JUL 12 1965

Twyford Laboratories Limited.

309,Elveden Road,
London, N.W.10.

Elgar 7213 / 4/5.

Ref, TLVU/JFS 7 July 1965

Prof. J. Lederberg

Dept. of Genetics

Stanford University School of Medicine
Palo Alto

California

U.S.A

Dear Professor Lederberg,

I was interested in your recent article in Nature,
"Signs of Life". Some time ago I wrote about the significance
of net optical activity and its possible mode of origin ("The
Optical Asymmetry of Metabolites", in Comparative Biochemistry,
ed. by Florkin and Mason, vol. 4, Academic Press 1962).

Incidentally, it is no longer quite correct to say
that the direct measurement of optical activity is weak by
comparison with other instrumental approaches. This depends on
the compound - whether it has a chromophore adjacent to an asymmetric
centre, and in which spectral region. It is possible to measure
the optical rotatory dispersion of nucleic acid derivatives in the
U.V. region, for example, on a hundredth of the material that would
be required for an I.R. spectrum.

Yours sincerely,
ale Ulhbi wr

TLV. Ulbricht,
Head, Nucleic Acid Unit.