11
$\begingroup$

Situation:

The vertebrate life of a distant planet uses biogenic silica for structural support. However, biogenic silica is soluble in water, but (according to this article) its solubility decreases by having aluminum within its matrix. Thus, the idea is to have aluminum-based blood produced from within the biogenic silica bones.

Question:

What would the attributes of aluminum-based blood be?

  • Color in oxygenated state
  • Color in deoxygenated state
  • Ability to transport oxygen
  • Ideal environment
$\endgroup$
10
  • 2
    $\begingroup$ Hello E.UCIT, welcome to Worldbuilding. Please note (a) You are allowed to ask one and only one question. You've asked at least two. (b) Questions cannot ask for what could conceivably be a book-length answer. The attributes of an AL-based blood exceeds that expectation considerably. (c) What do you mean by "plausible?" No such creature exists on this world and we know of no similar creatures on other worlds. Besides, we're here to help you build your world, not give you permission to build it. The help center says you can't give your answer and expect more. Sounds like you have one. $\endgroup$
    – JBH
    Aug 1 at 5:23
  • 1
    $\begingroup$ We're getting closer. In regard to that book-length answer, you're still asking for an off-topic infinite list of things and we need an on-topic finite list of things. Generally, we're not fans of list-style questions, which this is. The smaller the list you're asking for, the more tolerant we are. Can you limit your "E.G." list to, let's say, a bullet list of five specific characteristics? Otherwise we're still too broad. $\endgroup$
    – JBH
    Aug 1 at 5:34
  • 2
    $\begingroup$ That's all right! This is going to be a good question. It's the kind of topic we like to work with. We just need to get it into a form that we can consume. What are your goals for this question? How will you use the information? $\endgroup$
    – JBH
    Aug 1 at 5:36
  • 1
    $\begingroup$ It seems odd to me that you're trying to replace iron with aluminum but you're still assuming the blood's purpose is to convey oxygen rather than some other atom/molecule. Have you considered other gases (or even possibly liquids or particulate solids)? $\endgroup$ Aug 1 at 21:39
  • 1
    $\begingroup$ @E.UCIT I think perhaps you want to keep Aluminum in the bones rather than have it in the blood, so you may want to have Aluminum replace Calcium in the bones rather than the iron in the blood. $\endgroup$
    – Mathaddict
    Aug 1 at 22:59

6 Answers 6

18
$\begingroup$

I'm going to go for a slightly unsatisfactory answer here and say that you can make up anything you want and it'll be OK.

The problem is that there are no examples of biological processes that use aluminium. From the encyclopedia of metalloproteins, the entry for "aluminum in biological processes" says:

Aluminum is neither required by biological systems nor is it known to participate in any essential biological processes. While today all living organisms contain some aluminum, there is no scientific evidence that any organism uses aluminum for any biological purpose. There is similarly no evidence from the proteome or genome that any organism has utilized aluminum at any time in the evolutionary record. Aluminum’s abundance and paradoxical lack of biological function remains a biochemical enigma.

It is argued that aluminum’s absence from biochemical processes can be best explained in terms of its “historical” absence from biochemical evolution (Exley 2009a). In spite of its abundance in the Earth’s crust, aluminum was not biologically available for the greater part of biochemical evolution.

The linked reference (Using Darwin in helping to define the biological essentiality of silicon and aluminium) is behind a paywall, but does have some potentially interesting things to say...

  1. Aluminium biochemistry is potentially a bit rubbish compared to more commonly used metals

aluminium’s slow ligand exchange rates are suggested to preclude any efficacy as a metal co-factor for enzymes

  1. Aluminium has had historically very low bioavailability

There is evidence in DNA that non-essential heavy metals such as cadmium have at a previous time in biochemical evolution been both encountered and selected out of biochemistry... There are no known designed-for-purpose mechanisms by which aluminium is specifically either kept out of or removed from biota, nor is there evidence in biochemical evolution of significant encounters between biota and biologically available aluminium. Therefore, even allowing for its ubiquity within the Earth’s crust, the logical explanation of the non-essentiality of aluminium must be that biochemical evolution has proceeded in the absence of biologically-reactive forms of the metal

This all adds up to say that there are no real-world examples of the chemicals you're interested in, and so no-one can really answer your questions in a useful way. Not only that, but the chances of aluminium-using biota arising naturally are pretty small in the first place.

