Quantitation of nucleic acids is commonly performed using UV absorbance. Molecular Devices’ μMax Low Volume Microplate allows users to read up to 64 samples per plate on Spectra- Max® Microplate Readers, with sample volumes as low as 2 μL. The μMax Microplate incorporates a specially designed adapter and a slide pair whose optical clarity allows measurements in UV/Vis absorbance and fluorescence modes to meet users’ application needs. The μMax Microplate’s slide design (Figure 1) eliminates the need for calibration and gives consistent well-to-well reads.
Cleaning the µMax Slides
For most sample measurements, simply wiping the slides with disposable lab wipes is sufficient. If minimal background noise is required due to low sample concentration, more careful cleaning is recommended. After cleaning slides with a lint-free wiper, inspect them for dust particles against a dark background. Remove any visible dust using a canned air duster in short, gentle bursts.
DNA Standard Curve
To demonstrate sensitivity of DNA detection with the μMax Low Volume Microplate, DNA standards of known concentrations ranging from 1.9 to 190 ng/μL were pipetted onto the wells (spots) of the μMax Low Volume Plate, along with TE buffer blanks, in sets of three or six replicates using an 8-channel pipettor. Volume per spot was 2 μL using the μMax top slide with 0.5-mm spacers spacers. The μMax plate was read on a SpectraMax M5e microplate reader, and data were analyzed and graphed with SoftMax® Pro 6 Software (Figure 2). The lower limit of detection for doublestranded DNA based on a calculation of three times standard deviation of the background was less than 2 ng/μL.
DNA concentrations can be calculated directly from absorbance readings at 260 nm. This requires use of a pathlength value, which is either 0.5 mm or 1.0 mm for the μMax Low Volume Microplate, depending on which cover slide option is used. In SoftMax® Pro 6 software, preconfigured protocols simplify the calculation of DNA concentrations for samples read with the μMax Low Volume Microplate.
The μMax Low Volume Microplate enables sensitive measurement of small sample volumes without compromising accuracy. Its slides are easy to handle, and all optical surfaces are fully accessible for ease of cleaning. No calibration is required, as the spacer and slide design provide excellent well-to-well uniformity. 24- and 64-well sample slides, as well as cover slides with 0.5- or 1.0-mm spacers, are available to meet users’ throughput and sample volume needs. The μMax Low Volume Microplate is compatible with all SpectraMax Readers including the SpectraMax Paradigm® Platform, as well as the StakMax® Microplate Stacker.
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