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What is ferritin?:
There is a kind of protein that stores iron and it is called ferritin.This protein releases the iron in it in a trend that is controlled.Most of the living organisms, which consist also bacteria, algae and higher plants, and animals produced this protein. Therefore, nano bio electronic devices are introduced through this protein molecule. Due to the technology now for devices is a mechanical lithographic methods that may lead to both physical and technical constraints in future,it is good to implement it. In other words, these problems is able to be solved by such molecular electronic devices.Therefore it is important for us to study the structure of ferritin beforehand.
Structure and types :
A total of 24 protein subunits will bind with each other by non-covalent bond forming a globular protein complex that is ferritin.In terms of size,ferritin is about 12nm including 2nm thickness shell. Ferritin is divided to Apo-ferritin and Halo-ferritin. Apo-ferritin is ferritin that is not combined with iron .Apo-ferritin has less conductivity compared to Halo-ferritin.So why molecular memory devices are able to be fabricated by ferritin?The reason being is it is a redox active molecule.
Methods that are used:
- Fabricating ferritin-immobilized surface
- Immobilization is confirm
- Electrochemical Analysis
Gold substrates is cleaned by Pirahna Solution that is 30 vol% hydrogen peroxide and 70 vol% hydrogen sulphate at 70 degree Celcius in a period of around 5 minutes. Then,dip the substrate into the solution. Dip into pure ethanol solution for a few hours after washed by deionised water followed by twelve hours in a 20mM 11-MUA.After that, it is rinse with pure ethanol together with deionized water.Nitrogen gas is used to dry the substrate.Soak the 11-MUA modified gold surface in the ferritin solution.
By using Surface Plasmon Resonance spectroscopy.Besides, immobilization is certified using the image of Scanning Tunneling Microscopy.
Electrochemical workstation was used to analyse electrochemical properties that the ferritin immobilized structure has. This technique is called as cyclic voltammetry. It prepares the measuring of electrochemical cell. It consist of electrodes,working: Ag/AgCl reference:
and counter:Pt while electrolyte: Ammonium Acetate.
Ferritin immobilized on the modified gold surface was shown from SPR spectrums.An increase in the concentration of ferritin leads to an increase in the total of SPR angle shift before saturating at 0.5 mg/ml.The surface morphology analysis of ferritin immobilized substrate is done using Scanning Tunneling Microscopy .
Ferritin still had redox in ability immobilized state. This is shown through the cyclic voltammogram of ferritin The potential is applied from a range between 0.3V to -0.5V with 50mV/s scan rate. Reduction peak from 0.15V is observed at while oxidation peak was determined at -0.05V.By applying potential,oxidation and reduction of ferritin are regulated.The results are different in comparison with bare gold substrate or 11-MUA modified gold substrate.Open circuit voltage(OCV) was measured without appliying potential in the electrochemical cell . The potential of the point when equilibrium of the system is reached is -0.22V equivalent to the steady-state.Memory function is investigated by Open Circuit Potential Amperometry(OCPA). The reduced ferritin return to the steady-state with releasing electron when the open circuit voltage was applied getting positive current vice versa for oxidised ferritin.
This means that state of system and movement of electrons are regulated by applied voltage. It is applicable to the principle of memory.
It leads computers to built on thin films and develop ultrathin memory chips measuring less than 1 micron in thickness by:
- manufacturing process of computer memory is really hot (>1,000 degrees Celsius).This means substrate must have a high heat resistance.
- metal memory cells are able to arrange on substrates sans heat (compared to silicon) using ferritin allowing the application of thinner substrate materials (e.g plastics and glass)
- a biotech-based process that creates ultrathin computer memory has developed already(memory was built on thinner substrates through a protein available in mammals).Reason is high- temperature processing is no longer necessary.
- a substrate is applied with ferritin then assemble orderly and of high-density.The UV light irradiate the ferritin,destroying it wholely until tiny metal deposits are left on the substrate.