What is a Transilluminator used for?

Transilluminator

A transilluminator is standard equipment present in biosciences laboratories for the visualization of target proteins and DNA. The Ultra-Violet (UV) transilluminator functions by emission of higher levels of UV irradiation via the viewing surface. Light is allowed through the clear glass.

Types of Transilluminator

Depending on the type of sample, the UV transilluminator is operated in any of the three wavelength bands. 254, 312, and 365 nm are typical wavelengths. 312 nm are used for standard gel documentation in the gel doc system. 254 nm is used in crosslinking applications as it causes higher DNA damage. The intensity of illumination can be selected using high or low levels. This is used when ethidium bromide is used as a fluorescent tag.

Blue Light transilluminator is also used as a substitute for UV transilluminator as it avoids the need for harmful UV radiation. Also, some other dye can be substituted for ethidium bromide, which is a potent mutagen. Also, the background values are lower. It can be utilized for the visualization of a large range of dyes. Its wavelength is 470 nm. Since it is not harmful, there is no need for safety glass. Besides, there are white light transilluminators too. There is no damage to DNA and protein also. This is very handy in the case of downstream operations, which need gel after viewing in the gel doc system.

LED transilluminators can provide high contrast. They ensure even illumination of the area. The orange filter is adjustable for continuous viewing. Samples are saved from heating. The compatible markers are GelGreen, GFP, SYBR Green, SYBR Safe, SYBR Gold, and SYPRO Ruby. Here, an amber filter cover allows visualization of samples above 500 nm, blocking the blue light.

High intensity provides imaging with a lower concentration of the sample. Medium intensity is good to view a single bank quickly. Lower intensity focuses on photography on multiple bands. 

Extraordinary uniform intensity can produce high quality images. Multiple gels can be placed on the surface with uniform illumination of each lane and gel. The coefficient of variance is less than 5% in uniformity for the full filter area.

Low performance transilluminators have 8 watt bulbs, whereas high performance transilluminators have upto 25 watt bulbs. 

UV-to-blue converter plate can be placed on top of a transilluminator for conversion of UV to blue light. In addition, an amber filter should also be viewed for visualization.

UV-to-white converter plate converts UV to white light and is used in viewing colored dyes in table models. It is utilized to view colored samples like coomassie blue or silver stained gels. It serves as a cheaper alternative to white transilluminators.

Use and Applications of Transilluminator

The main usage of a UV transilluminator is in the visualization of protein and DNA polyacrylamide and agarose gels after the process of electrophoresis. It provides researchers with the compact footprint of the gel. The gels are placed directly on the UV transilluminator. But the wavelength will change depending on the specific application. It is used to find out the tumor masses and facilitate medical inspection. It is used in DNA fluorescence, protein fluorescence, and gel electrophoresis. When a transilluminator is used at 365 nm, there is no occurrence of photonicking, thus facilitating the usage of UV radiation for extended periods. This can be used for routine imaging in a gel doc system. 302 nm is useful for fast observation of a single band.  245 nm can be used for the recording of gels. 

Transilluminators are very useful for the below mentioned purposes:

• Chemiluminescence,
• Multiplex fluorescence,
• NIR, 
• RGB, (non-fluorescent) 
• DNA gels 
• Protein gels 
• Plant imaging 
• Fluorescent dyes 
• Colorimetric imaging, 
• Counting of colony
• Gel to gel comparison
• PCR product sizing
• Verification of integrity of RNA after extracting
• Purification of DNA fragments after digestion using restriction enzymes

Choosing a Transilluminator

For different sizes of gels, the viewing surface differs. Wavelength also differs as different fluorescent markers can be used for different biological samples loaded in gels. Some transilluminators have single wavelength, while some have dual wavelengths. The dimensions of the benchtop unit also vary as some are very compact, while some are elongated. In addition, some models are stationary, whereas some are hand-held. Some models have an option of variable intensity setting, whereas some are without intensity setting. Some models have options to choose high, medium and low levels of irradiation. Some models have choices to choose a high or low level of intensity. Some models have only a high level of setting. It is called triple intensity or dual intensity switch or single intensity switch depending on the availability. Smaller size transilluminators can accommodate midi and mini sized gels. For high demanding experiments, stationary models are chosen.

Protection while handing Transilluminator

Since intense UV light is used for visualization of fluorescent markers used in agarose gel electrophoresis, the radiation is perilous to both eyes and skin. Hence, UV absorbing cover must be fitted in the transilluminator. If the instrument is used without putting the cover or if there is no cover, then it is mandatory to protect the exposed eyes and skin of the operator. The glass door in the transilluminator should not be used in cutting the gel.

Protection is done by wearing:

• A face shield
• Long laboratory coats and sleeves
• Heavy-duty laboratory gloves

Conclusion

From the above paragraphs, we come to know about the types and usage of each type of illuminator. While choosing ethidium bromide fluorescent tag for UV light illumination, there is a compromise on safety and disposal. Hence, blue light and visible light transilluminators are easier and safer for laboratory use even though the dyes for visualization used for them are costlier.