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Home > Category Index for Science Quotations > Category Index H > Category: Helix

Helix Quotes (8 quotes)

An amino acid residue (other than glycine) has no symmetry elements. The general operation of conversion of one residue of a single chain into a second residue equivalent to the first is accordingly a rotation about an axis accompanied by translation along the axis. Hence the only configurations for a chain compatible with our postulate of equivalence of the residues are helical configurations.
[Co-author with American chemist, ert B. Corey (1897-1971) and H. R. Branson]
'The Structure of Proteins: Two Hydrogen-bonded Helical Configurations of the Polypeptide Chain', Proceedings of the National Academy of Sciences of the United States of America (1951), 37, 206.
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Are the atoms of the dextroacid (tartaric) grouped in the spirals of a right-hand helix or situated at the angles of an irregular tetrahedron, or arranged in such or such particular unsymmetrical fashion? We are unable to reply to these questions. But there can be no reason for doubting that the grouping of the atoms has an unsymmetrical arrangement with a non-superimposable image. It is not less certain that the atoms of the laevo-acid realize precisely an unsymmetrical arrangement of the inverse of the above.
Leηons de Chemie (1860), 25.
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Conclusion: Big helix in several chains, phosphates on outside, phosphate-phosphate inter-helical bonds disrupted by water. Phosphate links available to proteins.
Underlined in typewritten lecture notes, with handwritten annotations, as report (7 Feb 1952) on 'Colloquium November 1951'. As given in Anne Sayre, Rosalind Franklin and DNA (1975), 128.
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If the double helix was so important, how come you didn’t work on It?
Ther husband, Linus Pauling, when the Nobel Prize was awarded to Crick, Watson and Wilkins.
Pauling at a History of Science conference (1990). Quote contributed by W. H. Brock, in W. F.Bynum and Roy Porter (eds.), Oxford Dictionary of Scientific Quotations (2005), 485. Eva Helen Pauling was the wife of Linus Pauling.
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In describing a protein it is now common to distinguish the primary, secondary and tertiary structures. The primary structure is simply the order, or sequence, of the amino-acid residues along the polypeptide chains. This was first determined by Sanger using chemical techniques for the protein insulin, and has since been elucidated for a number of peptides and, in part, for one or two other small proteins. The secondary structure is the type of folding, coiling or puckering adopted by the polypeptide chain: the a-helix structure and the pleated sheet are examples. Secondary structure has been assigned in broad outline to a number of librous proteins such as silk, keratin and collagen; but we are ignorant of the nature of the secondary structure of any globular protein. True, there is suggestive evidence, though as yet no proof, that a-helices occur in globular proteins, to an extent which is difficult to gauge quantitatively in any particular case. The tertiary structure is the way in which the folded or coiled polypeptide chains are disposed to form the protein molecule as a three-dimensional object, in space. The chemical and physical properties of a protein cannot be fully interpreted until all three levels of structure are understood, for these properties depend on the spatial relationships between the amino-acids, and these in turn depend on the tertiary and secondary structures as much as on the primary. Only X-ray diffraction methods seem capable, even in principle, of unravelling the tertiary and secondary structures.
Co-author with G. Bodo, H. M. Dintzis, R. G. Parrish, H. Wyckoff, and D. C. Phillips
'A Three-Dimensional Model of the Myoglobin Molecule Obtained by X-ray Analysis', Nature (1958) 181, 662.
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Sodium thymonucleate fibres give two distinct types of X-ray diagram … [structures A and B]. The X-ray diagram of structure B (see photograph) shows in striking manner the features characteristic of helical structures, first worked out in this laboratory by Stokes (unpublished) and by Crick, Cochran and Vand2. Stokes and Wilkins were the first to propose such structures for nucleic acid as a result of direct studies of nucleic acid fibres, although a helical structure had been previously suggested by Furberg (thesis, London, 1949) on the basis of X-ray studies of nucleosides and nucleotides.
While the X-ray evidence cannot, at present, be taken as direct proof that the structure is helical, other considerations discussed below make the existence of a helical structure highly probable.
From Rosalind Franklin and R. G. Gosling,'Molecular Configuration in Sodium Thymonucleate', Nature (25 Apr 1953), 171, No. 4356, 740.
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When I saw the alpha-helix and saw what a beautiful, elegant structure it was, I was thunderstruck and was furious with myself for not having built this, but on the other hand, I wondered, was it really right?
So I cycled home for lunch and was so preoccupied with the turmoil in my mind that didn’t respond to anything. Then I had an idea, so I cycled back to the lab. I realized that I had a horse hair in a drawer. I set it up on the X-ray camera and gave it a two hour exposure, then took the film to the dark room with my heart in my mouth, wondering what it showed, and when I developed it, there was the 1.5 angstrom reflection which I had predicted and which excluded all structures other than the alpha-helix.
So on Monday morning I stormed into my professor’s office, into Bragg’s office and showed him this, and Bragg said, 'Whatever made you think of that?' And I said, 'Because I was so furious with myself for having missed that beautiful structure.' To which Bragg replied coldly, 'I wish I had made you angry earlier.'
From transcript of audio of Max Perutz in BBC programme, 'Lifestory: Linus Pauling' (1997). On 'Linus Pauling and the Race for DNA' webpage 'I Wish I Had Made You Angry Earlier.'
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[Professor Pauling] confesses that he had harboured the feeling that sooner or later he would be the one to get the DNA structure; and although he was pleased with the double-helix, he ‘rather wished the idea had been his’.
‘The Need to Understand’, New Scientist (1971), 50, 755.
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Carl Sagan Thumbnail In science it often happens that scientists say, 'You know that's a really good argument; my position is mistaken,' and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time something like that happened in politics or religion. (1987) -- Carl Sagan
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