Biomedical subjects

V L Ermakov

Publications and source records attributed to V L Ermakov.

2 recordsLinked to original sources

PubMed2005

PITANSEMA-MAS, a solid-state NMR method to measure heteronuclear dipolar couplings under MAS.

A 2D NMR method is presented for the measurement of the dipole-dipole interaction between a proton and a low-frequency nuclear spin species in the solid state under the magic angle spinning. It employs the time averaged nutation concept to dramatically reduce the required radio frequency (rf) power on the low γ nuclear channel and spin exchange at the magic angle is used to suppress (1)H-(1)H dipolar interactions and chemical shifts. The flexibility in choosing the spinning speed, rf power and the scaling factor of the pulse sequence are of considerable importance for the structural studies of biological solids. The performance of the pulse sequence has been numerically and experimentally demonstrated on several solids.

Journal Article↗

PubMed1996

Divergent double chirp pulses for refocusing quadrupolar interactions.

To excite and refocus single quantum coherences in a three-level system with a quadrupolar interaction, it is possible to use frequency-modulated pulses with two diverging frequency components that are swept simultaneously through the two single-quantum transitions. This is achieved by time-dependent amplitude-modulation of the carrier frequency, so as to generate two sidebands with frequencies that are diverging (or converging) symmetrically with respect to the carrier frequency. Simulations and experiments show that such modulated pulses can be used to refocus single quantum coherences to form quadrupole echoes, using much weaker RF amplitudes than in conventional echo sequences. To visualize the evolution of the coherences in a three-level system, a graphical representation of the density operator components is proposed.

Magnetic Resonance Spectroscopy↗