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Lysak DH, Grisi M, Marable K, Conley GM, Michal CA, Moxley-Paquette V, Wolff WW, Downey K, Kock FVC, Costa PM, Ronda K, Moraes TB, Steiner K, Colnago LA, Simpson AJ. Exploring the Potential of Broadband Complementary Metal Oxide Semiconductor Micro-Coil Nuclear Magnetic Resonance for Environmental Research. Molecules 2023; 28:5080. [PMID: 37446742 PMCID: PMC10343494 DOI: 10.3390/molecules28135080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 06/23/2023] [Accepted: 06/27/2023] [Indexed: 07/15/2023] Open
Abstract
With sensitivity being the Achilles' heel of nuclear magnetic resonance (NMR), the superior mass sensitivity offered by micro-coils can be an excellent choice for tiny, mass limited samples such as eggs and small organisms. Recently, complementary metal oxide semiconductor (CMOS)-based micro-coil transceivers have been reported and demonstrate excellent mass sensitivity. However, the ability of broadband CMOS micro-coils to study heteronuclei has yet to be investigated, and here their potential is explored within the lens of environmental research. Eleven nuclei including 7Li, 19F, 31P and, 205Tl were studied and detection limits in the low to mid picomole range were found for an extended experiment. Further, two environmentally relevant samples (a sprouting broccoli seed and a D. magna egg) were successfully studied using the CMOS micro-coil system. 13C NMR was used to help resolve broad signals in the 1H spectrum of the 13C enriched broccoli seed, and steady state free precession was used to improve the signal-to-noise ratio by a factor of six. 19F NMR was used to track fluorinated contaminants in a single D. magna egg, showing potential for studying egg-pollutant interactions. Overall, CMOS micro-coil NMR demonstrates significant promise in environmental research, especially when the future potential to scale to multiple coil arrays (greatly improving throughput) is considered.
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Affiliation(s)
- Daniel H. Lysak
- Environmental NMR Centre, University of Toronto, Toronto, ON M1C 1A4, Canada
| | - Marco Grisi
- Annaida Technologies, Innovation Park, 1015 Lausanne, Switzerland
| | - Kathryn Marable
- Annaida Technologies, Innovation Park, 1015 Lausanne, Switzerland
| | | | - Carl A. Michal
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | | | - William W. Wolff
- Environmental NMR Centre, University of Toronto, Toronto, ON M1C 1A4, Canada
| | - Katelyn Downey
- Environmental NMR Centre, University of Toronto, Toronto, ON M1C 1A4, Canada
| | - Flavio V. C. Kock
- Environmental NMR Centre, University of Toronto, Toronto, ON M1C 1A4, Canada
| | - Peter M. Costa
- Environmental NMR Centre, University of Toronto, Toronto, ON M1C 1A4, Canada
| | - Kiera Ronda
- Environmental NMR Centre, University of Toronto, Toronto, ON M1C 1A4, Canada
| | - Tiago B. Moraes
- Departamento Engenharia de Biossistemas, Universidade de São Paulo/ESALQ, Av. Páduas Dias, 11, Piracicaba 13418-900, SP, Brazil
| | - Katrina Steiner
- Environmental NMR Centre, University of Toronto, Toronto, ON M1C 1A4, Canada
| | - Luiz A. Colnago
- Embrapa Instrumentação, Rua XV de Novembro 1452, São Carlos 13560-970, SP, Brazil
| | - Andre J. Simpson
- Environmental NMR Centre, University of Toronto, Toronto, ON M1C 1A4, Canada
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Investigation of the Binding Behavior of PAMAMs-NH2 Dendrimers with Ofloxacin via NMR Studies. Colloids Surf A Physicochem Eng Asp 2022. [DOI: 10.1016/j.colsurfa.2022.130625] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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3
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Anaraki MT, Lysak DH, Downey K, Kock FVC, You X, Majumdar RD, Barison A, Lião LM, Ferreira AG, Decker V, Goerling B, Spraul M, Godejohann M, Helm PA, Kleywegt S, Jobst K, Soong R, Simpson MJ, Simpson AJ. NMR spectroscopy of wastewater: A review, case study, and future potential. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2021; 126-127:121-180. [PMID: 34852923 DOI: 10.1016/j.pnmrs.2021.08.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Revised: 08/12/2021] [Accepted: 08/13/2021] [Indexed: 06/13/2023]
Abstract
