title: Maximal force characteristics of the Ca(2+)-powered actuator of Vorticella convallaria.
abstract: The millisecond stalk contraction of the sessile ciliate Vorticella convallaria is powered by energy from Ca(2+) binding to generate contractile forces of ∼10 nN. Its contractile organelle, the spasmoneme, generates higher contractile force under increased stall resistances. By applying viscous drag force to contracting V. convallaria in a microfluidic channel, we observed that the mechanical force and work of the spasmoneme depended on the stalk length, i.e., the maximum tension (150-350 nN) and work linearly depended on the stalk length (∼2.5 nN and ∼30 fJ per 1 μm of the stalk). This stalk-length dependency suggests that motor units of the spasmoneme may be organized in such a way that the mechanical force and work of each unit cumulate in series along the spasmoneme.
authors.affiliation: Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
authors.forename: Sangjin
authors.initials: S
authors.lastname: Ryu
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Lang
authors.forename: Paul
authors.initials: P
authors.lastname: Matsudaira
mesh_terms: D001696:Biomechanical Phenomena; D002118:Calcium / Q000378:metabolism*; D055595:Mechanical Phenomena; D046210:Microfluidic Analytical Techniques; D016802:Oligohymenophorea / Q000166:cytology / Q000378:metabolism*; D013314:Stress, Mechanical; D014783:Viscosity
chemical_list: D002118:Calcium