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Maximum possible virus titers.

Greg Tobin tobin at fcs260c.ncifcrf.gov
Wed Aug 16 15:03:27 EST 1995

In article <01HTOAZO52N69TCQM5 at IRI.TUDELFT.NL> M.Schouwenburg at IRI.TUDelft.NL (Marcel Schouwenburg) writes:
>On 4-AUG-1995, poets at ccmail.orst.edu  "Steven Poet" wrote:
>> That seems like a pretty high dilution to me.  Are you sure your decimal
>> points are all in the right place?  I remember somewhere in the depths
>> of my memory that 10^17 poliovirus particles will fill a ping pong ball.
>> So I don't think 10^23 virus particles can be suspended in 1 ml of
>> cell culture medium.  I understand the difference between TCID50 and
>> absolute particle numbers, I'm just thinking intuitively.
>> krjk1 at stirling.ac.uk (Mr K R John Kollanoor) wrote:
>>> Is there a theoratical maximum for the number of virus progeny a cell 
>>> culture supernatant can have? 
>>> Is there any possibility of a titer of 10^-23(TCID50/ml) in any of the virus 
>>> infected cell culture supernatant ?
>>> I would appreciate if someone could answer these questions.
>You're right with this, but when you only look to the number: 10^23 you must
>realise that this is so high it must be wrong. If you had that much polio
>virus particles, you would be able to lift 1 ml of the supernatant of the
>culture. I will give the calculation:
>- Let us only consider the RNA of the virus and take 7500 nt for the length.
>- I assume an average weight of 310 Da for a nt.
>- 1 Da = 1.65 * 10^-24 g.
>If you calculate the weight for 10^23 virus particles, you'll get:
>  10^23 vp * 7500 nt/vp * 310 Da/nt * 1.65 * 10^-24 g/Da = 383625 g
>							   ========
>(vp = virusparticles)
>I think this makes clear that 10^23 is a very unlikely titer, or am I doiing
>something wrong or making the wrong assumptions?
>Does anybody have any comments on this?
>Kind regards,

Lentiviruses are diploid so there will be 700,000 g of vRNA in a mole.  There
The mass of the virus is more heavily weighted by the proteins, water, and 
lipid than the nucleic acid.

                       "mens sana in corpore sano"
> -----------------------------------------------------------------------------
>| Marcel Schouwenburg             | Besides working as a Radiation Safety     |
>| Health Physics Department       | Officer, I'm a student in both            |
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>| Delft, The Netherlands          | Open university, The Netherlands          |
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>- end -

Greg Tobin, Ph.D.                        tobin at lcms-1.ncifcrf.gov

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