Superposition of scalar and residual dipolar couplings: analytical transfer functions for three spins 1/2 under cylindrical mixing conditions.

The superposition of scalar and residual dipolar couplings gives rise to so-called cylindrical mixing Hamiltonians in dipolar coupling spectroscopy. General analytical polarization and coherence transfer functions are presented for three cylindrically coupled spins 12 under energy-matched conditions. In addition, the transfer efficiency is analyzed as a function of the relative coupling constants for characteristic special cases.

Analytical planar mixing transfer functions for two coupled spin-1 nuclei.

Analytical coherence transfer functions are presented for spin systems consisting of two spins 1 under planar mixing conditions. Compared to isotropic mixing experiments, larger transfer amplitudes are found and differences in the multiplet patterns are discussed.

Single-shot experiments for the acquisition of coherence-transfer functions in real time.

Simple pulse sequences are introduced that make it possible to acquire experimental Hartmann-Hahn transfer functions for arbitrary multiple-pulse sequences in a single shot. With this approach it is possible to study the detailed dependence of coherence-transfer functions on experimental parameters in real time.

Analytical polarization and coherence transfer functions for three dipolar coupled spins 12.

Analytical polarization and coherence transfer functions are presented for a spin system consisting of three dipolar coupled homonuclear spins 12 under energy matched conditions. Based on these transfer functions, optimal durations of Hartmann-Hahn mixing periods can be determined for arbitrary dipolar coupling constants D(12), D(13), and D(23). In addition, the dependence of the transfer efficiency on the relative size of the dipolar coupling constants is illustrated.

Broadband heteronuclear Hartmann-Hahn sequences with short cycle times.

For some applications, broadband heteronuclear Hartmann-Hahn sequences with very short cycle times are required. A quality factor is presented that makes it possible to assess the relative sizes of cycle time, bandwidth, and maximum RF amplitude for any given multiple-pulse sequence. This quality factor is determined for multiple-pulse sequences that are commonly used in HEHAHA experiments and for some favorable sequences that were so far only discussed in the context of heteronuclear decoupling.

S(3)E-E.COSY methods for the measurement of (19)F associated scalar and dipolar coupling constants.

A (1)H-(19)F spin state selective excitation (S(3)E) pulse sequence element has been applied in combination with (1)H homonuclear mixing to create E.COSY-type experiments designed to measure scalar J(HF2') and J(HH2') and residual dipolar D(HF2') and D(HH2') couplings in 2'-deoxy-2'-fluoro-sugars. The (1)H-(19)F S(3)E pulse sequence element, which resembles a simple INEPT sequence, achieves spin-state-selective correlation between geminal (1)H-(19)F spin pairs by linear combination of in-phase (19)F magnetization and anti-phase magnetization evolved from (1)H. Since the S(3)E sequence converts both (19)F and (1)H steady-state polarization into observable coherences, an approximately twofold signal increase is observed for fully relaxed (1)H-(19)F spin pairs with respect to a standard (1)H coupled (19)F 1D experiment. The improved sensitivity and resolution afforded by the use of (1)H-(19)F S(3)E E.COSY-type experiments for measuring couplings is demonstrated on the nucleoside 9-(2',3'-dideoxy-2'-fluoro-beta-D-threo-pentofuranosyl)adenine (beta-FddA) and on a selectively 2'-fluorine labeled 21mer RNA oligonucleotide.

Suicide, chemical abuse, and panic attacks: a preliminary report.

Seventy-two chemical abuse patients who either met DSM-III-R criteria for panic disorder (PD), experienced infrequent panic attacks (IP), or did not experience panic attacks in the past year (NP) were compared on several dimensions. PD subjects were more likely to be female and to have attempted suicide. Patients who had attempted suicide, when compared to non-suicide attempters, were more likely to be classified as having PD, and be non-married. IP and NP groups did not differ on any of the relevant variables. The similarities of these findings to those obtained with PD and chemical abuse patients are discussed.

"Kin " HEHAHA Sequences, Heteronuclear Hartmann-Hahn Transfer with Different Bandwidths for Spins I and S

A new class of heteronuclear Hartmann-Hahn experiments that is based on the simultaneous irradiation of two different multiple-pulse sequences is introduced. For these "kin " HEHAHA sequences, the scaling properties of the effective heteronuclear coupling constants are analyzed. Four kin sequences are presented with a ratio of the active bandwidths DeltanuI /DeltanuS ranging between 1/2 and 1/10. The offset dependence of the polarization-transfer efficiency is examined experimentally and with the help of numerical simulations.

Analytical polarization transfer functions for four coupled spins 12 under isotropic mixing conditions

Analytical polarization transfer functions are presented for spin systems consisting of four spins 12 with arbitrary coupling constants under isotropic mixing conditions. In addition, simplified transfer functions were derived for symmetric coupling topologies. Based on these transfer functions optimal durations for the mixing period can be determined for correlations of interest. Copyright 1999 Academic Press.

Measurement and application of 1H-19F dipolar couplings in the structure determination of 2'-fluorolabeled RNA.

Residual dipolar couplings can provide powerful restraints for determination and refinement of the solution structure of macromolecules. The application of these couplings in nucleic acid structure elucidation can have an especially dramatic impact, since they provide long-range restraints, typically absent in NOE and J-coupling measurements. Here we describe sensitive X-filtered-E.COSY-type methods designed to measure both the sign and magnitude of long-range 1H-19F dipolar couplings in selectively fluorine labeled RNA oligonucleotides oriented in solution by a liquid crystalline medium. The techniques for measuring 1H-19F dipolar couplings are demonstrated on a 21-mer RNA hairpin, which has been specifically labeled with fluorine at the 2'-hydroxyl position of three ribose sugars. Experimentally measured 1H-19F dipolar couplings for the 2'-deoxy-2'-fluoro-sugars located in the helical region of the RNA hairpin were found to be in excellent agreement with values predicted using canonical A-form helical geometry, demonstrating that these couplings can provide accurate restraints for the refinement of RNA structures determined by NMR.

Analytical Polarization and Coherence Transfer Functions for Three Coupled Spins 1/2 under Planar Mixing Conditions

Analytical polarization and coherence transfer functions are presented for spin systems consisting of three spins 1/2 with arbitrary coupling constants under planar mixing conditions. In addition, simplified transfer functions were derived for symmetric coupling topologies. Based on these transfer functions optimal durations for the mixing period can be determined for correlations of interest. Copyright 1998 Academic Press. Copyright 1998 Academic Press