Re: QUANTUM DOTS: MAXWELL'S DEMONS OF BIOLOGY
From: Dr. Jai Maharaj (usenet_at_mantra.com)
Date: 02/26/05
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Date: Sat, 26 Feb 2005 23:36:57 GMT
Quantum dots: the Maxwell's demons of biology
By By D. Balasubramanian
The Hindu
Thursday, February 24, 2005
WHILE DISCUSSING ideas in thermodynamics, on heat flow
from one place to another, physicists talk of a mythical
fellow called Maxwell's demon.
He is supposed to be the size of atoms and molecules
(more an imp or dwarf than a demon!) who acts as a
gatekeeper, allowing hot atoms or molecules to go across
while denying cold ones.
In a while, he thus creates order through selective
gating. Well, with the discovery and fabrication of
materials called nanoparticles, a Maxwell's demon of
sorts has left the world of fantasy and jumped into real
life.
Monitoring cell events
Nanoparticles are increasingly being used to monitor
events that happen within biological cells, as they occur
in real time. They are thus reporters of what happens
within cells and tissues in vivo and in situ.
A particular kind of these, called semiconductor
nanocrystals or quantum dots (qdots for short), have
evolved over the past 20 years from electronic materials
science to biological applications.
Two recent reviews by pioneers of these applications have
appeared, one from the group of Shuming Nie of Emory
University (Photochemistry and Photobiology, December
2004) and the other from the California group of Shimon
Weiss (Science, 28 Jan 2005).
Capturing attention
As the name suggests, nanoparticles are a collection of
atoms or molecules with sizes in the range of 10 to 100
nanometres or nm. They could even be a single molecule
such as C-60 or fullerene, a protein or DNA, or a
collection of many molecules such as those of cadmium
sulphide (CdS) or cadmium selenide (CdSe).
It is these nanoparticles of inorganic materials that
have captured the attention of scientists because of the
wide range of applications that they can be put to.
Novel and creative ways of assembling them in definite
numbers and sizes have been reported, and our own
Professor C. N. R. Rao is a well-known expert in the
creation and use of such nanoparticles and assemblies.
Using molecules to identify the component parts of
biological cells is not new.
It was first introduced by Heinrich Waldeyer, the teacher
of Paul Ehrlich, in 1863. He used the extract of logwood
(haematoxylon campechianum) to stain cells and biological
specimen. (Logwood itself has a hoary and bloody history,
since it was an excellent and cheaper alternative to the
ones then in use in Europe.
When colonial Spaniards and Englishmen found them in
Central America, they began a flourishing trade shipping
logwood from the New World to Europe. Colonials used
boatloads of slaves in the Yucatan, Belize and the
Caribbean to cut and ship logwood, and the conditions of
these slaves were inhuman.
These early woodcutters, called baymen, exported 13,000
tonnes of logwood yearly. After the colonials left, a new
nation called Belize was born, and to this day its flag
carries the images of baymen and the logwood tree.)
Dyes that specifically attach to the cell nucleus, or
membranes and other parts, and impart colour there or
emit fluorescence, have been known. A whole branch of
biology called histochemical staining deals with this.
But these are by and large static reporters and mostly do
not report 'live' action. They also 'bleach' and lose
their colour (and chemical identity) after a while, and
can also enter into chemical reactions with some
molecules in the cell.
It is in this area that qdots have emerged as versatile,
and multiplex, yet non-interfering reporters of events in
cells and tissues. A favourite qdot of biology is the
nanocrystal made of CdSe.
Assembling molecules
During the last two decades, it has become possible to
assemble molecules of CdSe (and similar material) in
precisely controlled numbers to produce nanocrystals of
well-defined sizes and surface. Typically around 10 nm in
diameter, nanocrystals are larger than molecules but
smaller than bulk solids.
It is this 'intermediacy' or the Trishanku state that
allows them to exhibit physical and chemical properties
somewhere in between. The fact that a nanocrystal is
virtually all surface and no interior makes its
properties vary considerably as the crystals grow in
size.
First of all, nanocrystals of CdSe (and similar
materials) are semiconductors. In a solid, the energy
states of electrons in the constituent atoms form
continuous 'bands.'
