- Check from AHP to Pearl M. Jordan for $26.52. [Filed under LP Biographical: (Business and Financial: Bank Statements and Canceled Checks, December 1954-February 1956), Box #4.023, Folder #23.1]
- Letter from A. Rahman, Director, Central Laboratories for Scientific and Industrial Research, India, to LP RE: Encloses a reprint of an article by this laboratory on "X-ray Studies of Some Indian Clays." Requests LP's comments. [Letter from LP to Rahman July 29, 1955] [Filed under LP Correspondence: (R: Correspondence, 1955-1959), #341.1]
- Letter from Beatrice Wulf, Secretary to LP, to Dr. Th. Foerster, c/o Professor D. S. McClure, University of California at Berkeley, RE: A reservation has been made for Dr. and Mrs. Foerster for a few days beginning July 25. If there is any change in Foerster's plans, requests that he let them know. [Letter from Foerster to LP May 28, 1955] [Filed under LP Correspondence: (F: Correspondence, 1935-1956), #128.20]
- Letter from LP to Dr. Kenneth J. Palmer, Western Utilization Research Branch, Agricultural Research Service, RE: Thanks Palmer for sending back the reprint by Albrecht and Corey and for telling LP about his conclusion concerning the interpretation of the nuclear resonance results. Agrees with Palmer on this. Suggests that Palmer consider a further investigation of lysozyme. Describes the details of his suggested investigation. [Letter from Palmer to LP July 5, 1955] [Filed under LP Correspondence: (P: Individual Correspondence. (Pais - Perry)), #304.3]
- Letter from LP to Lord Bertrand Russell RE: Harold Urey has sent LP a copy of the statement that Russell prepared, to be signed by people from various countries. Completely agrees with the statement and would be pleased to sign it. 3 copies of letter. [Letter from Russell to LP July 24, 1955] [Filed under LP Correspondence: (Russell, Bertrand, 1955-1967), #337.1]
- Letter from LP to Professor H.C. Longuet-Higgins, Chemical Laboratory, University of Cambridge. [Letter from Longuet-Higgins to LP August 8, 1955] [Filed under LP Correspondence: (L: Individual Correspondence. (Longuet-Higgins - LuValle)), #218.1]
11 July 1955
Professor H. C. Longuet-Higgins
The Chemical Laboratory
University of Cambridge
I have read with interest your paper by Roberts, in the last issue of the Proceedings of the Royal Society, on the electronic structure of an icosahedron of boron atoms. I am in general pleased with your results, but there is one point that I should like to discuss with you. Some years ago I began work along similar lines, and the work is in fact being continued now by Dr. Hoerni, who will remain here for another year.
You have reached the conclusion that the tetragonal structure for boron reported by Hoard and his co-workers cannot be of the closed-shell type. I think that there is a flaw in your argument. First, I am not sure that each of the two tetrahedral boron atoms in the unit must bear an extra electron, and form four single bonds with its neighbors. Let us, however, assume that this is so, and that 16 electrons of the total of 150 in the unit are tied up in this way. There remain 134 electrons. Let us assume that 26 electrons per icosahedron are then involved in filling the closed shells. There then remain 30 electrons per unit, which are to be assigned to the bonds connecting boron icosahedra. There are 20 bonds of this sort per unit, which would require 40 electrons if the bonds were single bonds. I suggest, however, that the bonds are not single bonds, but are three-quarters bonds, requiring only one and one half electrons per bond - that is, I suggest that a treatment of the entire crystal, with the icosahedra conjugated together, would show that this number of electrons corresponds to a closed shell.
I might point out that your assumption that the outward-pointing orbitals of the icosahedron are all involved in forming single bonds, rather than fractional bonds, does not correspond to the assumption made for the inward-pointing orbitals - namely, that only those with a positive value of the energy parameter (corresponding to stabilization) are to be occupied. In your Table 5 four of the outward-pointing orbitals, rather than 12, are given positive values of the energy parameter. By including the five orbitals with symmetry V, which have a small negative value of this parameter, a total of 9 would be obtained, corresponding to an average of three-quarters occupancy. This is not exactly right, of course, because it includes the two boron atoms bonded to tetrahedral borons, as well as the other ten. But, of course, the icosahedron of boron atoms does not have true icosahedral symmetry in this tetragonal structure, in which two of the twelve boron atoms are bonded to tetrahedral boron atoms, and the other ten are not. I do not think that the argument that you have given is justification for throwing doubt on the structure described by Hoard and his co-workers.
There is another point that I may make. If your assumption were correct, the boron-boron distance between icosahedra should be significantly less than that within an icosahedron. I do not think that the x-ray evidence supports this. It is true that the structure determinations for B4C and tetragonal boron are not precise ones. However, the problem is the same in CaB6, which is the substance which we have also been treating theoretically. In CaB6 each boron atom forms four bonds within an octahedron, and a fifth bond pointing out from the octahedron. You would probably treat this problem in an analogous way to that in which you have treated the problem of ocosahedral structures, whereas we have been considering the problem of the entire crystal, involving conjugated octahedra. Your assumption would in this case mean that the bonds pointing out from an octahedron are single bonds, involving two electrons per bond, and leaving only 1.2 electrons per bond within the octahedron. Twenty years ago Weinbaum and I made a very careful study of CaB6, and we were able to show that the boron-boron distances between octahedra are identical, to within 0.01 Å, with those within an octahedron. It is evident that these bonds are of essentially the same type, involving about 1.33 electrons per bond.