NMR spectroscopy is arguably the most powerful tool for the study of molecular structures and interactions, and is increasingly being applied to environmental research, such as the study of wastewater. With over 97% of the planet's water being saltwater, and two thirds of freshwater being frozen in the ice caps and glaciers, there is a significant need to maintain and reuse the remaining 1%, which is a precious resource, critical to the sustainability of most life on Earth. Sanitation and reutilization of wastewater is an important method of water conservation, especially in arid regions, making the understanding of wastewater itself, and of its treatment processes, a highly relevant area of environmental research. Here, the benefits, challenges and subtleties of using NMR spectroscopy for the analysis of wastewater are considered. First, the techniques available to overcome the specific challenges arising from the nature of wastewater (which is a complex and dilute matrix), including an examination of sample preparation and NMR techniques (such as solvent suppression), in both the solid and solution states, are discussed. Then, the arsenal of available NMR techniques for both structure elucidation (e.g., heteronuclear, multidimensional NMR, homonuclear scalar coupling-based experiments) and the study of intermolecular interactions (e.g., diffusion, nuclear Overhauser and saturation transfer-based techniques) in wastewater are examined. Examples of wastewater NMR studies from the literature are reviewed and potential areas for future research are identified. Organized by nucleus, this review includes the common heteronuclei (13C, 15N, 19F, 31P, 29Si) as well as other environmentally relevant nuclei and metals such as 27Al, 51V, 207Pb and 113Cd, among others. Further, the potential of additional NMR methods such as comprehensive multiphase NMR, NMR microscopy and hyphenated techniques (for example, LC-SPE-NMR-MS) for advancing the current understanding of wastewater are discussed. In addition, a case study that combines natural abundance (i.e. non-concentrated), targeted and non-targeted NMR to characterize wastewater, along with in vivo based NMR to understand its toxicity, is included. The study demonstrates that, when applied comprehensively, NMR can provide unique insights into not just the structure, but also potential impacts, of wastewater and wastewater treatment processes. Finally, low-field NMR, which holds considerable future potential for on-site wastewater monitoring, is briefly discussed. In summary, NMR spectroscopy is one of the most versatile tools in modern science, with abilities to study all phases (gases, liquids, gels and solids), chemical structures, interactions, interfaces, toxicity and much more. The authors hope this review will inspire more scientists to embrace NMR, given its huge potential for both wastewater analysis in particular and environmental research in general.
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Affiliation(s)
- Maryam Tabatabaei Anaraki
- Environmental NMR Center, University of Toronto Scarborough, 1265 Military Trail, Toronto M1C1A4, Canada
| | - Daniel H Lysak
- Environmental NMR Center, University of Toronto Scarborough, 1265 Military Trail, Toronto M1C1A4, Canada
| | - Katelyn Downey
- Environmental NMR Center, University of Toronto Scarborough, 1265 Military Trail, Toronto M1C1A4, Canada
| | - Flávio Vinicius Crizóstomo Kock
- Environmental NMR Center, University of Toronto Scarborough, 1265 Military Trail, Toronto M1C1A4, Canada; Department of Chemistry, Federal University of São Carlos-SP (UFSCar), São Carlos, SP, Brazil
| | - Xiang You
- Environmental NMR Center, University of Toronto Scarborough, 1265 Military Trail, Toronto M1C1A4, Canada
| | - Rudraksha D Majumdar
- Environmental NMR Center, University of Toronto Scarborough, 1265 Military Trail, Toronto M1C1A4, Canada; Synex Medical, 2 Bloor Street E, Suite 310, Toronto, ON M4W 1A8, Canada
| | - Andersson Barison
- NMR Center, Federal University of Paraná, CP 19081, 81530-900 Curitiba, PR, Brazil
| | - Luciano Morais Lião
- NMR Center, Institute of Chemistry, Universidade Federal de Goiás, Goiânia 74690-900, Brazil
| | | | - Venita Decker
- Bruker Biospin GmbH, Silberstreifen 4, 76287 Rheinstetten, Germany
| | | | - Manfred Spraul
- Bruker Biospin GmbH, Silberstreifen 4, 76287 Rheinstetten, Germany
| | | | - Paul A Helm
- Environmental Monitoring & Reporting Branch, Ontario Ministry of the Environment, Toronto M9P 3V6, Canada
| | - Sonya Kleywegt
- Technical Assessment and Standards Development Branch, Ontario Ministry of the Environment, Conservation and Parks, Toronto, ON M4V 1M2, Canada
| | - Karl Jobst
- Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada
| | - Ronald Soong
- Environmental NMR Center, University of Toronto Scarborough, 1265 Military Trail, Toronto M1C1A4, Canada
| | - Myrna J Simpson
- Environmental NMR Center, University of Toronto Scarborough, 1265 Military Trail, Toronto M1C1A4, Canada
| | - Andre J Simpson
- Environmental NMR Center, University of Toronto Scarborough, 1265 Military Trail, Toronto M1C1A4, Canada.
