Taipan Natriuretic Peptides Are Potent and Selective Agonists for the Natriuretic Peptide Receptor A.

Cardiovascular ailments are a major cause of mortality where over 1.3 billion people suffer from hypertension leading to heart-disease related deaths. Snake venoms possess a broad repertoire of natriuretic peptides with therapeutic potential for treating hypertension, congestive heart failure, and related cardiovascular disease.

Molecular details of aluminium-amyloid β peptide interaction by nuclear magnetic resonance.

Alzheimer's disease (AD) is a devastating neurodegenerative condition that poses major challenges to human health. Both amyloid β (Aβ) and metal ions such as aluminium are implicated in the development of AD. By the means of NMR, the interactions of Al with Aβ peptide as well as the Aβ analogues were studied, and the key binding sites of Al in Aβ determined.

Applications of WaterControl to TOCSY and COSY experiments.

WaterControl is a solvent suppression method based on WATERGATE and PGSTE and is very efficient in selectively reducing the solvent signal in 1D pulse-acquire and 2D NOESY of protein solutions. In this study, the WaterControl technique was appended to two common 2D NMR methods used in resonance assignment of proteins, namely TOCSY and CLIP-COSY. Similar to that observed in regular 1D pulse-acquire and 2D NOESY, the incorporation of WaterControl in these 2D methods led to excellent solvent suppression superior to that obtained using W3- or W5-based WATERGATE sequences.

A Simple and Effective Binomial Block Based Pulse Sequence Capable of Suppressing Multiple NMR Signals.

A binomial-like block based multiple suppression NMR pulse sequence, termed MULTI-GATE-FSB, that is simple to implement with outstanding suppression performance for multiple solvent signals (or multiple resonances) is investigated. The sequence was tested on two water-alcohol solvent systems, and a standard lysozyme sample, with suppression of three or four regions (though it is extendable to any number of regions). The suppression of all solvent signals was possible in the alcohol-water systems tested with both long and short recycle delays and without the requirement for lengthy presaturation pulses.

NMR diffusion and relaxation studies of 2-nitroimidazole and albumin interactions.

Nitroimidazole derivatives are of current interest in the development of hypoxia targeting agents and show potential in the establishment of quantitative measures of tumor hypoxia. In this study, the binding of 2-nitroimidazole to albumin was probed using NMR diffusion and relaxation measurements. Binding studies were conducted at three different protein concentrations (0.

NOESY-WaterControl: a new NOESY sequence for the observation of under-water protein resonances.

Highly selective and efficient water signal suppression is indispensable in biomolecular 2D nuclear Overhauser effect spectroscopy (NOESY) experiments. However, the application of conventional water suppression schemes can cause a significant or complete loss of the biomolecular resonances at and around the water chemical shift (ω). In this study, a new sequence, NOESY-WaterControl, was developed to address this issue.

Physical characterization using diffusion NMR spectroscopy.

NMR diffusion measurements (or dNMR) provide a powerful tool for analysis of solution organization and microgeometry of the environment by probing random molecular motion. Being a very versatile method, dNMR can be applied to a large variety of samples and systems. Here, a brief introduction into dNMR and a summary of recent advances in the field are presented.

WaterControl: self-diffusion based solvent signal suppression enhanced by selective inversion.

Selective inversion/excitation based solvent signal suppression techniques are widely used in various NMR experiments because of their high efficiency and general applicability. However, these techniques generate a 'null'/suppression region containing (non-quantitatively) degraded solvent and desired resonances because of their reliance on the rejection of the coherence transfer pathway corresponding to all the resonances within the suppression region. To address this issue, the WaterControl technique was developed by inserting a (pulsed gradient - selective inversion pulse - pulsed gradient) unit into each 'transverse' period of a standard stimulated echo pulse sequence so that the coherence transfer pathways corresponding to both the suppression and non-suppression regions can be selected in one transient.

Structure and antimicrobial activity of platypus 'intermediate' defensin-like peptide.

