Frequency-switched single-transition cross-polarization: a tool for selective experiments in biomolecular NMR.

Frequency-switched single-transition cross-polarization (FS-ST-CP) provides a versatile tool for selective coherence transfer in heteronuclear NMR of biomolecules such as proteins and nucleic acids. This type of coherence transfer is spin-state-selective and can therefore benefit from the extension of the life-times of selected coherences due to partial cancellation of interfering relaxation mechanisms. The limits of the selectivity of the transfer are discussed by theory and illustrated by experiment.

Thermodynamics of binding of 2-methoxy-3-isopropylpyrazine and 2-methoxy-3-isobutylpyrazine to the major urinary protein.

In the present study we examine the thermodynamics of binding of two related pyrazine-derived ligands to the major urinary protein, MUP-I, using a combination of isothermal titration calorimetry (ITC), X-ray crystallography, and NMR backbone (15)N and methyl side-chain (2)H relaxation measurements. Global thermodynamics data derived from ITC indicate that binding is driven by favorable enthalpic contributions, rather than the classical entropy-driven hydrophobic effect. Unfavorable entropic contributions from the protein backbone and side-chain residues in the vicinity of the binding pocket are partially offset by favorable entropic contributions at adjacent positions, suggesting a "conformational relay" mechanism whereby increased rigidity of residues on ligand binding are accompanied by increased conformational freedom of side chains in adjacent positions.

Evidence for slow motion in proteins by multiple refocusing of heteronuclear nitrogen/proton multiple quantum coherences in NMR.

A novel NMR method characterizes slow motions in proteins by multiple refocusing of double- and zero-quantum coherences of amide protons and nitrogen-15 nuclei. If both nuclei experience changes in their isotropic chemical shifts because of internal motions on slow time scales (mus - ms), this leads to a difference in the relaxation rates of double- and zero-quantum coherences. This is due to CSM/CSM (chemical shift modulation) cross-correlation effects that are related to the well-known chemical exchange contribution Rex to the decay rate R2 = 1/T2 of nitrogen-15 nuclei.

Evidence of slow motions by cross-correlated chemical shift modulation in deuterated and protonated proteins.

Cross-correlated fluctuations of isotropic chemical shifts can provide evidence for slow motions in biomolecules. Slow side-chain dynamics have been investigated in (15)N and (13)C enriched ubiquitin by monitoring the relaxation of C(alpha)-C(beta) two-spin coherences (Frueh et al., 2001).

Triple quantum decoherence under multiple refocusing: slow correlated chemical shift modulations of C' and N nuclei in proteins.

A new experiment allows the identification of residues that feature slow conformational exchange in macromolecules. Rotations about dihedral angles that are slower than the global correlation time tau(c) cause a modulation of the isotropic chemical shifts of the nuclei. If these fluctuations are correlated they induce a differential line broadening between three-spin single-quantum and triple-quantum coherences involving three nuclei such as the carbonyl C', the neighbouring amide nitrogen N and the amide proton H(N) belonging to a pair of consecutive amino acids.

Facing prejudice: implicit prejudice and the perception of facial threat.

We propose that social attitudes, and in particular implicit prejudice, bias people's perceptions of the facial emotion displayed by others. To test this hypothesis, we employed a facial emotion change-detection task in which European American participants detected the offset (Study 1) or onset (Study 2) of facial anger in both Black and White targets. Higher implicit (but not explicit) prejudice was associated with a greater readiness to perceive anger in Black faces, but neither explicit nor implicit prejudice predicted anger perceptions regarding similar White faces.

Hydrogen bonds lengths in nucleic acids estimated from longitudinal nitrogen-15 relaxation.

A new NMR method has been designed for the measurement of the longitudinal relaxation rates of both donor and acceptor nitrogen-15 nuclei in Watson-Crick base pairs in 15N-enriched nucleic acids. The experiment was applied to a 22-nucleotide RNA hairpin. The lengths of four hydrogen bonds could be estimated from the longitudinal relaxation rates.

Cross correlations between 13C-1H dipolar interactions and 15N chemical shift anisotropy in nucleic acids.

