VOL. 4 (1950) MYOSIN, ATP, AND MUSCLE CONTRACTION 49 



of groups can react together a second time, they must have been put back into their 

 original state by means of free energy provided by reaction with ATP, we see that ATP 

 breakdown could begin within the contraction phase, even though it were associated 

 with restoration of the chains. 



A. V. HiLL^s has shown that the relaxation phase of a twitch is free from heat, if 

 the work done is not allowed to degenerate into heat. During this period, on the view 

 under discussion, ATP breakdown would be continuing the process of separating the 

 reactive groups, a process leading now to the lengthening of the fibril. Since no heat 

 is associated with the relaxation phase, this process would seem to be 100% efficient, 

 and the waste heat associated with the contraction phase would appear to be due to 

 the primary reaction along the protein chains. As we have seen, the anaerobic recovery 

 process (immediately following an anaerobic contraction) is knov/n to go on with very 

 little heat wastage; it is not unhkely that there is a similar efficiency in the relaxation 

 process. A mechanism suggested for the transfer of energy (Kalckar^*^; Dainty et al.) is 

 the transfer of phosphate from ATP to the protein chains ; this still remains a possibility, 

 (see F. BuCHTHAL et al.^^). 



The Veykiirzungsort still retains its mystery but we begin perhaps to see in what 

 direction solution lies. 



I am indebted to Dr K. Bailey and Professor W. T. Astbury for the benefit of 

 discussion with them. 



REFERENCES 



1 A. V. Hill, Nature, 163 (1949) 320. 



2 H. Kalckar, /. Biol. Chem., 167 (1947) 445. 



3 M. N. LiuBiMOVA AND W. A. E. Engelhardt, Biochimia, 4 (1939) 716. 

 ■* K. Bailey, Biochem. J., 36 (1942) 121. 



* G. D. Greville and H. Lehmann, Nature, 152 (1943) 81. 



^ W. F. H. M. Mommaerts and K. Seraidarian, /. Gen. Physiol., 30 (1947) 401. 

 ^ W. W. Keilley and O. Meierhof, /. Biol. Chem., 176 (1948) 591. 



* A. Szent-Gyorgyi, Muscle Contraction, New York 1947. 



* W. C. Schneider, /. Biol. Chem., 165 (1946) 585. 



1° J. Needham, S.-C. Shen, D. M. Needham, and A. S. C. Lawrence, Nature, 147 (1941) 766- 



" i. Banga, T. Erdos, M. Gerendas, W. F. H. M. Mommaerts, F. B. Straub, and A. Szent- 



Gyorgyi, Studies Inst. Med. Chem. Szeged, i (1941) 42. 

 12 F. B. Straub, Studies Inst. Med. Chem. Univ. Szeged, 2 (1942) 3. 

 1^ W. J. Jordan and G. Oster, Science, 108 (1948) 188. 

 1^ K. Bailey and S. V. Perry, Biochim. Biophys. Acta, i (1947) 506. 

 15 M. Dainty, A. Kleinzeller, A. S. C. Lawrence, M. Miall, J. Needham, D. M. Needham, and 



S. Shen, /. Gen. Physiol., 27 (1944) 355- 

 1" M. F. Morales, Biochim. Biophys. Acta, 2 (1948) 618. 

 •^ W. A. Engelhardt, Advances in Enzymology, 6 (1946) 147. 

 '** F. Buchthal, a. Deutsch, G. G. Knappeis, and A.Petersen, Acta Physiol. Scand., 13 (1947) 167. 



19 S. V. Perry, R. Reed, W. T. Astbury, and L. C. Spark, Biochim. Biophys. Acta, 2 (1948) 674. 



20 F. Buchthal, G. G. Knappeis, and J. Lindhard, Skand. Arch. Physiol., 73 (1936) 162. 



21 C. E. Hall, M. A. Jakus, and F. O. Schmitt, Biol. Bull. Woods Hole, 90 (1946) 32. 



22 E. W. Dempsey, G. B. Wislocki, and M. Singer, Anat. Record, 96 (1946) 221. 

 2^ A. G. Matoltsy and M. Gerendas, Hung. Acta. Physiol., 1 (1947) 116. 



2* R. Caspersson and B. Thorell, Acta Physiol. Skand., 4 (1943) 97- 



25 R. Barer, Biol. Revs, 23 (1948) 159. 



-* G. H. Scott and D. M. Packer, Anat. Record, 74 (1939) 31. 



" C. C. Speidel, Am. J. Anat., 65 (1939) 471. 



28 A. V. Hill, Proc. Roy. Soc. Lond. Ser. B., 136 (1949) I95- 



29 A. V. Hill, /. Physiol., 107 (1948) 29 P. 



^° F. Buchthal, A. Deutsch, G. G. Knappeis, and A. Munch-Petersen, Acta Physiol. Skand. 

 16 (1948) 326. 



Received April 12th, 1949 



