ZfN: Search Results

1	Author	Ingrid Pilz, K. Arin Goral, FriedrichV D Haar	Requires cookie*
	Title	Phenylalanyl-tRNA Synthetase from Baker'Yeast: Structural Organization of the Enzyme and Its Complex with tRNAPhe as Determined by X-Ray Small-Angle Scattering
	Abstract	The quaternary structure of the phenylalanyl-tRNA synthetase and its complex with tRNAPhe was studied in dilute solutions by small angle X-ray scattering. For the free synthetase the radius of gyration was determ ined as 5.5 nm, the volume 523 nm 3, the maximum diam eter 17.5 nm and the m olecular weight as 260 000 using an isopotential specific volume of 0.735. The overall shape could be best approxim ated by a flat cylinder with dimensions 18.2 n m X l l .5 n m X 4 nm ; the loose structure was approxim ated by building up the cylinder by spheres (diam eter 4.2 n m). The corresponding param eters of the enzyme tRN A complex were the following: radius of gyration 5.9 nm, volume 543 nm 3, maximum diam eter 21 nm and m olecular weight 290 000. These param eters suggest an 1:1 complex, whereby it m ust be assumed that the tRN A m olecule is attached in the extension of the longer axis. From the difference in the distance distribution functions of the free enzyme and the complex it is evident that we have to assume a change of conform ation (contraction) of the enzyme upon the binding of the specific tRNA.
	Reference	Z. Naturforsch. 34c, 20 (1979); received November 20 1978
	Published	1979
	Keywords	X-Ray, Small-Angle, Scattering, Enzyme, Complex
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	TEI-XML for	default:Reihe_C/34/ZNC-1979-34c-0020.pdf
	Identifier	ZNC-1979-34c-0020
	Volume	34

2	Author	Wolfgang Flossmann, Herbert Zehner, Adolf Müller	Requires cookie*
	Title	Radicals Produced in Single Crystals of Thymine Derivatives by UV and X-Rays
	Abstract	Single crystals o f anhydrous thym ine (T), thym ine monohydrate (T ■ H 20) , 5,6-dihydrothym ine (T H 2), 1-methylthymine (mT) and thym idine (dT) were irradiated with X-rays and UV between 77 K and 300 K. Six types o f radicals were analyzed by ESR-spectroscopy at 9.5 G H z and 35 G H z after exposure to X-rays. The anion radical occurred only in T • H 20 at 77 K, the 4-yl radical only in T H 2 at 77 K and the 1-yl radical only in T between 77 K and 300 K. The 6 -yl radical was found in T, T H 2 and mT. It was converted into the 5-yl radical irreversibly by heat or white light (A < 600 nm). The 5-yl radical appeared in all compounds at room temperature. The highest thermal stability was found for the 7-yl radical which was present at room temperature in all compounds except T H 2 . U V -irradiation (A = 320 nm) produced radicals only in three crystals (T, T H 2 , dT). In T the 5-yl radical was found after exposure at 300 K, and two other radicals, 1-yl and 7-yl, at 77 K. A lso at 77 K, the 7-yl radical was present in dT and the 5-yl radical in TH 2 and dT.
	Reference	Z. Naturforsch. 35c, 20—2 (1980); received July 23 1979
	Published	1980
	Keywords	Radicals, Single Crystals, Thym ine, X-Rays, ESR
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	TEI-XML for	default:Reihe_C/35/ZNC-1980-35c-0020.pdf
	Identifier	ZNC-1980-35c-0020
	Volume	35

3	Author	Alfred Gieren, Michail Kokkinidis	Requires cookie*
	Title	Structure Investigations o f Agonists o f the Natural Neurotransmitter Acetylcholine II [1\| X-ray Structure Analysis o f Trimethyl(4-oxopentyl)ammonium-chloride
	Abstract	The crystal structure of Trimethyl(4-oxopentyl)ammonium-chloride ([(C H 3) 3 N —(CH^aCOCHjJCl-) (1) was determined by an X-ray structure analysis. 1 crystallizes in the orthorhombic space group P21 21 21 with a = 10.440 (3), b = 14.600 (9), c = 6.804 (9) A and with four formula units per unit cell. The structure was solved by a Patterson and a successive Fourier synthesis. The least squares refinement yielded an R-value o f 0.064 for 1077 observed reflections. The cation o f 1 is derived from acetylcholine by replacement o f the ester oxygen with a CH2 group. It shows a potent nicotinic activity and a significant difference in conformation as compared with acetylcholine. In the crystal structure the anions are oriented stereospecifically with respect to the tetrahedron of the quaternary ammonium group. The geometry o f two triangles formed by the quaternary nitrogen atom, the oxygen atom o f the carbonyl group, and by either o f the two anions nearest to the quaternary ammonium group is characteristic for the nicotinic activity o f 1.
	Reference	Z. Naturforsch. 37c, 282 (1982); received December 231981
	Published	1982
	Keywords	X-ray, Neurotransmitter, Cation-Anion Interactions, Structure-Activity Relationships
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	TEI-XML for	default:Reihe_C/37/ZNC-1982-37c-0282.pdf
	Identifier	ZNC-1982-37c-0282
	Volume	37