I'd suggest that you stablise your silica parts with aluminium-bearing chemicals from the environment, but give up on the idea of aluminium-based blood.

If you weren't prepared to do that, then you could just handwave in any colors and flavors that you like, because no-one is realistically going to be able to prove you wrong.

$\endgroup$
11
$\begingroup$

Frame challenge

You don't need anything as exotic as aluminum to stabilize silicate bones. Silica is only weakly soluble in water, and you want it to be possible to redissolve to allow bone remodeling anyway. The solubility of silica is strongly dependent on pH, because SiO2 dissolves by attaching hydroxide groups to form silicic acid, Si(OH)4. Silica bones can thus be stabilized simply by embedding silica crystals in a protein matrix which protects them from attack by hydroxyl ions; or by simply making the blood slightly acidic; or both.

$\endgroup$
10
$\begingroup$

Hemoglobin's transport of blood relies on its ability to reversibly bind its iron to oxygen. When hemoglobin releases oxygen, the iron captures water. When aluminum binds to ligands, it forms a strong bond and will not be able to easily release the captured oxygen. This makes it difficult for aluminum compounds to transport oxygen.

One alternative is a cell similar to a "respirocyte". Respirocytes are theoretical red blood cell substitutes with 236 times the capacity for oxygen storage. They are essentially nanoscale pressure vessels. A respirocyte would require a durable nanostructure. A nanostructure composed of aluminum nanograins encapsulated by aluminum-nickel metallic glass could allow your organisms to transport oxygen in aluminum cells or organelles. Some ribosome-like machine could synthesize these complex structures.

I don't know what color the blood would take on, but I do know that the color will not change between oxygenated and deoxygenated states because the oxygen is captured within a structure and not causing any chemical change. The ability to transport oxygen as I mentioned would be around 200 times greater than a red blood cell.

Information from The Ubiquity of Iron, Exploratory design in medical nanotechnology: a mechanical artificial red cell, Hierarchical nanostructured aluminum alloy with ultrahigh strength and large plasticity

$\endgroup$
4
  • $\begingroup$ How would a ~200x increase in oxygen storage affect life? $\endgroup$
    – E.UCIT
    Aug 1 at 18:57
  • 4
    $\begingroup$ @E.UCIT It might allow for more gigantic animals to evolve due to an increase in oxygen partial pressure within the blood, similar to giants during the Permian Period. Large lungs would be needed to facilitate such a high tidal volume. $\endgroup$
    – rubpy32
    Aug 1 at 19:18
  • $\begingroup$ Would a respirocyte cell be able to transport CO2? $\endgroup$
    – E.UCIT
    Aug 2 at 2:47
  • 1
    $\begingroup$ Any molecule could be transported. $\endgroup$
    – rubpy32
    Aug 2 at 2:49
4
$\begingroup$

Use enzymes centred on aluminium oxychloride nanoparticles

Aluminium is a tricky choice. It only forms soluble compounds at very low or very high pH. At high pH, you will not be able to deoxygenate it; you'll have a load of biologically useless aluminate ions.

Low pH is better; there are mixed species aluminium oxychlorides which can swap oxygen or chlorine in depending on pH, chlorine and oxygen concentration. The problem here is, they aren't soluble. The solution: nanoparticles.

Have the particles bonded to some organic bits that stabilise/control them, similar to an active metal site in a conventional enzyme (or the active cluster in photosystem II), in a blood teeming with HCl. When oxygen concentration is high, you replace chlorine with oxygen. The organic part of the enzyme does the work of regulating the details.

Your blood is white and milky regardless of oxygenation state. The lifeform is alien; we don't have blood with such low pH on earth.

Deodorant companies will try to slay your aliens by the billions and pack their blood into sticks / into emulsions on roller balls.

