9α-Methoxycortisol

Weeks, Charles M.; Duax, William L.; Wolff, M. E.

doi:10.1107/s0567740876002720

Cited by 13 publications

(3 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These results should be examined in the light of the X-ray crystallographic structure of compounds l,3 2,3 and 4. 23 In the case of 9a-fluorocortisol, Cl is shifted in the direction of the ß side of the molecule, but this is not the case for the 9a-bromo derivative (4). If this movement is due to steric interactions, it is not clear why C7, C12, and C14 in 2 are not similarly affected, nor why the effect should not be observed in 9a-bromocortisol (4).…”

Section: Discussionmentioning

confidence: 99%

Steric and electronic effects on carbon-13 nuclear magnetic resonance .alpha., .beta., and .gamma. shifts and fluorine-19-carbon-13 coupling constants in 9.alpha.-substituted cortisol derivatives

Giannini¹,

Kollman²,

Bhacca³

et al. 1974

J. Am. Chem. Soc.

View full text Add to dashboard Cite

The I3C nmr (cmr) spectra of 9a-fluoro-, 9a-chloro-, and 9a-bromocortisol are analyzed and compared. On the basis of the steric and electronic structure of these molecules previously obtained by X-ray diffraction methods and molecular orbital calculations, it is shown that current cmr theory does not account in a satisfactory way for a, ß, and y shifts induced by the 9a substituent. The magnitude of the 19F-' 3C coupling constant is found to be roughly proportional to the C2s-F2s bond order element.Recently we made a detailed analysis of the elec-. tronic2 and steric3 properties of 9a-substituted cortisol derivatives in an attempt to relate these features to the chemical and biological characteristics of these compounds. The analysis was made by means of X-ray crystallographic and molecular orbital (CNDO/2) techniques. 13C magnetic resonance (cmr), which can be used to assess the environment of each carbon atom in the steroid nucleus in solution, is an important supplement to these examinations of the crystal state.We have already studied the cmr spectra of cortisol (1) and related steroids,4 and in the following we compare these results with those obtained from 9a-substituted cortisol derivatives to assess the cmr effect of the 9a group. We have also considered whether the steric interactions measured by cmr are in harmony with the X-ray diffraction studies we have reported3 on cortisol (1), 9a-fluorocortisol (2), 9a-chlorocortisol (3), and 9a-bromocortisol (4). Finally, we have attempted M ch2oh

show abstract

Section: Discussionmentioning

confidence: 99%

Steric and electronic effects on carbon-13 nuclear magnetic resonance .alpha., .beta., and .gamma. shifts and fluorine-19-carbon-13 coupling constants in 9.alpha.-substituted cortisol derivatives

Giannini¹,

Kollman²,

Bhacca³

et al. 1974

J. Am. Chem. Soc.

View full text Add to dashboard Cite

show abstract

“…This structure, 9~-methoxycortisol (Weeks, Duax & Wolff, 1976), contains 22 carbon and six oxygen atoms in *Three measures of each peak are listed. The first is the ranked order of the peak in the peak list.…”

Section: Test Case 1-pr435mentioning

confidence: 99%

MERLOT, an integrated package of computer programs for the determination of crystal structures by molecular replacement