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Ning P, Lane D, Ghosh Biswas R, Jenne A, Bastawrous M, Soong R, Schmidig D, Frei T, De Castro P, Kovacevic I, Graf S, Wegner S, Bermel W, Busse F, Kuehn T, Kuemmerle R, Struppe J, Fey M, Stronks HJ, Monette M, Simpson MJ, Simpson AJ. Expanding current applications and permitting the analysis of larger intact samples by means of a 7 mm CMP-NMR probe. Analyst 2021; 146:4461-4472. [PMID: 34136891 DOI: 10.1039/d1an00809a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Comprehensive multiphase NMR combines the ability to study and differentiate all phases (solids, gels, and liquids) using a single NMR probe. The general goal of CMP-NMR is to study intact environmental and biological samples to better understand conformation, organization, association, and transfer between and across phases/interfaces that may be lost with conventional sample preparation such as drying or solubilization. To date, all CMP-NMR studies have used 4 mm probes and rotors. Here, a larger 7 mm probehead is introduced which provides ∼3 times the volume and ∼2.4 times the signal over a 4 mm version. This offers two main advantages: (1) the additional biomass reduces experiment time, making 13C detection at natural abundance more feasible; (2) it allows the analysis of larger samples that cannot fit within a 4 mm rotor. Chicken heart tissue and Hyalella azteca (freshwater shrimp) are used to demonstrate that phase-based spectral editing works with 7 mm rotors and that the additional biomass from the larger volumes allows detection with 13C at natural abundance. Additionally, a whole pomegranate seed berry (aril) and an intact softgel capsule of hydroxyzine hydrochloride are used to demonstrate the analysis of samples too large to fit inside a conventional 4 mm CMP probe. The 7 mm version introduced here extends the range of applications and sample types that can be studied and is recommended when 4 mm CMP probes cannot provide adequate signal-to-noise (S/N), or intact samples are simply too big for 4 mm rotors.
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Affiliation(s)
- Paris Ning
- Environmental NMR Centre, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada.
| | - Daniel Lane
- Environmental NMR Centre, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada.
| | - Rajshree Ghosh Biswas
- Environmental NMR Centre, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada.
| | - Amy Jenne
- Environmental NMR Centre, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada.
| | - Monica Bastawrous
- Environmental NMR Centre, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada.
| | - Ronald Soong
- Environmental NMR Centre, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada.
| | - Daniel Schmidig
- Bruker BioSpin AG, Industriestrasse 26, 8117 Fällanden, Switzerland
| | - Thomas Frei
- Bruker BioSpin AG, Industriestrasse 26, 8117 Fällanden, Switzerland
| | - Peter De Castro
- Bruker BioSpin AG, Industriestrasse 26, 8117 Fällanden, Switzerland
| | - Ivan Kovacevic
- Bruker BioSpin AG, Industriestrasse 26, 8117 Fällanden, Switzerland
| | - Stephan Graf
- Bruker BioSpin AG, Industriestrasse 26, 8117 Fällanden, Switzerland
| | - Sebastian Wegner
- Bruker BioSpin GmbH, Silberstreifen 4, 76287 Rheinstetten, Germany
| | - Wolfgang Bermel
- Bruker BioSpin GmbH, Silberstreifen 4, 76287 Rheinstetten, Germany
| | - Falko Busse
- Bruker BioSpin GmbH, Silberstreifen 4, 76287 Rheinstetten, Germany
| | - Till Kuehn
- Bruker BioSpin AG, Industriestrasse 26, 8117 Fällanden, Switzerland
| | - Rainer Kuemmerle
- Bruker BioSpin AG, Industriestrasse 26, 8117 Fällanden, Switzerland
| | - Jochem Struppe
- Bruker BioSpin Corp., 15 Fortune Drive, Billerica, Massachusetts 01821-3991, USA
| | - Michael Fey
- Bruker BioSpin Corp., 15 Fortune Drive, Billerica, Massachusetts 01821-3991, USA
| | - Henry J Stronks
- Bruker Ltd., 2800 High Point Drive, Milton, ON, L9T 6P4Canada
| | - Martine Monette
- Bruker Ltd., 2800 High Point Drive, Milton, ON, L9T 6P4Canada
| | - Myrna J Simpson
- Environmental NMR Centre, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada.
| | - André J Simpson
- Environmental NMR Centre, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada.
