Publications by Paul Romeo Vasos

Pyruvate cellular uptake and enzymatic conversion probed by dissolution DNP-NMR: the impact of overexpressed membrane transporters

Arnaud Comment, Paul Romeo Vasos, Riccardo Balzan

Pyruvate membrane crossing and its lactate dehydrogenase-mediated conversion to lactate in cells featuring different levels of expression of membrane monocarboxylate transporters (MCT4) were probed by dissolution dynamic nuclear polarization-enhanced NMR. ...

Wiley2017

Dissolution Dynamic Nuclear Polarization Instrumentation for Real-time Enzymatic Reaction Rate Measurements by NMR

Arnaud Comment, Paul Romeo Vasos, Riccardo Balzan

The main limitation of NMR-based investigations is low sensitivity. This prompts for long acquisition times, thus preventing real-time NMR measurements of metabolic transformations. Hyperpolarization via dissolution DNP circumvents part of the sensitivity ...

Journal Of Visualized Experiments2016

Method for nuclear magnetic resonance (NMR) spectroscopy measurements using long-lived coherences (LLC)

Geoffrey Bodenhausen, Riddhiman Sarkar, Paul Romeo Vasos, Puneet Ahuja

A method for nuclear magnetic resonance (NMR) spectroscopy of a sample comprises preparation of the sample and carrying out an NMR spectroscopy measurement. Preparation includes excitation of long lived coherences (LLC) between the singlet state S0 and the ...

2013

Methods for nuclear magnetic resonance (NMR) or magnetic resonance imaging (MRI) measurements using long-lived states

Arnaud Comment, Geoffrey Bodenhausen, Sami Jannin, Riddhiman Sarkar, Paul Romeo Vasos

A method for nuclear magnetic resonance (NMR) or magnetic resonance imaging (MRI) measurements, includes creation of enhanced polarization of nuclei of a first kind within a sample in a magnetic field at cryogenic temperatures and transfer of the polarized ...

2013

Long-Lived States to Monitor Protein Unfolding by Proton NMR

Geoffrey Bodenhausen, Riddhiman Sarkar, Aurélien Bornet, Paul Romeo Vasos, Puneet Ahuja

The relaxation of long-lived states (LLS) corresponds to the slow return to statistical thermal equilibrium between symmetric and antisymmetric proton spin states. This process is remarkably sensitive to the presence of external spins and can be used to ob ...

Wiley-Blackwell2011

Hyperpolarizing Gases via Dynamic Nuclear Polarization and Sublimation

Arnaud Comment, Jean-Philippe Ansermet, Geoffrey Bodenhausen, François Lazeyras, Rolf Gruetter, Sami Jannin, Riddhiman Sarkar, Paul Romeo Vasos, Puneet Ahuja, Pascal Miéville, Jean-Noël Hyacinthe

A high throughput method was designed to produce hyperpolarized gases by combining lowtemperature dynamic nuclear polarization with a sublimation procedure. It is illustrated by applications to 129Xe nuclear magnetic resonance in xenon gas, leading to a si ...

American Physical Society2010

Scavenging Free Radicals To Preserve Enhancement and Extend Relaxation Times in NMR using Dynamic Nuclear Polarization

Arnaud Comment, Geoffrey Bodenhausen, Sandrine Gerber, Rolf Gruetter, Sami Jannin, Riddhiman Sarkar, Paul Romeo Vasos, Puneet Ahuja, Pascal Miéville, Mor-Miri Mishkovsky

Vitamin C for longer lifetimes: N-oxide radicals that are widely used for dynamic nuclear polarization can be reduced by scavengers such as sodium ascorbate (vitamin C) during the dissolution process, thus diminishing losses of polarization during the tran ...

Wiley-Blackwell2010

In vivo simultaneous measurement of glutamine synthetase and glutamate dehydrogenase activity in the hyperammonemic rat brain using localized 1H and 15N MRS

Yves Pilloud, Bernard Lanz, Rolf Gruetter, Paul Romeo Vasos, Cristina Ramona Cudalbu

2010

Diffusion Coefficients of Biomolecules Using Long-Lived Spin States

Geoffrey Bodenhausen, Riddhiman Sarkar, Paul Romeo Vasos, Puneet Ahuja

We report the first observation of long-lived states (LLS) having lifetimes TLLS that exceed the corresponding spin−lattice relaxation times T1 by more than a factor 6 in a protein. Slow diffusion coefficients characteristic of large biomolecules can be de ...