Fitzgerald¹

1988

J Appl Cryst

398

176

View full text Add to dashboard Cite

SHORT COMMUNICATIONS 273 cellulose II. Oscillation films taken at the Cornell HighEnergy Synchrotron Source of protein crystals mounted on milkweed fibre plugs show, in addition to the 002 band, a thin ring of variable intensity at 4.62 A. Two other scarcely visible lines were observed, but the 2.58 A ring was missing. The films were remarkably free from background scattering. None of the lines should interfere with the data collection and the 4.62 A line can be used for calibrating the fluctuating wavelength of the synchrotron radiation.The rods are cut into short (2-3 mm) segments. The surface adjacent to the crystal must be quite smooth, and any loose fibres should be removed. The plug is then pushed through the funnel and as far as possible into the capillary by an appropriate glass rod. Some of the solution from the reservoir of the crystallization cell is then introduced by suction. It is important at this stage to remove the air bubbles within the plug, as they may interfere later with the proper positioning of the crystal. To accomplish this it is necessary to draw some liquid into the plug and then out of it in the opposite direction. If any bubbles appear in the liquid outside the plug, that liquid is sucked again slowly into the plug until the surface of the plug is just barely exposed to the air. The bubbles that have settled on the surface usually burst easily. This process should be repeated until no more bubbles appear on either side of the plug.The crystal, floating in a solution, is introduced into the capillary and then all the excess liquid is removed from the opposite side of the plug. The orientation of the crystal can be controlled by tilting the capillary while the crystal is still floating. If the position of the crystal is not satisfactory, the procedure can easily be repeated by again blowing some of the liquid through the plug to the crystal side.There is usually enough liquid trapped inside and between the fibres not to necessitate a second layer of the reservoir solution, especially if a strip of wet filter paper is left behind.If the funnel of the capillary is not broken off, and only easily melted wax or oil layers are used for sealing, it would be feasible to reintroduce solutions of inhibitors, haptens or heavy-atom compounds. This method, although quite different from the use of the flow cell (Wyckoffet al., 1967; Petsko, 1985), which ensures immobilization of a crystal while liquid is flowing, would enable an X-ray examination of the same crystal in a similar orientation after it has been soaked. Computer ProgramsJ. Appl. Cryst. (1988 AbstractMERLOT is an integrated package of computer programs for the determination of initial models of crystal structures using the molecular replacement technique. The package includes two programs for calculating the rotation function, three methods for solving the translation problem (a translation function, a packing function and an R-value mapping program) and a program for optimizing a potential solution. The programs are applicable to ...

show abstract

“…For each of these master/slave implementations, we also provide an analysis of the performance on a suite of four test structures. The first structure, 9a-methoxycortisol, is a small structure of only 28 nonhydrogen atoms (Weeks, Duax, and Wolff, 1976). The second and third structures, isoleucinomycin (Pletnev et al, 1980) and isoleucinomycin analogue (Pletnev et al, 1992), are moderately sized structures of 84 and 127 nonhydrogen atoms, respectively.…”

Section: Terminationmentioning

confidence: 99%

Using Parallel Computers To Solve the Phase Problem of X-Ray Crystallography

Chang

DeTitta

Hauptman

et al. 1993

The International Journal of Supercomputing Applications

View full text Add to dashboard Cite

Direct methods are commonly used by crystallographers to determine relatively small crystal structures.However, existing techniques do not appear to be extensible to larger structures. The recent development of a solution strategy called Shake-and-Bake, aimed at determining structures via local minimization and repeated Fourier transformations, allows for implicit constraints to be included. In this article, a description of the Shake-and-Bake algorithm is given, along with a detailed description of master/slave MIMD implementations on a network of Sun workstations, an Intel iPSC/860 Hypercube, and a Connection Machine CM-5. Our experimental results on known structures, including gramicidin A, are extremely encouraging. For example, based on efficient implementations of Shakeand-Bake on the iPSC/860 and CM-5, for known structures of 28, 84, and 127 nonhydrogen atoms, we obtain success rates of 19%, 1%, and 0.2%, as opposed to existing methods, which yield success rates of approximately 6%, 0.006%, and 0.0002%, respectively.

show abstract

9α-Methoxycortisol

Cited by 13 publications

References 2 publications

Steric and electronic effects on carbon-13 nuclear magnetic resonance .alpha., .beta., and .gamma. shifts and fluorine-19-carbon-13 coupling constants in 9.alpha.-substituted cortisol derivatives

Steric and electronic effects on carbon-13 nuclear magnetic resonance .alpha., .beta., and .gamma. shifts and fluorine-19-carbon-13 coupling constants in 9.alpha.-substituted cortisol derivatives

MERLOT, an integrated package of computer programs for the determination of crystal structures by molecular replacement

Using Parallel Computers To Solve the Phase Problem of X-Ray Crystallography

Contact Info

Product

Resources

About