The three-dimensional structure of a chemically synthesized peptide that we have called 'intermediate' defensin-like peptide (Int-DLP), from the platypus genome, was determined by nuclear magnetic resonance (NMR) spectroscopy; and its antimicrobial activity was investigated. The overall structural fold of Int-DLP was similar to that of the DLPs and β-defensins, however the presence of a third antiparallel β-strand makes its structure more similar to the β-defensins than the DLPs. Int-DLP displayed potent antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa.

Restricted diffusion in annular geometrical pores.

Nuclear magnetic resonance (NMR) diffusion (including diffusion MRI) experiments are only as powerful as the models used to analyse the NMR diffusion data. A major problem, especially with measurements on biological systems, is that the existing models are only very poor approximations of cellular shape. Here, diffusion propagators and pulsed gradient spin-echo attenuation equations are derived in the short gradient pulse limit for diffusion within the annular region of a concentric cylinder of finite length and, similarly, within the annular region of a concentric sphere.

Detection of platypus-type L/D-peptide isomerase activity in aqueous extracts of papaya fruit.

Peptide isomerase catalyses the post-translational isomerisation of the L: - to the D: -form of an amino acid residue around the N/C-termini of substrate peptides. To date, some peptide isomerases have been found in a limited number of animal secretions and cells. We show here that papaya extracts have weak peptide isomerase activity.

Insights into hERG K+ channel structure and function from NMR studies.

The unique gating kinetics of hERG K(+) channels are critical for normal cardiac repolarization, and patients with mutations in hERG have a markedly increased risk of cardiac arrhythmias and sudden cardiac arrest. HERG K(+) channels are also remarkably promiscuous with respect to drug binding, which has been a very significant problem for the pharmaceutical industry. Here, we review the progress that has been made in understanding the structure and function of hERG K(+) channels with a particular focus on nuclear magnetic resonance studies of the domains of the hERG K(+) channel.

NMR study of the structure and self-association of Core peptide in aqueous solution and DPC micelles.

Core peptide is a hydrophobic peptide derived from the T-cell antigen receptor-alpha chain (TCR-alpha) transmembrane region with therapeutic potential. The mechanism by which the peptide inserts into the membrane, including any requirements to change conformational or association states during the insertion, is unclear. Here, the self-association and secondary structure of Core peptide in aqueous solution and in dodecylphosphocholine (DPC) micelles were examined using various nuclear magnetic resonance (NMR) techniques.

NMR q-space imaging of macroscopic pores using singlet spin states.

NMR q-space imaging is a powerful non-invasive technique used to determine structural characteristics of pores in applications ranging from medical to material science. To date, the application of q-space imaging has primarily been limited to microscopic pores in part because of limitations of the effective observation time due to relaxation. Here we report on the use of singlet spin states for NMR q-space imaging, which allow significantly greater observation times.

J-compensated PGSE: an improved NMR diffusion experiment with fewer phase distortions.

Peak distortion caused by homonuclear (1)H J-coupling is a major problem in many spin-echo-based experiments such as pulsed gradient spin-echo (PGSE) experiments. Although peak phase distortions can be lessened by the incorporation of anti-phase purging sequences, the sensitivity is substantially decreased. Techniques for lessening the effect of homonuclear J-coupling evolution in spin-echo-based experiments have been investigated.

MQ-PGSTE: a new multi-quantum STE-based PGSE NMR sequence.

A new multi-quantum stimulated echo based pulsed gradient spin-echo sequence, MQ-PGSTE, has been developed for measuring translational diffusion. The new sequence provides a higher signal-to-noise ratio than the (Hahn spin-echo based) MAXY-D sequence at long diffusion times, and thus potentially affords better diffusion measurements on macromolecule samples. Based on multi-quantum coherence encoding, the MQ-PGSTE sequence needs considerably lower gradient strengths for diffusion characterization compared to standard single quantum pulsed gradient spin-echo sequences.

Structure of the pore-helix of the hERG K(+) channel.

