Zoltán Kovács

Advanced Imaging Research (United States)

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A. Dean Sherry

Advanced Imaging Research (United States)

F. Szelecsényi

HUN-REN Institute for Nuclear Research

Lloyd Lumata

The University of Texas at Dallas

G.F. Steyn

iThemba Laboratory

Craig R. Malloy

Advanced Imaging Research (United States)

Matthew E. Merritt

University of Florida

S. James Ratnakar

Advanced Imaging Research (United States)

Christiaan Vermeulen

Los Alamos National Laboratory

Gyula Tircsó

University of Debrecen

F. Tárkányi

HUN-REN Institute for Nuclear Research

Cooperative Institutions

The University of Texas Southwestern Medical Center

138

Advanced Imaging Research (United States)

University of Debrecen

Hungarian Academy of Sciences

Southwestern Medical Center

The University of Texas at Dallas

University of Szeged

Eötvös Loránd University

Centre National de la Recherche Scientifique

Semmelweis University

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Homologies between small nuclear RNAs and sequences and their possible role in the cytopathic effect of the virus

Medical Hypotheses (1987)

János Minárovits Judit Segesdi Zoltán Kovács I Földeş

10.1016/0306-9877(87)90005-3

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Citations (2)

Highly regioselective N-trans symmetrical diprotection of cyclen

Tetrahedron Letters (2006)

Luis M. De Leon Rodriguez Zoltán Kovács Ana Cristina Esqueda-Oliva Alma Delia Miranda-Olvera

Chloroformate

Cyclen

Succinimides

Carbamate

10.1016/j.tetlet.2006.07.135

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Citations (56)

Engineering a pH‐Sensitive Liposomal MRI Agent by Modification of a Bacterial Channel

Small (2018)

Limin Yang Hui Zheng James Ratnakar Bukola Adebesin N. Quyen

MscL is a bacterial mechanosensitive channel that serves as a cellular emergency release valve, protecting the cell from lysis upon a drop in external osmolarity. The channel has an extremely large pore (30 Å) and can be purified and reconstituted into artificial membranes. Moreover, MscL is modified to open in response to alternative external stimuli including changes in pH. These properties suggest this channel's potential as a triggered "nanopore" for localized release of vesicular contents such as magnetic resonance imaging (MRI) contrast agents and drugs. Toward this end, several variants of pH-triggered MscL nanovalves are engineered. Stealth vesicles previously been shown to evade normal in vivo clearance and passively accumulate in inflamed and malignant tissues are reconstituted. These vesicles are loaded with 1,4,7,10-tetraazacyclododecane tetraacetic acid gadolinium complex (Gd-DOTA), an MRI contrast reagent, and the resulting nanodevices tested for their ability to release Gd-DOTA as evidenced by enhancement of the longitudinal relaxation rate (R1 ) of the bulk water proton spins. Nanovalves that are responsive to physiological pH changes are identified, but differ in sensitivity and efficacy, thus giving an array of nanovalves that could potentially be useful in different settings. These triggered nanodevices may be useful in delivering both diagnostic and therapeutic agents.

DOTA

Nanopore

10.1002/smll.201704256

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Citations (18)

Production possibility of 186Re via the 192Os(p,α3n)186Re nuclear reaction

Journal of Radioanalytical and Nuclear Chemistry (2009)

F. Szelecsényi G.F. Steyn Zoltán Kovács K. Aardaneh Christiaan Vermeulen

Excitation function

Beam energy

10.1007/s10967-009-0147-y

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Citations (16)

Corrigendum to “Excitation functions of natZr + p nuclear processes up to 70 MeV: New measurements and compilation” [Nucl. Instr. Meth. Phys. Res. Sect. B 343 (2015) 173–191]

Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms (2019)

F. Szelecsényi G.F. Steyn Zoltán Kovács Christiaan Vermeulen Kotaro Nagatsu

Meth-

Sect

10.1016/j.nimb.2019.04.009

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Citations (0)

Modulation of CEST Images in Vivo by T₁ Relaxation: A New Approach in the Design of Responsive PARACEST Agents

Journal of the American Chemical Society (2013)

S. James Ratnakar Todd C. Soesbe Lloyd Lumata N. Quyen S. Viswanathan

A novel approach for the design of responsive paramagnetic chemical exchange saturation transfer (PARACEST) magnetic resonance imaging (MRI) agents has been developed where the signal is "turned on" by altering the longitudinal relaxation time (T1) of bulk water protons. To demonstrate this approach, a model Eu(DOTA-tetraamide) complex (DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) containing two nitroxide free radical units was synthesized. The nitroxide groups substantially shortened the T1 of the bulk water protons which, in turn, resulted in quenching of the CEST signal. Reduction of paramagnetic nitroxide moieties to a diamagnetic species resulted in the appearance of CEST. The modulation of CEST by T1 relaxation provides a new platform for designing biologically responsive MRI agents.

