Could human skin be photosynthetic?

billb@eskimo.com

I've always thought that, were it possible for biology to harness
ionizing radiation for energy, some organism would already have done
so. The ground contains vast fungal and bacterial communities, but
also contains "light sources" in the form of uranium ore deposits.

Well, it looks like my suspicions were correct:

Inside the Chernobyl reactor: fungus feeds on radiation
http://www.wtnrradio.com/news/story.php?story=262

But there's more... Apparently the fungus uses an unsuspected
photosynthetic molecule: melanin. It's not green like light-loving
plants, instead it's brown and eats gamma rays.

What other organism deals with hard radiation and employs the melanin
molecule? People?

Expose caucasian skin to ionizing radiation (hard UV sunlight) and it
ramps up melanin production. Melanin absorbs UV and acts as a
shield. "Getting a sun tan." Or be of non-European ancestry and
you're already shielded.

But wait a minute. What if human skin was bright green. Would you
think to yourself "ah, our skin contains a dye molecule which shields
against visible light?" Or instead would you think "ah, skin
contains an energy-harvesting molecule which uses visible light to
synthesize it's own fuel?"

In other words... if I have a dark tan, and I go sit in summer
sunlight without eating, will avoid starvation longer than if I stayed
indoors without eating? Maybe vitamin-D isn't the only thing made by
human skin in sunlight.

Another question: does human melanin production respond to ALL
ionizing radiation? If I stick my hand under a high-power gamma ray
source for a few minutes per day, will I receive a nice dark tan?
(I'd be sure to start slowly so I don't get a bone-deep sunburn at the
start.)

And just how effective is melanin as a shielding material for high
energy photons? (When compared to equal mass of, say, metallic lead?)


((((((((((((((((((((((( ( ( (o) ) ) )))))))))))))))))))))))
William J. Beaty Research Engineer
beaty a chem washington edu UW Chem Dept, Bagley Hall RM74
billb a eskimo com Box 351700, Seattle, WA 98195-1700
ph425-222-5066 http://staff.washington.edu/wbeaty/

Uncle Al

[ Mod. Note: Please restrict further comments to relevant physics. -ik ]

billb@eskimo.com wrote:
>
> I've always thought that, were it possible for biology to harness
> ionizing radiation for energy, some organism would already have done
> so. The ground contains vast fungal and bacterial communities, but
> also contains "light sources" in the form of uranium ore deposits.
>
> Well, it looks like my suspicions were correct:
>
> Inside the Chernobyl reactor: fungus feeds on radiation
> http://www.wtnrradio.com/news/story.php?story=262
>
> But there's more... Apparently the fungus uses an unsuspected
> photosynthetic molecule: melanin. It's not green like light-loving
> plants, instead it's brown and eats gamma rays.
>
> What other organism deals with hard radiation and employs the melanin
> molecule? People?
[snip]

The cited article is sensationalist not technical.

How will you couple incoming energy to biochemistry, specifically
production of sugar or ATP? Chloroplasts are the best organelles from
evolution, and they are limited in sugar fixation by RuBisCO. RuBisCO
is possibly the worst enzyme on Earth - the slowest (~3 turnovers/sec)
and least efficient (~1%; poisoned by oxygen). 30% of the soluble
protein in leaves is RuBisCO. Optical membrane ion pumps giving
direct charge separation are no improvement (e.g., purple bacteria).

The "Green Revolution" is crap. 50 years of Mendelian breeding could
be replaced by a year in MIT or Caltech gene-gineering labs.
Site-specific mutagenesis of RuBisCO to raise its loathsome
performance to still pitiful 50 turnovers/second and 10% efficency
would increase farm productivity 16,600%. Now put *those*
chloroplasts into soldiers and watch them lay naked in the sun feeding
themselves.

(The "Green Revolution" is crap anyway. 1970s' 0.1 wt-% mixed THC
isomer marijuana was classically bred by stoners to 30 wt-% /_\-9 THC
single isomer by the 1990s - Northern Lights 100% cloned female
hydroponic boo. Where was the corresponding progress in corn, wheat,
and rice by batallions of PhDs with high eight-figure annual budgets
worlwide?)

