Photostatins are inhibitors that can be switched on and off ''in vivo'' by visible light, to optically control

microtubule Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm and have an inner diameter between 11 an ...

dynamics. Photostatins are a form of

photopharmacology Photopharmacology, an emerging approach in medicine, involves activating and deactivating photoswitchable molecules with light for target drug delivery. Clinicians use the energy of light to change the shape and chemical properties of a drug, res ...

. As a cell prepares to divide, its microtubules, arrange themselves into a spindle that permits its

chromosomes A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...

to split into two bundles. These bundles become the nuclei of the daughter cells, Out-of-control cell replication is the underlying cause of cancer, developing drugs that interfere with microtubule activity offers one potential therapeutic approach. They can operate microtubule dynamics with a subsecond response time and control

mitosis In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is mainta ...

in living organisms with single-cell spatial precision. Most microtubule inhibitors affect both cancerous and healthy cells, requiring lower doses to avoid severe side effects. Because photostatins are inactive in the absence of light, they only affect cells that are illuminated. Focusing light on tumors directs their activities to appropriate targets with fewer side effects.

Combretastatin A-4

One phostatin is

combretastatin Combretastatin is a dihydrostilbenoid found in '' Combretum caffrum''. As a class Combretastatins are a class of natural phenols. A variety of different natural combretastatin molecules are present in the bark of '' Combretum caffrum'', commonly ...

A-4, one of several combretastatins found in the bark of the

South African bushwillow ''Combretum caffrum'' is the Eastern Cape South African bushwillow tree. Biochemistry In ''C. caffrum'', combretastatins A-1, A-4 and B-1 can be found.isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Iso ...

s, that share a single composition, but different shapes. One isomer is a poor disrupter of tubule activity while the other is effective. Replacing two adjacent carbon atoms in the molecule with nitrogen atoms changes the non-toxic isomer, which does little to disrupt tubules, into the toxic one in the presence of blue light. This transformation is reversed simply by switching the light off. The drug proved 200 times more toxic when exposed to light in this way than in the dark. The effect increased to 250 times under violet light and decreased to 75 times when exposed to cyan.

References

External links

* {{Cite web, url=http://www.eurekalert.org/multimedia/pub/94897.php, title=Photostatin Added to Human Cancer Cell Line, website=EurekAlert!, access-date=2016-05-01 Cancer treatments

Combretastatin A-4

See also

References

External links