34.3% of the 5 "Mn, 5.6% of the 65 Zn, and 1.3% of the 109 Cd had been incor- 

 porated into mineral concretions present in kidney cells. Gel permeation 

 chromatography of renal cytosol fractions showed the isotopes to be bound to 

 macromolecules with molecular weight of approximately 60,000, 12,000, and 

 7,500. - J.L.M. 



2091 



Chandler, R. A. 1965. 



Shoal-water relaying of ocean quahogs before canning. Fish. Res. Bd. Canada, 

 Manuscript report, Atl . Biol. Sta. 1017, 11 p. 



Fisheries Research Board could not locate. Search terminated. - J.L.M. 



2092 



Chantler, Peter D., and Andrew G. Szent-Gyorgyi . 1978. 



Spectroscopic studies on invertebrate myosins and light chains. Biochem- 

 istry 17(25): 5440-5448. 



Myosin was isolated from 14 invertebrate muscles, including Mereenaria mer- 

 cenavia, all of which exhibited myosin-linked regulation: 9 of these muscles 

 solely exhibited this form of regulation. None of these myosins showed any 

 change in tryptophan (Trp) or tyrosine (Tyr) fluorescence upon addition of 

 Ca 2+ in the presence or absence of MgATP, and all myosins showed either a 

 small or zero Trp fluorescence change upon addition of MgATP in the presence 

 or absence of calcium. Thus a conf ormationally sensitive Trp, such as that 

 present in rabbit myosin, is not a necessary requirement for the myosin 

 ATPase. Several light chains were modified with the fluorophore N-iodoacetyl- 

 N ' - (l-sulfo-5-naphthyl) ethylenediamine and each modified light chain was 

 added back to 0°C-desensitized scallop myosin, and the fluorescence and fluo- 

 rescence polarization were examined. No change in these parameters occurred 

 upon addition of MgATP and/or calcium. Circular dichroism (CD) spectra of 

 scallop myosin and desensitized scallop myosin showed no change upon addition 

 of MgATP and/or calcium. Similarly, no change was observed in the electron 

 spin resonance spectra of scallop myosin or myofibrils using 0°C-desensitized 

 preparations that had been resensitized with spin-label-modified light chains. 

 CD studies on isolated regulatory light chains reveal a low affinity divalent- 

 cation-dependent transition [for the scallop regulatory light chain, pK=3 

 7±0.1(Ca 2+ ); 3 . 1+0 . 1 (Mg 2+ ) ] monitored at 220 nm, while an analogous change 

 in the rabbit 5, 5 ' -dithiobis (2-nitrobenzoic acid) light chain has a pK of 

 5.1+0.2. These results are discussed in light of the fact that the above 

 techniques indicate large conformational changes when applied to other 

 calcium-binding proteins such as troponin C and parvalbumin. It is concluded 

 that the calcium switch in regulatory myosins is of a more subtle nature. 

 - modified authors' abstract - J.L.M. 



2093 



Chantler, P. D., and A. G. Szent-Gyorgyi. 1978. 



Reversible dissociation of both regulatory light chains from scallop. 

 Biophys. J. 21, Muscle proteins II: 45a (abstract M-PM-E9). 



EDTA treatment at 30 °C removes both regulatory light chains completely from 

 Plaeopecten magellanicus (>90%) and extensively (>75%) from Aequipecten 

 irradians . Myofibrils free of regulatory light chains fully retain their 

 K+-EDTA and Ca ++ -activated ATPase (lOmM CaCl 2 ). Their actin activated 

 ATPase has no calcium sensitivity and the activity in the presence of . ImM 

 CaCl 2 is reduced by about 60%. Regulatory light chains readily rebind in 

 stoichiometric amounts and restore the actin activated ATPase and the Ca 

 sensitivity. Ca binding is proportional to light chain content. Regulatory 

 light chains of Mercenaria meroenaria can fully substitute for scallop light 

 chains. - J.L.M. 



581 