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5
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Ma M, Gao X, Guo Z, Qiao Y. New Insights into the Binding Site and Affinity of the Interaction between Biotin and PAMAMs-NH 2 via NMR Studies. J Phys Chem B 2021; 125:4076-4085. [PMID: 33876645 DOI: 10.1021/acs.jpcb.0c10202] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Biotin-dendrimer conjugates (such as biotin-PAMAMs-NH2) are important macromolecules in the field of host-guest chemistry and widely used systems for delivery. The similar chemical structures of the inner and outer layers of PAMAM-NH2 make it difficult to illuminate the interaction and the binding affinity of biotin-PAMAMs-NH2. By utilizing NMR techniques including 1H NMR titration, CSSF-TOCSY, STDD methods, and 2D DOSY analysis, we demonstrate a method to sort out these interactions. The methylene protons of the inner and outer layers of PAMAM-NH2 are successfully identified and accurately positioned so that the carboxylic acid groups of biotins are having ionic interactions with the outermost amine groups of PAMAM-NH2. The inner PAMAM-NH2 is protonated when reaching the isoelectric point of PAMAM-NH2, increasing the hydrodynamic radius. On the basis of the NMR experiments, a model is proposed, where the carboxylic acid groups and heterocyclic skeleton of biotin arched over the outer layers of PAMAM-NH2 like a bridge. Furthermore, using STDD epitope mapping, the binding affinity between biotin and PAMAM-NH2 was quantified. The diffusion behavior of biotin-G5 PAMAM-NH2 complex is more complicated than that of biotin-G3 PAMAM-NH2 complex due to steric hindrance. The results provide a theoretical basis for understanding these complicated drug delivery systems.
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Affiliation(s)
- Minjun Ma
- State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, 27 South Taoyuan Road, Taiyuan 030001, China.,Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xueke Gao
- State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, 27 South Taoyuan Road, Taiyuan 030001, China.,Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhaohui Guo
- State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, 27 South Taoyuan Road, Taiyuan 030001, China.,Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yan Qiao
- State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, 27 South Taoyuan Road, Taiyuan 030001, China.,Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
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Chaubey B, Singh P, Pal S. Solution-state NMR evaluation of molecular interaction between monoaromatic carboxylic acids and dissolved humic acid. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2021; 28:17775-17788. [PMID: 33400107 DOI: 10.1007/s11356-020-12092-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Accepted: 12/14/2020] [Indexed: 06/12/2023]
Abstract
Understanding the nature of interactions between the aromatic organic pollutants with dissolved humic acid (HA) is fundamental for the prediction of their environmental fate and subsequent development of efficient remediation methods. The present study employs solution-state 1H/19F NMR methods to investigate the non-covalent interaction between aqueous peat humic acid (Aldrich HA) and monoaromatic carboxylic acids (CA), viz., 2, 6 diflourobenzoic acid (DFBA) and its non-fluorinated analog, benzoic acid (BA). NMR self-diffusion measurement of HA protons confirmed micellar nature indicating possibility of encapsulation of small molecules through host-guest interaction. 19F-1H and 1H-1H saturation transfer difference (STD) experiments reveal the mode of insertion of CA into HA superstructure. The strength of interaction has been evaluated by analyzing T1/T2 relaxation times and self-diffusion coefficients of CA as a function of HA concentration. Association constants extracted for CA-HA complexes from NMR diffusion experiments reflected that the association between DFBA-HA (2.34 mM-1) is significantly higher than that of BA-HA (0.97 mM-1). The experimental outcome reiterated that substitution of -H with halogen atoms (-F in specific) to aromatic ring plays a dominant role in modulating the strength of association and mode of insertion of organic pollutants into HA superstructure. The present study emphasizes that AHA can be a potential remediating agent for organic contaminants due to its superior binding affinity compared to less humified extracted HA (EHA) from Karwar, Rajasthan, India.
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Affiliation(s)
- Bhawna Chaubey
- Department of Chemistry, Indian Institute of Technology Jodhpur, Jodhpur, Rajasthan, 342037, India
| | - Pooja Singh
- Department of Chemistry, Indian Institute of Technology Jodhpur, Jodhpur, Rajasthan, 342037, India
| | - Samanwita Pal
- Department of Chemistry, Indian Institute of Technology Jodhpur, Jodhpur, Rajasthan, 342037, India.
