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[NMR paper] 1H-detected MAS solid-state NMR experiments enable the simultaneous mapping of rigid and dynamic domains of membrane proteins
Nov 24, 2017 - 5:56 PM - by nmrlearner
nmrlearner's Avatar 1H-detected MAS solid-state NMR experiments enable the simultaneous mapping of rigid and dynamic domains of membrane proteins

Publication date: December 2017
Source:Journal of Magnetic Resonance, Volume 285

Author(s): T. Gopinath, Sarah E.D. Nelson, Gianluigi Veglia

Magic angle spinning (MAS) solid-state NMR (ssNMR) spectroscopy is emerging as a unique method for the atomic resolution structure determination of native membrane proteins in lipid bilayers. Although 13C-detected ssNMR experiments continue to play a major role, recent technological developments have made it possible to carry out 1H-detected experiments, boosting both sensitivity and resolution. Here, we describe a new set of 1H-detected hybrid pulse sequences that combine through-bond and through-space correlation elements into single experiments, enabling the simultaneous detection of rigid and dynamic domains of membrane proteins. As proof-of-principle, we applied these new pulse sequences to the membrane protein phospholamban (PLN) reconstituted in lipid bilayers under moderate MAS conditions. The cross-polarization (CP) based elements enabled the detection of the relatively immobile residues of PLN in the transmembrane domain using through-space correlations; whereas the most dynamic region, which is in equilibrium between folded and unfolded states, was mapped by through-bond INEPT-based elements. These new 1H-detected experiments will... [Read More]
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Dissolution DNP using trityl radicals at 7 T field #DNPNMR
Nov 24, 2017 - 5:56 PM - by nmrlearner
nmrlearner's Avatar From The DNP-NMR Blog:

Dissolution DNP using trityl radicals at 7 T field #DNPNMR

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Jahnig, F., et al., Dissolution DNP using trityl radicals at 7 T field. Phys. Chem. Chem. Phys., 2017. 19(29): p. 19196-19204.


https://www.ncbi.nlm.nih.gov/pubmed/28702550


Dissolution DNP has become an important method to generate highly polarized substrates such as pyruvic acid for in vivo imaging and localized spectroscopy. In a quest to further increase the polarization levels, which is important for in vivo MRI employing 13C detection, we describe the design and implementation of a new DNP polarizer that is suitable for dissolution operation at 7 T static magnetic field and a temperature of 1.4 K. We describe all important sample preparation steps and experimental details necessary to optimize trityl based samples for use in our polarizer at this higher field. In [1-13C]-pyruvic acid polarization levels of about 56% are achieved, compared to typical polarization levels of about 35-45% at a standard field of 3.4 T. At the same time, the polarization build-up time increases significantly from about 670 s at 3.4 T to around 1300-1900 s at 7 T, depending on the trityl derivate used. We also investigate the effect of adding trace amounts of Gd3+ to the samples. While one trityl compound does not exhibit any benefit, the other profits significantly, boosting achievable polarization by 6%.
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[NMR paper] Short two-armed lanthanide-binding tags for paramagnetic NMR spectroscopy based on chiral 1,4,7,10-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane scaffolds.
Nov 24, 2017 - 4:57 AM - by nmrlearner
nmrlearner's Avatar Short two-armed lanthanide-binding tags for paramagnetic NMR spectroscopy based on chiral 1,4,7,10-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane scaffolds.

Short two-armed lanthanide-binding tags for paramagnetic NMR spectroscopy based on chiral 1,4,7,10-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane scaffolds.

Chem Commun (Camb). 2017 Nov 22;:

Authors: Lee MD, Dennis ML, Graham B, Swarbrick JD

Abstract
A new pair of enantiomeric two-armed lanthanide-binding tags have been developed for paramagnetic NMR studies of proteins. The tags produce large and significantly different paramagnetic effects to one another when bound to the same tagging site. Additionally, they are less sensitive to sample pH than our previous two-armed tag designs.


PMID: 29165449 [PubMed - as supplied by publisher]



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NMR structure and localization of a large fragment of the SARS-CoV fusion protein: Implications in viral cell fusion
Nov 23, 2017 - 8:38 AM - by nmrlearner
nmrlearner's Avatar NMR structure and localization of a large fragment of the SARS-CoV fusion protein: Implications in viral cell fusion

Publication date: February 2018
Source:Biochimica et Biophysica Acta (BBA) - Biomembranes, Volume 1860, Issue 2

Author(s): Mukesh Mahajan, Deepak Chatterjee, Kannaian Bhuvaneswari, Shubhadra Pillay, Surajit Bhattacharjya

The lethal Coronaviruses (CoVs), Severe Acute Respiratory Syndrome-associated Coronavirus (SARS-CoV) and most recently Middle East Respiratory Syndrome Coronavirus, (MERS-CoV) are serious human health hazard. A successful viral infection requires fusion between virus and host cells carried out by the surface spike glycoprotein or S protein of CoV. Current models propose that the S2 subunit of S protein assembled into a hexameric helical bundle exposing hydrophobic fusogenic peptides or fusion peptides (FPs) for membrane insertion. The N-terminus of S2 subunit of SARS-CoV reported to be active in cell fusion whereby FPs have been identified. Atomic-resolution structure of FPs derived either in model membranes or in membrane mimic environment would glean insights toward viral cell fusion mechanism. Here, we have solved 3D structure, dynamics and micelle localization of a 64-residue long fusion peptide or LFP in DPC detergent micelles by NMR methods. Micelle bound structure of LFP is elucidated by the presence of discretely folded helical and intervening loops. The... [Read More]
0 Replies | 16 Views
Quantifying reaction kinetics of the non-enzymatic decarboxylation of pyruvate and production of peroxymonocarbonate with hyperpolarized 13C-NMR
Nov 23, 2017 - 8:38 AM - by nmrlearner
nmrlearner's Avatar From The DNP-NMR Blog:

Quantifying reaction kinetics of the non-enzymatic decarboxylation of pyruvate and production of peroxymonocarbonate with hyperpolarized 13C-NMR

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Drachman, N., et al., Quantifying reaction kinetics of the non-enzymatic decarboxylation of pyruvate and production of peroxymonocarbonate with hyperpolarized 13C-NMR. Phys. Chem. Chem. Phys., 2017. 19(29): p. 19316-19325.


http://dx.doi.org/10.1039/C7CP02041D


<div style="text-align: justify;">The transient nature of intermediate states in chemical reactions has made their detailed investigation difficult. In this study, we demonstrate the utility of hyperpolarized 13C-NMR to directly observe and quantify the kinetics of the intermediate compound in the non-enzymatic decarboxylation of pyruvate via H2O2 with time resolutions of
0 Replies | 15 Views
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