Q1. In the life sciences, spectrophotometry is a valuable research tool used widely for the measurement of nucleic acids, proteins and even cell cultures. ‘NanoDrop’ speCtrophotometers are unique from other spectrophotometers in that they use a ‘sample retention’system. Could you explain how this syStem works?
The patented sample retention system combines fiber optic technology and surface tension to capture and hold minute amounts of sample for spectroscopic measurements. The new NanoDrop 2000 and 2000c instruments both utilise the sample retention system and can measure micro-volume samples as small as 0.5 µL. The user simply pipets a droplet of sample onto a lower optical pedestal, lowers the lever arm and selects 'measure' in the software. An upper optical pedestal engages the droplet, forming a column of liquid. A xenon flash lamp light source fires through the sample vertically to acquire a full UV-Vis spectrophotometric measurement (190nm-840nm). The distance between optical pedestals determines the path length, which adjusts automatically to shorter distances for samples that are highly concentrated. The ability to change path length in real time affords a large dynamic range of sample concentrations to be measured (2ng/µL to 15,000 ng/µL for dsDNA), essentially removing the need to perform dilutions. Although both the new NanoDrop 2000 and 2000c models offer the pedestal retention measurement system, the 2000c also contains a cuvette measurement compartment for those who prefer traditional cuvette measurements or require specific attributes that cuvette measurements can provide. These include kinetic assays at room temperature or 37 degrees celcius, volatile sample analysis, and cell cultures. The combination of pedestal and cuvette options on the NanoDrop 2000c provide the largest known dynamic range of any spectrophotometer (0.4ng/µL to 15,000 ng/µL for dsDNA).
Q2. The ‘NanoDrop’ spectrophoto-meters have been proven to reduce the variation that occurs between sample readings. What is the reason for this?
Firstly, the automatic, self-adjusting path lengths of the sample retention system are precisely controlled, essentially eliminating the need to perform dilutions. The system removes human error associated with performing dilutions as well as the reliance on the accuracy and calibration of liquid handlers, such as common pipettors. Secondly, the closed circuit of the sample retention system is optically ideal. Traditional systems require the light source to pass through air as well as the wall of the sample container several times before reaching the detector. The NanoDrop retention system couples the sample directly to the optical surfaces, completing a closed loop from the xenon flash lamp to the CCD array detector. This optical efficiency also reduces variation.
Q3. Can you give a brief outline of the different types of applications that the spectrophotometers can be used for?
The NanoDrop 2000 and 2000c can measure any chromophore that absorbs light between 180nm and 840nm. Common biologic chromophores include nucleic acids, such as DNA and RNA, as well as proteins, such as BSA and antibodies. NanoDrop instruments are often integrated into molecular biology workflows including sequencing, microarrays, and quantitative PCR. Often, these instruments are used for quality assessment steps to assess the amount of material acquired post cell extraction as well as determining the proper amount of material in preparation of a specific assay such as PCR.
Q4. What advantages has the ‘NanoDrop’ spectrophotometer used by the researchers given them over the use of a more traditional machine?
The answer is simple: small, easy and fast. The novel design of the NanoDrop 2000 and 2000c models allow scientists unprecedented range of concentration measurements, while using as little as only 0.5µL of material. The system requires no dilutions prior to measurement and preparation for the next sample simply involves cleaning the optical pedestal surfaces with an ordinary lab wipe. The entire process takes less than 5 seconds.
THERMO FISHER SCIENTIFIC
3411 Silverside Rd
Bancroft Building
Wilmington,
DE 19810, USA
Tel.: +1 302-479-7707
www.nanodrop.com
