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Correspondence
| Alexander L Dounce to LP, LP's reply. March 18, 1953. |
Alexander L Dounce to LP - Page 02
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Author: Linus Pauling
Alexander L Dounce to LP - Page 02
| Title: |
Alexander L. Dounce's correspondence to Linus Pauling [2 of 2] |
| Alternative Title: |
Alexander L. Dounce's correspondence to Linus Pauling, March 18, 1953 |
| Creator: |
Dounce, Alexander L. |
| Publisher: |
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| Date: |
1953-03-18 |
| Subject: |
Dounce, Alexander L. -- Correspondence
Nucleic acids -- Structure
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| Description: |
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| Type: |
Text |
| Format: |
text/plain |
| Language: |
en |
| Identifier: |
dounce01-pg02.jpg |
| Source: |
Master file format: TIFF, 600 dpi, Epson GT-10000+ flatbed scanner. |
| Rights: |
http://osulibrary.oregonstate.edu/specialcollections/coll/pauling/dna/copyright.html |
| Full Text: |
No. 2 How is the evidence for the cross-sectional area of the DNA molecule? Astbury makes a rough calculation of cross-sectional
area based on estimates of dimensions of a nucleotide molecule (15 x 7.5 A) = 112.5 A(2). As far as I can see this assumes
a ribbonlike molecule with or without coiling. It this value of Astbury for area is divided into 338 A(3), your figure for
the volume per nucleotide, obtained from the average residue molecular weight and the density, we obtained at figure out about
3.0 A which is somewhere near the distance along the fiber links occupied by a repeating unit (3.4 A) as calculated from the
x-ray measurements. This would indicate as I understand it that he observes they seem probably corresponds to the distance
between nucleotides and a single chain. On the other hand if we use your figure for area, obtained I presume from an assumed
circular cross-section with radius of about 10 A, we get for the distance occupied by a nucleotide residue along the fiber
axis of value of about 1.12 A which is only about a third of the observed spacing (3.4 A). For this reason, I take it, you
feel that there have to be free nucleotide residue spur distance of 3.4 A long the chain, and therefore construct the model
with three intertwined chains. Hence the crux of the matter seems to be to get an accurate estimate of the cross-sectional
area, S3 is possible from assumptions, and that is why I am asking questions No. 2.
No. 3 regardless of the mechanisms propose for nucleic acid synthesis, it seems likely to enzymes must be involved. Although
this question obviously cannot be answered with a certainty, I wonder whether difficulties will not arise in allowing access
of synthetic enzymes to a close tax structure of three interwoven helixes such as you propose. The same question might be
a state regarding enzymes of depolymerization which cause rupture of inter-nucleotide linkage is enhanced must presumably
form complexes with groups very close to the phosphate groups. Incidentally, which are structure predict the products of
DNA-ase action as well as a single chain or helix?
No. 4 how much change is likely to occur in structure on liberating nucleic acids from the proteins to which they abound,
presumably through purines and pyrimidines, in the natural state?
I'm enclosing, I might state that I'm not trained and advanced physical chemistry or physics, and might therefore not appreciate
all the basis for your model, but I would enjoy hearing from you regarding the questions even if only briefly. I would also
appreciate having any comments which he might have regarding my hypothetical duplicate mechanism, if you feel that it is worthy
of comment. Sincerely yours, Alexander L.. Dounce
P.S. I should appreciate reprint of your article (referred to in the letter), any reprints which you might be able to spare
on peptide chain structure and hemoglobin chemistry.
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