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Zhu X, Song X, Schwarzbauer J. First insights into the formation and long-term dynamic behaviors of nonextractable perfluorooctanesulfonate and its alternative 6:2 chlorinated polyfluorinated ether sulfonate residues in a silty clay soil. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 761:143230. [PMID: 33158517 DOI: 10.1016/j.scitotenv.2020.143230] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 10/15/2020] [Accepted: 10/17/2020] [Indexed: 06/11/2023]
Abstract
Per- and polyfluoroalkyl substances (PFAS) are persistent and toxic contaminants that are ubiquitous in the environment. They can incorporate into soil as nonextractable residues (NER) which are not detectable with conventional analytical protocols but are still possible to remobilize with changes of surrounding conditions, and thus will be bioavailable again. Therefore, there is a need to investigate thoroughly the long-term fate of NER-PFAS. In this study, a 240-day incubation of perfluorooctanesulfonate (PFOS) and its alternative 6:2 chlorinated polyfluorinated ether sulfonate (F-53B) in a silty clay topsoil was carried out. Solvent extraction, alkaline hydrolysis and sequential chemical degradation were applied on periodically sampled soil to obtain extractable, moderately bound and deeply bound PFAS, respectively. The results confirmed the formation of NER of both compounds but with different preferences of incorporating mechanisms. NER-PFOS was formed predominantly by covalent binding (via head group) and strong adsorption (via tail group). The formation of NER-F-53B was mainly driven by physical entrapment. Both bound compounds within the incubation period showed three-stage behaviors including an initial period with slight release followed by a (re) incorporating stage and a subsequent remobilizing stage. This work provides some first insights on the long-term dynamic behaviors of nonextractable PFAS and will be conducive to their risk assessment and remediation (e.g. estimating potential NER-PFAS level based on their free extractable level, and selecting remediation methods according to their prevailing binding mechanisms).
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Affiliation(s)
- Xiaojing Zhu
- Institute of Geology and Geochemistry of Petroleum and Coal, RWTH Aachen University, Lochnerstr, 4-20, 52064 Aachen, Germany.
| | - Xin Song
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, 210008 Nanjing, China.
| | - Jan Schwarzbauer
- Institute of Geology and Geochemistry of Petroleum and Coal, RWTH Aachen University, Lochnerstr, 4-20, 52064 Aachen, Germany.
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Sorption of Organic Pollutants by Humic Acids: A Review. Molecules 2020; 25:molecules25040918. [PMID: 32092867 PMCID: PMC7071110 DOI: 10.3390/molecules25040918] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2020] [Revised: 02/12/2020] [Accepted: 02/18/2020] [Indexed: 11/17/2022] Open
Abstract
Humic acids (HA) are promising green materials for water and wastewater treatment. They show a strong ability to sorb cationic and hydrophobic organic pollutants. Cationic compounds interact mainly by electrostatic interaction with the deprotonated carboxylic groups of HA. Other functional groups of HA such as quinones, may form covalent bonds with aromatic ammines or similar organic compounds. Computational and experimental works show that the interaction of HA with hydrophobic organics is mainly due to π-π interactions, hydrophobic effect and hydrogen bonding. Several works report that sorbing efficiency is related to the hydrophobicity of the sorbate. Papers about the interaction between organic pollutants and humic acids dissolved in solution, in the solid state and adsorbed onto solid particles, like aluminosilicates and magnetic materials, are reviewed and discussed. A short discussion of the thermodynamics and kinetics of the sorption process, with indication of the main mistakes reported in literature, is also given.
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Simpson AJ, Simpson MJ, Soong R. Environmental Nuclear Magnetic Resonance Spectroscopy: An Overview and a Primer. Anal Chem 2017; 90:628-639. [PMID: 29131590 DOI: 10.1021/acs.analchem.7b03241] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
NMR spectroscopy is a versatile tool for the study of structure and interactions in environmental media such as air, soil, and water as well as monitoring the metabolic responses of living organisms to an ever changing environment. Part review, part perspective, and part tutorial, this Feature is aimed at nonspecialists who are interested in learning more about the potential and impact of NMR spectroscopy in environmental research.
