Ca(2+)-responsive extensible monolayer membrane of calmodulin-albumin conjugate

A Ca(2+)-responsive monolayer protein membrane was prepared by developing calmodulin and bovine serum albumin at the air-water interface and by conjugating them with a bifunctional agent. In the case of the BSA monolayer, complex formation with Mg2+ generated a larger change in surface pressure than that with Ca2+. On the other hand, a drastic change in surface pressure was observed for the conjugated thin membrane associated with Ca2+ than that associated with Mg2+. Due to a drastic change in the conformation of calmodulin, the conjugated protein film changes its morphology (STM image), depending on Ca2+ concentration: the extended structure in the presence of Ca2+ transforms to a shrinked structure in the absence of Ca2+. The largest surface pressure change was detected when calmodulin was mixed with an equimolar amount of bovine serum albumin.