The economic value of the even-toed ungulates of the camelid family known as llamas (pictured) has been principally founded on their use as pack animals and as a source of hide and wool in their native South America. That llama antibodies are suited to measuring levels of caffeine in drinks had been overlooked, an omission now corrected by Ruth C. Ladenson and colleagues (Anal. Chem. doi:10.1021/ac058044j; 2006).
Although caffeine-specific antibodies for use in immunoassays are available commercially, they become irreversibly denatured at high temperatures. But camelids produce certain antibodies that consist exclusively of heat-resistant chains of amino acids. Such antibodies would be ideal for assessing the caffeine content of both hot and cold beverages.
Over a period of ten weeks, the authors immunized five camelids — three llamas and two camels — with caffeine linked to an immune stimulant called keyhole limpet haemocyanin. They subsequently identified and isolated antibody fragments that bind only to caffeine in blood samples from the immunized animals, and produced one of these as a soluble protein.
The chosen antibody preparation retained almost all of its activity after incubation at temperatures up to 90 °C, whereas that of comparable preparations derived from mice dropped away sharply above 70 °C. Swilled through regular and decaffeinated coffee and caffeinated soft drinks, in each case it registered caffeine levels in good agreement with established values.
The authors' next step is to produce a dipstick assay, similar to that used in home pregnancy tests, for point-of-consumption use.