Two sets of cross-correlated relaxation rates involving chemical shift anisotropy and dipolar interactions have been measured in an RNA kissing complex. In one case, both the CSA and dipolar interaction tensors are located on the same nucleotide base and are rigidly fixed with respect to each other. In the other case, the CSA tensor is located on the nucleotide base whereas the dipolar interaction is located on the adjoining ribose unit.

Transferred cross-relaxation and cross-correlation in NMR: effects of intermediate exchange on the determination of the conformation of bound ligands.

Exchange transferred effects in solution-state NMR experiments allow one to determine the conformation of ligands that are weakly bound to macromolecules. Exchange-transferred nuclear Overhauser effect spectroscopy ('TR-NOESY') provides information about internuclear distances in a ligand in the bound state. Recently the possibility of obtaining dihedral angle information from a ligand in the bound state by exchange-transferred cross-correlation spectroscopy ('TR-CCSY') has been reported.

Cross-correlation between a carbonyl C' chemical shift anisotropy and a long-range dipolar C'HA coupling in proteins using symmetrical reconversion.

A new sequence is described to measure the cross-correlation rates between the chemical shift anisotropy of the carbonyl carbon-13 nucleus and the dipole-dipole interaction between this carbonyl and the alpha-proton in proteins. The sequence is based on the symmetrical reconversion principle and is insensitive to experimental errors and to violations of the secular approximation. The cross-correlation rate depends on the backbone angle psi.

Demonstrating translational research for mental health services: an example from stigma research.

In seeking to understand how the goal of providing efficient and effective mental health services can best be attained, services researchers have developed principles and methods that distinguish it from other research approaches. In 2000, the National Institute of Mental Health called for translational research paradigms that seek to expand the conceptual and methodological base of mental health services with knowledge gained from basic behavioral sciences such as cognitive, developmental, and social psychology. The goal of this paper is to enter the discussion of what is translational research by illustrating a services research program of the Chicago Consortium for Stigma Research on mental illness stigma.

Similarities between intra- and intermolecular hydrogen bonds in RNA kissing complexes found by means of cross-correlated relaxation.

The bond lengths and dynamics of intra- and intermolecular hydrogen bonds in an RNA kissing complex have been characterized by determining the NMR relaxation rates of various double- and triple-quantum coherences that involve an imino proton and two neighboring nitrogen-15 nuclei belonging to opposite bases. New experiments allow one to determine the chemical shift anisotropy of the imino protons. The bond lengths derived from dipolar relaxation and the lack of modulations of the nitrogen chemical shifts indicate that the intermolecular hydrogen bonds which hold the kissing complex together are very similar to the intramolecular hydrogen bonds in the double-stranded stem of the RNA.

Correlated motions of successive amide N-H bonds in proteins.

New nuclear magnetic resonance (NMR) methods are described for the measurement of cross-correlation rates of zero- and double-quantum coherences involving two nitrogen nuclei belonging to successive amino acids in proteins and peptides. Rates due to the concerted fluctuations of two NH(N) dipole-dipole interactions and to the correlated modulations of two nitrogen chemical shift anisotropies have been obtained in a sample of doubly labeled Ubiquitin. Ambiguities in the determination of dihedral angles can be lifted by comparison of different rates.

Symmetrical reconversion: measuring cross-correlation rates with enhanced accuracy.

A new strategy has been developed to measure cross-correlation rates with much enhanced accuracy. The method relies on the use of four complementary experiments. Errors due to pulse miscalibration and to uncontrolled attenuation factors associated with relaxation are cancelled out.

Slow diffusion of macromolecular assemblies by a new pulsed field gradient NMR method.

The translational diffusion coefficient of an integral membrane protein/surfactant complex has been measured using a novel pulsed field gradient NMR method. In this new approach, the information about the localization of the molecules is temporarily stored in the form of longitudinal magnetization of isotopes with long spin-lattice relaxation times. This allows one to increase the duration of the diffusion interval by about 1 order of magnitude.

Accurate measurement of residual dipolar couplings in anisotropic phase.