The valence band is the highest electronic level
occupied; when a small amount of energy is provided
(heat, light, magnet), these electrons can go from the
valence band to the 'conduction band,' generating
electric conduction.
In an insulator, this gap between the valence and
conduction band is way too large and no electric
conduction is possible. In a semiconductor, the situation
is in between.
The valence and conduction bands do not overlap as in a
conductor, but the band gap is small enough that some
electrons may be excited at room temperature to form
charge carriers.
But what is fascinating about semiconductors is that the
band gap is not only dependent on the composition of the
material but also the particle size. When the size is
reduced to the nanometre regime, or the 'quantum well'
dimension, the material has energy levels that allow it
to absorb light over a broad range but fluoresce at a
definite wavelength region.
The fluorescent wavelength emission depends on the
particle size. In other words, the colour the materials
emit is 'tuneable' through their particle sizes.
The consequences
It is for this reason that they are called quantum dots --
thanks to the quantum well effect and the dot-like size.
As the size of CdSe nanocrystal is tuned between 2-7 nm,
its fluorescence can be tuned to be between 450 and 650
nm (from bluish to orange).
Imagine the consequences. We can make CdSe in three or
four different dot sizes, illuminate them all with the
same light -- and they emit different colours. They can
thus be used as 'reporters.' Great, but they should be
made water- soluble so that they can enter cells as inert
reporters.
Next, they should be made to report on specific zones or
regions of the cell. Dr. Nie's group, as those of others,
has achieved both.
They attach some organic acids or amine to the surface,
and then attach chosen proteins or peptides on them. Dr.
Shiman Weiss's group has specialised in the latter
attachment strategies, making qdot reporting very
versatile. Of course, qdots can be used as histological
markers and diagnostic tools.
Nie's group recently linked monoclonal antibodies to
qdots and were able to detect the membrane antigen
present specifically on the cell surface of prostate
cancer. They injected living mice with these qdots and
detected the cancer cells at the very initial stage.
Diagnosis of this kind allows very early intervention and
treatment.
Whether benign or toxic
Dr. E. Rouslalti's group loaded three different kinds of
peptides on qdots and monitored lung cells, brain cells
and human breast carcinoma cells in vivo and in vitro.
Targeting qdots to specific molecules in the cell has
thus become possible.
Qdots are being used increasingly in living animals -- to
image and monitor blood vessels, liver, bone marrow and
lymph nodes.
Whether the introduction of qdots in live animals is
benign or toxic is currently being investigated. While so
far, no adverse effects on cell viability, size and
shape, function or development have been reported for
several days, extensive scrutiny is called for since
these are but initial and sparse results.
As better and more specific coatings, optimal dosage of
injection, and range of qdot size are examined, safe
dosages will emerge.
The perspectives
The perspectives of qdots in imaging, diagnostics and
even site-specific drug delivery into cells and live
animals are exciting and extensive. They will emerge as
biosensors, bioanalytical agents, monitors of events and
development stages, as surgical and therapeutic agents.
Multiplex monitoring of cells by using qdots of varying
sizes and coatings, to report on what is happening at
different cellular locales through colour coding, is
still in its infancy. When this is developed in the next
several years, we shall truly have a rainbow of
applications of these biological Maxwell's demons.
More at:
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peace, but a sword.
"For I am come to set a man at variance against his father, and the
daughter against her mother, and the daughter in law against her mother in
law.
"And a man's foes shall be they of his own household.
- Matthew 10:34-36.
