5 X-Ray Crystallography
Introductory biophysics A. Y. 2016-17 5. X-ray crystallography and its applications to the structural problems of biology Edoardo Milotti Dipartimento di Fisica, Università di Trieste The interatomic distance in a metallic crystal can be roughly estimated as follows. Take, e.g., iron • density: 7.874 g/cm3 • atomic weight: 56 3 • molar volume: VM = 7.1 cm /mole then the interatomic distance is roughly VM d ≈ 3 ≈ 2.2nm N A Edoardo Milotti - Introductory biophysics - A.Y. 2016-17 The atomic lattice can be used a sort of diffraction grating for short-wavelength radiation, about 100 times shorter than visible light which is in the range 400-750 nm. Since hc 2·10−25 J m 1.24 eV µm E = ≈ ≈ γ λ λ λ 1 nm radiation corresponds to about 1 keV photon energy. Edoardo Milotti - Introductory biophysics - A.Y. 2016-17 !"#$%&'$(")* S#%/J&T&U2*#<.%&CKET3&VG$GG./"#%G3&W.%-$/; +(."J&AN&>,%()&CTDB3&S.%)(/3&X.1*&W.%-$/; Y#<.)&V%(Z.&(/&V=;1(21&(/&CTCL&[G#%&=(1&"(12#5.%;&#G&*=.& "(GG%$2*(#/&#G&\8%$;1&<;&2%;1*$)1] 9/(*($));&=.&1*:"(."&H(*=&^_/F*./3&$/"&*=./&H(*=&'$`&V)$/2I&(/& S.%)(/3&H=.%.&=.&=$<()(*$*."&(/&CTBD&H(*=&$&*=.1(1&[a<.% "(.& 9/*.%G.%./Z.%12=.(/:/F./ $/&,)$/,$%$)).)./ V)$**./[?& 7=./&=.&H#%I."&$*&*=.&9/1*(*:*.&#G&7=.#%.*(2$)&V=;1(213&=.$"."& <;&>%/#)"&Q#--.%G.)"3&:/*()&=.&H$1&$,,#(/*."&G:))&,%#G.11#%&$*& *=.&4/(5.%1(*;&#G&0%$/IG:%*&(/&CTCL3&H=./&=.&$)1#&%.2.(5."&=(1& Y#<.)&V%(Z.?& !"#$%"#&'()#**(&8 9/*%#":2*#%;&<(#,=;1(21&8 >?@?&ABCD8CE Arnold Sommerfeld (1868-1951) ... Four of Sommerfeld's doctoral students, Werner Heisenberg, Wolfgang Pauli, Peter Debye, and Hans Bethe went on to win Nobel Prizes, while others, most notably, Walter Heitler, Rudolf Peierls, Karl Bechert, Hermann Brück, Paul Peter Ewald, Eugene Feenberg, Herbert Fröhlich, Erwin Fues, Ernst Guillemin, Helmut Hönl, Ludwig Hopf, Adolf KratZer, Otto Laporte, Wilhelm LenZ, Karl Meissner, Rudolf Seeliger, Ernst C.
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