Crowfoot

Crowfoot D, Bunn C W, Rogers-Low B W and Turner-Jones A 1949 The X-ray orystallographio investigation of the struoture of penioiiiin Chemistry of Penicillin ed H T Ciarke, J R Johnson and R Robinson (Prinoeton, NJ Prinoeton University Press) pp 310-66... 

Cobalt is one of twenty-seven known elements essential to humans (28) (see Mineral NUTRIENTS). It is an integral part of the cyanocobalamin [68-19-9] molecule, ie, vitamin B 2> only documented biochemically active cobalt component in humans (29,30) (see Vitamins, VITAMIN Vitamin B 2 is not synthesized by animals or higher plants, rather the primary source is bacterial flora in the digestive system of sheep and cattle (8). Except for humans, nonmminants do not appear to requite cobalt. Humans have between 2 and 5 mg of vitamin B22, and deficiency results in the development of pernicious anemia. The wasting disease in sheep and cattle is known as bush sickness in New Zealand, salt sickness in Florida, pine sickness in Scotland, and coast disease in AustraUa. These are essentially the same symptomatically, and are caused by cobalt deficiency. Symptoms include initial lack of appetite followed by scaliness of skin, lack of coordination, loss of flesh, pale mucous membranes, and retarded growth. The total laboratory synthesis of vitamin B 2 was completed in 65—70 steps over a period of eleven years (31). The complex stmcture was reported by Dorothy Crowfoot-Hodgkin in 1961 (32) for which she was awarded a Nobel prize in 1964. 

P. Senhard and D. Hodgkin, Nature 192, 937 (1961) D. Crowfoot-Hodgkin, Proc. RoyalSoc. (Eondon) A288, 294 (1965). 

In spite of the slow development of crystal structure analysis, once it did take olT it involved a huge number of investigators tens of thousands of crystal structures were determined, and as experimental and interpretational techniques became more sophisticated, the technique was extended to extremely complex biological molecules. The most notable early achievement was the structure analysis, in 1949, of crystalline penicillin by Dorothy Crowfoot-Hodgkin and Charles Bunn this analysis achieved something that traditional chemical examination had not been able to do. By this time, the crystal structure, and crystal chemistry, of a huge variety of inorganic compounds had been established, and that was most certainly a prerequisite for the creation of modern materials science. 

Cevanthrol, C jH gO, crystallises from benzene in plates, m.p. 197-8°, behaves as a phenol and gives an acetyl derivative, m.p. 138-9°. X-ray analysis (Bloxmt and Crowfoot indicates that it is a phenanthrene derivative, with a hydroxyl group, possibly at C . 

In the 6jS-bromoacetyI derivative of 3,5a-cyclo-cholestan-6jS-oI, the 6 -oxygen-l9 carbon distance in the crystal is about 3.19 A (private communication from Prof. Dorothy Hodgkin, Oxford), (f. also H. R. Harrison, D. Crowfoot Hodgkin, E. N. Maslen and W. D. S. Motherwell./. Chem. Soc. C, 1971, 1275). 

Dorothy Crowfoot Hodgkin (Oxford) determinations by X-ray techniques of the structures of important biochemical substances. 

Hahnen-fett, n. stopcock grease, -fuss, m. lit., cock s foot Ceram.) cockspur Bot.) crowfoot, ranunculus. 

A special case is defined the numbers 6 and 9 describe the crowfoot/water course design of most natural diamond and many TSP bits. Such designs are further described as having either radial flow, crossflow (feeder/collector), or other hydraulics. Thus, the letters R (radial flow), X (crossflow), or O (other) are used as the hydraulic design code for such bits. 

Hodgkin, Dorothy Crowfoot, 248 Homarus Americanus, 157 Homogeneous Uniform in composition, 2,4-5... 

In 1933, Bernal and Crowfoot [1] reported on the solid state polymorphism of p-azoxyanisole. They found two crystalline modifications of this compound, a stable yellow form and an unstable white polymorph. Krigbaum et al. [31 reexamined the crystal structure of the stable yellow form. The compound shows an imbricated structure which is the basic packing required for nematic behaviour according to Gray [132]. 

Kathleen Lonsdale, an x-ray crystallographer, was the first woman elected to the Royal Society of London Dorothy Crowfoot Hodgkin was the first woman chemist elected. 

F. Ming Miao, D. Chantry, T. Harper and D. Crowfoot Hodgkin, Acta Crystallogr., B38, 3152 (1982). 

Globular proteins were much more difficult to prepare in an ordered form. In 1934, Bernal and Crowfoot (Hodgkin) found, that crystals were better preserved if they were kept in contact with their mother liquor sealed in thin-walled glass capillaries. By the early 1940s crystal classes and unit cell dimensions had been determined for insulin, horse haemoglobin, RNAase, pepsin, and chymotrypsin. Complete resolution of the structures required identification of the crystal axes and some knowledge of the amino acid sequence of the protein—requirements which could not be met until the 1950s. 

Chemists commonly use a process called X-ray diffraction to determine the structure of a compound. Two pioneers of X-ray diffraction were Rosalind Franklin and Dorothy Crowfoot Hodgkin. Franklin s work on the DNA molecule was instrumental in the discovery of its helical shape. Nobel Prize winner Hodgkin discovered the structure of complex molecules, such as cholesterol, penicillin, insulin, and vitamin B-12. Find out about X-ray diffraction how it works and the types of scientists who employ this technology. 

The isolation of the pure material was not the end of the story. Deducing the structure of vitamin B12 was a saga itself. Dorothy Crowfoot Hodgkin, an English scientist, won a Nobel Prize in Chemistry in 1964 in part for getting this structure. This was one of the early triumphs of the technique of X-ray diffraction. She was a amazingly productive structural chemist, getting the structures for cholesterol and insulin as weU. 

Crowfoot, D. and Schmidt, G. M. J. (1945). X-ray crystallographic measurements on a single crystal of a tobacco necrosis virus derivative. Nature 155,504-505. 

Dorothy Crowfoot Great Britain x-ray techniques of the structmes of biochem-... 

A number of reviews, papers, and one book of theoretical and synthetic interest have appeared in recent years on various aspects of nitroso chemistry. The work of Turney and Wright [1], Touster [2], Gowenlock and Luttke [3], Hamer et al. [4], Ogata [5], Dietrich and Crowfoot Hodgkin [6], Ridd [7], Griffis and Henry [8], Theilacker [9], Cook [10], Boyer [11], Feuer [12] and Hoffmann and Woodward [13] represents a selection of pertinent material. The reader is directed particularly to Gowenlock and Luttke [3]. 

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