Introduction
1.1 What is DNA?
DNA or deoxyribonucleic acid is a macro molecule which is the building block of living organisms. It consists of a double helical structure of two pairs of cross linked organic bases viz. adenine – thymine and guanine -cytosine. The double helical model was proposed by scientists Watson and Crick, is present in nearly all living organisms and is the carrier of genetic information from one generation to another.
It consists of nitrogen bases also called nucleotides.
A is for adenine
T is for thymine
G is for guanine
C is for cytosine
Nitrogen base A & T are attracted by each other & same is the case with C & G. A is having double bond with T & C is having triple bond with G.
@ A=T
@ C≡G
This structure basically stores the information about the complete life sciences of a human being.
The basic structure of DNA is shown in the following figure:
1.2 How does a DNA function?
DNA is the building block of life sciences. They are responsible for the complete structural as well as mental change in the human beings.
Some of their functions are:
Self Replicating: DNA can replicate by itself from one strand to several strands. They do this by simple process of duplication of themselves with the help of bases available in the organism. They scan themselves and build a duplicate copy as soon as they find suitable condition and environment for a dwelling. These help them to have multiple copies of themselves in case they are damaged.
Self Assembling: DNA are self assembling molecules i.e. they do not require some external process to assemble them. They manage this by their own as they have the information of what bases is to be used next as what is the sequence. The sequence is never changed in any case because it stores the information in terms of both sequence as well as the arrangements of bonds between themselves.
Self Correction: DNA molecules can correct themselves as they have a fixed bond of A=T and G≡C so in case there is a damage to one of the strand the other strand still has the information for the counter base and they correct the order of attachment. The sequence is also verified from the basic molecule of proper functioning molecule.
It stores our gene information and replicates it to each cell. Hence our behavior depends on the DNA.
1.3 DNA to e-DNA
DNA plays a pivotal role in biology as a career of genetic information in all the living species. However the electronic properties of “living molecule” were the controversial topic of physists and chemists. According to some it was a molecular wire that has no resistance while the other claimed that it was an insulator until Jacqueline Barton and group at the California Institute of Technology measured the florescence produced by the excited molecule and found that it no longer emitted light when it was attached to DNA molecule i.e. the light was lost, this is termed as Fluorescence Quenching. The molecule had lost the light and hence it donated the electron to the DNA which is possible only if DNA was a conductor.
The working can be explained as the moving electron from one site to another i.e. the movement of charge from one molecule to another is the most fundamental in chemistry and fundamental material sciences. Thus it was concluded that the DNA has electronic property. Moreover DNA has a backbone of phosphate group and the phosphate is group is negatively charged; hence it can be easily proved that DNA does have the electronic property and the electron transfers by thermal tunneling in the experiment. Hence it is now known that the DNA is a semi conductor as it shows insulation properties also.
1.4 What is e-DNA?
The electronic DNA or e-DNA for short is the electronic form of a DNA that is used now-a-days to sense the crime is the result of the DNA verification from the crime site to the suspect and if the results are matched there is no doubt that the suspect is a criminal but how does that verification happen ? There are several tests for the same which is possible only if we know the basic structure of electronic forms of the molecules.
The eSensorTM system employs small DNA biochips containing electronically active electrodes coated with specific DNA probes. These probes on the chip's surface "capture" specific target DNA present in the sample. The capture event generates a unique, characteristic electrical signal. It is a FET based transistor.
FET Structure:
-Channel
-Gate
-Drain
-Source
-Electrode
How works with FET
Besides other surface sensitive measurements the possibility of electrochemical impedance and field effect measurements for the detection of biomolecular has been discussed. The detection principle using our standard FET devices formerly developed for extra cellular recording from neuronal and cardiac cells has already been proved. In future we will design new electronics, new FET designs and a micro fluidic solution to enhance the sensitivity of the DNA sensor.
DNA Detection Principle
Left: Accumulation of - charges at the FET gate is causing a shift of the flat band voltage of the transistor
Right: Immobilization and hybridization of a natural DNA sequence
The approach to detect the hybridization of DNA sequences using oxide semiconductor field-effect transistors (FETs). The phosphate backbone of the DNA molecule is intrinsically negatively charged. The semiconductor devices are sensitive to electrical charge variations that occur at the surface/electrolyte interface i.e. upon hybridization of oligonucleotides with complementary single stranded oligonucleotides immobilized on the silicon oxide surface of the gate.
