Spectrophotometers come in handy for almost all routine laboratory work including the estimation of protein or nucleic acid samples, or for density measurements of bacterial cultures. The Eppendorf Biophotometer is just the right instrument for quick and routine measurements of the optical density of samples at predefined wavelengths.
The light source is a Xenon flash lamp. For those who have turned on spectrophotometers and waited (sometimes for over 30 minutes) for the lamp to completely warm-up, this is a boon - there is no need to wait for the Xe lamp in this biophotometer to stabilize. The Xe lamp also has a long lifetime (about 10 years) so frequent changing of the lamp is avoided. A set of pre-fixed wavelengths for the estimation of concentrations of different types of biological samples is provided and one only needs to choose the appropriate button as per the sample being studied.
Cuvettes for the measurement of sample concentrations are provided along with the machine. A pack of 80 disposable cuvettes is supplied. The minimum volume required for these cuvettes is only 50ul. I find this feature extremely useful, especially when working concentrations of protein are highly limited. The cuvette capacity is up to 1ml. The path length is physically defined in the spectrophotometer as 1cm. This can, however, be set in the software to 1, 2 or 5mm.
The soft touchpad of the instrument is very convenient for quick handling and easy access. Additionally, it is quite sturdy when compared to some other instruments whose touch pads tend to get 'desensitized' with constant use. A printer can easily be hooked up to the spectrophotometer to print out readings.
The instrument can generate a standard curve, so once I feed the unknown sample (after reading the standard curve samples) into the spectrophotometer, I get a direct reading of the calculated protein concentration. The machine can also be used for the estimation of bacterial culture density; I would recommend not using the Uvettes for this very purpose. Uvettes are disposable cuvettes provided with the machine; they are a bit expensive compared to plastic cuvettes which can be used for readings of bacterial cultures. All of the data that is stored in the instrument can be retrieved later. It should be noted that once a reading is obtained, the next reading can be recorded only after a delay of 2-3 seconds.
There are several advantages to using the Eppendorf Biophotometer. I use the instrument regularly for measuring the concentration of DNA, RNA and protein samples. With a one-touch button, the readings can be obtained. Estimating protein concentration using Lowry’s method or Bradford method are experiments I carry out frequently. Accurate quantification of these biomolecules is important in my experiments, which are mostly enzymatic assays. I find the Biophotometer easy and quick for obtaining readings of protein samples. I occasionally monitor the A260/280 for DNA samples too using this instrument, as it has the facility to directly provide the ratio.
The machine is extremely useful for routine measurements of concentrations at specified wavelengths. The machine is also very small and can be described as 'portable'. Despite these advantages, experiments that require recording complete spectra over a given set of wavelengths or across a window of time (for example, enzymatic assays and time-course experiments), cannot be performed with this system. In other words, spectral scanning cannot be done.
R. Mahalakshmi
Scientist
Bharathiar University
Department of Biochemistry