Photoactivated peptides are modified natural or synthetic peptides the functions of which can be activated with light. This can be done either irreversibly or in a reversible way. Caged peptides which contain photocleavable protecting groups belong to irreversibly activated peptides. Reversible activation/deactivation of peptide function are achieved by incorporation photo-controllable fragments (molecular

photoswitch A photoswitch is a type of molecule that can change its structural geometry and chemical properties upon irradiation with electromagnetic radiation. Although often used interchangeably with the term molecular machine, a switch does not perform work ...

es) in the side chains or in the backbone of peptide templates to get the photo-controlled peptides, which can reversibly change their structure upon irradiation with light of different wavelength. As the consequence, the properties, function and

biological activity In pharmacology, biological activity or pharmacological activity describes the beneficial or adverse effects of a drug on living matter. When a drug is a complex chemical mixture, this activity is exerted by the substance's active ingredient or ...

of the modified peptides can be controlled by light. Since light can be directed to specific areas, such

peptide Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. A ...

s can be activated only at targeted sites.

Azobenzene Azobenzene is a photoswitchable chemical compound composed of two phenyl rings linked by a N=N double bond. It is the simplest example of an aryl azo compound. The term 'azobenzene' or simply 'azo' is often used to refer to a wide class of simi ...

s, and

diarylethene Diarylethene is the general name of a class of chemical compounds that have aromatic functional groups bonded to each end of a carbon–carbon double bond. The simplest example is stilbene, which has two geometric isomers, E and Z. Under the influe ...

s can be used as the photoswitches. For therapeutic use, photoswitches with longer wavelengths (near-infrared, to penetrate tissue) or the use of two-photon excitation are required, coupled with improved methods for peptide delivery to live cells.

Applications

Photoactivated peptides are potentially useful for cancer therapy, other light-controlled drugs and in tools to probe molecular interactions in intact cells and whole organisms. The initial peptides were successfully used to kill

B-cell lymphoma The B-cell lymphomas are types of lymphoma affecting B cells. Lymphomas are "blood cancers" in the lymph nodes. They develop more frequently in older adults and in immunocompromised individuals. B-cell lymphomas include both Hodgkin's lympho ...

cancer cells. The reference synthetic short peptide was alkylated with

azobenzene Azobenzene is a photoswitchable chemical compound composed of two phenyl rings linked by a N=N double bond. It is the simplest example of an aryl azo compound. The term 'azobenzene' or simply 'azo' is often used to refer to a wide class of simi ...

crosslinkers and used to photo-stimulate

mitochondrial membrane A mitochondrion (; ) is an organelle found in the cells of most Eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used t ...

depolarization and

cytochrome c The cytochrome complex, or cyt ''c'', is a small hemeprotein found loosely associated with the inner membrane of the mitochondrion. It belongs to the cytochrome c family of proteins and plays a major role in cell apoptosis. Cytochrome c is hig ...

release in permeabilised cells, which were the initial events of the intrinsic

apoptosis Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death. These changes incl ...

pathway.

Gramicidin S Gramicidin S or Gramicidin Soviet is an antibiotic that is effective against some gram-positive and gram-negative bacteria as well as some fungi. It is a derivative of gramicidin, produced by the gram-positive bacterium ''Brevibacillus brevis'' ...

analogues containing a diarylethene fragment display clear-cut reversible change of

antimicrobial An antimicrobial is an agent that kills microorganisms or stops their growth. Antimicrobial medicines can be grouped according to the microorganisms they act primarily against. For example, antibiotics are used against bacteria, and antifungals ar ...

activity. In an inactive, UV-inducible photo-form they are harmless to

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

cells, but are bactericidal after the activation with visible (amber) light. Photoswitchable peptides to inhibit protein-protein interactions in a light-controlled manner have been developed and applied to inhibit

clathrin-mediated endocytosis Receptor-mediated endocytosis (RME), also called clathrin-mediated endocytosis, is a process by which cells absorb metabolites, hormones, proteins – and in some cases viruses – by the inward budding of the plasma membrane (invagination). This ...

in mammalian cells and in yeast. The same design principle has been applied to inhibit protein-protein interactions involved in cancer and can be used for any interaction mediated by a helical motif.

References

{{reflist Peptides Experimental cancer treatments

Applications

See also

References