Mechano-chemical effects of Ca(2+) in cross-linked troponin-C films

Changes in troponin C (TnC) conformation upon Ca(2+) binding forms the basis for regulatory and structural functions of TnC molecules. In the present study, Ca(2+)-induced conformational changes in TnC were observed by mechanical measurements. TnC films were prepared by drying or electrospraying TnC solutions, cross-linked with glutaraldehyde, and isometric tension and stiffness measured as a function of pCa. An increase in Ca(2+) from a pCa of 9 to 4 induced large-scale mechanical changes in the TnC films causing several percent shrinkage of the unloaded films. This shrinkage could be partially assigned to Ca(2+) binding to the Ca(2+)/Mg(2+) sites of TnC.