The NanoDrop ND-8000 8-sample Spectrophotometer is a high throughput, full-spectrum (220-750 nm) spectrophotometer that can measure 8 individual 1 µl samples with high accuracy and reproducibility. It utilizes the same patented sample retention technology as the NanoDrop ND-1000 spectrophotometer
and the NanoDrop ND-3300 fluorospectrometer
. One to eight 1 µl samples can be guided by the ‘pipettor guide’ and pipetted onto the lower pedestals. Each lower pedestal is actually the end of a fiber optic cable (receiving fiber). A second set of fiber optic cables (source fibers) from the upper pedestals are then brought into contact with the samples by gently compressing the sampling arm. This causes the liquid to bridge the gaps between the fiber optic ends for spectrum measurement. The pathlengths are automatically controlled to 1 mm and 0.2 mm paths and readings are acquired through sequential measurement across the 8 positions (marked A and H on each end). A pulsed xenon flash lamp provides the light source and a spectrometer utilizing a linear CCD array is used to analyze the light that passes through the samples. The instrument is connected to a PC by a USB cable to perform the measurement as well as archiving the data to print as reports. The ND-8000 v1.0.2 software is compatible with Windows 2000, XP (32 bit), or Vista but not with Windows 98, ME, or XP (64 bit).
The NanoDropND-8000 has many application modules:
A) Nucleic acid – this module can measure 2.5-3,700 ng/µl of dsDNA, 2.5-2,400 ng/µl of ssDNA, and 2.5-3,000 ng/µl of RNA. The concentrations (in ng/µl), the absorbance values of 230 nm, 260 nm, and 280 nm, and the ratios of 260/280 and 260/230 are automatically calculated by the software.
B) Microarray – this module accurately measures fluorescent-dye concentrations in fluorescent-tagged hybridization probes for gene expression in microarray assays. Sample types include Cy3, Cy3.5, Alexa Fluor 555 and Alexa Fluor 660 (0.25-100 pmol/µl), Cy5, Cy5.5 and Alexa Fluor 647 (0.17-60 pmol/µl), Alexa Fluor 488 and Alexa Fluor 594 (0.5-215 pmol/µl), and Alexa Fluor 546 (0.42-145 pmol/µl).
C) UV-Vis – the ‘UV/VIS Absorbance’ module allows this instrument to function as a conventional spectrophotometer. Sample absorbance is displayed on the screen from 220 nm to 750 nm and cursors permit the measurement of individual peaks. Users can select to normalize the spectrum based on the lowest absorbance value in the range of 400 to 700 nm.
D) Cell culture – the shorter pathlength (1 mm vs. 1 cm) in the NanoDrop ND-8000 (as compared with a standard cuvette) can measure absorbencies that are 10-fold higher in microbial cultures. Since the entire spectrum (250 to 700 nm) is displayed, diluted samples exhibiting very low absorbance at 600 nm can be monitored at lower wavelengths (e.g. 300 nm).
E) Protein A280 – this module displays the UV spectrum, measures the protein absorbance at 280 nm and calculates the concentration (mg/ml) automatically, ranging from 0.15-100 mg/ml (for BSA). Users can choose between BSA, IgG, lysozyme, or three other options (user selected) as a reference to obtain the mass extinction coefficient.
F) Proteins & labels – this module can be used to determine the protein concentration (A280nm), fluorescent dye concentration for protein array conjugates, and the purity of metalloproteins such as hemoglobin using wavelength ratios. The detection limit is 0.15-20 mg/ml for purified BSA and 0.25-100 µM for Cy3.
G) BCA, Bradford, and Lowry – this instrument can also measure protein concentrations from these alternative protein assays using a standard curve.
Sample data from all application modules is automatically stored in archive files and can be opened by either the integrated Data Viewer software program or spreadsheet programs such as Microsoft Excel.
In our laboratory, we usually use the NanoDrop 8000 to measure mouse tail DNA and purified plasmid DNA for transgenic purposes. Since we receive most of our DNA from clients, the volume and concentration can vary significantly and it is important that we use the smallest sample volume for measurement. The ND-8000 serves our purposes well as it needs only 1 µl of sample, without any dilution, for measuring a range of 2-3700 ng/µl DNA. The higher throughput of measuring 8 samples simultaneously saves us critical work time when we receive a large batch of samples. We can measure a full plate of 96-well samples in less than 15 minutes.
Compared with the NanoDrop ND-1000, with which I have had experience, the NanoDrop ND-8000 is a higher throughput instrument that can also allow the user to upload a plate file containing sample IDs from a .txt file. In addition, bar-coded samples can be entered by scanning into the text file. The data reports are more concise, but without losing any important information. In short, the NanoDrop ND-8000 is a compact, user-friendly spectrophotometer that provides us with very fast and yet accurate measurements.