The hERG K(+) channel undergoes rapid inactivation that is mediated by 'collapse' of the selectivity filter, thereby preventing ion conduction. Previous studies have suggested that the pore-helix of hERG may be up to seven residues longer than that predicted by homology with channels with known crystal structures. In the present work, we determined structural features of a peptide from the pore loop region of hERG (residues 600-642) in both sodium dodecyl sulfate (SDS) and dodecyl phosphocholine (DPC) micelles using NMR spectroscopy.

Understanding and utilising mammalian venom via a platypus venom transcriptome.

Only five mammalian species are known to be venomous, and while a large amount of research has been carried out on reptile venom, mammalian venom has been poorly studied to date. Here we describe the status of current research into the venom of the platypus, a semi-aquatic egg-laying Australian mammal, and discuss our approach to platypus venom transcriptomics. We propose that such construction and analysis of mammalian venom transcriptomes from small samples of venom gland, in tandem with proteomics studies, will allow the identification of the full range of mammalian venom components.

The pore domain outer helix contributes to both activation and inactivation of the HERG K+ channel.

Ion flow in many voltage-gated K(+) channels (VGK), including the (human ether-a-go-go-related gene) hERG channel, is regulated by reversible collapse of the selectivity filter. hERG channels, however, exhibit low sequence homology to other VGKs, particularly in the outer pore helix (S5) domain, and we hypothesize that this contributes to the unique activation and inactivation kinetics in hERG K(+) channels that are so important for cardiac electrical activity. The S5 domain in hERG identified by NMR spectroscopy closely corresponded to the segment predicted by bioinformatics analysis of 676 members of the VGK superfamily.

Solvent suppression using phase-modulated binomial-like sequences and applications to diffusion measurements.

Two phase-modulated binomial-like pi pulses have been developed by simultaneously optimizing pulse durations and phases. In combination with excitation sculpting, both of the new binomial-like sequences outperform the well-known 3-9-19 sequence in selectivity and inversion width. The new sequences provide similar selectivity and inversion width to the W5 sequence but with significantly shorter sequence durations.

An improved approach to calibrating high magnetic field gradients for pulsed field gradient experiments.

Probes capable of generating short high intensity pulsed magnetic field gradients are commonly used in diffusion studies of systems with very short T(2). Traditional methods of calibrating magnetic field gradients present unique challenges at ultrahigh field strengths and are often inapplicable. Currently the most accurate method of determining magnetic gradient strength is to use the known diffusion coefficient of a standard sample and determine gradient strength from the echo attenuation plot of a diffusion experiment, however, there are problems with finding suitable standards for high intensity gradients.

Removal of J-coupling peak distortion in PGSE experiments.

Peak distortion caused by homonuclear J-coupling is a major problem that limits the utility of the pulsed-field gradient spin-echo (PGSE) method for studying translational diffusion. This unwanted effect can be removed by incorporation of anti-phase magnetization purging pulse elements at the end of the spin-echo sequence. Three methods, namely, trim-pulse, homospoil pulse gradient and chirp based z-filter were evaluated as potential candidates for an improved NMR diffusion method that is less sensitive to J-coupling peak distortion.

Defensins and the convergent evolution of platypus and reptile venom genes.

When the platypus (Ornithorhynchus anatinus) was first discovered, it was thought to be a taxidermist's hoax, as it has a blend of mammalian and reptilian features. It is a most remarkable mammal, not only because it lays eggs but also because it is venomous. Rather than delivering venom through a bite, as do snakes and shrews, male platypuses have venomous spurs on each hind leg.

Examination of cucurbit[7]uril and its host-guest complexes by diffusion nuclear magnetic resonance.

The self-diffusion of cucurbit[7]uril (CB[7]) and its host-guest complexes in D2O has been examined using pulsed gradient spin-echo nuclear magnetic resonance spectroscopy. CB[7] diffuses freely at a concentration of 2 mM with a diffusion coefficient (D) of 3.07 x 10(-10) m(2) s(-1).