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I was popped this questions today, "what is a glycerinated muscle fiber, and what is required for its contraction," and had little idea. I'm assuming the question is "what's required for its contraction as compared to normal muscle tissue?"

There's a limited amount of information out there about this. It appears that it is a type of in vitro system requiring special preparation of typical muscle tissue. I was wondering if anyone here had a little more information. Is this something that's just used in teaching lab exercises?

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From: http://www.acad.carleton.edu/curricular/BIOL/classes/bio126/Documents/Lab_5.pdf

Glycerination disrupts the membranes of the muscle cells, ruptures mitochondria, and leaches out soluble constituents such as ATP and inorganic ions. However, glycerinated muscle retains the organized structural array of myosin thick filaments and actin thin filaments, actin-associated proteins like troponin and tropomyosin which regulate contraction, and the functional capacity for contraction.

I would expect that because the sample has lost ATP and inorganic ions, you would need to supply ATP (the source of energy), $Mg^{2+}$ (which is necessary for ATP hydrolysis) and $Ca^{2+}$ (to induce the contraction).

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  • $\begingroup$ this is the answer I was looking for. You may want to double check info the Mg2+ though, I know free mg+ will inhibit hydrolysis, while calcium alone can act as a cofactor. Your right though mg will help nucleophillic attack I just think Ca is ok alone, this is one of the reasons why the cell prefers the sarcoplasmic reticulum is quenched with ca2+. $\endgroup$ – rhill45 Oct 19 '14 at 6:21
  • $\begingroup$ I included the bit about magnesium based on the protocol linked to in the answer. Here is an article discussing myosin catalysed ATP hydrolysis which includes magnesium in the reaction mechanism (pubs.acs.org/doi/abs/10.1021/bi052433q). However, I have also found articles describing how magnesium inhibits myosin, so I don't know. $\endgroup$ – canadianer Oct 19 '14 at 8:31
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Calcium ions aren't needed (like normal muscle cells), because the glycerination process disrupts the troponin-tropomyosin complex so that the binding sites on the actin are exposed. However, glycerol makes the membrane permeable to small molecules, including ATP. That means that a glycerinated muscle requires addition of ATP so that the myosin heads can actually bind to the binding sites and create cross-bridges.

Magnesium ions aren't required, but they act as catalysts that help the muscle contract more.

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