FWIW, I did my masters on certain synthetic amorphous aluminosilicates; I recommend keeping the bones separate from the blood question. Calcium phosphate is insoluble and we make bones out of it just fine (Our bodies take soluble calcium and phosphate separately and join them together as needed). If you want to stick Al in as a strengthening impurity, fine,but you won't easily make bones by precipitating aluminosilicates. If you really really want those bones and don't actually care about blood, google aluminosilicate geopolymers.

$\endgroup$
4
  • $\begingroup$ So the enzyme will separate Aluminum Oxychloride into HCl and AlO2, leaving the latter in the enzyme to react to the HCl and O2 again? Also, wouldn't the hydrochloric acid dissolve the biogenic silica bones? Just making sure I understand it. $\endgroup$
    – E.UCIT
    Aug 3 at 5:56
  • 1
    $\begingroup$ 1) Not quite. The enzyme will add a few oxygens and remove a few chlorines (or vice versa) from a mixed block of AlnCl(3n-m)(OH)m. The oxygenation and deoxygenation depend on local O2 concentrations just like hemoglobin does, and in this case also HCl concentration. The 'lungs' will have high O2 and low HCl, the other organs the reverse. 2) Silica is completely insoluble in acid (as calcium phosphate is in water). Bones aren't formed by simple precipitation. $\endgroup$ Aug 3 at 10:04
  • $\begingroup$ Sorry about what might be excessive amounts of questions, but how would this enzyme go about transporting CO2, or would it require a separate enzyme? Also, how could these extraterrestrial vertebrates consume, digest, and resist this acidic blood and not have internal bleeding or prey burn through their body? $\endgroup$
    – E.UCIT
    Aug 3 at 23:57
  • $\begingroup$ Turn it into bicarbonate using carbonic anhydrase? Bubble it straight out? I don't know, I like burning purely inorganic compounds at extreme temperatures, my interest was only really in the aluminium! Maybe all your aliens are acidic and silicaceous? $\endgroup$ Aug 4 at 6:48
3
$\begingroup$

I'm not sure that you will like the answer, but aluminium salts are colourless. Aluminium is most commonly found in it's +3 oxidation state although +2 and +1 are known. Aluminium reacts very readily with oxygen forming its trivalent oxide Al2O3 which is very stable and also insoluble.

$\endgroup$
1
$\begingroup$

Biological aluminum can be reddish purple! However I don't know if this kind of molecule could carry oxygen the way an iron containing protein complex like hemoglobin can.

From Biology SE's Do cochineals ("scale bugs") form aluminum complexes themselves? Where do they get such large quantities so quickly and how do they handle it safely?

Figure 2. Salasaca dyer showing red woollen cloths with modified cochineal red colours. Ecuador. Photo: A. Roquero. from Ana Roquero (2008) Textile Society of America Symposium Proceedings "Identification of Red Dyes in Textiles from the Andean Region" "Dactylopius confusus crushed scale insect, Fort Collins, Colorado, United States" from Wikimedia

Click figures for full size. above first: "Figure 2. Salasaca dyer showing red woollen cloths with modified cochineal red colours. Ecuador. Photo: A. Roquero." from Ana Roquero (2008) Textile Society of America Symposium Proceedings Identification of Red Dyes in Textiles from the Andean Region above second: "Dactylopius confusus crushed scale insect, Fort Collins, Colorado, United States" from Wikimedia. below first: "scale bugs" on my houseplant, perhaps female Dactylopius confusus or Dactylopius coccus, from https://biology.stackexchange.com/q/108276/27918 below second: Structure of carmine from Wikipedia

is this a scale bug (northern Taiwan nursery plant) Structure of carmine

$\endgroup$
2
  • 2
    $\begingroup$ I'd forgotten about these. From memory from 15 years ago, there's a whole class of dyes called 'lakes' (not very google friendly), or 'mordants' more generally. $\endgroup$ Aug 7 at 11:00
  • 1
    $\begingroup$ @SeanOConnor indeed! From the linked question: "Wikipedia's Carmine begins: 'Carmine (/ˈkɑːrmən, ˈkɑːrmaɪn/) – also called cochineal (for the insect from which it is extracted), cochineal extract, crimson lake, or carmine lake...'" $\endgroup$
    – uhoh
    Aug 7 at 13:37

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .