¹⁵ N ₄ -1,2,4,5-tetrazines as potential molecular tags: Integrating bioorthogonal chemistry with hyperpolarization and unearthing para -N ₂

Abstract

A bioorthogonal reaction–based HP-MR strategy affords novel hyperpolarized products from tetrazine, including para-15N2 gas.

A role for low concentration reaction intermediates in the signal amplification by reversible exchange process revealed by theory and experiment

“…20 Specially created longer-lived states have been harnessed to alleviate these relaxation issues, often in conjunction with rationally designed substrates and catalysts. 14,[21][22][23][24][25][26] The role of the catalyst in SABRE has recently been reviewed. 27 Because of the catalytic nature of SABRE, hard to detect reaction intermediates might be expected to play a role in this process and we show here that their effect is currently underestimated.…”

Multiple Quantum Coherences Hyperpolarized at Ultra‐Low Fields

“…[40] Much effort is being undertaken to bring SABRE to "life sciences", but despite considerable efforts, a clean, highly polarized, highly concentrated biologically relevant contrast agent was not produced yet. [27,35,36,[47][48][49] This observation illustrates that the transfer of pH 2 spin order to a substrate at the low magnetic field can be greatly improved by using more targeted polarization transfer techniques discussed elsewhere. Here, we report the opposite effect: we discovered that in SABRE experiments at low magnetic fields various multiple spin orders are hyperpolarized.…”

“…This confirms that redistribution of pH 2 spin alignment in SABRE results not only in the substrate's magnetization but also in the population of multiple spin orders, including homo-and heteronuclear zz-orders and singlet spin states. [27,35,36,[47][48][49] This observation illustrates that the transfer of pH 2 spin order to a substrate at the low magnetic field can be greatly improved by using more targeted polarization transfer techniques discussed elsewhere. [40,50] The redistribution of pH 2 spin alignment and hyperpolarized multiple quantum coherences were revealed using a superconducting quantum interference device (SQUID)-based ULF MR spectrometer, designed as a field-cycling system, which operates in the magnetic field range of 10 μT to 20 mT.…”

“…During the past decades, various hyperpolarization techniques have been developed [1][2][3][4][5][6][7][8][9][10][11][12][13][14] to boost the magnetic resonance (MR) signal in order to bring new applications to industry [15][16][17] and life-sciences. [18][19][20][21][22][23][24][25] One of these methods is signal amplification by reversible exchange (SABRE), [26][27][28][29][30][31][32][33][34][35][36] where parahydrogen (pH 2 ) is used to polarize dissolved molecules by their mutual exchange with a transient complex. SABRE is unique in providing continuous hyperpolarization in the liquid state with high-throughput [26,37] and is relatively cost-efficient.…”

Front Cover: Simulating Non‐linear Chemical and Physical (CAP) Dynamics of Signal Amplification By Reversible Exchange (SABRE) (Chem. Eur. J. 32/2019)

“…Amongo thers, signal amplification by reversible exchange (SABRE), discovered in 2008, [16] is an up-and-coming technique with unique properties,i ncluding continuous hyperpolarization. [17][18][19] SABRE is one of the parahydrogen (pH 2 )-basedh yperpolarization techniques, [20,21] which takes advantage of the perfectly ordered, easy-to-produce singlets tate of dihydrogen. [22][23][24] In SABRE,p H 2 and the substrate-to-be-polarized undergo ar eversible exchange facilitated by an iridium catalyst ( Figure 1).…”