542 



Wilhelm Menke 



horizontally. The X-ray had a quadratic cross -section. Curve 6a repro- 

 duces the scattering in the meridian, while curve b corresponds to the equa- 

 torial scattering. (The preparation was oriented vertically for photograph b. ) 

 The curve was multiplied by m (m/^/'»5 ; I = intensity) in order to eliminate 

 the leaflet factor. Curve c was obtained by subtraction of curve b from curve 

 a. It indicates the scattering caused by the stacking of thylakoids. 



The scattering curve 6c is to be decomposed into a form factor and a lat- 

 tice factor. The form factor corresponds to the scattering of the individual 

 thylakoid and is therefore calledthylakoid function here. The lattice factor 

 takes into account the stacking of the thylakoids. In the present case the task 

 is that of finding the thylakoid function. Since the lattice factor has a con- 

 stant value in the maxima of the scattering curve, the intensities of the scat- 

 tering curve at these maxima is determined by the thylakoid function, there- 

 fore the maxima of the scattering curve are points of the thylakoid function. 

 Fig. 8a shows the model, the scattering curve of which most closely approxi- 

 mates the thylakoid function. Fig. 8b shows the amplitude function of this 



-K-SO'tC-X K tc eo K 4 



Fig. 8. b^ -Theoretical amplitude function of the model a. 



O- • -OValues taken from the experimental scattering 



curve. 

 c Distribution of electron density parallel to the 



surface normal of the thylakoid (Fourier- 

 analysis) (p (r) in relative units. 



model. The values taken from the experimental scattering curve have been 

 drawn in for comparison, choosing the signs according to the nnodel. On the 

 basis of this approximate amplitude function it was possible to compute the 

 distribution of electron density (^(r) parallel to the surface normal of the 

 thylakoid. The unidimensional Fourier -analysis gives the distribution of 

 electron density shown in Fig. 8c. Quantitative estimation of the electron 

 densities of the components participating in the building up of the thylakoids 

 leads to the result that the two outer zones of maximum electron density cor- 

 respond to the protein layers, which therefore^^orm the external boundary of 

 the thylakoid. Their thickness amounts to 47 A each and thus agrees with the 

 value obtained formerly. This conformity is all the more remarkable be- 

 cause the thickness of the protein layer had previously been connputed under 

 the assumption of a continuous layer. A thigkness of 42 A each results for 

 the lipid films. The whole thylakoid is 178 A in thickness. 



