The Structure of Ribonucleic Acid

M7. Markham, R., and Smith, J. D., The structure of ribonucleic acids. I. Cyclic nucleotides produced by ribonuclease and by alkaline hydrolysis. Biochem. J. 62, 552-557 (1952). 

A very important use of XRD is in the determination of the structure of single crystals, that is, identifying the exact position in 3D space of every atom (molecules, ion) in the crystal. Single crystal XRD was a major tool in elucidating the structure of ribonucleic acid (RNA) and deoxyribonucleic acid (DNA), insulin, vitamins, and proteins. Single crystal diffractometry is used for structural determination of biomolecules, natural products, pharmaceuticals, inorganic coordination complexes, and organometallic compounds. 

Total internal reflection fluorescence (TIRF) microscopes are employed to study a diverse phenomena, including cell transport, signaUng, replication, motility, adhesion, and migration cell membranes and transport the structure of ribonucleic acid (RNA) neurotransmitters and virology. 

Limitations of space have forced the rather arbitrary selection of only a few topics from this large field. For the most part, only mononucleotides will be considered. Brief reference will be made to some current views on the structure of ribonucleic acid in order that the mononucleotides may be more intelligently discussed. 

Franklin, R. M., Wecker, E. Inactivation of some animal viruses by hydroxylamine and the structure of ribonucleic acid. Nature (Lond.) 184, 343-345 (1959). 

British molecular biologist. Maurice Wilkins was one of the key figures in the determination of the structure of DNA. He was originally a physicist but turned to biophysics after the end of World War II. He began to study DNA by x-ray diffraction. Some of the x-ray diffraction pictures produced by his colleague Rosalind FRANKLIN provided essential clues to Francis crick and James WATSON in their search for the structure of DNA. Wilkins shared the 1962 Nobel Prize for Medicine with Crick and Watson. Wilkins also determined the structure of ribonucleic acid (RNA) using x-ray diffraction. In 2003 Wilkins published his autobiography. 

D-ribose, CjHioOj. M.p. 87 0. The sugar of ribonucleic acid it is therefore present in all plant and animal cells. It has the furanose structure shown. 

The discovery of the base-paired, double-helical structure of deoxyribonucleic acid (DNA) provides the theoretic framework for determining how the information coded into DNA sequences is replicated and how these sequences direct the synthesis of ribonucleic acid (RNA) and proteins. Already clinical medicine has taken advantage of many of these discoveries, and the future promises much more. For example, the biochemistry of the nucleic acids is central to an understanding of virus-induced diseases, the immune re-sponse, the mechanism of action of drugs and antibiotics, and the spectrum of inherited diseases. 

Fresco, J., Alberts, B., et al. (1960). Some molecular details of the secondary structure of ribonucleic acid. Nature 188, 98—101. 

If you ve had a cup of coffee and your brain is functioning normally, you may have already guessed that /3-ribose is the sugar in the backbone of ribonucleic acids (RNA), while /3-2-deoxyribose forms the skeletal structure of deoxyribonucleic acid (DNA). In both types of polymers, these sugars are strung together by condensation reactions (remember those ) involving phosphoric... 

A solution leading to a successful algorithm was recently found for the folding of ribonucleic acid (RNA) [36], Natural RNA polymers (figure C2.14.1) are mainly made up from four different bases . A, C, G and U. As with DNA, multiple hydrogen bonding favours the formation of G-C and A-U pairs [16, 37, 38] which leads to the appearance of certain characteristic structures. Loop closure is considered to be the most important folding event. 

As an example of an enzyme reaction which has been studied with fast-reaction techniques, we consider the mechanism of action of pancreatic ribonuclease A. Ribonuclease catalyzes the breakdown of ribonucleic acid in two distinct steps as shown in Fig. 9-6. First the diester linkage is broken, and a pyrimidine 2 3 -cyclic phosphate is formed then the cyclic phosphate is hydrolyzed to give the pyrimidine 3 -monophosphate and purine oligonucleotides with a terminal pyrimidine 3 -phosphate. Ribonuclease has been extensively studied with a variety of chemical and physical techniques, and its three-dimensional structure is known (cf. Richards and Wyckoff [12] for a comprehensive review). 

There are two important differences between the primary structure of ribonucleic acids (RNA) and DNA ... 

Reactions of Ribonuclease. The degradation of ribonucleic acid by RNAase was found to result in the accumulation of a mixture of pyrimidine mononucleotides and a so-called core. The core is not an individual structure it is a mixture of oligonucleotides in which the bases are predominantly purines. These compounds indicate the random nature of the ribonucleic acid structure. Ribonuclease hydrolyzes esters of doubly esterified phosphate in which one of the substituents is the hydroxyl group in position 3 of a pyrimidine nucleotide the other substituent, which in ribonucleic acid is a 5 hydroxyl group, is removed. Since groups substituted on phosphates esterified with 3 positions of purine... 

The isolation of ribonucleic acids is difficult which makes the determination of their structure and composition difficult also. However it can be shown that the ribonucleic acid of animals differs from that of yeast, and that the ribonucleic acids from different organs of the same species are less alike than are those from a given organ obtained from several species. Unlike the desoxyribonucleic acids, the ribonucleic acids differ not only from species to species but also from tissue to tissue in the same species. Moreover, the ribonucleic acids of the nucleus differ from that of the cytoplasm, and external conditions also cause variations. 

Spirin, A. S., 1963, Some Problems in the Macromolecular Structure of Ribonucleic Acids, Izd. AN SSSR, Moscow. 

Secondary Structure of Ribonucleic Acid. Compared to the DNA, very little is known about the spatial arrangement of the RNA chain, i.e., about its secondary structure. For soluble RNA it is assumed that a single strand is folded back on itself giving rise in parts of the molecule to a DNA-like double helix (cf. Fig. 30 and Adaptor Hypothesis, Section 6). Base pairing and possibly double strandedness play a role also with high molecular weight ribonucleic acids, but a well-substantiated model does not exist yet. 

Ribonucleic acids RNAs). Besides reproducing itself, DNA acts as a template for the synthesis of ribonucleic acids, of which the three principal kinds are messenger RNA (mRNA), transfer RNA (tRNA) sometimes called soluble RNA , and ribosomal RNA (rRNA). The RNAs closely resemble DNA in general structure, but only a portion of each molecule is in the helical form, and they have ribose in place of deoxyribose, and uracil in place of thymine. All three kinds of RNA have some methylated bases. All types of RNA have their part to play in the synthesis of proteins. The details of protein synthesis differ little, whether taking place in bacteria or in the most highly evolved organisms. The molecular weights of all RNAs are lower than that of the parent DNA that of a typical mRNA is often about one million, and of a tRNA about 25 000. 

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