The future of DNA in Nanotechnology

Avisek ChatterjeeCHEM 750

Outline

• what is DNA?

• DNA Technology

• Proposed applications of DNA in nanotech

• Nanotechnology– founder’s view. • References

What is DNA?

Every living thing has DNA. That means that you have something in common with a zebra, a tree, a mushroom and a beetle!!!!

DNA stands for:D: DeoxyriboseN: NucleicA: Acid

DNA is too small to see, but under a microscope it looks like a twisted up ladder!

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– C G

Kim, et al., 1996. Cell 84: 643-650.

DNA Structure

• 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 DwyerAssistant 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 & Gomez-Herrero.

• “Nanotechnolog”,Quan Zhou,HelsinkiUniversity 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