Alternative DNA Structures

Ø AFM: a very useful technique for imaging biological molecules

Ø Optical microscopes- up to 1000 times magnification

Ø Electron microscope- harsh imaging conditions

Ø Electron beam will hit the image, with a temperature of 100.

Ø Scanning probe microscope- resolution in nm… suitable for biological samples

Ø Advantage:

User can determine the amount of force required

Can preform it in fluids

Flexible in scale

Ø Each nucleosome consists of eight histone proteins around which the DNA wraps 1.65 times.

Ø Plasmids often contains antibacterial resistance

Ø Cruciform structures, triplex DNA structures and slipped-strand DNA are DNA alternative DNA structures.

Ø Due to mechanical stress or during normal opening of DNA, you got cruciform. Instead of binding to their pairs they bind to their neighbors.

Ø Triplex form when the DNA open and will bind to free nucleotides and the DNA pair.

Ø Slipped strand DNA forms when the DNA bind to neighbors. Often found in linear forms.

Ø DNA unwinding elements is when the DNA unwinds but doesn’t join back- very often A and T, due to less energy needed to break them apart.

Ø Even if they bond with neighboring particles they still follow Watsons and Cricks principle.

Ø Telomere is lost after very set of DNA replication.

Ø G-Quadruplex DNA is when a linear strand of DNA containing G will form a quadruplex.

Ø Telomerase cannot do its work if a G-Quadruplex DNA is formed. Telomerase goes to the replicated DNA and makes it longer, which makes the cell immortal. If Quadruplex DNA is used in cancer cells we could stop cancer cells from growing as the telomerase will not be able to work. Doesn’t follow Watsons and cricks principle.

Ø DNA Origami:

A way to use DNA to form a pre-designed shape

Ø Uses:

Study of protein interactions

1.   Where proteins have to be in a cell in order for them to interact.

2.   Box made of DNA: will have lid which can be opened when specific DNA strand is introduced as a key. The technology may allow for targeted drug delivery, with the lid opening when sensing the presence of a particular pathogen.

3.   Self-assembling and self destructing drug delivery vessels done by Harvard Uni.- Has a clam shell shape. The surface of the basket will react with the surface of the target. Linker strand is linked with payload. The locks are made of double helix DNA. Can target a small population of the target cells in a large population of bystanders. The nano-robot will only target the targeted cells with minimal damage.

Ø AFM IS A TECHNIQUE IDEALLY SUITED TO VISUALISING BIOMOLECULES.

Ø The control assemble of DNA can be of use in many different fields

Ø Single stranded DNA can be folded into different shapes, using ‘staple strands’.

Ø Drug delivery

Ø high precision study tool for protein interactions

Ø Disadvantages:
Single molecules can cause cancer and enter cell, but the DNA origami are huge structures which cannot target the cells, hence the nano-robot was designed.