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From: howard@cpocd2.UUCP (Howard A. Landman)
Newsgroups: sci.physics,sci.philosophy.tech,sci.research,sci.misc,misc.misc
Subject: Re: Einstein's relativity and daily life
Message-ID: <896@cpocd2.UUCP>
Date: Fri, 9-Oct-87 15:17:25 EDT
Article-I.D.: cpocd2.896
Posted: Fri Oct  9 15:17:25 1987
Date-Received: Mon, 12-Oct-87 05:24:02 EDT
References: <391@nikhefh.UUCP> <695@cfa.cfa.harvard.EDU> <756@elbereth.rutgers.edu>
Reply-To: howard@cpocd2.UUCP (Howard A. Landman)
Organization: Intel Corp. ASIC Systems Organization, Chandler AZ
Lines: 31
Keywords: science for the people
Xref: mnetor sci.physics:2467 sci.philosophy.tech:519 sci.research:254 sci.misc:537 misc.misc:1933

In article <756@elbereth.rutgers.edu> cje@elbereth.rutgers.edu (Cthulhu's Jersey Epopt) writes:
>Beg pardon?  Is our understanding of photosynthesis really so recent that it
>depended on radioactive tracers?  I'm not disputing this; it's just that the
>claim comes as quite a surprise to me.

Yes.  Melvin Calvin got the Nobel Prize for this.  The technique was
essentially, you have some algae photosynthesizing in a flask, through
which is bubbling CO2.  You introduce some radioactive CO2 into the
stream, wait 5 seconds, and dump the algae into a vat of alcohol and dry
ice, which kills them and stops the reaction.  Then you spend a few weeks
determining what all the radioactive carbon compounds you found were.

When you're done with that, repeat the experiment, but this time wait 10
seconds.  Then 15 seconds.  Then ...

Variations with radioactive oxygen, strobe lamps instead of continuous
illumination, algae in the dark or exposed to different wavelengths of
light, etc., give you some of the boundary conditions.  Don't forget to
use several diferent kinds of algae to confirm your results.

A few hundred or thousand experiments like that, and you know exactly
what's going on, and even how fast.

If you want an even better example of how radioisotopes are used in biology,
take a look at radioimmunoassay.  Especially the sensitivity figures.

-- 
	Howard A. Landman
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	"Unpick a ninny - recall Mecham"