecule would "eat" it's own host up.)

This [google.com] might be of interest to you.

Re:Energy output = input?

[wetfeetl33t]

Yes, that's true if this were a closed system. However, this isn't a closed system. Energy is entering it (from the sun), and mass is entering and leaving (water, hydrogen and oxygen). So yes, total entropy is increasing somewhere, but it just isn't in this hypothetical system

Re:How effecient is this?

[Hubristically Yours]

Not sure about the recombinant albumin, but part of my job involves pharmaceutical purchasing, and a vial of 20mL of 25% human serum albumin can be obtained for approximately $13. The human version is produced by precipitation from donated blood and is used quite routinely in the hospital to treat various conditions such as shock or malnutrition. Also, many medications are packaged with albumin in the vial (to provide a binding surface for the drug molecules).

I would say though that the "manufactured in an industrial scale" statement is a bit misleading. Purified blood proteins in general are ungodly expensive. For instance, immunoglobins, which you might get to protect you against infection if you've been exposed to, say, Hepatitis B or C, are some of the most expensive drugs we have, ranging up into the thousands of $ per shot. Most of these are refined from human blood, but even if you have trillions of bacteria slaving away for you producing recombinant proteins, it's the purification and quality control steps that are the killer.