Multiple rotation function.

Alexandre Urzhumtsev; Ludmila Urzhumtseva

doi:10.1107/s0907444902016992

Home/Archive/PubMed

PubMed · 12454466

Multiple rotation function.

Alexandre Urzhumtsev·Ludmila Urzhumtseva

View original source ↗Export metadata ↓

Abstract

A simultaneous analysis of several rotation functions allows identification of the model orientation in situations when a single rotation function fails to find the answer. Multiple rotation functions can be obtained by the usual modification of the search model or by variation of the resolution at which the function is calculated. A specially suitable case is a search with several NMR models. When the orientation of the model becomes available, its position can be found much more easily; low-resolution data can help in such a search. Many difficult cases of molecular replacement can be solved by new tools discussed in the article.

Explore related subjects

Magnetic Resonance Spectroscopy Models, Molecular Molecular Structure Journal Article Research Support, Non-U.S. Gov't

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Alexandre Urzhumtsev, Ludmila Urzhumtseva. 2002-11-23. Multiple rotation function.. https://doi.org/10.1107/s0907444902016992

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2003

Total diastereofacial selective iodofunctionalization of terpene derivatives based on Ipy2BF4.

Acetonides 1, easily obtained from simple terpenes, react with bispyridine iodonium (I) tetrafluoroborate (Ipy(2)BF(4)) and tetrafluoroboric acid in the presence of nucleophiles to give the corresponding adducts 2 with complete regio and diastereofacial control. Acetonides 1 containing a properly located phenyl or benzyloxy group easily undergo iodocyclization to furnish compounds 3 and 4.

Magnetic Resonance Spectroscopy↗

PubMed2003

Increase in signal-to-noise ratio of > 10,000 times in liquid-state NMR.

A method for obtaining strongly polarized nuclear spins in solution has been developed. The method uses low temperature, high magnetic field, and dynamic nuclear polarization (DNP) to strongly polarize nuclear spins in the solid state. The solid sample is subsequently dissolved rapidly in a suitable solvent to create a solution of molecules with hyperpolarized nuclear spins. The polarization is performed in a DNP polarizer, consisting of a super-conducting magnet (3.35 T) and a liquid-helium cooled sample space. The sample is irradiated with microwaves at approximately 94 GHz. Subsequent to polarization, the sample is dissolved by an injection system inside the DNP magnet. The dissolution process effectively preserves the nuclear polarization. The resulting hyperpolarized liquid sample can be transferred to a high-resolution NMR spectrometer, where an enhanced NMR signal can be acquired, or it may be used as an agent for in vivo imaging or spectroscopy. In this article we describe the use of the method on aqueous solutions of [13C]urea. Polarizations of 37% for 13C and 7.8% for 15N, respectively, were obtained after the dissolution. These polarizations correspond to an enhancement of 44,400 for 13C and 23,500 for 15N, respectively, compared with thermal equilibrium at 9.4 T and room temperature. The method can be used generally for signal enhancement and reduction of measurement time in liquid-state NMR and opens up for a variety of in vitro and in vivo applications of DNP-enhanced NMR.

Magnetic Resonance Spectroscopy↗

PubMed2003

Calyciphyllines A and B, two novel hexacyclic alkaloids from Daphniphyllum calycinum.

[structure: see text] Two types of Daphniphyllum alkaloids with unprecedented fused-hexacyclic ring systems, calyciphyllines A (1) and B (2), have been isolated from the leaves of Daphniphyllum calycinum (Daphniphyllaceae), and the structures and relative stereochemistry were elucidated on the basis of spectroscopic data.

Magnetic Resonance Spectroscopy↗