Lowering density of water

[Josh Perfetto]

Anyone know of a way to lower the density of water in a way that will not be toxic to cells?

-Josh

[Cathal Garvey]

Lower the ambient pressure? This won't make much of an impact though.

You could try to use water lacking many of the ions normally found in tapwater, but the effects will be pretty marginal!

Is there a way your needs could be turned around somehow so the question becomes "how do I make a fluid/medium denser *relative* to water without harming my cells?"

On Mar 22, 2010 4:15 AM, "Josh Perfetto" <jo...@snowrise.com> wrote:

Anyone know of a way to lower the density of water in a way that will not be toxic to cells?

-Josh

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[Isabelle Hakala]

Yes, I think telling us to what end this would help you might actually generate you some alternatives for what you are trying to achieve:)

I, myself, am totally fascinated:) -Isabelle

~~~~~~~~~~~~~~~~~~~~~~~
Isabelle Hakala
"Any person who says 'it can't be done' shouldn't be interrupting the people getting it done."
"Do every single thing in life with love in your heart."

[J. S. John]

Why do you need it? Whats the purpose?

[Peter Nguyen]

Using deuterated water will increase the density by 11%, bacteria will just grow slower. See wikipedia:

http://en.wikipedia.org/wiki/Heavy_water


Otherwise, bacteria/cells will survive just fine in 25% glycerol.


How dense are we talking about?

-P

[Simon Quellen Field]

Didn't he ask for lower density?

Glycerol and heavy water are higher density.

Raising the temperature will lower the density a little.

Most things that mix with water will raise the density, even those that are less

dense than water.

You might consider making the cells magnetic.  Get some iron oxide into them,

and you can pull them up with a magnet (which pushes down on the diamagnetic

water just a tiny bit also).

Instead of making the water less dense, why not make the critters denser?

Feed them the heavy water, or some bismuth compound or something, and

then transfer them to the normal density culture medium.  Gold nanoparticles

might also work.

[Josh Perfetto]

Thanks for all the comments guys. Yes I want to make the water less dense, not more dense. It's quite easy to make it more dense :) I need this for a directed evolution selection system to select cells that are even less dense than would be required to float on the surface of water at standard pressure.

-Josh

[Cathal Garvey]

Dissolved stuff generally increases density, but the relationship between water and alcohol isn't quite a solution, there's another name fot it that eludes me. Suffice to say, the density of alcoholic solutions is lower than that of water, to the extent that apparently falling into a vat of wine is very dangerous even for experienced swimmers, as people simply sink in it.

So, get your bugs accustomed to a little ethanol, and then grow in ethanol solution for your low-density medium?

On Mar 22, 2010 6:33 PM, "Josh Perfetto" <jo...@snowrise.com> wrote:

Thanks for all the comments guys. Yes I want to make the water less dense, not more dense. It's quite easy to make it more dense :) I need this for a directed evolution selection system to select cells that are even less dense than would be required to float on the surface of water at standard pressure.

-Josh

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[Nathan McCorkle]

On Mon, Mar 22, 2010 at 3:56 PM, Cathal Garvey <cathal...@gmail.com> wrote:
> Dissolved stuff generally increases density, but the relationship between
> water and alcohol isn't quite a solution, there's another name fot it that
> eludes me.

miscible??

> Suffice to say, the density of alcoholic solutions is lower than
> that of water, to the extent that apparently falling into a vat of wine is
> very dangerous even for experienced swimmers, as people simply sink in it.
>
> So, get your bugs accustomed to a little ethanol, and then grow in ethanol
> solution for your low-density medium?
>
> On Mar 22, 2010 6:33 PM, "Josh Perfetto" <jo...@snowrise.com> wrote:
>
> Thanks for all the comments guys. Yes I want to make the water less dense,
> not more dense. It's quite easy to make it more dense :) I need this for a
> directed evolution selection system to select cells that are even less dense
> than would be required to float on the surface of water at standard
> pressure.
>
> -Josh
>
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Rochester Institute of Technology
College of Science, Biotechnology/Bioinformatics

[Simon Quellen Field]

While I am sure that falling into a vat of wine is not the lucky event many

people might expect, it is not because of the specific gravity.

Sweet wines are denser than water, but even dry wines are only 0.990 in

specific gravity (water is 1.000).  You would not notice swimming in that

to be any different than in pure water.

But dry wine would kill the bacteria.  At 12.3% alcohol, wine is denser than

water (1.090).

The critters are going to need food.  It is unlikely that water plus food plus

any level of alcohol they could survive would be less dense than water, or

would make any appreciable difference in Josh's directed evolution experiment.

Josh -- breeding for oil production or gas production in vacuoles might be your

best bet.  You might also try breeding anaerobes in a centrifuge, since only the

less dense ones would be close to the air they need.  The centrifuge might be

what you were looking for anyway -- it amplifies the effective difference in density

between the critters and the water.  That's why they are used to pellet bugs

in the first place.

Your experimental design seems to assume that the bugs will want to float.

That may not be the case.  You didn't mention which bugs you are working

with.

[Cathal Garvey]

The latter point there is particularly important I'd say: if you are raising an aerobe, it might be prone to dying due to sinking already.

I don't think the food vs. density issue is a problem. Just cycle the bugs through low density fluid and skim off the floaters for the next culture. The low density medium only needs to not kill them.

On Mar 22, 2010 8:29 PM, "Simon Quellen Field" <sfi...@scitoys.com> wrote:

While I am sure that falling into a vat of wine is not the lucky event many

people might expect, it is not because of the specific gravity.

Sweet wines are denser than water, but even dry wines are only 0.990 in

specific gravity (water is 1.000).  You would not notice swimming in that

to be any different than in pure water.

But dry wine would kill the bacteria.  At 12.3% alcohol, wine is denser than

water (1.090).

The critters are going to need food.  It is unlikely that water plus food plus

