150 MACROMOLECULAR COMPLEXES 



described by Favard and Carasso (1958), showing the mitochon- 

 drial origin of these paracrvstalhne granules. Further studies will 

 contribute to a better understanding of the functional significance of 

 this type of paracrystalline component in the cytoplasm of the dif- 

 ferent kinds of cells. 



Discussion 



After this survey of representative lamellar structures as revealed 

 by different preparation methods, it may be profitable to discuss the 

 suggested molecular organization of lamellar systems in relation to 

 general concepts of energy transfer processes which are emerging 

 from recent biochemical and biophysical studies. 



Molecular Organization of Lamellar Systems. From a consid- 

 eration of the common structural pattern revealed at the macro- 

 molecular level in the myelin sheath, photoreceptors, mitochondria, 

 cytoplasmic lamellar complexes, and other lamellar systems, the 

 following general picture of their molecular organization is obtained. 

 The highly ordered lipoprotein layers derived from close packing 

 of structurally asymmetric unit cell membranes, permeated with 

 hydration water of possil^le icelike character, serve as a "paracrys- 

 talline" matrix in which assemblies of specific enzymes, associated 

 photopigments, or specialized electron-transfer systems ( Lehninger, 

 1959; Wolken, 1958a; Kropf and Hubbard, 1958; Szent-Gyorgyi, 

 1957) are precisely arranged in regular patterns. 



Of special interest are the recent studies of Calvin and associates 

 ( Calvin, 1958, 1959a, 1959b ) on energy-transfer processes in photo- 

 synthesis. These studies indicate that the initial process of energy 

 reception and transfer is dependent on the specific organization of 

 the chlorophyll and associated pigments in the highlv ordered 

 lamellar systems. Absorption of a light quantum by chlorophvll in 

 the ground state would raise it to its lowest singlet excited state, 

 allowing it to move around among the chlorophvll molecules by 

 resonance transfer. The "exciton," visualized as a charge-pair which 

 cannot move separately, migrates as an electron and "hole" through 

 the oriented array of chlorophyll molecules. The conjugated carot- 

 enoid molecules would act as conductors of electrons, while the 

 lipids in the chloroplasts would function as an insulator permitting 

 a separation of charges when the electrons are "trapped" in suitable 

 places of low potential energy on one side of the layer and the 