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PROFILE OF ABUSER ALAN SCHWARTZ aka 'Uncle Al' <uncleal0@ix.netcom.com>
There's more information about Alan Schwartz
in the public archives at:
[ Subject: Profile: Schwartz, Alan
[ From: serialkiller90002@hotmail.com
[ Newsgroups: sci.physics
[ Date: 21 Mar 2004 13:34:46 -0800
[ Message-ID: <b31a8173.0403211334.25f9abc5@posting.google.com>
[ NNTP-Posting-Host: 61.11.26.150
[ X-Trace: posting.google.com 1079904887 30505 127.0.0.1
[ (21 Mar 2004 21:34:47 GMT)
[ NNTP-Posting-Date: Sun, 21 Mar 2004 21:34:47 +0000 (UTC)
[
[
[ Name: Schwartz, Alan
[ Country: USA
[ Residential Address: SANTA ANA, CA 92705
[ Map: http://www.mapquest.com/maps/map.adp?country=US&countryid=250&addtohistory=&address=&city=SANTA+ANA&state=CA&zipcode=92705&submit=Get+Map
[ Postal Address:
[ Alan Schwartz
[ 49 Fabriano
[ P.O. Box 005
[ Irvine, CA 92620-2525
[ E-mail(s): uncleal0@ix.netcom.com, UncleAl0@ix.netcom.com
[ Tel: 714-771-2526 (+1 714 771 2526 for international callers)
[ Spouse: Jackie Schwartz
[ Spouse Occupation: Para-legal
[ Spouse workplace: <pending disclosure>
[
[ ISP: http://www.earthlink.net
[ Email: http://support.earthlink.net/support/MYACCT/forms/csform.jsp
End of forwarded message from
Or,
http://groups.google.com/groups?selm=b31a8173.0403211334.25f9abc5%40posting.google.com&output=gplain
In article <43d9f575.0408101155.15fe136e@posting.google.com>,
eagleson2004123@yahoo.com posted:
> > EXPOSED - Lying scum and stalker 'Uncle Al' aka "Alan Schwartz"
> <uncleal0@ix.netcom.com>
> >
> > How to handle stalkers and
> > 'Uncle Al' aka "Alan Schwartz" <uncleal0@ix.netcom.com>
> >
> > [ Subject: How to handle stalkers and Uncle Al
> > [ From: Archimedes Plutonium <plutoniu@willinet.net>
> > [ Newsgroups: sci.chem,sci.physics,sci.archaeology
> > [ Message-ID: <3A6128B1.7ED158B6@willinet.net>
> > [ Date: Sat, 13 Jan 2001
> > [
> > [
> > [ Ryan Doherty wrote:
> > [
> > [ > Uncle Al (24.16.181.181),
> > [ >
> > [ > I am consider this message of yours SPAM, so please
> > [ > keep your childish postings to yourself!
> > [ > By the way, Grow up.. you are wasting more bandwidth
> > [ > with your repeated responces that Archimedes and his
> > [ > questions!
> > [ >
> > [ > Ryan
> > [
> > [ > Ryan, you are talking to a fence post when you talk to
> > [ > Uncle Al. He and his motley crew of cohorts have stalked
> > [ > me for years. In fact they have stalked me nonstop for 7
> > [ > years now.
> > [ >
> > [ > Uncle Al feels he is a police cop of sci.chem and
> > [ > sci.physics and wants to chase out any poster he does not
> > [ > like. Many chemistry professors have put Al Schwartz into
> > [ > their killfile. That is about the only real solution.
> > [ >
> > [ > Some say Al Schwartz is a failed chemistry professor of
> > [ > 80s in age living in Tallahassee Florida or Denton Texas.
> > [ > He is old, cranky with nothing to do but post to the
> > [ > Internet. He feels a righteous duty to stalk me. No
> > [ > matter if I post pure chemistry to sci. chem or pure
> > [ > physics to sci.physics, Uncle Al feels that none of my
> > [ > posts belongs to those newsgroups.
> > [ >
> > [ > He has set himself up as a self righteous self imposed
> > [ > police cop of sci.chem.
> > [ >
> > [ > Many other people have complained about Uncle Al in sci.
> > [ > chem.
> > [ >
> > [ > SOLUTION: the only solution that I can see is to killfile
> > [ > Uncle Al and all Al supporters. And to add sci.chem and
> > [ > sci.physics to all of your posts to the Internet. Let
> > [ > Uncle Al stalk you everywhere, not just sci. chem or sci
> > [ > physics. Make it so that everyday Uncle Al wakes up, his
> > [ > chores and work are to stalk people on the Internet. Make
> > [ > it such that the essence of life for Uncle Al will now be
> > [ > to stalk 1 or 3 or 20 or 117 people every day.
> > [ >
> > [ > So, I am asking of all those people on the Internet who
> > [ > have been attacked by Uncle Al, to give Uncle Al what he
> > [ > craves. Add sci.chem and sci.physics to all of your
> > [ > Internet posts. And killfile Uncle Al.
> > [ >
> > [ > Uncle Al is already a crackpot and is insane, but drive
> > [ > him wildly insane.
