The Chicago Center for Green Technology: life-cycle assessment of a brownfield redevelopment project

The sustainable development of brownfields reflects a fundamental, yet logical, shift in thinking and policymaking regarding pollution prevention. Life-cycle assessment (LCA) is a tool that can be used to assist in determining the conformity of brownfield development projects to the sustainability paradigm. LCA was applied to the process of a real brownfield redevelopment project, now known as the Chicago Center for Green Technology, to determine the cumulative energy required to complete the following redevelopment stages: (1) brownfield assessment and remediation, (2) building rehabilitation and site development and (3) ten years of operation. The results of the LCA have shown that operational energy is the dominant life-cycle stage after ten years of operation. The preservation and rehabilitation of the existing building, the installation of renewable energy systems (geothermal and photovoltaic) on-site and the use of more sustainable building products resulted in 72 terajoules (TJ) of avoided energy impacts, which would provide 14 years of operational energy for the site

Proton-Only Sensing of Hyperpolarized [1,2-¹³C₂]Pyruvate

Hyperpolarized MRI is emerging as a next-generation molecular imaging modality that can detect metabolic transformations in real time deep inside tissue and organs. 13C-hyperpolarized pyruvate is the leading hyperpolarized contrast agent that can probe cellular energetics in real time. Currently, hyperpolarized MRI requires specialized “multinuclear” MRI scanners that have the ability to excite and detect 13C signals. The objective of this work is the development of an approach that works on conventional (i.e., proton-only) MRI systems while taking advantage of long-lived 13C hyperpolarization. The long-lived singlet state of [1,2-13C2]pyruvate is hyperpolarized with parahydrogen in reversible exchange, and subsequently, the polarization is transferred from the 13C2 spin pair to the methyl protons of pyruvate for detection. This polarization transfer is accomplished with spin-lock induced crossing pulses that are only applied to the methyl protons yet access the hyperpolarization stored in the 13C2 singlet state. Theory and first experimental demonstrations are provided for our method, which obviates 13C excitation and detection for proton sensing of 13C-hyperpolarized pyruvate with an overall experimental-polarization transfer efficiency of ∼22% versus a theoretically predicted polarization transfer efficiency of 25%

Delivering Robust Proton-Only Sensing of Hyperpolarized [1,2-¹³C₂]‑Pyruvate Using Broad-Spectral-Range Nuclear Magnetic Resonance Pulse Sequences

Hyperpolarized [1-13C]pyruvate is the leading hyperpolarized injectable contrast agent and is currently under evaluation in clinical trials for molecular imaging of metabolic diseases, including cardiovascular disease and cancer. One aspect limiting broad scalability of the technique is that hyperpolarized 13C MRI requires specialized 13C hardware and software that are not generally available on clinical MRI scanners, which employ proton-only detection. Here, we present an approach that uses pulse sequences to transfer 13C hyperpolarization to methyl protons for detection of the 13C–13C pyruvate singlet, employing proton-only excitation and detection only. The new pulse sequences are robust to the B1 and B0 magnetic field inhomogeneities. The work focuses on singlet-to-magnetization (S2M) and rotor-synchronized (R) pulses, both relying on trains of hard pulses with broad spectral width coverage designed to effectively transform hyperpolarized 13C2-singlet hyperpolarization to 1H polarization on the CH3 group of [1,2-13C2]pyruvate. This approach may enable a broader adoption of hyperpolarized MRI as a molecular imaging technique

Accessing Long-Lived Disconnected Spin‑¹/₂ Eigenstates through Spins > ¹/₂

Pairs of chemically equivalent (or nearly equivalent) spin-¹/₂ nuclei have been shown to create disconnected eigenstates that are very long-lived compared with the lifetime of pure magnetization (<i>T</i>₁). Here the classes of molecules known to have accessible long-lived states are extended to include those with chemically equivalent spin-¹/₂ nuclei accessed by coupling to nuclei with spin > ¹/₂, in this case deuterium. At first, this appears surprising because the quadrupolar interactions present in nuclei with spin > ¹/₂ are known to cause fast relaxation. Yet it is shown that scalar couplings between deuterium and carbon can guide population into and out of long-lived states, i.e., those immune from the dominant relaxation mechanisms. This implies that it may be practical to consider compounds with ¹³C pairs directly bound to deuterium (or even ¹⁴N) as candidates for storage of polarization. In addition, experiments show that simple deuteration of molecules with ¹³C pairs at their natural abundance is sufficient for successful lifetime measurements

Storage of Hydrogen Spin Polarization in Long-Lived ¹³C₂ Singlet Order and Implications for Hyperpolarized Magnetic Resonance Imaging

Hyperpolarized magnetic resonance imaging (MRI) is a powerful technique enabling real-time monitoring of metabolites at concentration levels not accessible by standard MRI techniques. A considerable challenge this technique faces is the <i>T</i>₁ decay of the hyperpolarization upon injection into the system under study. Here we show that A_<i>n</i>A′_<i>n</i>XX′ spin systems such as ¹³C₂-1,2-diphenylacetylene (¹³C₂-DPA) sustain long-lived polarization for both ¹³C and ¹H spins with decay constants of almost 4.5 min at high magnetic fields of up to 16.44 T without spin-locking; the <i>T</i>₁ of proton polarization is only 3.8 s. Therefore, storage of the proton polarization in a ¹³C₂-singlet state causes a 69-fold extension of the spin lifetime. Notably, this extension is demonstrated with proton-only pulse sequences, which can be readily implemented on standard clinical scanners