- Letter from LP to Professor J.L. Hoard, Baker Chemical Laboratory, Cornell University, RE: Has read an article by Longuet-Higgins and Roberts in the last issue of the Proceedings of the Royal Society. Has written to Longuet-Higgins saying that he does not think Longuet-Higgins has a sound argument about tetragonal boron. Encloses a copy of the letter sent to Longuet-Higgins. [Letter from Hoard to LP August 12, 1955] [Filed under LP Correspondence: (H: Individual Correspondence. (Hicks - Hodgkin)), #159.10]
- Letter from Mary D. Alexander, Production Editor, University of Chicago Press, to LP RE: Realizes that this is an unusual procedure, but given the nature of E.C. Kemble's inquiry, wonders if LP might referee the paper sent by Kemble on behalf of Professor Herbert Jehle. [Letter from Kemble to the Proceedings July 8, 1955, Letter from LP to Kemble July 15, 1955] [Filed under LP Correspondence: (K: Correspondence, 1936-1956), #200.20]
- Letter from Professor Paul A. Beck, Mining and Metallurgical Engineering Dept., University of Illinois, to LP RE: Pleased to hear that LP will be participating in the Symposium on the "Theory of Alloy Phases" on October 15-16. Requests that LP let him know his preference for the title of the contribution. ASM hopes to receive the manuscript of each contribution at the time of the meeting so that they can promptly begin publication of the material in book form. [Letter from LP to Beck July 6, 1955, Letter from Beck to LP July 15, 1955] [Filed under LP Speeches: 1955s.22]
- Letter from Robert I. Parson, to President Dwight D. Eisenhower RE: Requests that further testing of nuclear weapons be terminated by the US. Gives his argument. [Filed under LP Correspondence: (P: Correspondence, 1953-1959) #313.6]
- Memo from Makio Murayama, Caltech, to LP RE: Encloses a brief report on cryoglobulin. Hopes that it meets with LP's approval. [Filed under LP Correspondence: (M: Correspondence, 1950-1955), #256.6]
- Memorandum from Herbert Segall to Linus Pauling. [Filed under LP Science: Box #6.004, Folder 4.17]
To: Professor Pauling From: H. Segall Date: 7-11-55 E
SUBJECT: The Average of Amino Acid Residues Contained in the Unit Cell of Collagen.
A survey of the recent literature was made to collect consistent on the unit cell dimensions, density and average residue weight for collagen. The most complete work on dry and wet untreated kangaroo tail tendon was reported by Rougvie and Bear (J. Amer. Leather Chemists Assn., 48, 735 (1953)). A less comprehensive investigation was made by Dr. R. A. Pasternak of this Institute and was contained in a report to Professor Pauling on March 11, 1954.
According to the report of Dr. Schroeder of Nov. 6, 1952 the existing chemical analyses of the amino acid content of mammalian collagen are sufficiently consistent not to warrant any further determinations at present. An average residue weight of 92.6 was taken from the work of Bowes and Kenton (Biochem. J., 43, 358 (1948))
(1) Rougvie and Bear reported the equatorial spacing of exhaustively dried kangaroo tail tendon as 10.6 A. The sample was dried for one week over P2O5 at room temperature. Although this value is slightly higher than other reported values it is consistent with their measurements of the equatorial spacing as a function of the water content of collagen from dry to water saturated specimens. The usual meridional distance of 2.86 Å was also reported. The volume of the hexagonal unit cell is accordingly V = 2.86 x 10.62/cos 30 = 371.1 A3.
The density of dry unpurified collagen was determined by flotation in bromheptane and carbon tetrachloride by Rougvie and Bear. Their reported value of 1.34 is close to other reported values of dry collagen and gelatin. The weight for a mole of units is then
M = V x d x N = 371.1 x 10-24 x 1.34 x 6.023 x 1023 = 299.5 gms
By taking 92.6 as the average residue weight the average number of amino acid residues in the unit cell, n, is found to be
The uncertainties in this value of n are the average residue weight (1 or 2%) and the density. The presence of non-collagenous material in the unpurified sample may affect the observed density.
(2) The experimental values as determined by Dr. Pasternak for hydrated collagen containing 16.3% water are as follows:
meridional spacing = 2.88 Å
equatorial spacing = 11.54 Å
density = 1.32
By taking an average residue weight of 93.3 and adding 18.6 for the water associated with it he obtained an apparent molecular weight of 111.9. The calculated value of n was 3.15.
Rougvie and Bear have shown that from 0 to about 20 g water/100 g collagen the sorbed water was effective in increasing the volume of the unit cell according to its normal density of 1.00. Greater hydration increases the volume at a considerable smaller rate. Thus it can be said that Dr. Pasternak’s value of n is fortuitously close to Bear’s value since his water of hydration falls within the 0 to 20 range.
(3) The value of 3.23 as the average number of amino acid residues in the unit cell of collagen calculated from the data of Rougvie and Bear is probably accurate to 3 or 4 per cent. The reasonably exhaustive work of Rougvie is sufficient for the present.
- Research Notebook of LP RE: Does calculations regarding effective radii of Sn, Si, and Ge in Cu, Sn and Ge in Ag, and Sn and Ge in Au pp.29. [Filed under LP Research Notebooks: 19R]