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2

David Winsemius

Uncle Al <UncleAl0@hate.spam.net> wrote in news:47067C65.28499B03@hate.spam.net:

> [ Mod. Note: Please restrict further comments to relevant physics. -ik ]
>
> billb@eskimo.com wrote:
>>
>> I've always thought that, were it possible for biology to harness
>> ionizing radiation for energy, some organism would already have done
>> so. The ground contains vast fungal and bacterial communities, but
>> also contains "light sources" in the form of uranium ore deposits.
>>
>> Well, it looks like my suspicions were correct:
>>
>> Inside the Chernobyl reactor: fungus feeds on radiation
>> http://www.wtnrradio.com/news/story.php?story=262
>>
>> But there's more... Apparently the fungus uses an unsuspected
>> photosynthetic molecule: melanin. It's not green like light-loving
>> plants, instead it's brown and eats gamma rays.
>>
>> What other organism deals with hard radiation and employs the melanin
>> molecule? People?
> [snip]
>
> The cited article is sensationalist not technical.

The original is available for comment at PLoS-One:

<http://www.plosone.org/article/fetchArticle.action?articleURI=info:doi/10.1371/journal.pone.0000457>

or <http://tinyurl.com/yp73eg> for the word-wrap happy news clients.

> How will you couple incoming energy to biochemistry, specifically
> production of sugar or ATP?

>From their abstract:
---------
Methodology/Principal Findings

Ionizing irradiation changed the electron spin resonance (ESR) signal of
melanin, consistent with changes in electronic structure. Irradiated
melanin manifested a 4-fold increase in its capacity to reduce NADH
relative to non-irradiated melanin.
-----end snippet----------

I would quibble that NADH _is_ the reduced form of NAD. I assume they
meant that the capacity to reduce NAD was enhanced. If you can reduce
NAD, you can make sugar.

--
David Winsemius

Uncle Al

David Winsemius wrote:
>
> Uncle Al <UncleAl0@hate.spam.net> wrote in news:47067C65.28499B03@hate.spam.net:
>
> > [ Mod. Note: Please restrict further comments to relevant physics. -ik ]
> >
> > billb@eskimo.com wrote:
> >>
> >> I've always thought that, were it possible for biology to harness
> >> ionizing radiation for energy, some organism would already have done
> >> so. The ground contains vast fungal and bacterial communities, but
> >> also contains "light sources" in the form of uranium ore deposits.
> >>
> >> Well, it looks like my suspicions were correct:
> >>
> >> Inside the Chernobyl reactor: fungus feeds on radiation
> >> http://www.wtnrradio.com/news/story.php?story=262
> >>
> >> But there's more... Apparently the fungus uses an unsuspected
> >> photosynthetic molecule: melanin. It's not green like light-loving
> >> plants, instead it's brown and eats gamma rays.
> >>
> >> What other organism deals with hard radiation and employs the melanin
> >> molecule? People?
> > [snip]
> >
> > The cited article is sensationalist not technical.
>
> The original is available for comment at PLoS-One:
>
> <http://www.plosone.org/article/fetchArticle.action?articleURI=info:doi/10.1371/journal.pone.0000457>
>
> or <http://tinyurl.com/yp73eg> for the word-wrap happy news clients.
>
> > How will you couple incoming energy to biochemistry, specifically
> > production of sugar or ATP?
>
> >From their abstract:
> ---------
> Methodology/Principal Findings
>
> Ionizing irradiation changed the electron spin resonance (ESR) signal of
> melanin, consistent with changes in electronic structure. Irradiated
> melanin manifested a 4-fold increase in its capacity to reduce NADH
> relative to non-irradiated melanin.
> -----end snippet----------
>
> I would quibble that NADH _is_ the reduced form of NAD. I assume they
> meant that the capacity to reduce NAD was enhanced. If you can reduce
> NAD, you can make sugar.

Cut through the grantology,

1) What is the native capacity of melanin to reduce NAD that is now
4X increased? "the capacity to reduce NAD was enhanced" Didn't say
it worked, or at what efficiency, or if more than one cycle was
possible.

2) How much radiation need one absorb to *net* 2000 Cal/day
metabolism? A rad is 100 ergs/gram. Human LD50 is ~500 rads or
50,000 ergs/gram deposited. 50,000 ergs is 1.2x10^(-6) Calories.

