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 DNA in 3D

DNA Background:

The genetic makeup of all living organisms is contained in their DNA molecule. Replication occurs by the splitting of the DNA molecule, which duplicates itself through a transformation of its structure. Parts of the DNA molecule have been given names such as pyrimidine bases, cytosine, thymine or uracil that form a group of biochemical's that sustains life. The long DNA molecule holds itself together by using simple bonds like those found in sugars.

Researchers believe that the energy of the UV photon causes the formation of a strong (covalent) bond to develop between specific biochemicals. However, the bond strength of the covalent bond is very dependent on the relative position of the participating atoms. When the bond is symmetrical on both sides of a hydrogen atom in the bond, it is referred to as a dimer. A dimer is a very strong bond and is not generally broken during the vaporization of the liquid. UV light is known to produce Thymine, cytosine-thymine, and cytosine dimers. After the formation of the dimer, further replication of the DNA stops.

DNA light absorption:

DNA action spectra show that absorption increases as the wavelength decreases, with a relative maxima at 260 nm and largest at 200 nm. Many articles indicate the principal action spectra of the DNA absorption is from 245 to 280 nm range and do not address the 200 nm peak. Since water absorption significantly increases below 235 nm, it becomes apparent that DNA effectiveness curves that omit the 200 nm peak apply only to organisms in water. MS-2 Phage is a marker virus that is used to measure reproduction viability after UV irradiation. Light absorption is more than tripled at this lower peak.

Mercury based lamps have become the commercial light source for UV irradiation of virus and bacteria because it emits photons near the longer wavelength relative absorption peak of DNA. The mercury gas and its pressure in the lamp determine the wavelength of the emitting light. For low-pressure (LP) and low-pressure high output (LPHO) lamps, the emitting wavelength is 254 nm. For medium pressure lamps, the emission ranges from 200 nm to above 300 nm. However, the strength of the emitted light is not effective below 245 nm for the continuous emitting lamps and below 235 nm for medium pressure lamps. Xenon gas in pulsed lamps produces a similar emission as the medium pressure mercury lamps.

Recent technical papers suggest that dimmer formation is not the only requirement to inactivate DNA. Absorption of other molecular groups in the long DNA chain increase as the wavelength is reduced from 254 nm. Damaging or destroying these bonds may be more effective in deactivating the DNA than compared to the 254 nm band. No one has done a detailed study of the effectiveness of inactivation for a single line UV emission that is produced by the new UV source (NUV) lamps. Reports show that damage caused by 254 nm light can be reversed by longer wavelength UV and blue light. The NUV source photons with their higher energy are not expected to cause this "photo-reactivation" phenomenon and initial tests show that to be true.


Far-UV Sterilray™ is considered the most effective source because DNA chains and biochemical's have greater absorption at this wavelength. The steep rise in absorption below 245 nm is exhibited by all proteins. It has been fairly well established that peptide bond absorption is responsible for the steep rise in absorption exhibited by all proteins. This occurs as well for nucleo-proteins, aromatic amino-acids, diglycine, triglycine, and bovine albumin. An organic chemist suggests that Sterilray™ is more effective in breaking bonds and producing dimers in the purine bases and sugar phosphates instead of the pyrimidines. Sterilray™ is not strongly absorbed by water vapor and oxygen in the air. No other UV source can be as effective in killing DNA and at the same time not be rendered ineffective by water vapor and oxygen absorption in the air.


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