Radio frequency gradient enhanced diffusion-edited semi-solid state NMR spectroscopy for detailed structural characterization of chemically modified hyaluronic acid hydrogels.

Applications of functionalized hyaluronic acid (HA) hydrogels for numerous biomedical applications requires their detailed structural characterization. Since these materials are prepared by multistep chemical modifications in the solid phase and not amenable to characterization by standard analytical tools, we employed high-resolution solid-state NMR spectroscopy to gain detailed insights into the structures of the functionalized HA hydrogels. Divinyl sulfone crosslinked HA hydrogels were converted into maleimide-functionalized hydrogels, which were subjected to chemoselective thiol-maleimide reaction using L-cysteine as the protein mimetic thiol reagent.

Efficient Access to Elusive 1D C NMR Spectra through Highly Resolved H, C-Long-Range Correlation Spectroscopy.

A method for obtaining 1D C NMR spectra from natural products or metabolites using proton detection is described. The approach delivers singlets for every C signal without conducting any broadband H decoupling (CPD) and is based on calculating C projections from constant-time HMBC and conventional HSQC experiments, recorded at high digital resolution and processed to pure phases. Paramount to the proposed method is the implication of nonuniform sampling and echo processing.

Synthetic Peptide Antibodies as TNF-α Inhibitors: Molecularly Imprinted Polymer Nanogels Neutralize the Inflammatory Activity of TNF-α in THP-1 Derived Macrophages.

Tumor Necrosis Factor-α (TNF-α) is a cytokine that is normally produced by immune cells when fighting an infection. But, when too much TNF-α is produced as in autoimmune diseases, this leads to unwanted and persistent inflammation. Anti-TNF-α monoclonal antibodies have revolutionized the therapy of these disorders by blocking TNF-α and preventing its binding to TNF-α receptors, thus suppressing the inflammation.

Boosting the resolution of multidimensional NMR spectra by complete removal of proton spin multiplicities.

Over decades multidimensional NMR spectroscopy has become an indispensable tool for structure elucidation of natural products, peptides and medium sized to large proteins. Heteronuclear single quantum coherence (HSQC) spectroscopy is one of the work horses in that field often used to map structural connectivity between protons and carbons or other hetero nuclei. In overcrowded HSQC spectra, proton multiplet structures of cross peaks set a limit to the power of resolution and make a straightforward assignment difficult.

Molecularly Imprinted Polymer Nanogels for Protein Recognition: Direct Proof of Specific Binding Sites by Solution STD and WaterLOGSY NMR Spectroscopies.

Molecularly imprinted polymers (MIPs) are tailor-made synthetic antibodies possessing specific binding cavities designed for a target molecule. Currently, MIPs for protein targets are synthesized by imprinting a short surface-exposed fragment of the protein, called epitope or antigenic determinant. However, finding the epitope par excellence that will yield a peptide "synthetic antibody" cross-reacting exclusively with the protein from which it is derived, is not easy.

Mirror symmetric broadband homodecoupled perfect echo spectroscopy.

A new experiment for recording phase sensitive ω-broadband homodecoupled TOCSY spectra is presented. The method is an extension of the already existing perfect echo (PE) filter, proposed to sample t chemical shift under sustained homodecoupling. The modification is made by attaching a time reversed perfect echo filter to a regular perfect echo scheme.

Small angle double quantum spectroscopy (SAQS NMR).

A new experiment for recording double quantum spectra is introduced. The 2D DQ NMR experiment yields phase sensitive spectra with double quantum frequencies in F. The appearance of remote peaks is vastly suppressed by using a small flip angle double quantum excitation and reconversion.

Svetamycins A-G, Unusual Piperazic Acid-Containing Peptides from Streptomyces sp.

Seven new halogenated peptides termed svetamycins A-G (1-7) have been isolated from laboratory cultures of a Streptomyces sp. Svetamycins A-D, F, and G are cyclic depsipeptides, whereas svetamycin E is a linear analogue of svetamycin C. Their structures were determined using extensive spectroscopic analysis, and their stereochemical configuration was established by a combination of NMR data, quantum mechanical calculations, and chemical derivatizations.

Faster and cleaner real-time pure shift NMR experiments.

Real-time pure shift experiments provide highly resolved proton NMR spectra which do not require any special processing. Although being more sensitive than their pseudo 2D counterparts, their signal intensities per unit time are still far below regular NMR spectra. In addition, scalar coupling evolution during the individual data chunks produces decoupling sidebands.

A different approach to multiplicity-edited heteronuclear single quantum correlation spectroscopy.