100 ergs = 2.39x10^(-9) food Calories. 2000 food Calories =
8.4x10^(11) ergs. Divide that by the overall conversion efficency for
incident daily irradiation. Easier to eat a Twinkie.

3) Tell us how to power a photosynthetic animal without frying it
outright at any frequency, microwave to visible to Co-60 gamma.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2

David Winsemius

Uncle Al <UncleAl0@hate.spam.net> wrote in
news:470A4CDB.70BC41BC@hate.spam.net:

> David Winsemius wrote:
>>
>> Uncle Al <UncleAl0@hate.spam.net> wrote in
>> news:47067C65.28499B03@hate.spam.net:
>>
>> > [ Mod. Note: Please restrict further comments to relevant physics.
>> > -ik ]
snipped Bill's original
>> >
>> > The cited article is sensationalist not technical.
>>
>> The original is available for comment at PLoS-One:
>>
>> <http://www.plosone.org/article/fetch...cleURI=info:do
>> i/10.1371/journal.pone.0000457>
>>
>> or <http://tinyurl.com/yp73eg> for the word-wrap happy news clients.
>>
>> > How will you couple incoming energy to biochemistry, specifically
>> > production of sugar or ATP?
>>
>> >From their abstract:
>> --------- Methodology/Principal Findings
>>
>> Ionizing irradiation changed the electron spin resonance (ESR) signal
>> of melanin, consistent with changes in electronic structure.
>> Irradiated melanin manifested a 4-fold increase in its capacity to
>> reduce NADH relative to non-irradiated melanin. -----end
>> snippet----------
>>
>> I would quibble that NADH _is_ the reduced form of NAD. I assume they
>> meant that the capacity to reduce NAD was enhanced. If you can reduce
>> NAD, you can make sugar.
>

> 1) What is the native capacity of melanin to reduce NAD that is now
> 4X increased? "the capacity to reduce NAD was enhanced" Didn't say
> it worked, or at what efficiency, or if more than one cycle was
> possible.

Appears they showed only that irradiated melanin could act as catalytic
enhancer of a coupled reaction between NADH (the energy source) and
ferricyanide. Since they didn't reduce NAD with the irradiated melanin, I
take back what I said about potential coupling to gluconeogenesis.

> 3) Tell us how to power a photosynthetic animal without frying it
> outright at any frequency, microwave to visible to Co-60 gamma.

Talk to Bill. He is the science fiction writer.

Put aside absorptive efficiency for the moment. I suspect that even the
661.65 keV gamma rays that did interact with melanin would not be absorbed,
only scattered, and secondary radiation scatter would be almost as harmful
to a complex organism as the incident radation.

--
David Winsemius

Rock Brentwood

On Oct 8, 12:41 pm, Uncle Al <Uncle...@hate.spam.net> wrote:
> 3) Tell us how to power a photosynthetic animal without frying it
> outright at any frequency, microwave to visible to Co-60 gamma.

It was stated elsewhere in the thread that the solar intensity is 1000
watts per square meter. I'm pretty sure that's only 100 watts per
square meter.

The mere fact that plants aren't mobile and (unlike Ents) don't walk
should have settled the issue, even before getting to the detailed
Physics. If there is a way, nature would have found it by now.

Phillip Helbig---remove CLOTHES to reply

In article <1191968604.918399.82150@50g2000hsm.googlegroups.com>, Rock
Brentwood <markwh04@yahoo.com> writes:

> It was stated elsewhere in the thread that the solar intensity is 1000
> watts per square meter. I'm pretty sure that's only 100 watts per
> square meter.

Wrong. 1.37 kW / m² is a standard value. This is above the atmosphere;
below the atmosphere, it's about a kW per square meter. (Of course, the
"solar constant" is not really constant, even above the atmosphere, due
to the slight variability of the sun, but this is a small effect.)

