We have exposed a number of bioactive pure compounds to lasers of a given nm wavelength and energy level for varying periods of time, followed the result of exposure via thin layer chromatography, isolated and characterized the products high pressure chromatography and evaluated their bioactivity against a panel of bacteria or cancer cells. Without exception, the products from exposure of a bioactive phenothiazine such as thioridazine, caused a many-fold increase in the antibacterial effects against salmonella, E. coli, Staphylococcus aureus and Mycobacterium tuberculosis. In some cases, antibacterial effects included inhibition of the main efflux pump of given bacterial species. The references below suggest that perhaps exposure of bioactive compounds to given lasers and energy levels produces new compounds with increased bioactivity over that of the parental, non-laser exposed compound. The main advantage from the use of the method is that unlike pyrogenic methods, once the laser beam is stopped, the chemical reactions cease.
References
1: Pascu ML, Danko B, Martins A, Jedlinszki N, Alexandru T, Nastasa V, Boni M,
Militaru A, Andrei IR, Staicu A, Hunyadi A, Fanning S, Amaral L. Exposure of
chlorpromazine to 266 nm laser beam generates new species with antibacterial
properties: contributions to development of a new process for drug discovery.
PLoS One. 2013;8(2):e55767. doi: 10.1371/journal.pone.0055767. Epub 2013 Feb 6.
PubMed PMID: 23405212; PubMed Central PMCID: PMC3566004.
2: Hunyadi A, Danko B, Boni M, Militaru A, Alexandru T, Nastasa V, Andrei IR,
Pascu ML, Amaral L. Rapid, laser-induced conversion of 20-hydroxyecdysone and its
diacetonide -- experimental set-up of a system for photochemical transformation
of bioactive substances. Anticancer Res. 2012 Apr;32(4):1291-7. PubMed PMID:
22493361.
3: Pascu ML, Nastasa V, Smarandache A, Militaru A, Martins A, Viveiros M, Boni M,
Andrei IR, Pascu A, Staicu A, Molnar J, Fanning S, Amaral, Direct modification
of bioactive phenothiazines by exposure to laser radiation. Recent Pat Antiinfect
Drug Discov. 2011 May;6(2):147-57. PubMed PMID: 21517738.
4. T. Alexandru, A. Armada, A. Militaru , M. Boni, V. Nastasa, M. Viveiros, M. L Pascu, L. Amaral. Biological evaluation of products formed from the irradiation of Chlorpromazine with a 266 nm laser beam. Biochem & Pharmacol Open Access J. Biochem Pharmacol 2013, 2:1.
5. B DANKO, A MARTINS, D W CHUANG, H C WANG, L AMARAL, J MOLNAR, F R CHANG, W U YC, A HUNYADI (2012) In Vitro Cytotoxic Activity of Novel Protoflavone Analogs –Selectivity Towards a Multidrug Resistant Cancer Cell Line Anticancer Research 32;2863-2869.
6. Nastasa V, Boni M, Andrei IR, Amaral L, Staicu A, Pascu ML. "Optical investigation of medicine solutions in micro-droplets formed at interaction with laser radiation." PHYSICAL CHEMISTRY OF INTERFACES AND NANOMATERIALS 2011;8098: Article Number
809815; DOI 10.1117/12.898487
http://www.ncbi.nlm.nih.gov/pubmed/23405212
The simple answer is yesc (I give a brief explanation here but suggest googleing 2+2 and 2+4 cycloadditions and/or frontier orbitals, there is an abundence of diagrams out there which will help).
Anyway, A common example of this is cycloadditions and the so called "frontier orbitals" with reagrds the symmetry of adjoining molecular oribatls and their phase as they would orientate themsleves.
The 2+2 case is the case of a cycloaddition between two molecules each cotaining a delocalised pi bond between 2 adjacent carbon atoms, to consider whether the reaction would be photochemically allowed or thermochemically allowed a consideration for the orientation of the two pibonds, in order for each of the two pi bonds to form 2 new sigma bonds the sign (or phase) on each wavefunction-description of the bond must match so as to generate thebonding orbitals, in this case the wavefunction signs only match if both pi bonds are photochemically excited from π to π*. (a diagarm would really help in understanding this - http://pms.iitk.ernet.in/wiki/index.php/Pericyclic_Reactions_Electrocyclizations,_Cycloadditions_and_Sigmatropic_Rearrangements), basically the principle can applied to any complex pair of molecules, if they form a bonding-bonding interaction when in an excited state but not in a ground state then the reaction will only be possible via photochemical means.
Also if you want to consider the counter point, look up 4+2 cycoladditons (diels-alder reactions) which proceed via thermochemical means and serve as a classical example of reactions forbidden in excited states.
Hope that is of some help.
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