Indian Microwave Recipes

by Harald Zähringer Labtimes 02/2015

Cooking food in a microwave oven is fast and convenient. The same holds true for microwave-assisted molecular biology reactions, such as enzymatic modifications of nucleic acids. Fioto: Harvard Medical School

Microwaves are mostly applied by life science researchers to melt agarose or to heat food in lunchboxes. They may, however, also be exploited to accelerate the enzymatic modifications of nucleic acids.

Microwave energy is not only used in kitchens to heat food but also in the laboratory for chemical syntheses. The oscillating electric field of microwaves interacts with dipolar molecules and/or ions, and induces molecular rotations, which are rapidly converted into heat. Many materials, such as the plastics of lunchboxes or the walls of reaction vessels and tubes are transparent to microwaves and are not heated.

Despite the obvious advantages of microwave-assisted reactions, applications in life science labs, other than heating agarose or someone’s meal, are still pretty rare. But the interest in microwave-assisted life science reactions may be sparked by a recent publication from Pradip Nahar’s group at the CSIR-Institute of Genomics and Integrative Biology in Delhi, India (Hari Das et al, Anal. Biochem., 471, 26-8).

Seconds instead of hours

The Indian group delivers a simple protocol for microwave-induced cleavage, ligation, dephosphorylation and phosphorylation of nucleic acids that reduces the reaction times to 20 to 50 seconds. The method is as simple as it can get. Nahar’s group performed the enzymatic reactions in a domestic microwave oven, operating at a ­frequency of 2450 MHz with a maximum output power of approximately 700W. Reaction tubes containing the necessary enzymes and buffers were placed in the middle of the rotating micro-oven disc and irradiated for 20 to 50 seconds. To prevent lids from bursting open, due to an increased pressure during microwave-heating, the group perforated the caps with a syringe before the experiments. They stopped the reactions of restriction enzymes by heating at 65 °C for five minutes and terminated dephosphorylation reactions by the addition of 2 µl of 0.5 mM EDTA (pH 8.0), followed by incubation at 75 °C for 15 minutes.

No additional costs

The microwave-assisted cleavage reactions were verified by ligation of the DNA fragments with microwave-irradiated T4 ligase, which was completed after 20 seconds. Needless to say, the control reactions carried out at room temperature for the same reaction times showed no products at all.

Bottom-line: microwave-mediated DNA modification may save a lot of time without additional expenses.

Last Changed: 25.03.2015