This method will allow direct and in situ detection of specific DNA sequences without any labeling. In combination with nano-transistors a PCR-free detection system is feasible.
In future new transistor structures specially designed for the detection of DNA hybridization signals will be developed and fabricated in the clean room facilities of our department. In combination with improved amplifier electronics and a microfludic system for administration of analyst DNA a fully electronic PCR-free (polymerase chain reaction - free) detection of DNA will be feasible. The electrical PCR-free detection method will provide a very simple but powerful tool in many different bioassays. *Nano transistor design and development by: J. Moers, S. Trellenkamp, M. Goryll, A. van der Hart, A. Steffen, M. Marso, P. Kordos and H. Lüth ( ISG1, Forschungszentrum Jülich)
The eSensor™ DNA Biochip consists of a small circuit board containing gold electrodes and single-stranded DNA molecules. Each biochip contains a panel of test sites that detects a different DNA sequence or SNP relying on the ability of a strand of DNA to chemically recognize its complementary partner. Finding the matching chemical "code" of the target DNA or RNA in a sample creates a characteristic bioelectronics signal
How the System Works
Bioelectronics detection proceeds via a sandwich hybridization assay, wherein three critical components (capture probe, target, and signaling probe) are each present in the cartridge. The signaling probe serves to label the target upon hybridization. Electrons flow to the electrode surface only when the target is present and specifically hybridized to both signaling probe and capture probe. The current generated by this system is measured and interpreted by the eSensor™ DNA Detection Reader and Software.
2.1 What is electronic Identity?
In today’s world we need to carry all the documents with us whether it is a passport or a credit card or any verification tools. Now imagine a world where there is nothing to carry all we need is a central database that would verify the person just by the DNA tests and that too very easily. This would lead into a complete new set of world where there is a security as well as there is no one who can get into other’s belongings without permission as there will be a central lookup authority always watching the activity.
The e-DNA chips can be used for any transaction and that too very securely, this usage of e-DNA chips for verification is called the electronic identity verification and the identity is called the electronic identity which is biological but it is used in electronic forms.
2.2 Advantages & disadvantages of e-Identity
Advantages:-
- You don not need to carry any extra documents for your verification.
- You can be centrally connected to verify yourself.
- The vendors dealing with you would be safe for you are known by the central database and can be traced anytime needed.
- Frauds would get down to minimum level.
- You do not require a guarantor to sign for you for you are a self guarantor.
Disadvantages:-
- Thefts of e-Identity can be suspected.
- Misuse can always be projected
- Costlier
- Feasibility is less as the central data base can be hacked.
DNA Computers
3.1 Introduction
Huge financial and intellectual investments over a half-century have made electronic computers the marvels of our age. Much of our scientific, technological, military and economic future depends on the availability of an ever-increasing supply of computational power. But the incessant demand for computational power has pushed electronic technology to the limit of physical feasibility and has raised the concern that this technology may not be able to sustain our growth in this new millennium. For this reason, it becomes important to consider the future of computation and alternative means of achieving computational power. In this regard, two technologies have surfaced: quantum computation and molecular computation. The Laboratory for Molecular Science explores the latter.
3.2 History
The scientists at the forefront of the DNA computer revolution are a brilliant breed indeed. It was all started by a professor of Computer Science at USC by the name of Leonard M. Adleman, who utilized recombinant DNA to solve a simple Hamiltonian path problem which is classified as NP-complete. His article in the Nov. '94 issue of Science magazine, Molecular Computations of Solutions to Combinatorial Problems touched off the current wave of interest in molecular computation. The Hamiltonian path problem, on a large scale, is effectively unsolvable by conventional computer systems (it's theoretically possible, but would take an extremely long time).
His work was picked up by Dr. Donald Beaver, among others, who analyzed the approach and organized it into a highly accessible web page which includes a concise annotated bibliography. One major contributor to this page is the research group of Dr. Richard Lipton, Dan Boneh, and Christopher Dunworth- a professor of Computer Science and two graduate students at Princeton University. They are currently using a DNA Computer to break the government's data encryption standard (DES), as described in the article Breaking DES Using a Molecular Computer.
