title: Titin: quantitative mass measurements by scanning transmission electron microscopy and structural implications for the sarcomere matrix of skeletal muscle.
abstract: Scanning transmission electron microscopy has been used to investigate mass and linear mass density of native titin-2, a large soluble fragment of intact titin, from rabbit skeletal muscle. Dark field images of unstained, freeze-dried titin-2 appeared as either compact globules or looser and larger balls of string. Direct mass measurements indicated that the compact forms have an average mass of 2.40 +/- 0.50 x 10(6) Da. The mass to length ratio, determined from well-spread portions of titin strands (3-5 nm wide) from the ball of string forms, averaged 2.7 +/- 0.9 kDa/nm. Thus a single native intact titin molecule has a calculated contour length of well above approximately 1 micron, sufficient to span unidirectionally between the Z line and M line region in a resting-length sarcomere.
authors.affiliation: Department of Biology, Brookhaven National Laboratory, Upton, NY 11973.
authors.forename: J F
authors.initials: JF
authors.lastname: Hainfeld
authors.forename: J S
authors.initials: JS
authors.lastname: Wall
authors.forename: K
authors.initials: K
authors.lastname: Wang
mesh_terms: D000818:Animals; D002352:Carrier Proteins; D064211:Connectin; D008565:Membrane Proteins / Q000032:analysis; D008855:Microscopy, Electron, Scanning; D009124:Muscle Proteins / Q000032:analysis*; D009132:Muscles / Q000032:analysis* / Q000648:ultrastructure; D009210:Myofibrils / Q000648:ultrastructure*; D011494:Protein Kinases; D011817:Rabbits; D012518:Sarcomeres / Q000648:ultrastructure*
chemical_list: D002352:Carrier Proteins; D064211:Connectin; D008565:Membrane Proteins; D009124:Muscle Proteins; D011494:Protein Kinases