Re: [DIYbio] Re: What DNA separation techniques other than electrophoresis?

On Thu, Feb 28, 2013 at 7:27 AM, John Griessen <john@industromatic.com> wrote:
> On 02/27/2013 11:35 PM, Nancy Liu wrote:
>
>> Please have a look at www.ehsystems.com
>
>
> Are you saying some additions to a product like CEM-7000 Integrated CE
> System
> would allow separation as well as detection?
> Or are you referring to product MFL-4100 Microfluidic System as a starting
> point?
>
> The CEM-7000 page says 100 PSI can be provided. Does that mean
> electrophoresis
> buffer/gel can be pumped to any of the capillaries in your carousel at 100
> PSI
> to make the effective length of a capillary longer and separation of bands
> larger?
> Can you switch that cleanly to the next capillary in the carousel and so on
> till all done?
> Clean switching would mean, no air bubble created, buffer same as that in
> capillary, no dirt introduced.

I know in HPLC and such, they use rotary valves to switch from buffer
to sample and back, in the beginning of a run when they need to inject
sample. To one-up that type of sample injection, there's
electroinjection, which is basically electrophoresis in an orthogonal
direction to the main flow. I say one-up because this is usually
touted in the books as being able to highly concentrate samples (into
one tight band in the separation column) and minimize loss.

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

>
> If one could make a microfluidic valve that unwanted DNA could flow past
> with none getting stuck there,
> one could then open that valve and close the normal exit, then operate the
> pump to move that DNA band into
> the collection channel of your microfluidic plate? Instead of a Tee in the
> path and a valve at the Tee,
> a capillary end that is switchable to seal against a collection port could
> serve as the "valve".

Maybe a Tee filled with gel. I've read about gel-free nanochannel
separations recently, it takes advantage of side-walI interactions
dominating, but I'm not sure what scale that effect becomes apparent
(5000nm, 1000nm, 100nm, 50nm, etc).

> Another alternative would be to use capillaries with scored snap-off zones,

A fluids guy was telling me a while back that sharp corners can cause
pressure drops which can cause precipitation of stuff in solution, and
can eventually lead to clogs in a fluid line. I get that score-snapped
ends would be perfect or close to being flat, if
precipitation/clogging was a problem I bet a quick glass etch would
round things out but still leave a common-plane surface to seal
against. Or maybe a silicone Tee would take care of any sealing
problems?

> and use the detectors,
> electrophoresis applied voltage, and buffer pumping to get the desired DNA
> in the zone, then stop
> and switch to another capillary to process.
>
> The last idea of a scored snap-off zone in a capillary might be the
> cleanest, lowest contamination way.
>
> So now that idea is patent-proof, right? Since I said it here? :-)
>
>
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--
-Nathan

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