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<DIV><FONT face=Arial size=2>Anders wrote:</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV>> Now, our big disagreement really seems to be the constructability of
<DIV>> bilayers. I say they probably can be put together according to
fairly<BR>> complex specifications by working a LN temperatures and then
</DIV>
<DIV>> thawing, you say it cannot be done. Maybe we should start a
separate</DIV>
<DIV>> thread to actually hash it out freshly, stating assumptions and
all that?<BR><BR>[ this paper seems relevant, but I haven't found the full text
yet:<BR><A
href="">http://journals.cambridge.org/action/displayAbstract;jsessionid=2DB1538444172C5407EB5A708E22DA6E.tomcat1?fromPage=online&aid=365124</A><BR>]</DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Okay. Sure. The relevant bilayers for cells, that
are functional as cells, are</FONT></DIV>
<DIV><FONT face=Arial size=2>not flat </FONT><FONT face=Arial size=2>ones like
</FONT><FONT face=Arial size=2>sheets of fat floating on water, they are volume
containing </FONT></DIV>
<DIV><FONT face=Arial size=2>3D ones like </FONT><FONT face=Arial
size=2>balloons of different shapes and sizes </FONT><FONT face=Arial
size=2>that separate what is </FONT></DIV>
<DIV><FONT face=Arial size=2>inside </FONT><FONT face=Arial size=2>from
what is outside them. They can be as thin as 6 nm. In neurons</FONT></DIV>
<DIV><FONT face=Arial><FONT size=2>the bilayers, like a skin, have
an arboreal shape of the interleaving neurons</FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT size=2>themselves </FONT></FONT><FONT
face=Arial><FONT size=2>and may </FONT></FONT><FONT face=Arial><FONT
size=2><FONT>extend in individual neurons extend unbroken from
the</FONT></FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT size=2><FONT>axon to </FONT></FONT></FONT><FONT
face=Arial><FONT size=2><FONT>dendrite tips which may be
</FONT></FONT></FONT><FONT face=Arial><FONT size=2><FONT>separated
</FONT></FONT></FONT><FONT face=Arial size=2>by distances as much as
a</FONT></DIV>
<DIV><FONT face=Arial size=2>metre. </FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>These bilayers are found for instance in the plasma
membrane that is </FONT></DIV>
<DIV><FONT face=Arial size=2>around the cell </FONT><FONT face=Arial
size=2>overall </FONT><FONT face=Arial size=2>around mitochondria
</FONT><FONT face=Arial size=2>where the </FONT><FONT face=Arial size=2>bilayers
</FONT><FONT face=Arial size=2>are crucial</FONT></DIV>
<DIV><FONT face=Arial size=2>to the functioning of the hydrogen ion pumping
</FONT><FONT face=Arial size=2>of the mitochondria</FONT><FONT face=Arial
size=2>, </FONT><FONT face=Arial size=2>in </FONT><FONT face=Arial
size=2>the</FONT></DIV>
<DIV><FONT face=Arial size=2>ER </FONT><FONT face=Arial size=2>and
the </FONT><FONT face=Arial size=2>nucleus, in the golgi, and
in </FONT><FONT face=Arial size=2>lysosomes </FONT><FONT face=Arial
size=2>etc and, </FONT><FONT face=Arial size=2>rupturing </FONT></DIV>
<DIV><FONT face=Arial size=2>these </FONT><FONT face=Arial size=2>bilayers is
often going to be fatal to the </FONT><FONT face=Arial size=2>cell.
Vesicles also have</FONT></DIV>
<DIV><FONT face=Arial size=2>bilayers. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>The human brain has a volume on average of 1450
millilitres or cubic</FONT></DIV>
<DIV><FONT face=Arial size=2>centimetres. (figure 1 associated email attachment)
This volume is </FONT></DIV>
<DIV><FONT face=Arial size=2>approximately equivalent to that </FONT><FONT
face=Arial size=2>of a cube </FONT><FONT face=Arial size=2>with sides of
11.318512 cm</FONT></DIV>
<DIV><FONT face=Arial size=2>or 113,185,120 nanometres.(fig
2) </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Assume 50 nanometre cubic volumes are sufficient
for requisite level</FONT></DIV>
<DIV><FONT face=Arial size=2>of molecular detail. (fig 4) </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>This means that the human brain could
be conceptualised </FONT><FONT face=Arial size=2>as </FONT></DIV>
<DIV><FONT face=Arial size=2>comprising </FONT><FONT face=Arial size=2>about
1.45 10^24 such cubic volumes. </FONT><FONT face=Arial size=2>1.45 trillion
trillion</FONT></DIV>
<DIV><FONT face=Arial size=2>cubes.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Lipid bilayers will be disperse throughout those
cubes not necessarily</FONT></DIV>
<DIV><FONT face=Arial size=2>evenly and of course without particular structures
like filopodia falling</FONT></DIV>
<DIV><FONT face=Arial size=2>neatly into those 50 nm volumes.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>If the 50 nm cubes can be put together using a
manufacturing process</FONT></DIV>
<DIV><FONT face=Arial size=2>and attached to each other such that the lipid
bilayers fuse and their</FONT></DIV>
<DIV><FONT face=Arial size=2>contents are not spilled then you'd have a
successful reconstruction</FONT></DIV>
<DIV><FONT face=Arial size=2>of the biological brain. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>But I say, it can't be done. The
physics and chemistry of the </FONT><FONT face=Arial
size=2>biomolecules</FONT></DIV>
<DIV><FONT face=Arial size=2>won't allow it to be done as a manufacturing
</FONT><FONT face=Arial size=2>process. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Anders you say it can? Then let's see
how. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>- Brett Paatsch</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>PS: Apologies for the very rough sketches.
</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>For simplicity I'm assuming a filopodia
containing a single actin "strut"</FONT></DIV>
<DIV><FONT face=Arial size=2>is the finest </FONT><FONT face=Arial
size=2>scale of bilayer-enclosed </FONT><FONT face=Arial size=2>structure
than formed by cells</FONT></DIV>
<DIV><FONT face=Arial size=2>in the brain. I'm assuming that you need
to be able to restore to brain</FONT></DIV>
<DIV><FONT face=Arial size=2>to the </FONT><FONT face=Arial size=2>filopodial
scale. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Late last year I asked a Melbourne University
neuroscientist and </FONT></DIV>
<DIV><FONT face=Arial size=2>lecturer in the school of anatomy and cell biology
</FONT><FONT face=Arial size=2>what </FONT><FONT face=Arial size=2>level of
</FONT></DIV>
<DIV><FONT face=Arial size=2>detail would be needed to accurately pick up the
structural</FONT></DIV>
<DIV><FONT face=Arial size=2>information of the brain - he said 50 nm.
</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I think 50 nm seems reasonable based on two lipid
bilayers of</FONT></DIV>
<DIV><FONT face=Arial size=2>6 nm each, 1 actin strut of 5-9 nm, some
space around the</FONT></DIV>
<DIV><FONT face=Arial size=2>strut for assembling it say 12nm
and build into the lipid </FONT></DIV>
<DIV><FONT face=Arial size=2>bilayer are molecules such as integrins which
bind cadherins</FONT></DIV>
<DIV><FONT face=Arial size=2>and the extracellular matix, as well as other
proteins and</FONT></DIV>
<DIV><FONT face=Arial size=2>sugars getting to around 50 nm in cross
section. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Sizes of structures taken from Alberts Molecular
Biology</FONT></DIV>
<DIV><FONT face=Arial size=2>of the Cell 4th Edition 2002 available at the NCBI
bookshelf. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
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