DONT. CROMER
1388
large number of resonance structures present in proteins (structures such as N...c:..o~o) 3 and has been demonstrated by Setlow and Doyle30 who found that an enzyme which is complexed with its substrate and irradiated in the dry state has a target volume equal to the sum of the molecular volumes. Shore and PardeeZ7 have measured the fluorescence efficiencies of dyes bound to proteins, where the initial quantum was absorbed in the protein; and Szent-GyorgyP has presented an extremely interesting discussion of the possible role of water (actually ice) in facilitating energy transport by mediating the formation of triplet states. According t o our hypothesis, large film pressures should maintain the molecular configuration, even after the rupture of the second S S bond, for a sufficient time t o allow the broken bonds associated (29) L. Pauling, R.Corey and H. Branson, Proc. Natl. Acad. Sci., 87, 205 (1951). (30) R. Betlow and B. Doyle, Rad. Reaearch, 2, 15 (1955).
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with the weak-link to reconstitute in a large percentage of the cases and thim reduce the level of inactivation produced by irradiation. Similarly, very low film pressures should offer little or no maintenance of structure and therefore should not modify the radiation effect. I n agreement with this, irradiation a t large surface concentrations and thus large film pressure does seem to produce a lower quantum yield, about 0.01, than the corresponding values, 0.0174.031, reported for irradiations in solution and the dry statemlabRecognizing the limitations of the data, one might say that a high film pressure is "3 effective in reversal of inactivation or else inactivation has a 1:3 chance of proceeding by some as yet unpostulated mechanism. Thus, the hypothesis predicts correctly the direction in which the radiosensitivity changes in films with large surface concentrations; however, it does not account for the change observed in the shape of the dose-response curves a t low surface concentrations (see Fig. 4 of ref. 18b).
THE CRYSTAL STRUCTURE OF KCu(CN)z1 BY DONT. CROMER University of Calijornia, Los Alamos Scientific Laboratory, Los Alamos, New Mexko Received March 6, 1967
KCU(UN)~ is monoclinic, space group P2,/c(C;,) with four formula units per unit cell. The cell constants are a = 7.57, The trial structure was deduced from a three-dimensional Patterson followed by a three-dimensional Fourier synthesis. This structure was refined by the least-squares method. All computations were made on the Maniac. The analogous silver and gold com ounds have discrete linear complex ions formed by sp hybridization of the metal. The copper compound has an entirely lifferent structure. The complex ions form spiral polymer chains of composition [Cu CN)2-] The twofold screw axes pass through t,he centers of the chains. The chains are held to ether by the K + ions. $he Cu atom has assumed a threefold hybridized state, probably a distorted sp2 hybrid. The Cu(8N)eunits are held together by a Cu-N bond of 2.05 f 0.02 b. One CN group forms this bond while the other CK group protrudeR from the chain. Good evidence is presented for making a distinction between the C and N atoms. The two Cu-C bond lengths are 1.92 f 0.02 b. The C-N bonds are 1.15 f 0.03 and 1.13 A 0.03 A. The C-Cu-C angle is 134.2 f 0.9".
b = 7.82, c = 7.45 A. and p = 102.2'.
-.
structure of KCu(CN)2 has been determined. Introduction Compounds of the type KM(CN)z are formed by This structure has proved t o be entirely different all of the Group I-B elements. The structure of from those of the analogous silver and gold comKAg(CN)Z was determined "by Hoard2 in 1932. pounds. Experimental I n this compound, which crystallizes in the hexThe crystals of KCu( CN), used in this investigation were agonal system, the complex ion [NCAgCNI- is linear. Although the analogous gold compound, prepared by R. A. Penneman, of this Laboratory. The of preparation of these crystals has been given by KCU(CN)~,crystallizes in the rhombohedral sys- method Staritzky and Walker4 who also give the space group and tem, the two structures are very similaraa The cell size. They find that I