any level of alcohol they could survive would be less dense than water, or

would make any appreciable difference in Josh's directed evolution experiment.

Josh -- breeding for oil production or gas production in vacuoles might be your

best bet.  You might also try breeding anaerobes in a centrifuge, since only the

less dense ones would be close to the air they need.  The centrifuge might be

what you were looking for anyway -- it amplifies the effective difference in density

between the critters and the water.  That's why they are used to pellet bugs

in the first place.

Your experimental design seems to assume that the bugs will want to float.

That may not be the case.  You didn't mention which bugs you are working

with.

On Mon, Mar 22, 2010 at 12:56 PM, Cathal Garvey <cathal...@gmail.com> wrote:

> > Dissolved stuff generally increases density, but the relationship between water and alcohol isn'...

> > -- > You received this message because you are subscribed to the Google Groups "DIYbio" group....

> To post to this group, send email to diy...@googlegroups.com. > To unsubscribe from this group, se...

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[Josh Perfetto]

On Mon, Mar 22, 2010 at 1:28 PM, Simon Quellen Field <sfi...@scitoys.com> wrote:

Josh -- breeding for oil production or gas production in vacuoles might be your

best bet.  You might also try breeding anaerobes in a centrifuge, since only the

less dense ones would be close to the air they need.  The centrifuge might be

what you were looking for anyway -- it amplifies the effective difference in density

between the critters and the water.  That's why they are used to pellet bugs

in the first place.

Your experimental design seems to assume that the bugs will want to float.

That may not be the case.  You didn't mention which bugs you are working

with.

Yes I have Botryococcus braunii which already floats due to lipid production. It prefers to float as it gets more access to CO2, and reproduces much more readily at the top.

Since the organism already floats, I'm not sure how to develop a selection system for the less dense organisms without lowering the density of water so that not all of the organisms float. It is a good point about the centrifuge - this could be done to amplify the density difference. I still need to reduce the water/media density to start with though, right? Otherwise they will all just float even faster.

I read something that ammonia may lower the density, but not sure by how much or how toxic it would be. High concentrations of ethanol would work except that it is definitely toxic.

-Josh

[leaking pen]

are you wanting to select for those that are less effective at taking
up co2, or those are more efficient at turning c02 into lipids? I
could think of methods for both situations.
alex

[Peter Nguyen]

Sorry, I misunderstood your question earlier; I thought you wanted to increase the density. I agree that density gradient centrifugation would be the ideal screening method. As for amplifying density differences within a cell population,  increasing the effective density of the cells by a non-genetic manner (mentioned earlier by several people) is I think a fertile strategy. If there is an antibody to any outer coat protein or antigen (such that you could bind to the cell itself), perhaps you can add in an antibody conjugated to a high-density polymer, or a magnetic particle. Thus, you are increasing the density of the cell without internally altering it. With the magnetic particle, you can apply a magnetic field to tune the separation. You'd probably have to be careful not to select for bugs that have lower expression of whatever outer membrane protein/antigen you are binding to.

See:

http://www3.interscience.wiley.com/journal/107622973/abstract

[Cathal Garvey]

Excellent idea! Perhaps you could do without the antibody if you can find a relatively heavy membrane stain that won't kill the cells.

On Mar 26, 2010 2:41 PM, "Peter Nguyen" <pnguy...@gmail.com> wrote:

Sorry, I misunderstood your question earlier; I thought you wanted to increase the density. I agree that density gradient centrifugation would be the ideal screening method. As for amplifying density differences within a cell population,  increasing the effective density of the cells by a non-genetic manner (mentioned earlier by several people) is I think a fertile strategy. If there is an antibody to any outer coat protein or antigen (such that you could bind to the cell itself), perhaps you can add in an antibody conjugated to a high-density polymer, or a magnetic particle. Thus, you are increasing the density of the cell without internally altering it. With the magnetic particle, you can apply a magnetic field to tune the separation. You'd probably have to be careful not to select for bugs that have lower expression of whatever outer membrane protein/antigen you are binding to.

See:

http://www3.interscience.wiley.com/journal/107622973/abstract

On Mon, Mar 22, 2010 at 11:11 PM, leaking pen <itsa...@gmail.com> wrote: > > are you wanting to...

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[Josh Perfetto]

Hi Alex,

Neither exactly, what I'd like to select for is the ability to amass the greatest quantity of oils while still being able to hold on to them (and benefit from their buoyancy). I'm not concerned with the metabolic rate of producing oils within reason (if it were much too slow, it would not have a chance to compete).

I'm curious as to what methods you would use to select for the conditions you mentioned though. The design of selection systems is very interesting and would like to learn more about it in general,

-Josh

[Josh Perfetto]

Thanks for the article and ideas. What I've been worried about is indirect effects. Like in the article you mentioned, they attach a magnetic seed to the outside of the cell in an irreversible manner. So wouldn't such a selection system also select against smaller organisms, since they have greater surface area per unit volume? How would I prevent directed evolution from simply favoring these smaller organisms, or ones having a lower expression of some membrane protein as you mentioned?

-Josh

[leaking pen]

I would have skimmed the surface at a certain periodic rate to get the
top floaters and fastest to the top.

So, lower density, because you'd then get a larger range of spread to
physically separate the fattest, juiciest cells? You dont need a
growth solution thats less dense. You just need a lower density for a
couple of minutes. pour your colture into a solution of lower
density, give it five minutes to layer up, skim the top whatever.

Alternately, give a light centrifuging, and what DOESNT mat at the
bottom is what you want.

Alex

[Brian Degger]

How did the experiment go?
cheers
B