Jme 30, I.977

   Dr. A. Klug, ?.R.S,'
   MRC Medical Reetsrnrch Cmlucil
  Laboratory of W~lecular Biology
I   Uaitirsity Pdstgradma EQpsdicsl S&ml

w   Hills &ad, Cm&ridge, CB2 2X@
     Eu&md

  Thank you fur you revi8sd varrsioa caf your paper.  A8 you mnt 5t OlcI
23 June you would not hmm got my lrtter of 20 Ytnw.

n     You will have &ready noted my re#aazb &mat tb bw%an crystals.
  KkZhey 8hould put an ewlfelt reference nt the bq&m%rmg sad alao perhaps
    aear the beginning bf page 6,

  f think you ashmId put
un page 12.'         "abtW? llfh&t~7 both Ln the Surslarar$ snd
      Aho, Yt would 8U~$j~8t"Z'OU~~ly I S/4".  f eee you have not yet
got over your obtreaeiou that these must be +mctly 80 (or perhaps 90)
base-paira per tuta.  The argrmrsat 9uu @ve i8 a good me ta explcrin why
D&tlpls 1 Cut8 at @BXakctly'  Bvery 10th baea but $t does not 8Uj'J$eSt that
the 8uparhelix has to have au exact nmltipla of 10.  1s tmpla% thi8
by eeyiug that your srgtataeurt would ImpSy that the A fom af lS?A had to
be orthorhombic rather than raon~cliuic.  X am mre ym will me the
psrrsllel t  Incidmtally you m&t the argument that ..glm 'kystal forcer"
in the 13; @ona would tend to pruduce an %ntea;raX mmber of ham-pairs
per turs. Yuur argment about 160 baste-pafre being $exactly two turns $8
al80 Vetp f4WbbB,  Why shotid exactly f?rea, tUrc18 be needed to pmduce a
pause?

  I had not Prpprecfated from 9clu~ aarSier draft (dthough it is
obvioue emmgh) that 9ou gut the Oiw for ths prtBjectiOu8 (and thi "aw
project%on ia particular) frma thus 8igus af ar#m pictures af 8 ahruukerq
crystal.  With a shrinltaga of 10 to 20%, this could giua ycru false
signs far the Ugher order reflectious.  Strictly you need to kmw how

continued . . . . . . e .


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