What forms of iron are bioavailable?

[taricha]

I think that may be incorrect.

Iron Oxide Hydroxide (GFO) Phosphate Binders by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2004-11/rhf/index.htm

Another possible role may be played by the iron itself. GFO is not completely insoluble. The solubility of iron hydroxide in natural seawater is small, but still significant (0.02 - 2 ppb), although it is largely controlled by the availability of organic ligands.11-13 One interesting possibility lies in the way that soluble iron actually impacts the precipitation of calcium carbonate...

Thanks! This is good to know. I was thinking GFO as a source of soluble Iron required some elaborate unobserved biological or chemical bankshot to occur. I much prefer simpler explanations.

"What else does iron oxide hydroxide bind? Metals
...including trace metals, arsenic, selenium, silicate, and organics."

How would this be different for an Aluminum-based Phosphate binding media? Would it bind mostly the same things, with the possibly important difference being the Al media can't be a source of Fe?

 

[Randy Holmes-Farley]

Thanks! This is good to know. I was thinking GFO as a source of soluble Iron required some elaborate unobserved biological or chemical bankshot to occur. I much prefer simpler explanations.

"What else does iron oxide hydroxide bind? Metals
...including trace metals, arsenic, selenium, silicate, and organics."

How would this be different for an Aluminum-based Phosphate binding media? Would it bind mostly the same things, with the possibly important difference being the Al media can't be a source of Fe?

I'm sure there are differences as to what exactly is bound and how strongly, but many things will be similar.

For example, negatively charged things that bind to aluminum oxide will be binding (at least in large part) to the aluminum ions. For GFO, those things are binding the the ferric ion (Fe+++). Those have somewhat different affinity for different negatively charges ions, but they are fairly similar.

 

[kecked]

I have an idea and want to see if anyone has read or seen this. I'm still back on the modulation of toxin by dinos via iron. I an wondering if they want the iron or there is phosphate stuck to the iron they want and capture the iron to get the phos. Just can't see why they want all that iron. Setting up to do 785 raman so some toxin results soon I hope. Running out of dinos!

 

[mcarroll]

Running out of dinos!

Awwww.

NOT!

 

[mcarroll]

I an wondering if they want the iron or there is phosphate stuck to the iron they want and capture the iron to get the phos.

I like your theory...siderophores (and all they entail) could even be one of the main reasons they target bacteria as food when dissolved nutrient sources fail them.

In fact, plugging a couple things into Google Scholar yeilded:
The importance of siderophores in iron nutrition of heterotrophic marine bacteria
...as well as several others of interest.

Nothing conclusive to your question so far tho...

 

[Randy Holmes-Farley]

I have an idea and want to see if anyone has read or seen this. I'm still back on the modulation of toxin by dinos via iron. I an wondering if they want the iron or there is phosphate stuck to the iron they want and capture the iron to get the phos. Just can't see why they want all that iron. Setting up to do 785 raman so some toxin results soon I hope. Running out of dinos!

The iron they take up is almost certainly not bound to phosphate. Two reasons: there is very, very little iron in seawater relative to phosphate, and even if every iron atom taken up has a phosphate attached, it would be a trivially small amount of phosphate relative to the need.

Also siderophores and other iron binding molecules do not bind iron phosphate.

 

[kecked]

Thanks for that input I was not away of that. Still can’t see why structurally they need so much iron. Also how about in freshwater environment where there is a ton of iron present. Thinking Lake Erie. I’ve just about got my Raman setup on my microscope. Hoping I don’t fry the cells when I measure! Real balance between fluorescence and signal. Really need 1064 but too much heating. Well hplc plus Raman plus nmr should do it. Found some library spectra for sax paly and cig toxins. Would like o hook up to my confocal and image the cells to find where the toxin is actually produced but doubt I can get a scan on live cells. They move too much.

Last do you see chelating the iron a good way to remove iron from the biological availability?

 

[Scott Weinrich]

Along these lines, I have tried to instill in some folks the caution that oxidizers like Lugols or hydrogen peroxide or reducers like vitamin C, may be altering the bioavailability of trace elements, so when folks observe effects, it may not be due to iodine supplementation or the direct effects of these additives on things like dinos.

I'm curious whether the acetanilide stabilizer in hydrogen peroxide also has a role in limiting the bioavailibity of iron through complexation with ferric ions.

 

[Randy Holmes-Farley]

Thanks for that input I was not away of that. Still can’t see why structurally they need so much iron. Also how about in freshwater environment where there is a ton of iron present. Thinking Lake Erie.

In surface seawater, there is very little iron available, and so it can easily become depleted.

I'm not sure what you mean by structural, but a lot of iron is taken up by all photosynthetic organisms for a wide variety of different enzymes and other functional proteins. Algae (micro and micro) can be a big sink for iron

I also expect that much of the iron we dose to reef tanks just precipitates out unused.

