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Metabonomic analysis of urine utilizing high-resolution NMR spectroscopy and chemometric techniques has proven valuable in characterizing the biochemical response to an intervention. To assess the effect of magnetic field strength on information contained in NMR-based metabonomic data sets, IH NMR spectra were acquired on 250-, 400-, 500-, and 800-MHz instruments, respectively, on the same set of human urine samples collected before and after dietary interventions with milk and with meat proteins. Partial least-squares regression discriminant analyses (PLS-DA) were performed in order to elucidate the ability of the [sup.1]H spectra acquired at various field strengths to identify possible spectral differences and discriminate between pre- and postintervention samples. The loadings from PLS-DA contained the same spectral regions, implying that the same metabolites were involved in the discrimination independent of magnetic field strength. The investigation revealed a strong increase in prediction performance and thereby spectral information content when increasing the magnetic field strength from 250 to 500 MHz, while from 500 to 800 MHz the increase was less pronounced.

Sampling of quadrupolar-echo solid-state NMR spectra during a quadrupolar Carr-Purcell-Meiboom-Gill pulse sequence was undertaken.

The magnitudes and relative orientations of chemical shielding dipolar and J coupling tensors for isolated (super31)P-(supe31)P spin pairs was studied using iterative fitting of (super)31P magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectra. Results showed that iterative fitting of (super31)P MAS NMR spectra present in transition-metal phosphine complexes can accurately determine parameters for isotropic and anisotropic interactions of isolated (super31)P-(super31)P spin pairs. These further demonstrated that the orientation of the chemical shielding tensors relative to each other and relative to the internuclear axis can be accurately measured.

Accurate data on the chemical shielding anisotropy parameters, quadrupole coupling constant (CQ) and associated asymmetry parameter (eta-Q), shielding tensors and quadrupole coupling exhibiting relative orientation were derived using the MAS NMR method. The relationship between the shielding anisotropy delta(sub sigma) and CQ, and the structure of the VO4 tetrahedra were exhibited in two isomorphous metavanadates KVO3, NH4VO3 and TlVO3, and LiVO3 and alpha-NAO3. A comparative analysis of the accuracy of the data proves that the 51V MAS NMR method more effective than the NMR method.

A new method is described for obtaining information about the conformational dynamics of membrane-proteins by using solid-state NMR experiments of oriented samples. The method is shown for the antimicrobial peptaibol alamethicin for which combined analysis of anisotropic interactions for the [Aib.sub.8] residue has given information about helix-tilt angle, wobbling and oscillatory rotation around the helix axis in the membrane bound state.

A combination of HBTU and acid fluoride mediated couplings for normal and [alpha],[alpha]-dialkylated amino acids are used to demonstrate an automated approach to peptaibols using microwave-assisted solid-phase peptide synthesis. The efficient and robust synthesis method could be used to synthesize eight different full-length peptaibols.

A new method is developed for improving the resolution in the [super 15]N dimension of 1D [super 15]N and 2D [super 1]H - [super 15]N separated local field (SLF) experiments for oriented membrane protein systems. The resolution enhancement is necessary for assignment and structural exploitation of spectra for large oriented membrane proteins.

The [super 2]H magic angle spinning solid-state NMR spectroscopy technique is employed to examine the membrane-bound conformation of peptaibols with metal-deuterated [alpha]-amino isobutyric acids.

The versatility of optical control theory is utilized for the design of multiple-quantum magic-angle spinning experiments for quadrupolar nuclei. The experiment offers high-resolution solid-state NMR spectra of quadrupolar nuclei with half-integer nuclear spin, normally displaying significant line broadening due to the second-order term of the quadrupole coupling interaction.

The study of the interactions between calbindin D9k (S100D) and the detergent dodecyl phosphcholine (DPC) is presented using NMR spectroscopy. Site-specific analysis of the data indicates that calbidin D9k has a core of three tightly packed helices (A, B, and D) with a dynamic fourth helix (C) more loosely associated.

The optimal control theory applied to the development of solid state NMR dipolar recouping experiments where the challenge is to minimize the loss of signal due to crystallite-orientation dependencies is reported. It is felt that the approach could have an impact on future solid-state NMR experiments.