The field of molecular computation began in earnest with the 1994 publication of the paper `Molecular computation of solutions to combinatorial problems' by the labs leader Leonard Adleman. It immediately became clear that molecular computers had many attractive properties, including: extremely dense information storage, enormous parallelism and extraordinary energy efficiency. We wish to determine if this potential can be put to practical use and whether a large-scale molecular computer can be built.
3.3 Fundamental Parts:
- e-DNA chips
- Supporting computation machine
- Permanent Storage media
We know that the IC chips are not going to change scales anymore i.e. they will not double themselves after a small period of time which is now on the very verge of extinct ness of further compaction.
But the hunger of computation is not going to end and the power we need would increase more and more, there are two ways to go ahead for this the first is the Quantum Computers and the second is the Molecular Computing.
Next Generation of Micro processors:
The next generation microprocessors will no longer have silicon based materials, instead it will have modified DNA molecules which can compute faster then even the fastest computers available today.
If we look at our body as a computer we will see brain as a microprocessor which is capable of doing things very fast and it is a known fact that we don’t even use 10% of our brain during the whole life time, now imagine the total power it might be having when it is used in full throttle with extra load.
If we somehow are able to develop the computers that resemble brain we can do enormous amount of work with them at a very cheap cost. The initial costs are always higher in any technology but after sometime the research work would pay off to get an unimagined power.
Data Storage:
DNA: A unique data structure
The data density of DNA is impressive. Just like a string of binary data is encoded with ones and zeros, a strand of DNA is encoded with four bases, represented by the letters A, T, C, and G. The bases (also known as nucleotides) are spaced every 0.35 nanometers along the DNA molecule, giving DNA a remarkable data density of nearly 18 Mbits per inch. In two dimensions, if you assume one base per square nanometer, the data density is over one million Gbits per square inch. Compare this to the data density of a typical high
Performance hard drive, which is about 7 Gbits per square inch -- a factor of over 100,000 smaller.
Another important property of DNA is its double stranded nature. The bases A and T, and C and G, can bind together, forming base pairs. Therefore every DNA sequence has a natural complement. For example if sequence S is ATTACGTCG, its complement, S', is TAATGCAGC. Both S and S' will come together (or hybridize) to form double stranded DNA. These complementarities make DNA a unique data structure for computation and can be exploited in many ways. Error correction is one example. Errors in DNA happen due to many factors. Occasionally, DNA enzymes simply make mistakes, cutting where they shouldn't, or inserting a T for a G. DNA can also be damaged by thermal energy and UV energy from the sun. If the error occurs in one of the strands of double stranded DNA, repair enzymes can restore the proper DNA sequence by using the complement strand as a reference.
In this sense, double stranded DNA is similar to a RAID 1 array, where data is mirrored on two drives, allowing data to be recovered from the second drive if errors occur on the first. In biological systems, this facility for error correction means that the error rate can be quite low. For example, in DNA replication, there is one error for every 10^9 copied bases or in other words an error rate of 10-9.
In the cell, DNA is modified bio-chemically by a variety of enzymes, which are tiny protein machines that read and process DNA according to nature's design. There is a wide variety and number of these "operational" proteins, which manipulate DNA on the molecular level. For example, there are enzymes that cut DNA and enzymes that paste it back together. Other enzymes function as copiers and others as repair units. Molecular biology, Biochemistry, and Biotechnology have developed techniques that allow us to perform many of these cellular functions in the test tube. It's this cellular machinery, along with some synthetic chemistry, that makes up the palette of operations available for computation. Just like a CPU has a basic suite of operations like addition, bit-shifting, logical operators (AND, OR, NOT NOR), etc. that allow it to perform even the most complex calculations, DNA has cutting, copying, pasting, repairing, and many others. And note that in the test tube; enzymes do not function sequentially, working on one DNA at a time. Rather, many copies of the enzyme can work on many DNA molecules simultaneously. This is the power of DNA computing, that it can work in a massively parallel fashion.