Two points: First, these days it is easy to check such values on the
internet in a matter of seconds with a search engine. (Of course, not
everything on the internet is true, but I don't detect a conspiracy to
populate the internet with bogus values for the solar constant.)
Second, think about it. Imagine yourself in a dark room with a 100-Watt
light bulb positioned so that it illuminates a square meter. How does
it feel? Now, go outside on a sunny day. It probably feels warmer. Or
do the comparison with a solar-cell powered calculator or something and
see which produces more current.

p.kinsler@ic.ac.uk

Rock Brentwood <markwh04@yahoo.com> wrote:
> On Oct 8, 12:41 pm, Uncle Al <Uncle...@hate.spam.net> wrote:
> > 3) Tell us how to power a photosynthetic animal without frying it
> > outright at any frequency, microwave to visible to Co-60 gamma.

> It was stated elsewhere in the thread that the solar intensity is 1000
> watts per square meter. I'm pretty sure that's only 100 watts per
> square meter.

Physics Today March 2007 p37 "Solar energy conversion" states that
the sun delivers a power of P = 1.2x10^5 TW to the earth; the radius
of the earth is r = 6.37 Mm; so the area of the earth's disk is
A = pi r^2 = 1.3x10^14 m^2.

This gives an average intensity of P/A = 940 W/m^2.

--
---------------------------------+---------------------------------
Dr. Paul Kinsler
Blackett Laboratory (QOLS) (ph) +44-20-759-47520 (fax) 47714
Imperial College London, Dr.Paul.Kinsler@physics.org
SW7 2BW, United Kingdom. http://www.qols.ph.ic.ac.uk/~kinsle/

billb@eskimo.com

On Oct 8, 10:41 am, Uncle Al <Uncle...@hate.spam.net> wrote:
>
> 3) Tell us how to power a photosynthetic animal without frying it
> outright at any frequency, microwave to visible to Co-60 gamma.
>

Straw man. Why not also tell us how to create a complete eye
from one mutation? My point being that to receive some
incremental benefit, there's no need to power the entire animal
(e.g. vitamin-D production exists, even though it doesn't power an
entire animal.) If death by starvation is common among mammals,
then those which receive even a fairly small energy gain via
sunlight,
might squeak by while their non-photosynthesizing competitors
are selected out.

Of course the benefit could be so insignificant that it would be
too far down in the noise, and wouldn't be "noticed" and amplified
by evolution. And why are all of us not already like Euglenas:
both motile and green-skinned?

On Oct 9, 8:16 pm, Rock Brentwood <markw...@yahoo.com> wrote:
> It was stated elsewhere in the thread that the solar intensity is 1000
> watts per square meter. I'm pretty sure that's only 100 watts per
> square meter.

Nope, search on "solar constant.

> If there is a way, nature would have found it by now.

That's what *I* said. The melanin discovery looks interesting,
and gives me an excuse for wild speculation about any other
common melanin-using organisms.

:)

((((((((((((((((((((((( ( ( (o) ) ) )))))))))))))))))))))))
William J. Beaty Research Engineer
beaty a chem washington edu UW Chem Dept, Bagley Hall RM74
billb a eskimo com Box 351700, Seattle, WA 98195-1700
ph425-222-5066 http://staff.washington.edu/wbeaty/

PhysiksFreak

That's a damn interesting question. But isn't melanin in plants and animals different? Let's assume that they are. Alright, so can we photosynthesize, or create our own food from sunlight, oxygen, and water. Maybe, if we have chlorophyll and chloroplasts - though I wouldn't recommend experimenting with that. The results, I admit, I do not know and cannot percieve.

Sophonioas

There is a type of Elysia spp. (Sea Slugs) that have specialised gut epithelial cells that allow them to take up the chloroplasts of the algae that they eat and maintain their function. This allows them to survive almost indefinately on light alone. They even produced enough energy to afford procreation. The slug is translucent and has projections of it's gut out to it's skin to allow effective photosynthesis. Could human skin be manipulated to act in a similar way and just spread a chloroplast-containing gel upon our skin, or tattoo the chloroplasts in for cellular uptake?

Refering to the use of melanin with hard radiation...
Even if this could be done, the radiation would continue through the skin to deeper layers and cause major damage to many cell functions and structures. Using chlorophyll to access light radiation would be much safer as there is a high degree of resistance to this through evolutionary means. Also the damage that UV light causes could soon be irrelevant with the recent advances in treating and preventing skin cancers etc.