High-Resolution Zero-Field NMR <i>J</i>‑Spectroscopy of Aromatic Compounds

We report the acquisition and interpretation of nuclear magnetic resonance (NMR) <i>J</i>-spectra at zero magnetic field for a series of benzene derivatives, demonstrating the analytical capabilities of zero-field NMR. The zeroth-order spectral patterns do not overlap, which allows for straightforward determination of the spin interactions of substituent functional groups. Higher-order effects cause additional line splittings, revealing additional molecular information. We demonstrate resonance linewidths as narrow as 11 mHz, permitting resolution of minute frequency differences and precise determination of long-range <i>J</i>-couplings. The measurement of <i>J</i>-couplings with the high precision offered by zero-field NMR may allow further refinements in the determination of molecular structure and conformation

High-Resolution Zero-Field NMR <i>J</i>‑Spectroscopy of Aromatic Compounds

We report the acquisition and interpretation of nuclear magnetic resonance (NMR) <i>J</i>-spectra at zero magnetic field for a series of benzene derivatives, demonstrating the analytical capabilities of zero-field NMR. The zeroth-order spectral patterns do not overlap, which allows for straightforward determination of the spin interactions of substituent functional groups. Higher-order effects cause additional line splittings, revealing additional molecular information. We demonstrate resonance linewidths as narrow as 11 mHz, permitting resolution of minute frequency differences and precise determination of long-range <i>J</i>-couplings. The measurement of <i>J</i>-couplings with the high precision offered by zero-field NMR may allow further refinements in the determination of molecular structure and conformation

High-Resolution Zero-Field NMR <i>J</i>‑Spectroscopy of Aromatic Compounds

We report the acquisition and interpretation of nuclear magnetic resonance (NMR) <i>J</i>-spectra at zero magnetic field for a series of benzene derivatives, demonstrating the analytical capabilities of zero-field NMR. The zeroth-order spectral patterns do not overlap, which allows for straightforward determination of the spin interactions of substituent functional groups. Higher-order effects cause additional line splittings, revealing additional molecular information. We demonstrate resonance linewidths as narrow as 11 mHz, permitting resolution of minute frequency differences and precise determination of long-range <i>J</i>-couplings. The measurement of <i>J</i>-couplings with the high precision offered by zero-field NMR may allow further refinements in the determination of molecular structure and conformation

Spin Relays Enable Efficient Long-Range Heteronuclear Signal Amplification by Reversible Exchange

A systematic experimental study is reported on the polarization transfer to distant spins, which do not directly bind to the polarization transfer complexes employed in Signal Amplification By Reversible Exchange (SABRE) experiments. Both long-range transfer to protons and long-range transfer to heteronuclei, i.e., ¹³C and ¹⁵N, are examined. Selective destruction of hyperpolarization on ¹H, ¹³C, and ¹⁵N sites is employed, followed by their rehyperpolarization from neighboring spins within the molecules of interest (pyridine for ¹H studies and metronidazole-¹⁵<i>N</i>₂-¹³<i>C</i>₂ for ¹³C and ¹⁵N studies). We conclude that long-range sites can be efficiently hyperpolarized when a network of spin-1/2 nuclei enables relayed polarization transfer (i.e., via short-range interactions between sites). In the case of proton SABRE in the millitesla regime, a relay network consisting of protons only is sufficient. However, in case ¹³C and ¹⁵N are targeted (i.e., via SABRE in SHield Enables Alignment Transfer to Heteronuclei or SABRE-SHEATH experiment), the presence of a heteronuclear network (e.g., consisting of ¹⁵N) enables a relay mechanism that is significantly more efficient than the direct transfer of spin order from para-H₂-derived hydrides

Catalyst-Free Aqueous Hyperpolarized [1-¹³C]Pyruvate Obtained by Re-Dissolution Signal Amplification by Reversible Exchange

Despite great successes in oncology, patient outcomes are often still discouraging, and hence the diagnostic imaging paradigm is increasingly shifting toward functional imaging of the pathology to better understand individual disease biology and to personalize therapies. The dissolution Dynamic Nuclear Polarization (d-DNP) hyperpolarization method has enabled unprecedented real-time MRI sensing of metabolism and tissue pH using hyperpolarized [1-13C]pyruvate as a biosensor with great potential for diagnosis and monitoring of cancer patients. However, current d-DNP is expensive and suffers from long hyperpolarization times, posing a substantial translational roadblock. Here, we report the development of Re-Dissolution Signal Amplification By Reversible Exchange (Re-D SABRE), which relies on fast and low-cost hyperpolarization of [1-13C]pyruvate by chemical exchange with parahydrogen at microtesla magnetic fields. [1-13C]pyruvate is precipitated from catalyst-containing methanol using ethyl acetate and rapidly reconstituted in aqueous media. 13C polarization of 9 ± 1% is demonstrated after redissolution in water with residual iridium mass fraction of 8.5 ± 1.5 ppm; further improvement is anticipated via process automation. Re-D SABRE makes hyperpolarized [1-13C]pyruvate biosensor available at a fraction of the cost (<$10,000) and production time (≈1 min) of currently used techniques and makes aqueous hyperpolarized [1-13C]pyruvate “ready” for in vivo applications