Download DNA - K.T. Leung

The future of DNA in
Nanotechnology
Avisek Chatterjee
CHEM 750
Outline
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what is DNA?
DNA Technology
Proposed applications of DNA in nanotech
Nanotechnology– founder’s view.
References
What is DNA?
DNA stands for:
D: Deoxyribose
N: Nucleic
A: Acid
DNA is too
small to see,
but under a
microscope it
looks like a
twisted up
ladder!
Every living thing has DNA. That means
that you have something in common with a
zebra, a tree, a mushroom and a beetle!!!!
What is DNA?
• It is stored inside the cell nucleus of
living organisms.
• All living things contain DNA!!!!!
• The main goal of DNA in the cell is
long-term storage of information.
• Various enzymes act on DNA & copy
its information into either more DNA,
in DNA replication, or transcribe &
translate it into protein.
• Encodes the sequence of amino acid
residues in protein.
www.earthlife.net/images/eury-cell.gif
Structure of DNA
• DNA is a long chain polymer of simple
chemical units called nucleotides. Which are
held together by a backbone made of sugar and
phosphate groups.
• The backbone carries four types of molecules
called bases (purines & pyrimidines).
.
Kim, et al., 1996. Cell 84: 643-650
DNA Structure
• Hydrogen bonded nucleotides on
opposite sides.
• DNA helices are antiparallel.
• Carbon & sugar define ends..5’ & 3’.
• Pyrimidines bond with purines.
–T A
– CÖG
.
Kim, et al., 1996. Cell 84: 643-650
DNA Structure
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Helical structure of DNA
Major & minor groves.
10Å radius & 20Å diameter
3.4Å between nucleotide base
pairs.
34Å / 360° turn.
10 nucleotide base pairs /
360° turn.
The process that forms
double helix is called DNA
hybridization.
The order or sequence of
these bases along the chain
forms the genetic code.
.
Kim, et al., 1996. Cell 84: 643-650
• DNA contains all the information necessary to make a
complete organism.
• DNA is organized into genes.
• Cells decode the information to build proteins.
• Each protein carries out unique function.
• Proteins work together to carry out cell functions.
DNA Technology
DNA technology
DNA technology involves the concepts of :
• Restriction enzymes
• Nucleic acid electrophoresis
• DNA polymorphism.
Restriction enzymes
• Each restriction enzymes cuts the DNA into
defined fragments by acting at specific target
molecules.
• These enzymes act as scissors, cutting the DNA
into specific sites.
• Restriction enzymes are commonly available.
IPGRI and Cornell University, 2003
Nucleic acid Electrophoresis
• A method to separate DNA fragments to allow
their visualization and/or identification.
IPGRI and Cornell University, 2003
DNA polymorphism
• Various events give rise to variants, more or less
complex, in the DNA sequence. Such variants are
usually described as polymorphism.
• Point mutation, rearrangement.
Why DNA is in nanotech?
• Size ~1nm.
• Information storage
ability.
• Biosensing.
• Suitable to be used
as nanoscale
construction material
as proposed in the
famous “bottom up”
approach.
Chris Dwyer
Assistant Professor
Proposed applications of DNA in
Nanotechnology
Future computing
Chemical nanocomputing:
• Computing is based on chemical reactions (bond
breaking & bond making)
• Inputs are encoded in the molecular structure of
the reactants and outputs are can be extracted
from the structure of the products.
• DNA computing is most promising in this
respect.
DNA computers!!!!!!
Why limit ourselves to electronics ????
• DNA the molecule of life can store
vast quantities data in its sequence
of four bases (A,G,T,C). & natural
enzymes can manipulate this
information.
• In 1994 Adleman showed that DNA
based computer can solve a problem
which is particularly difficult for
ordinary computers.
• Introduction of DNA computers.
Devices go molecular– Molecular & Electronics
• Currently fabricated with CMOS
transistors.
• Higher transistor density--- faster
circuit performance.
• Limitation towards higher
integration is restricted by current
lithographic techniques, heat
dissipation etc.
• Search for a novel technology--leads us towards Molecular
electronics.
• Use individual molecules as wires,
switches, rectifiers & memories.
http://www.ircc.iitb.ac.in/~webadm/update/archives/images/focus10.jpg
DNA the prospective candidate!
• Charge transport in DNA & the
feasibility of constructing DNA
based devices
• Development of novel
bioelectronics systems.
• Molecular recognition & special
structuring that suggests its use
for self assembly.
• Molecular recognition drives the
fabrication of devices &
integrated circuits.
• Self assembly drives the design of
well structured systems.
http://www.rsc.org/ejga/NP/2006/b504754b-ga.gif
Bioelectronics
Two potential applications have
been up to now envisioned for
DNA:
(i) as template in molecular
electronic circuits, and
(ii)as wiring system (molecular
wire).
It has been proven that charge can
propagate through DNA!!
Biosensors
DNA biosensors
• Target DNA molecules are captured at the
recognition layer and the resulting hybridization
signal is transduced into a usable electronic signal
for display and analysis.
Applications: diagnosis, therapy selection & follow
up of severe diseases.
Nature Biotechnology,21, 10, Oct 2003
DNA nanotweezers
• Consists of three single
strands of synthetic
DNA.
• When the fourth DNA
is added to the test
tube it grabs the
unpaired bases and
zips the tweezers shut.
• Test tube based
nanofabrication.
References
• Nature Biotechnology,21,10,Oct 2003.
• “Charge transport in DNA-based Devices”,
Danny Porath, Noa Lapidot & GomezHerrero.
• “Nanotechnolog”,Quan Zhou,Helsinki
University of Technology.
• T.G.Drummond,M.G.Hill & J.K.Barton,
Nature Biotechnology,21,10,2003.
Thank you
I would like to Thank Prof.
K.T.Leung
& all of you for your kind attention