Research was conducted to examine the hypothesis that 67Zn QCPMG NMR represents a feasible approach to study Zn2+ coordination in model complexes for metalloenzymes. The significant sensitivity enhancement of 67Zn QCPMG NMR approach as compared to QE NMR was proven to be a powerful method in studies of zinc complexes. It is anticipated that 67Zn QCPMG NMR will play a critical role in solid-state investigations of 67Zn-enriched metalloproteins.

INADEQUATE CR (composite refocusing) suitably attains high possible sensitivity through singular-value decomposition bound on the spin dynamics. This technique nearly doubles the sensitivity of INADEQUATE CR. The procedure is suitable for analysing the carbon skeleton of organic molecules in isotropic liquids. The sensitivity of 1H and 13C-detected INADEQUATE should be based on eliminating the quaternary pairs absent in 1H. The echo and antiecho parts of INADEQUATE CR contains different phi phases.

We present a new method to obtain information about the conformational dynamics of membrane- proteins using solid-state NMR experiments of oriented samples. By measuring the orientation-dependent 1H-15N dipole-dipole coupling, 15N anisotropic chemical shift, and 2H quadrupole coupling parameters for a single residue, it is possible to obtain information about the local dynamics of each residue in the protein. This may be interpreted on an individual basis or through models extended to study conformational motion of membrane-protein segments. The method is demonstrated for the antimicrobial peptaibol alamethicin for which combined analysis of anisotropic interactions for the Aib8 residue provides detailed information about helix-tilt angle, wobbling, and oscillatory rotation around the helix axis in the membrane bound state. This information is in very good agreement with coarse-grained MD simulations of the peptide in lipid bilayers. [ABSTRACT FROM AUTHOR]

We present the use of 2H magic-angle spinning (MAS) NMR on methyl-deuterated α-amino isobutyric acid (Aib) as a new method to obtain fast and accurate structural constraints on peptaibols in membrane-bound environments. Using nonoriented vesicle-reconstituted samples we avoid the delicate preparation of oriented samples, and the use of MAS ensures high sensitivity and thereby very fast acquisition of experimental spectra. Furthermore, given the high content (~40%) of Aib in peptaibols and the fact that the amino acid Aib may be synthesized from cheap starting materials, even in the case of 2H, or 13C, or 15N labeling, this method is ideally suited for studies of the membrane-bound conformation of peptaibols. [ABSTRACT FROM AUTHOR]

The optimal processing of animal slurry with a minimal environmental impact either as an organic fertilizer or as an energy source for biogas production fundamentally requires accurate, fast, cost-effective, and mobile analytical techniques for the measurement of nitrogen and phosphorus in large volumes of liquid animal slurry. Based on more than 300 different slurries from different species and origins, we provide here an extensive analysis of low-field NMR and standard laboratory measurements for animal slurry analysis. It is found that low-field NMR provides higher precision than wet chemistry laboratory measurements for ammonium nitrogen and total nitrogen, while it provides slightly lower precision for total phosphorus measurements. Low-field NMR may, through a square-root dependency between time and precision, be adapted for analysis at farms, in slurry tankers/transporters, in biogas digesters, or in laboratories., Competing Interests: The authors declare the following competing financial interest(s): Filled a patent in the area. The authors O.J., M.B., M.K.S., and N.C.N. are affiliated with NanoNord A/S selling the TVESKAEG NMR sensor for industrial and scientific applications., (© 2021 The Authors. Published by American Chemical Society.)

We present a method to calculate (31)P solid-state NMR spectra based on the dynamic input from extended molecular dynamics (MD) simulations. The dynamic information confered by MD simulations is much more comprehensive than the information provided by traditional NMR dynamics models based on, for example, order parameters. Therefore, valuable insight into the dynamics of biomolecules may be achieved by the present method. We have applied this method to study the dynamics of lipid bilayers containing the antimicrobial peptide alamethicin, and we show that the calculated (31)P spectra obtained with input from MD simulations are in agreement with experiments under a large range of different sample conditions, including vesicles and oriented samples with and without peptides. We find that the changes in the (31)P spectra upon addition of peptide stem from lipids with reduced diffusion due to peptide-lipid interactions.

