title: Cross-helix separation of tropomyosin molecules in acto-tropomyosin as determined by neutron scattering.
abstract: The cross-helix separation of Tm molecules in acto-tropomyosin has been determined using neutron scattering. Deuterated Dictyostelium discoideum actin was density matched in a 93% D2O buffer so that effectively only the protonated tropomyosin was "visible" to neutrons. Analysis of the solution scattering pattern in the region of the first oscillation yielded a value for the cross-helix separation of 7.9 +/- 0.3 nm. The implications of this value for the mechanism of the regulation of muscle contraction are discussed in light of recent results by others.
authors.affiliation: Cardiovascular Research Institute, University of California, San Francisco 94143.
authors.forename: D B
authors.initials: DB
authors.lastname: Bivin
authors.forename: D B
authors.initials: DB
authors.lastname: Stone
authors.forename: D K
authors.initials: DK
authors.lastname: Schneider
authors.forename: R A
authors.initials: RA
authors.lastname: Mendelson
mesh_terms: D000199:Actins / Q000302:isolation & purification / Q000502:physiology*; D000818:Animals; D004023:Dictyostelium / Q000502:physiology; D007700:Kinetics; D009132:Muscles / Q000502:physiology; D015879:Myosin Subfragments / Q000378:metabolism; D009218:Myosins / Q000378:metabolism; D009502:Neutrons; D011487:Protein Conformation; D011817:Rabbits; D012542:Scattering, Radiation; D014335:Tropomyosin / Q000302:isolation & purification / Q000502:physiology*
chemical_list: D000199:Actins; D015879:Myosin Subfragments; D014335:Tropomyosin; D009218:Myosins