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Damped elastic recoil of the titin spring in myofibrils of human myocardium

Research output: Contribution to journalArticle

Published copy (DOI)


  • Christiane A Opitz
  • Michael Kulke
  • Mark C Leake
  • Ciprian Neagoe
  • Horst Hinssen
  • Roger J Hajjar
  • Wolfgang A Linke


Publication details

JournalProceedings of the National Academy of Sciences of the United States of America
DatePublished - 28 Oct 2003
Issue number22
Number of pages6
Pages (from-to)12688-93
Original languageEnglish


The giant protein titin functions as a molecular spring in muscle and is responsible for most of the passive tension of myocardium. Because the titin spring is extended during diastolic stretch, it will recoil elastically during systole and potentially may influence the overall shortening behavior of cardiac muscle. Here, titin elastic recoil was quantified in single human heart myofibrils by using a high-speed charge-coupled device-line camera and a nanonewtonrange force sensor. Application of a slack-test protocol revealed that the passive shortening velocity (Vp) of nonactivated cardiomyofibrils depends on: (i) initial sarcomere length, (ii) release-step amplitude, and (iii) temperature. Selective digestion of titin, with low doses of trypsin, decelerated myofibrillar passive recoil and eventually stopped it. Selective extraction of actin filaments with a Ca2+-independent gelsolin fragment greatly reduced the dependency of Vp on release-step size and temperature. These results are explained by the presence of viscous forces opposing myofibrillar passive recoil that are caused mainly by weak actin-titin interactions. Thus, Vp is determined by two distinct factors: titin elastic recoil and internal viscous drag forces. The recoil could be modeled as that of a damped entropic spring consisting of independent worm-like chains. The functional importance of myofibrillar elastic recoil was addressed by comparing instantaneous Vp to unloaded shortening velocity, which was measured in demembranated, fully Ca2+-activated, human cardiac fibers. Titin-driven passive recoil was much faster than active unloaded shortening velocity in early phases of isotonic contraction. Damped myofibrillar elastic recoil could help accelerate active contraction speed of human myocardium during early systolic shortening.

    Research areas

  • Actins, Calmodulin-Binding Proteins, Connectin, Elasticity, Heart, Humans, Muscle Proteins, Myofibrils, Myosins, Protein Kinases, Sarcomeres, Thermodynamics

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