Many severe diseases are associated with amyloid fibril deposits in the body caused by protein misfolding. Structural information on amyloid fibrils is accumulating rapidly, but little is known about the assembly of peptides into fibrils at the level of individual molecules. Here we investigate self-assembly of the fibril-forming tetrapeptides KFFE and KVVE on a gold surface under ultraclean vacuum conditions using scanning tunneling microscopy. Combined with restrained molecular dynamics modeling, we identify peptide arrangements with interesting similarities to fibril structures. By resolving individual peptide residues and revealing conformational heterogeneities and dynamics, we demonstrate how conformational correlations may be involved in cooperative fibril growth. Most interestingly, intermolecular interactions prevail over intramolecular interactions, and assembly of the phenyl-rich KFFE peptide appears not to be dominated by π-π interactions. This study offers interesting perspectives for obtaining fundamental single-molecule insights into fibril formation using a surface science approach to study idealized model systems.

Bacterial resistance to classical antibiotics is a serious medical problem, which continues to grow. Small antimicrobial peptides represent a potential solution and are increasingly being developed as novel therapeutic agents. Many of these peptides owe their antibacterial activity to the formation of trans-membrane ion-channels resulting in cell lysis. However, to further develop the field of peptide antibiotics, a thorough understanding of their mechanism of action is needed. Alamethicin belongs to a class of peptides called peptaibols and represents one of these antimicrobial peptides. To examine the dynamics of assembly and to facilitate a thorough structural evaluation of the alamethicin ion-channels, we have applied click chemistry for the synthesis of templated alamethicin multimers covalently attached to cyclodextrin-scaffolds. Using oriented circular dichroism, calcein release assays, and single-channel current measurements, the α-helices of the templated multimers were demonstrated to insert into lipid bilayers forming highly efficient and remarkably stable ion-channels.

We present a new and highly efficient approach for heteronuclear coherence transfer in solid-state NMR spectroscopy under high-speed spinning conditions. The so-called (RESPIRATION)CP experiment exploits phase-alternated recoupling on only one of the two rf channels intertwined in a synchronized train of short rf pulses on both channels. The method provides significantly higher efficiencies than state-of-the art techniques including ramped and adiabatic cross-polarization experiments with long durations of intense rf irradiation. At the same time, it is easier to setup experimentally and significantly more robust toward imperfections such as rf inhomogeneity, misadjustments, and sample-induced variations in the rf tuning. The method is described analytically, numerically, and experimentally for biological solids. We demonstrate sensitivity gains of factors of 1.3 and 1.8 for typical (1)H→(15)N and (15)N→(13)C transfers and a combined gain of a factor of 2-4 for a typical NCA experiment for biological solid-state NMR.

We present a novel concept for rf pulses and optimal control designed cross-polarization experiments for quadrupolar nuclei. The methods are demonstrated for (2)H CP-MAS and (2)H multiple-pulse NMR of perdeuterated proteins, for which sensitivity enhancements up to an order of magnitude are presented relative to commonly used approaches. The so-called RESPIRATION rf pulses combines the concept of short broad-band pulses with generation of pulses with large flip angles through distribution of the rf pulse over several rotor echoes. This lead to close-to-ideal rf pulses, facilitating implementation of experiments relying on the ability to realize high-performance 90 and 180° pulses, as, for example, in refocused INEPT and double-to-single quantum coherence experiments, or just pulses that provide a true representation of the quadrupolar powder pattern to extract information about the structure or dynamics. The optimal control (2)H → (13)C CP-MAS method demonstrates transfer efficiencies up to around 85% while being extremely robust toward rf inhomogeneity and resonance offsets.

