The GE Healthcare (formerly Amersham Biosciences) GeneQuant™
pro RNA/DNA Calculator Spectrophotometer is used in our laboratory primarily to measure RNA, DNA and protein concentrations. One of the reasons we use this spectrophotometer is that it can detect as little as 20ng of DNA. For RNA and DNA readings, it calculates the A260/A280 and A260/A230 ratios for nucleic acid purity. It can determine the concentration of your sample in a variety of units. In determining protein concentrations, it can include up to 27 BSA standards in a standard curve. The spectrophotometer can also measure absorbance at 600 nm, for measuring growth of bacterial cultures. It has a long-lasting, pulsed deuterium, borosilicate glass lamp, which comes with a 3 year warranty.
This unit is very compact and it only takes a couple of minutes to warm up, perform initialization and calibration, and be ready for measurements. It comes with a re-usuable cuvette for determining protein concentrations, but it can accommodate disposable ones as well. It also comes with a cuvette that holds the small glass capillaries for measuring RNA and DNA. The display is conveniently located on the front, right-hand side - it is a little bit small, but it is easy enough to read. It is a 128 x 64 pixel backlit display. The keypad has 28 keys organized into 3 areas: numeric keypad, utility keys, and reading keys. The ‘set reference’ key is one of the utility keys for measuring your blank. The ‘read’ key gives you different options for the type of measurement (i.e. DNA, RNA, protein 595 or cell culture). Once you set your blank as the reference, you are ready to measure your samples.
Very little maintenance is required and I get consistent readings with my BSA standards. Unfortunately, our model does not have a printout built in, so I have to write down the readings after each measurement by hand. It has a port for connecting to a printer, but it would be nice if a small printer was built into the unit. Also, I’ve noticed that on occasion I get ‘invalid’ readings, but when I re-measure the same sample, I get a numerical reading. There are also instances where I have re-measured the same samples and obtained a different reading (off by 10-20% from the previous reading). Since I need accurate measurements of my RNA and cDNA samples for RT-PCR analysis, it can get somewhat frustrating to try to determine which values are accurate. This variability is supported by my RT-PCR analysis: I get very diverse cDNA quantity readings even though supposedly I am loading similar amounts of cDNA per reaction. Even the protein concentration can be somewhat off. For instance, based on my OD595 readings, I am loading similar amounts of protein per well for my Western, but my actin blot shows otherwise. Having used a nice Hitachi model previously in another laboratory, I am a little disappointed with this unit. But, if you are looking for a somewhat decent spectrophotometer that isn’t too expensive, then this unit would fill the bill.
Hee Chul Lee
Research Fellow
University of Michigan Medical School
Internal Medicine