The determination of residual dipolar couplings (RDCs) by quantitative J spectroscopy methods such as Heteronuclear Single Quantum Correlation with Phase Encoded Coupling (HSQC-PEC) is prone to systematic errors that may be caused by differential attenuation during the conversion of orthogonal density operator components into observable terms. The attenuation may be caused by miscalibration of radio-frequency pulses and by relaxation effects. A simple method is presented that allows one to remove most of these systematic errors without losses in sensitivity or resolution.

Measurement of long-range cross-correlation rates using a combination of single- and multiple-quantum NMR spectroscopy in one experiment.

A method is described to determine long-range cross-correlations between the modulations of an anisotropic chemical shift (e.g., of a C' carbonyl carbon in a protein) and the fluctuations of a weak long-range dipolar interaction (e.

Highly selective excitation in biomolecular NMR by frequency-switched single-transition cross-polarization.

A new method for selective excitation in biomolecular NMR uses two-fold single-transition cross-polarization between protons and nitrogen-15 or carbon-13 nuclei. Switching the frequencies between the forward and backward transfer steps allows one to select a multiplet pattern that is associated with a single pair of spins in a medium-size protein. The efficiency of the transfer benefits from so-called TROSY line-narrowing effects which arise from interference between relaxation mechanisms.

I know you are, but what am I? Self-evaluative consequences of judging in-group and out-group members.

When judging another person, people often spontaneously compare this person with themselves. Six studies examined the self-evaluative consequences of such spontaneous comparisons with in-group versus out-group members. They demonstrate that spontaneous comparisons with in-group members primarily involved the activation of specific individuating knowledge about the self.

Social cognition: Categorical person perception.

In attempting to make sense of others, perceivers regularly construct and use categorical representations (e.g. stereotypes) to streamline the person perception process.

Creating memory illusions: expectancy-based processing and the generation of false memories.

The present research investigated the generation of memory illusions. In particular, it attempted to delineate the conditions under which category-based thinking prompts the elicitation of false memories. Noting fundamental differences in the manner in which expected and unexpected person-related information is processed and represented in the mind, it was anticipated that, via gist-based recognition, participants would display a pronounced propensity to generate expectancy-consistent false memories.

Anisotropy of rotational diffusion, dipole-dipole cross-correlated NMR relaxation and angles between bond vectors in proteins.

Cross correlations between the fluctuations of dipolar (13)C(α)-(1)H(α) interactions yield information about the relative orientation of successive (13)C(α)-(1)H(α) bond vectors in proteins, in turn providing a direct handle on their structure and dynamics in solution. However, overall anisotropic reorientation must be taken into account in the interpretation of cross-correlation rates. The protein shown, human ubiquitin, has amino acid residues in white where the cross-correlation rates deviate from those predicted for a rigid structure.

Cross-correlated chemical shift modulation: a signature of slow internal motions in proteins.

A novel NMR experiment allows one to characterize slow motion in macromolecules. The method exploits the fact that motions, such as rotation about dihedral angles, induce correlated fluctuations of the isotropic chemical shifts of the nuclei in the vicinity. The relaxation of two-spin coherences involving C(alpha) and Cbeta nuclei in proteins provides information about correlated fluctuations of the isotropic chemical shifts of C(alpha) and Cbeta.

Probing aerogels by multiple quantum filtered (131)Xe NMR spectroscopy.

At the interface between solid surfaces and cavities filled with gaseous or liquid xenon, the nuclear magnetization of (131)Xe (S = (3)/(2)) is subject to quadrupolar interactions which may lead to higher rank single-quantum coherences that can be described by tensor elements T(2,)(+/-)(1) and T(3,)(+/-)(1). This can be demonstrated by multiple-quantum filtered (MQF) NMR experiments. In gaseous xenon on Pyrex surfaces, the primary source of such coherences was shown to be coherent evolution induced by a nonvanishing average quadrupolar coupling.

Sadness and susceptibility to judgmental bias: the case of anchoring.

In a wide range of empirical paradigms, sadness has been associated with more extensive and detail-oriented thinking than happiness, resulting in reductions in judgmental bias that arise from reliance on stereotypes and other simple decision heuristics. It was hypothesized that anchoring would constitute a significant exception to this general pattern. Recent research on anchoring indicates that an active thought process underlies the emergence of this bias.