A new experiment for recording multiplicity-edited HSQC spectra is presented. In standard multiplicity-edited HSQC experiments, the amplitude of CH2 signals is negative compared to those of CH and CH3 groups. We propose to reverse the sign of (13)C frequencies of CH2 groups in t1 as criteria for editing.

Improving the sensitivity of conventional spin echo spectra by preservation of initial signal-to-noise ratio.

A simple processing strategy is introduced to enhance the spectral quality and signal-to-noise ratio in conventional J resolved spectra. The idea of pseudo echo filtering is extended to conserve the primary signal-to-noise, predominating at the beginning of the FID in the indirect dimension. This is achieved by matching the maximum amplitude of the FID with that of the sine window function.

Broadband homodecoupled NMR spectroscopy with enhanced sensitivity.

A new type of broadband homodecoupling technique is described, which is based on the original version of the Zangger-Sterk experiment, but results in a spectrum with higher sensitivity. The homodecoupling is performed by a combination of selective and non-selective 180° RF pulses in the presence of weak rectangular pulsed field gradients in a pseudo 2D experiment. The proposed experiment uses a fast pulsing approach to increase the signal-to-noise ratio per unit time.

Monitoring fast reactions by spatially-selective and frequency-shifted continuous NMR spectroscopy: application to rapid-injection protein unfolding.

The repetition rate of an NMR experiment is usually limited by the longitudinal relaxation times of the investigated molecule. Here we show that continuous excitation and data acquisition, without any interscan delay, is possible by a spatially resolved experiment where different nuclei are excited in consecutive scans.

Broadband homodecoupled heteronuclear multiple bond correlation spectroscopy.

A general concept for removing proton-proton scalar J couplings in 2D NMR spectroscopy is proposed. The idea is based on introducing an additional J resolved dimension into the pulse sequence of a conventional 2D experiment to design a pseudo 3D NMR experiment. The practical demonstration is exemplified on the widely used gradient coherence selected heteronuclear long-range correlation spectroscopy (HMBC).

Experimental access to HSQC spectra decoupled in all frequency dimensions.

A new operator called RESET "Reducing nuclEar Spin multiplicitiEs to singuleTs" is presented to acquire broadband proton decoupled proton spectra in one and two dimensions. Basically, the homonuclear decoupling is achieved through the application of bilinear rotation pulses and delays. A [BIRD](r,x) pulse building block is used to selectively invert all proton magnetization remotely attached to (13)C isotopes, which is equivalent to a scalar J decoupling of the protons directly attached to (13)C from all other protons in the spin system.

An alternative approach for recording of multidimensional NMR data based on frequency dependent folding mechanism.

A new scheme for obtaining HSQC spectra with improved resolution or in a shorter time called SHARC (Shaped Arrayed data aCquisition protocol) is proposed, which uses region selective RF pulses and allows the sweep width to be adjusted individually for each region. It thus bypasses the problems with the Nyquist theorem associated with other method suggested for this purpose. Assignment of the cross-peaks to their respective region is achieved by manipulating the phases of the RF pulses and/or their frequencies.

Convenient synthesis of multifunctional EDTA-based chiral metal chelates substituted with an S-mesylcysteine.

We describe the synthetic route to ethylenediaminetetraacetic acid (EDTA) derivatives that can be attached to surface-exposed thiol functional groups of cysteine residues in proteins, via a methylthiosulfonate moiety that is connected in a stereochemically unique way to the C-1 carbon atom of EDTA. Such compounds can be used to align proteins in solution without the need to add liquid crystalline media, and are, therefore, of great interest for the NMR spectroscopic analysis of biomolecules. The binding constant for the paramagnetic tag to lanthanide ions was determined by measuring luminescence.

Novel techniques for weak alignment of proteins in solution using chemical tags coordinating lanthanide ions.

A molecule with an anisotropic magnetic susceptibility is spontaneously aligned in a static magnetic field. Alignment of such a molecule yields residual dipolar couplings and pseudocontact shifts. Lanthanide ions have recently been successfully used to provide an anisotropic magnetic susceptibility in target molecules either by replacing a calcium ion with a lanthanide ion in calcium-binding proteins or by attaching an EDTA derivative to a cysteine residue via a disulfide bond.

Measurement of long range H,C couplings in natural products in orienting media: a tool for structure elucidation of natural products.

In this paper we show that water insoluble compounds dissolved in poly-gamma-benzyl-glutamate are amenable to the measurement of a number of homo- and heteronuclear dipolar couplings. The sensitivity and experimental precision of dipolar couplings are sufficient to obtain a good match with the structure. In order to achieve the necessary precision for H,C dipolar couplings between protons and carbons that are not directly bound a new method for the measurement of heteronuclear long range couplings is introduced that allows a one-parameter fit to a HSQC-based experiment as reference experiment.