Iron is also used in organism locations where very high strength are needed, such as chiton teeth. For exampkle"


Analysis of an ultra hard magnetic biomineral in chiton radular teeth
https://www.sciencedirect.com/science/article/pii/S136970211070016X

Cross-sectional examinations by scanning electron microscopy (Fig. 2f1, 2) and energy dispersive spectroscopy (EDS) of the radular teeth of C. stelleri reveal that they are composed of two distinct mineral phases2,4 (Fig. 3a). The core region of the teeth is enriched in iron phosphate and the exterior of the teeth in iron oxide (Fig. 3a,b). EDS analysis also reveals a significantly higher C content in the tooth core as well as small amounts of Ca, K, Na, Mg, and Si (Fig. 3b). X-ray and electron diffraction (Figs. 3c; 5d) of the tooth exterior region reveal that it is composed of ferromagnetic iron oxide (magnetite)2,4,15, while EDS, Raman spectroscopy11,12,16 and dark-field transmission electron microscopy of the tooth core material suggest the presence of weakly crystalline hydrated iron phosphate (Figs. 3b,d; 5e)2,4.

 

[Randy Holmes-Farley]

I'm curious whether the acetanilide stabilizer in hydrogen peroxide also has a role in limiting the bioavailibity of iron through complexation with ferric ions.

I'm not sure exactly what structure you are asking about, but acetanilide itself is not going to strongly bind iron.

 

[Randy Holmes-Farley]

Last do you see chelating the iron a good way to remove iron from the biological availability?

In a reef tank? For what purpose?

It might be hard to limit bioavailability of iron only since most chelators will bind other transition metals as well.

 

[Scott Weinrich]

I'm not sure exactly what structure you are asking about, but acetanilide itself is not going to strongly bind iron.

I know ferric/ferrous ions can coordinate with aromatics systems, but I don't know the range of typical equilibrium constants. I may have been thinking of this because ferrocene (which is a bit different) is coordination complex with an aromatic system and quite stable.

 

[Randy Holmes-Farley]

I know ferric/ferrous ions can coordinate with aromatics systems, but I don't know the range of typical equilibrium constants. I may have been thinking of this because ferrocene (which is a bit different) is coordination complex with an aromatic system and quite stable.

Ferrocene is iron metal, not ionic iron. The aromatics won't bind Fe++ or Fe+++eciably in water.

Strong chelators are needed to prevent bioavailability of ionic iron in water, and those will typically have multiple arms to bind the metal, and the end of the arms will be specific N or O groups. The ordinary amide int he above molecule won't bind iron in seawater.

These sorts of molecules will bind strongly:

https://www.sciencedirect.com/science/article/pii/S1198743X14607242

iron EDTA:

http://www.dojindo.com/store/p/729-Fe-III-EDTA.html

 

[Scott Weinrich]

Ferrocene is iron metal, not ionic iron. The aromatics won't bind Fe++ or Fe+++eciably in water.

Strong chelators are needed to prevent bioavailability of ionic iron in water, and those will typically have multiple arms to bind the metal, and the end of the arms will be specific N or O groups. The ordinary amide int he above molecule won't bind iron in seawater.

These sorts of molecules will bind strongly:

https://www.sciencedirect.com/science/article/pii/S1198743X14607242

iron EDTA:

http://www.dojindo.com/store/p/729-Fe-III-EDTA.html

Well, the iron in ferrocene is in a +2 oxidation state, so ferrous, not elemental. Perhaps the aromatic in acetanilide won't complex strongly in aqueous solution, but things like hydroxamic acids can act as bidentate chelators. Acetanilide is missing the crucial nitroso-oxygen to make it bidentate though. So, maybe it has no real effect at all. Just a thought.

Edit: Nevermind, didn't catch your statement about the amide group.

 

[Randy Holmes-Farley]

Well, the iron in ferrocene is in a +2 oxidation state, so ferrous, not elemental. Perhaps the aromatic in acetanilide won't complex strongly in aqueous solution, but things like hydroxamic acids can act as bidentate chelators. Acetanilide is missing the crucial nitroso-oxygen to make it bidentate though. So, maybe it has no real effect at all. Just a thought.

Edit: Nevermind, didn't catch your statement about the amide group.

IMO, that's not an appropriate way to think of ferocene. Fe++ does not bind to aromatics in water.

Ferrocene is an organometallic. It is not an ionic complex. It may have a formal charge of +2, but that does not make it similar to Fe++ in water.

I certainly agree that hydroxamic acids are a great way to bind iron. I've designed iron binding polymers with them for a program on treating iron overload disease.

Hydroxamic acid-containing hydrogels for nonabsorbed iron chelation therapy: synthesis, characterization, and biological evaluation.
Polomoscanik SC1, Cannon CP, Neenan TX, Holmes-Farley SR, Mandeville WH, Dhal PK.
https://www.ncbi.nlm.nih.gov/pubmed/16283713

"In this study, hydrogels containing pendant hydroxamic acid groups have been synthesized as potential nonabsorbed chelators for iron in the gastrointestinal tract. "

 

[Scott Weinrich]

IMO, that's not an appropriate way to think of ferocene. Fe++ does not bind to aromatics in water.