Recently, ether lipids have been introduced as long-term stable alternatives to the more natural, albeit easier degradable, ester lipids in the preparation of oriented lipid bilayers and bicelles for oriented-sample solid-state NMR spectroscopy. Here we report that ether lipids such as the frequently used 14-O-PC (1,2-di-O-tetradecyl-sn-glycero-3-phosphocholine) may induce significant changes in the structure and dynamics, including altered interaction between peptides and lipids relative to what is observed with the more conventionally used DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) bilayers. Such effects are demonstrated for the antimicrobial peptide novicidin, for which 2D separate-local-field NMR and circular dichroism experiments reveal significant structural/conformational differences for the peptide in the two different lipid systems. Likewise, we observe altered secondary structure and different temperature-dependent membrane anchoring for the antimicrobial peptide alamethicin depending on whether the peptide is reconstituted into ester or ether lipids. Such observations are not particularly surprising considering the significant difference of the lipids in the phosphorus headgroup and they may provide important new insight into the delicate peptide-membrane interactions in the systems studied. In contrast, these observations reinforce the need to carefully consider potential structural changes in addition to long-term stability prior to the selection of membrane environment of membrane proteins in the analysis of their structure and dynamics. In more general terms, the results underscore the necessity in structural biology to address both the protein and its environments in studies relating structure to function., (© 2011 American Chemical Society)

We present a novel solid-state NMR method for heteronuclear dipolar recoupling without decoupling. The method, which introduces the concept of exponentially modulated rf fields, provides efficient broadband recoupling with large flexibility with respect to hetero- or homonuclear applications, sample spinning frequency, and operation without the need for high-power (1)H decoupling. For previous methods, the latter has been a severe source of sample heating which may cause detoriation of costly samples. The so-called EXPonentially mOdulated Recoupling Technique (EXPORT) is described analytically and numerically, and demonstrated experimentally by 1D (13)C spectra and 2D (13)C-(15)N correlation spectra of (13)C,(15)N-labeled samples of GB1, ubiquitin, and fibrils of the SNNFGAILSS fragment of amylin. Through its flexible operation, robustness, and strong performance, it is anticipated that EXPORT will find immediate application for both hetero- and homonuclear dipolar recoupling in solid-state NMR of (13)C,(15)N-labeled proteins and compounds of relevance in chemistry.

We present a new method to obtain information about the conformational dynamics of membrane-proteins using solid-state NMR experiments of oriented samples. By measuring the orientation-dependent (1)H-(15)N dipole-dipole coupling, (15)N anisotropic chemical shift, and (2)H quadrupole coupling parameters for a single residue, it is possible to obtain information about the local dynamics of each residue in the protein. This may be interpreted on an individual basis or through models extended to study conformational motion of membrane-protein segments. The method is demonstrated for the antimicrobial peptaibol alamethicin for which combined analysis of anisotropic interactions for the Aib(8) residue provides detailed information about helix-tilt angle, wobbling, and oscillatory rotation around the helix axis in the membrane bound state. This information is in very good agreement with coarse-grained MD simulations of the peptide in lipid bilayers.

Application of the Sonogashira coupling reaction followed by a trans-selective alkyne reduction proved highly adaptable for the efficient synthesis of a class of beta-amyloid fibril binding compounds possessing a styrylbenzene motif such as FSB, an FSB dimer, and (19)F-BAY94-9172.

We present the use of 2H magic-angle spinning (MAS) NMR on methyl-deuterated alpha-amino isobutyric acid (Aib) as a new method to obtain fast and accurate structural constraints on peptaibols in membrane-bound environments. Using nonoriented vesicle-reconstituted samples we avoid the delicate preparation of oriented samples, and the use of MAS ensures high sensitivity and thereby very fast acquisition of experimental spectra. Furthermore, given the high content ( approximately 40%) of Aib in peptaibols and the fact that the amino acid Aib may be synthesized from cheap starting materials, even in the case of 2H, 13C, or 15N labeling, this method is ideally suited for studies of the membrane-bound conformation of peptaibols.

Cation binding to Na,K-ATPase is characterized in native membranes at room temperature by solid-state NMR spectroscopy using the K(+) congener (205)Tl. It has been demonstrated that the signals from occluded Tl(+) and nonspecifically bound Tl(+) can be detected and distinguished by NMR. Effects of dipole-dipole coupling between (1)H and (205)Tl in the occlusion sites show that the ions are rigidly bound, rather than just occluded. Furthermore, a low chemical shift suggests occlusion site geometries with a relatively small contribution from carboxylate and hydroxyl groups. Nonspecific binding of Tl(+) is characterized by rapid chemical exchange, in agreement with the observed low binding affinity.