Diamagnetism

DOTA

Nitroxyl

10.1021/ja406738y

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Citations (52)

<title>New route to macrocyclic-based phosphonate acetoxymethyl (AM)-esters: synthesis, cell loading, and <formula><sup><roman>31</roman></sup></formula>P NMR</title>

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (1999)

Medardo R. Chavez Zoltán Kovács A. Dean Sherry

The ligand, 1,4,7,10-tetraazacyclododecane-1,4,7,10- tetrakis(methylenephosphonic acid, ethyl ester) (DOTPME) was made membrane permeable by preparing its acetoxymethyl (AM) derivative (DOTPME-AM). The synthetic approach was to prepare the AM ester of the phosphonate side-chain prior to attachment to the macrocyclic ring. P NMR was used to demonstrate that DOTPME-AM can penetrate cell membranes, get hydrolyzed by cellular esterases to regenerate charged DOTPME, and hence become trapped inside cells. This technology offers the potential of designing Ca²⁺ and Mg²⁺ specific ligands for analytical, noninvasive measurement of these ions by ³¹P NMR.

Phosphonate

Derivative (finance)

10.1117/12.351017

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Citations (0)

Dissolution Dynamic Nuclear Polarization of the ⁷⁷Se Nucleus

Analysis & Sensing (2022)

Eul Hyun Suh James Ratnakar Jaspal Singh Zoltán Kovács

Abstract 77 Se is a spin , low sensitivity nucleus with a natural abundance of 7.6 %. Although 77 Se NMR is very useful in the characterization of selenium containing molecules including seleno‐proteins, the detection of 77 Se is challenging in biological samples without enrichment. Therefore, the goal of this work was to establish whether the 77 Se signal could be enhanced in the liquid state by dissolution dynamic nuclear polarization (DNP) NMR without the need of enrichment. The dominant spin‐lattice relaxation mechanism for 77 Se is via chemical shift anisotropy, which is highly dependent on the molecular symmetry. Here we tested three selenium compounds (sodium selenate, sodium selenite and selenocystine) with different molecular symmetries in dissolution DNP experiments and demonstrated that 77 Se DNP using commercially available hardware is feasible but the achieved NMR signal enhancements (1368‐fold for selenate, 125‐fold for selenite and no enhancement for selenocystine at 9.4 T) were strongly dependent on molecular symmetry.

Selenate

10.1002/anse.202200086

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Citations (1)

Hyperpolarized [2-¹³C, 3-²H₃]Pyruvate Detects Hepatic Gluconeogenesis In Vivo

ACS Sensors (2024)

Mai T. Huynh Zohreh Erfani Zoltán Kovács Jae Mo Park

The feasibility of hyperpolarized [2-13C, 3-2H3]pyruvate for probing gluconeogenesis in vivo was investigated in this study. Whereas hyperpolarized [1-13C]pyruvate has clear access to metabolic pathways that convert pyruvate to lactate, alanine, and bicarbonate, its utility for assessing pyruvate carboxylation and gluconeogenesis has been limited by technical challenges, including spectral overlap and an obscure enzymatic step that decarboxylates the labeled carbon. To achieve unambiguous detection of gluconeogenic products, the carbonyl carbon in pyruvate was labeled with 13C. To prolong the T1 relaxation time, [2-13C, 3-2H3]pyruvate was synthesized and dissolved with D2O after dynamic nuclear polarization. The T1 of [2-13C, 3-2H3]pyruvate in D2O could be improved by 76.9% (79.6 s at 1 T and 74.5 s at 3 T) as compared to [2-13C]pyruvate in water. Hyperpolarized [2-13C, 3-2H3]pyruvate with D2O dissolution was applied to rat livers in vivo under normal feeding and fasting conditions. A gluconeogenic product, [2-13C]phosphoenolpyruvate, was observed at 149.9 ppm from fasted rats only, highlighting the utility of [2-13C, 3-2H3]pyruvate in detecting key gluconeogenic enzyme activities such as pyruvate carboxylase and phosphoenolpyruvate carboxykinase in vivo.

Gluconeogenesis

Pyruvic acid

Alanine

10.1021/acssensors.4c00734

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Citations (1)

Hyperpolarized 15N-pyridine Derivatives as pH-Sensitive MRI Agents

Scientific Reports (2015)

Weina Jiang Lloyd Lumata Wei Chen Shanrong Zhang Zoltán Kovács

Highly sensitive MR imaging agents that can accurately and rapidly monitor changes in pH would have diagnostic and prognostic value for many diseases. Here, we report an investigation of hyperpolarized (15)N-pyridine derivatives as ultrasensitive pH-sensitive imaging probes. These molecules are easily polarized to high levels using standard dynamic nuclear polarization (DNP) techniques and their (15)N chemical shifts were found to be highly sensitive to pH. These probes displayed sharp (15)N resonances and large differences in chemical shifts (Δδ > 90 ppm) between their free base and protonated forms. These favorable features make these agents highly suitable candidates for the detection of small changes in tissue pH near physiological values.

10.1038/srep09104

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Citations (98)