Ferrocene is an organometallic. It is not an ionic complex. It may have a formal charge of +2, but that does not make it similar to Fe++ in water.

I certainly agree that hydroxamic acids are a great way to bind iron. I've designed iron binding polymers with them for a program on treating iron overload disease.

Hydroxamic acid-containing hydrogels for nonabsorbed iron chelation therapy: synthesis, characterization, and biological evaluation.
Polomoscanik SC1, Cannon CP, Neenan TX, Holmes-Farley SR, Mandeville WH, Dhal PK.
https://www.ncbi.nlm.nih.gov/pubmed/16283713

"In this study, hydrogels containing pendant hydroxamic acid groups have been synthesized as potential nonabsorbed chelators for iron in the gastrointestinal tract. "

I guess ferrocene is a better of perspective. I view it as a metal ion strongly coordinating with the pi orbitals on the rings. When you use it in cyclic voltammetry, it oxidizes at a 1-2 volts, similar to a free ion.

I tried to look it up and didn't find much, but is it possible for acetanilide to be oxidized to the corresponding hydroxamic acid by hydrogen peroxide? I'm guessing that you'd need a stronger oxidizer.

 

[Jose Mayo]

Wow...
Just following!

 

[Randy Holmes-Farley]

I guess ferrocene is a better of perspective. I view it as a metal ion strongly coordinating with the pi orbitals on the rings. When you use it in cyclic voltammetry, it oxidizes at a 1-2 volts, similar to a free ion.

I tried to look it up and didn't find much, but is it possible for acetanilide to be oxidized to the corresponding hydroxamic acid by hydrogen peroxide? I'm guessing that you'd need a stronger oxidizer.

Are you trying to explain a particular observation?

Hydrogen peroxide will alter the speciation of several trace metals, including iron, by driving them to a higher oxidation state.

 

[kecked]

Ok so what I’m trying to look at is less my fish tank and more eventually Lake Erie. My fish tank is just what got me interested in the problem. My thought is why are the toxic algae a problem and what limiting reagents could be used to throttle them. We know excess phosphate from run off feeds them. We know there is already a ton of iron present but in what form and could that iron be activated or added to to dunk the phosphate. If we just had algae it would be a problem but less so. Getting there now...what if you could turn off the toxin production or minimize it. Now it’s less of an issue. There all cards on table. The prize is 10 million dollars. The iron connection has been proven by a Canadian university. They published in March last year. I found it during a lit search last week. So they beat me to the punch. What they did is not exactly what I had in mind but I’ll post the link in few after I cut the grass. I am less interested in the money and more in public health though it would be nice.

My advanced idea is a plasmid but yea not happening in a home lab.

Ferrocene is expensive toxic and of little use in this problem though an intersting topic by itself. It’s one thing to treat 300g and another to treat Lake Erie. I’m looking at marine for the moment as that is what I can grow. I gave to rent a boat to go get and learn to culture the freshwater varieties. Btw nasa flys a plane that tells them where to sample. I dont have that ability.

I very much enjoy these discussions. I hope the level of discussion is ok for this forum. I believe you don’t have to be a scientist to both learn and contribute. So if I’m annoying please tell me so.

http://www.rcinet.ca/en/2016/02/29/beating-blue-green-algae-with-iron/

Second read...not really modulating the toxin. Basically says run gfo on lake. But...they don’t deplete it entirely so they keep- the microculture in balance.

I’ll add one last item to this monster post. Saying make me a Star Trek transporter is a good idea and actually making one are very different animals so just because I want to shutdown the toxin doesn’t mean you can

 

[taricha]

We know excess phosphate from run off feeds them. We know there is already a ton of iron present but in what form and could that iron be activated or added to to dunk the phosphate. If we just had algae it would be a problem but less so.

The Chem side is totally not something I have any basis in, so I'll just throw out unproven hunches from watching a bunch of reef tanks with blooms that come and go.
I suspect Fe is the most important hard-to-see-trace element regulator of blooms - seems broad agreement there. It's not the only one though, and I think in a tank that has ample N, P, etc... if Iron is also provided, something else would become limiting. I don't have a good suspect there, nor a concept of how long that would take, but it sounds like that might be a more practical solution if you know Fe, N,P in a body of water is crazy high - identify and target next suspect down the list.

On the biological need for Fe in algae, one of the players in electron transport during photosynthesis is ferredoxin - built on Iron, and interestingly some algae living in ocean environments that get Fe-depleted, can make their own Iron-free version of ferredoxin - called flavodoxin.
Characterization of ferredoxin and flavodoxin as markers of iron limitation in marine phytoplankton