2009

Long-lived states to sustain hyperpolarized magnetization

Arnaud Comment, Jean-Philippe Ansermet, Geoffrey Bodenhausen, Sami Jannin, Riddhiman Sarkar, Paul Romeo Vasos, Puneet Ahuja

Major breakthroughs have recently been reported that can help overcome two inherent drawbacks of NMR: the lack of sensitivity and the limited memory of longitudinal magnetization. Dynamic nuclear polarization (DNP) couples nuclear spins to the large reserv ...

National Academy of Sciences2009

Proton NMR of15N-choline metabolites enhanced by dynamic nuclear polarization

Arnaud Comment, Geoffrey Bodenhausen, Rolf Gruetter, Sami Jannin, Riddhiman Sarkar, Paul Romeo Vasos

(Figure Presented) Chemical shifts of protons can report on metabolic transformations such as the conversion of choline to phosphocholine. To follow such processes in vivo, magnetization can be enhanced by dynamic nuclear polarization (DNP). We have hyperp ...

2009

Long-lived States in Multiple-Spin Systems

Geoffrey Bodenhausen, Riddhiman Sarkar, Paul Romeo Vasos, Puneet Ahuja

Long-lived spin states are excited in molecules featuring more than two isolated coupled spins, including amino acids. The figure shows the exponential recovery with the longest time-constant in aspartic acid, T1max=5.842±0.004 s, and of the decay of the l ...

2009

Singlet-state exchange NMR spectroscopy for the study of very slow dynamic processes

Geoffrey Bodenhausen, Riddhiman Sarkar, Paul Romeo Vasos

Solution-state nuclear magnetic resonance method for singlet-state nuclear magnetic resonance-spectroscopy, involves performing transformation of zero-quantum coherences into singlet-state populations by radio frequency irradiation ...

2009

Measurement of Slow Diffusion Coefficients of Molecules with Arbitrary Scalar Couplings via Long-Lived Spin States

Geoffrey Bodenhausen, Riddhiman Sarkar, Paul Romeo Vasos, Puneet Ahuja

New experiments are described for the determination of very slow diffusion constants by nuclear magnetic resonance (NMR) using long-lived (singlet) states. These experiments are suitable for molecules or conformations featuring a wide range of J-couplings. ...

2008

Singlet states open the way to longer time-scales in the measurement of diffusion by NMR spectroscopy

Simone Cavadini, Paul Romeo Vasos

Nuclear magnetic resonance is a powerful nonintrusive technique for measuring diffusion coefficients through the use of pulsed field gradients. The main limitation to the application range of this method is imposed by the relaxation time constants of the m ...

2008

Single or triple gradients?

Geoffrey Bodenhausen, Riddhiman Sarkar, Paul Romeo Vasos, Fabien Ferrage

Pulsed Field Gradients (PFGs) have become ubiquitous tools not only for Magnetic Resonance Imaging (MRI), but also for NMR experiments designed to study translational diffusion, for spatial encoding in ultra-fast spectroscopy, for the selection of desirabl ...

Academic Press Inc - Elsevier Science2008

Extending the Scope of Singlet-State Spectroscopy

Geoffrey Bodenhausen, Riddhiman Sarkar, Paul Romeo Vasos, Puneet Ahuja

Different decoupling sequences are tested - using various shaped radio-frequency (RF) pulses - to achieve the longest possible lifetimes of singlet-state populations over the widest possible bandwidths, that is, ranges of offsets and relative chemical shif ...

2007

Molecular Properties Determined from Relaxation of Long-Lived Spin States

Geoffrey Bodenhausen, Riddhiman Sarkar, Paul Romeo Vasos, Puneet Ahuja

The populations of long-lived spin states, in particular, populations of singlet states that are comprised of antisymmetric combinations of product states, ∣αIβS⟩−∣βIαS⟩, are characterized by very long lifetimes because the dipole-dipole interaction betwee ...

2007

Singlet-State Exchange NMR Spectroscopy for the Study of Very Slow Dynamic Processes

Geoffrey Bodenhausen, Riddhiman Sarkar, Paul Romeo Vasos

2007