> > [ >
> > [ > Force him to waste minutes and hours every day of his
> > [ > life stalking you.
> > [ >
> > [ > And you just sit back and laugh at how the idiot Uncle Al
> > [ > is making himself a monkey idiot.
> > [ >
> > [ > Last year someone emailed me saying that sci.chem was
> > [ > back to normal and that Uncle Al had been put under
> > [ > sedation and it was safe to post to sci.chem again.
> > [ > Sci.chem was flooded by outsiders because Uncle Al had
> > [ > pissed them off.
> > [ >
> > [ > Well, that is not the way to handle the self imposed
> > [ > sci.chem police dog of Uncle Al. The way to handle Uncle
> > [ > Al and other stalkers like him is to "killfile them" and
> > [ > then force them to stalk you all over the Internet. Let
> > [ > everyone see what a fool he is, not just sci.chem folk.
> > [ >
> > [ > I wish that someone is archiving all of the Uncle Al
> > [ > stalks of Archimedes Plutonium. I have him killfiled and
> > [ > so I have zero. But I would imagine that Uncle Al has
> > [ > about 500 posts per year of attacks.
> > [ >
> > [ > So, I ask everyone who knows Uncle Al, to add sci. chem
> > [ > to their Internet posts and to killfile Uncle Al. Let the
> > [ > fool make himself a larger fool.
> > [ >
> > [ > And it takes little energy for me or for you to add
> > [ > "sci.chem" but think of how much energy and how much rage
> > [ > it gives Uncle Al. Why, I just burst out into laughter at
> > [ > all the energy spent by Uncle Al in stalking this and
> > [ > other posts of mine. Uncle Al is too stupid to realize he
> > [ > has been defeated and that the world laughs at his cop
> > [ > enforcement. That method (if they have a newsgroup
> > [ > hangout) will deal with all stalkers of the Internet, not
> > [ > just Uncle Al.
> > End of copy
> >
> >
> >
> > [ Subject: Re: How to handle stalker Alan 'Uncle Al' Schwartz
> > [ Date: Wed, 10 Mar 2004
> >
> > In article <ZcednUDSG4Zb5NPdRVn-jg@comcast.com>,
> > Bill Vajk <bill9north@hotmailDITCHTHIS.com> posted:
> >
> > > Arindam Banerjee wrote:
> > >> Dr. Jai Maharaj wrote in message
> > > news:<Stalker-Uncle-Al-27hf3.20040308@news.mantra.com>...
> > >
> > >>> In article <404D34BE.30087280@hate.spam.net>,
> > >>> Uncle Al <UncleAl0@hate.spam.net> posted:
> > >>>>[... reference to lies and defamation...]
> > >>>How to handle stalkers and "Uncle Al"
> > >> - snip -
> > >> Thanks, Jai, looks like this fellow was not worth my attention. It is
> > >> depressing to think, that those in power in the field of modern
> > >> physics are what chaps like these want to be.
> > >
> > > Al is a chemist wannabe physicist.
> >
> > Alan Schwartz has published his contact information:
> >
> > Alan Schwartz
> > 49 Fabriano
> > P.O. Box 005
> > Irvine, CA 92620-2525
> >
> >
> > http://66.102.7.104/search?q=cache:Nu16TComWkEJ:www.mazepath.com/uncleal/advert.htm+%22Schwartz%22+%22Uncle+Al%22&hl=en&ie=UTF-8
> >
> > and e-mail addresses:
> >
> > "Alan Schwartz" <uncleal0@ix.netcom.com>
> >
> > "Alan Schwartz" <UncleAl0@ix.netcom.com>
> >
> > - - - - -
> Thanks for the warning about the modern sceintist who defends
> science all the time. Uncle Al is ignored. He is the
> flip side of the open thinking philosopher scinetist.
>
> Meaning he requires litterally a falsified predicate thinking.
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- Previous message: Archimedes Plutonium: "concept of Triple Point for Superconductivity?? Re: magnetism in hydrides of oxides at 390K Re: a report from Liverpool Univ. Re: specialness of 390 degree Kelvin; Meissner Effect"
- Maybe in reply to: Dr. Jai Maharaj: "QUANTUM DOTS: MAXWELL'S DEMONS OF BIOLOGY"
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