Write an abstract for the previous article. An abstract summarizes, usually in o

Question

Write an abstract for the previous article. An abstract summarizes, usually in one paragraph of 300 words or less, the major aspects of the entire paper in a prescribed sequence that includes: 1) the overall purpose of the study and the research problem(s) investigated; 2) the basic design of the study; 3) major findings or trends found as a result of your analysis; and, 4) a brief summary of the interpretations and conclusions.

NATURE equipment, and to Dr. G. E. R. Deacon and the is a residue on esch chain every 3-4 A. in the z-diree captain and officers of R.R.S. Discovery II for their tion We have asaumed an angle of 38 between Young, P. B., Gerrard, H., and Jevons, W., P. Mag., 40, 19 structure ropeats after 10 residues on each chain, that is, after 34 A. The distance of phosphorus atom from the fibre axis is 10 A. As the phosphates are on 'Longuet-iggins, M, S., Mon, Not, Roy. Aetro. Sor., Gevphye. Supp. Von Arx, w. s, woods Hole Papers in Phys. 0ceanog. Meteor., 11 ‘Ekman, r. w., Arkte. Afat. Arron. Fysik. (8tockhain), 2(11) (1905) the outside, cations have easy access to them. The structure is an open ono, and its water content MOLECULAR STRUCTURE OF NUCLEIC ACIDS A Structure for Deoxyribose Nucleic Acid in which the two chains are held together by the together in pairs, a single base from one chain being E wish to suggest a structure for the salt ohain, so that the two lie side by side with identical of deoxyribose nucleic acid D.N.A This structure has novel features which are of considerable the other a pyrimidine for bonding to oeeur The hydrogen bonds are made as follows: purine position A structure for nucleie aceid has already been to pyrimidine position 1; purine position 6 to proposed by Pauling and Corey1. They kindly made pyrimidine position 6 their manuseript available to us in advance of If it is assumed that the bases only oecur in the publication. Their model consista of three inter struoture in the most plausible tautomeric forms twined chains, with the phosphates near the fibre (that is, with the keto rather thanthe enol con axis, and the bases on the outside. In our opinion, figurations) it is found that only specific pairs of this struoture is unsatisfactory for two reasons: bases can bond together. Theso pairs are: adenine (1) We believe that the material whieh gives the (purine) with thymine (pyrimidine), and guanine X-ray diagrams is the salt, not the free acid. Without (purine) with the acidic hydrogen atoms it is not clear what fors In other would hold the structure together, especially n the a pair, on either chain, then on these agsumptions negatively charged phosphates near the axis l tho other member must be thymine; similarly for repel each other. (2) Some of the van der Waals guanine and cytosine. The sequence of bases on a single chain doos not appear to be restrieted in any gested by Fraser (in the press). In his model the formed, it follows that if the sequence of bases on phoaphates aro on the outside and the bases on the one ehain ia given, then the sequence on the other structure as described is rather ill-defined, and for It has been found experimentally that the ratio this reason we shall not eomment of the amounts of adenine to thymine, and the ratio of guanine to cytosine, are always very close to unity We wish to put forward a for deoxyribose nucleic seid radically different structure for It is probably impossible to build this structure the salt of deoxyribose nueleie with a ribose augar in place of tho deoxyribose, as acid. This structure has two the extra oxygen atom would make too close a van helical chains each coiled round der Waals contact. the sume axis (see diagram. W The previously published X-ray data on deoxy- have made the usual ehemical ribose nucleic acid are insufficient for a rigorous test that each of our structure. So far as we can tell, t is roughly sphate di compatible with the experimental data, but it must ester groups joining -D-deoxy- be regarded as unproved until it has been checked ribofurarnose residues with 3,5' against more exaot results. Some of these are given linkages. The two chains (but in the following not their bases) are related by of the details of the results presented there when we to the fibre devised our structure, which rests mainly though not axis. Both chains follow right entirely on published experimental data and stereo- the dyad the soquences of the It has not esçaped our notice that the specific berg's model No. I that is, ditions assumed in building it, together with a set the bases are on the nside of of co-ordinates for the ato, w be published We are much indebted to Dr. Jerry Donohue for ribbons syrabolize the of the sugar and the atoms constant edvice and criticiam, especially on inter- outal rods the pairs of 'standard configuration' the knowledge of the general nature of the unpublished line marka the flbre axi cular to the attached base. There Wilkins, Dr. R. E. Franklin and their co-workers at sugar being roughly perpendi experimental results and ideas of Dr. M. H. F

Explanation / Answer

The propose of this investigation is study of complexity in molecular structure of DNA by X- ray diffraction technique. In this study discribe some experimental evidence for the polynucleotide chain configuration being helical, and existing in this form when in the natural state is the double helix.

Through X-ray diffraction we gained the same linear group of polynucleotide chains may pack together parallel in different ways to give crystallinel- 3, semi-crystalline or paracrystalline material. In this study found experimentally that the ratio of the amounts of adenine to thymine, and the ratio of guanine to cytosine in deoxyribose nucleic acid. And, briefly analyse effects of the shape and size of the repeat unit or nucleotide on the diffraction pattern. Two type of diffraction patterns are found. First, the nucleotide consists of a unit having circular symmetry about an axis parallel to the helix axis. Second, the nucleotide consists of a series of points on a radius at right-angles to the helix axis, the phases of radiation scattered by the helices of different diameter passing through each point are the same. After the study, we conclude the DNA is very complexed double helical structure.

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