Israeli scientists have built a computer that uses enzymes to perform calculations. Itamar Willner, who built the molecular computing unit together with his colleagues, believes that such systems could one day be implanted in a human body in order to administer medication in a targeted manner, tailored to the patient’s metabolism. To develop the ‘computer’, the team used two enzymes: ‘glucose dehydrogenase’ (GDH) and ‘horseradish peroxidase’ (HRP) to trigger two chemical reactions. The experiment was performed with hydrogen peroxide and glucose, with the presence of each of these elements representing a binary one and the absence of one element representing a binary zero. With the help of the molecules it was possible to perform two fundamental calculations, more precisely the AND and XOR calculations. By then adding two additional enzymes – ‘glucose oxidase’ and ‘catalase’ – the scientists were able to connect the calculations and create logical functions with binary numbers.