Re: Radio opaque biomolecule?


Back to imaging in vivo stuff, you will need to keep water in the sample. And with water in the sample you are limited by the water absorption spectrum, which I guess also shows why evolution selected ~600 nm radio waves for imaging in the first place:

On the x-ray subject, I'm pretty sure X-rays will kill live samples really quick if you attempt to image something clearly on <1 um scale. It works for medical reasons because you spread out the photo damage over a lot cells.

I guess the luciferin trick that Cathal mentioned is one of the few options left, although I wonder if the mice survived such a laser attack ...


On Mon, Jan 2, 2012 at 6:31 PM, Cathal Garvey <cathalgarvey@gmail.com> wrote:
Oh, real-time imaging sure. But "radio opaque" isn't the same thing as
"precisely detectable".

For example, there's luminescence or fluorescence to consider as
alternatives, or merely pigmentation.

I used to work in a lab that used a (stupidly, criminally expensive)
CCD-coupled camera in a darkroom to image bioluminescence in mice
through whole-body imaging. Essentially they'd inject luciferin (which
apparently isn't toxic), knock the mice out with anaesthetics, and then
image them for 30s+. You'd clearly see the areas that were expressing
luciferase using this method.

Alternatively, there are other systems (also requiring anaesthetics for
animals you can't train/ask to sit perfectly still) that use confocal
lasers to excite fluorescent molecules and image them by scanning at
variable resolution. The laser allows deep penetration of
excitement-frequency light, but you still need to be able to see any
emissions. If, even after saturating your fluorescent molecules, there
simply isn't enough light to see a few photons escape the body and hit
the camera, then you're out of luck.

On 02/01/12 17:26, Veera wrote:
> hmmm i'll dig in to it. so far people have been successful in imaging
> realtime gene expression in single living cells.
>
> On Jan 2, 10:11 pm, Cathal Garvey <cathalgar...@gmail.com> wrote:
>> As pointed out by Jelmer, there probably isn't much in the "radio" area
>> of the spectrum, but if you meant more generally "Are there any
>> molecules that block useful scanning frequencies", then yes, there are.
>> I believe (i.e. am not certain) that melanin can block X-rays to some
>> extent, so a tight clot of melanin might be slightly X-ray opaque.
>> Calcified matter is X-ray opaque, as is fibrosis, so it's probable that
>> any knot of tightly woven protein would be somewhat opaque also.
>>
>> That's all structural stuff, of course. But structure's where it's at;
>> for some frequencies, you'll need larger obstructions to absorb the
>> light effectively. For radio, you'd need conductive bones or something;
>> ask a radio tech for the specifics on absorption of radio and translate
>> that into a biotech context. It wouldn't be easy, certainly.
>>
>> On 02/01/12 06:40, Veera wrote:
>>
>>> Recently i had some ideas about radioimaging gene expression. There
>>> are many ways to study gene expression like using flourescent protien
>>> tags. but all those requires sacrificing the animal for taking tissue
>>> sections for immuno histochemistry. so i was searching some concepts
>>> for visualizing gene expression within specific tissues inside the
>>> body by some imaging techniques.Incidentally i came across bio
>>> activated contrast agents.You can see that in this link <link>http://
>>> www.nibib.nih.gov/HealthEdu/eAdvances/23Oct06<link>. But instead of
>>> using contrast agent i'm just curious to know is there anything like
>>> any protien or any biomolecule which is naturally radio opaque whose
>>> gene can be sandwiched with the promoter of the gene of interest and
>>> so we can image the the tissue and study the gene expression without
>>> killing the animal.....
>>
>> --www.indiebiotech.com
>> twitter.com/onetruecathal
>> joindiaspora.com/u/cathalgarvey
>> PGP Public Key:http://bit.ly/CathalGKey
>


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