3.4 The potential of DNA
One existing application of the assembly properties of DNA is in so-called DNA chips. These devices exploit the fact that short single strands will bind to other segments of DNA that have complementary sequences, and can thus be used to probe whether certain genetic codes are present in a given specimen of DNA.
The unique assembly properties of DNA together with its unparallel recognition, optical characteristics, stability and adaptability suggest that DNA may become one of the most important species in the general area of molecular electronics. Often, molecular electronics is viewed only as the formation of logic devices and memories with single conducting molecules. But it can also be defined more broadly as the area of science and technology that studies electronics and sensors based on molecular organization. There is little doubt that DNA is destined to be a major component in the toolkit of molecular electronics.
Other Applications
Agriculture & Food Safety
Food safety
Food-borne pathogens such as E. coli strain 0157:H7, and antibiotic-resistant Salmonella, Campylobacter, pose significant health risks to the public. DNA detection in the food industry offers major advantages, whether monitoring the cleanliness of food processing plants, evaluating the efficiency of the cooking process, or testing for microorganisms in dairy products.
Grain safety
Both fungi and bacteria specific to wheat, corn, soy and other crops pose potential economic and health related concerns. Testing at storage and transportation points can detect problems before they cause harm to people, crops or animals.
Genetically modified crops (GMOs)
Increasingly, producers and shippers need to identify and trace the transport and marketing of genetically engineered crops from the field to the supermarket or restaurant. DNA testing can assist in meeting labeling and other requirements, monitoring the distribution, shipment and use of genetically engineered materials.
Environmental Monitoring
Motorola's eSensor™ bioelectronic technology is well suited for identifying disease organisms based on their DNA signatures. This is valuable for environmental monitoring, public health, and military purposes.
CMS's eSensorTM technology relies on bioelectronics, a major advance in DNA analysis that will broaden the use of DNA tests to monitor and improve health. The eSensorTM system employs small DNA biochips containing electronically active electrodes coated with specific DNA probes. These probes on the chip's surface "capture" specific target DNA present in the sample. The capture event generates a unique, characteristic electrical signal. Each CMS chip can detect several different types of DNA sequences at once from a single patient sample.
In the study, CMS used eSensorTM technology to analyze residual DNA samples from patients undergoing testing for hereditary hemochromatosis at the University of Wisconsin Hospital and Clinics in Madison. Hereditary hemochromatosis, an iron overload disease, is a potentially fatal disorder affecting millions that is sometimes overlooked by physicians because of its non-specific symptoms.
Dr. Karl V. Voelkerding, M.D., Medical Director, Molecular Diagnostics at the University, and his team compared CMS eSensorTM results with PCR-RFLP analysis, a procedure performed only in High-Complexity Clinical Laboratories. The PCR-RFLP test is generally regarded as the "gold standard" for genetic diagnosis of hereditary hemochromatosis.
The Wisconsin clinical laboratory reported 100 per cent agreement between their PCR-RFLP analysis of the samples and the results obtained using CMS eSensorTM technology.
The eSensorTM system successfully identified patients with normal DNA, those harboring the disease-causing mutations, and those classified as carriers for hereditary hemochromatosis. "CMS results showed 100 per cent concordance with PCR-RFLP in identifying normal DNA and DNA samples carrying the mutations," comments Dr. Voelkerding. "This is an impressive performance for a chip-based technology designed to meet the cost-conscious requirements of
Health care today," he adds.
There are also some application based on the DNA related Computers as follows:
- Making the most efficient routes between the major cities of the country.
In Web applications, WAN path & connection of computers in diff. topologies, becomes much easier to understand.
- Solving of complex problems also leads to efficient working of complex structures such as ANNs (Artificial Neural Networks) .
Conclusion
It can be concluded that if we use the DNA into a power of future we would surely benefit from the same and it has got a varied applications in other fields too which would in all over enhance the human life to a next generation power where there would be no silicon but all DNA as basic material in electronic world.
It is a new technology and so it is very difficult to develop and requires great understanding and is expensive also but in the times to come it will emerge as the only surviving technology with no limits to computations.
Moreover if we look ourselves as surviving forces then e-DNA will surely survive for we are a e-DNA as a whole and the matrix theory says that very clearly.
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