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Affiliation(s)
- André J Simpson
- Environmental NMR Centre and Department of Physical & Environmental Sciences, University of Toronto Scarborough , Toronto, Ontario, Canada , M1C 1A4
| | - Myrna J Simpson
- Environmental NMR Centre and Department of Physical & Environmental Sciences, University of Toronto Scarborough , Toronto, Ontario, Canada , M1C 1A4
| | - Ronald Soong
- Environmental NMR Centre and Department of Physical & Environmental Sciences, University of Toronto Scarborough , Toronto, Ontario, Canada , M1C 1A4
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10
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Effective combined water and sideband suppression for low-speed tissue and in vivo MAS NMR. Anal Bioanal Chem 2017. [DOI: 10.1007/s00216-017-0450-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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11
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Courtier-Murias D, Michel E, Rodts S, Lafolie F. Novel Experimental-Modeling Approach for Characterizing Perfluorinated Surfactants in Soils. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:2602-2610. [PMID: 28165731 DOI: 10.1021/acs.est.6b05671] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Soil contamination is still poorly understood and modeled in part because of the difficulties of looking inside the "black box" constituted by soils. Here, we investigated the application of a recently developed 1H NMR technique to 19F NMR relaxometry experiments and utilized the results as inputs for an existing model. This novel approach yields 19F T2 NMR relaxation values of any fluorinated contaminant, which are among the most dangerous contaminants, allowing us to noninvasively and directly monitor their fate in soils. Using this protocol, we quantified the amount of a fluorinated xenobiotic (heptafluorobutyric acid, HFBA) in three different environments in soil aggregate packings and monitored contaminant exchange dynamics between these compartments. A model computing HFBA partition dynamics between different soil compartments showed that these three environments corresponded to HFBA in solution (i) between and (ii) inside the soil aggregates and (iii) to HFBA adsorbed to (or strongly interacting with) the soil constituents. In addition to providing a straightforward way of determining the sorption kinetics of any fluorinated contaminant, this work also highlights the strengths of a combined experimental-modeling approach to unambiguously understand experimental data and more generally to study contaminant fate in soils.
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Affiliation(s)
- Denis Courtier-Murias
- Université Paris-Est, Laboratoire Navier (ENPC-IFSTTAR-CNRS), 77420 Champs-sur-Marne, France
| | - Eric Michel
- EMMAH, INRA, Université d'Avignon et des Pays de Vaucluse, 84000 Avignon, France
| | - Stéphane Rodts
- Université Paris-Est, Laboratoire Navier (ENPC-IFSTTAR-CNRS), 77420 Champs-sur-Marne, France
| | - François Lafolie
- EMMAH, INRA, Université d'Avignon et des Pays de Vaucluse, 84000 Avignon, France
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12
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Bliumkin L, Dutta Majumdar R, Soong R, Adamo A, Abbatt JPD, Zhao R, Reiner E, Simpson AJ. Development of an in Situ NMR Photoreactor To Study Environmental Photochemistry. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:5506-5516. [PMID: 27172272 DOI: 10.1021/acs.est.6b00361] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Photochemistry is a key environmental process directly linked to the fate, source, and toxicity of pollutants in the environment. This study explores two approaches for integrating light sources with nuclear magnetic resonance (NMR) spectroscopy: sample irradiation using a "sunlight simulator" outside the magnet versus direct irradiation of the sample inside the magnet. To assess their applicability, the in situ NMR photoreactors were applied to a series of environmental systems: an atmospheric pollutant (p-nitrophenol), crude oil extracts, and groundwater. The study successfully illustrates that environmentally relevant aqueous photochemical processes can be monitored in situ and in real time using NMR spectroscopy. A range of intermediates and degradation products were identified and matched to the literature. Preliminary measurements of half-lives were also obtained from kinetic curves. The sunlight simulator was shown to be the most suitable model to explore environmental photolytic processes in situ. Other light sources with more intense UV output hold potential for evaluating UV as a remediation alternative in areas such as wastewater treatment plants or oil spills. Finally, the ability to analyze the photolytic fate of trace chemicals at natural abundance in groundwater, using a cryogenic probe, demonstrates the viability of NMR spectroscopy as a powerful and complementary technique for environmental applications in general.
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Affiliation(s)
- Liora Bliumkin
- Department of Chemistry, University of Toronto , Toronto, Ontario M5S 3H6, Canada
| | | | | | | | - Jonathan P D Abbatt
- Department of Chemistry, University of Toronto , Toronto, Ontario M5S 3H6, Canada
| | - Ran Zhao
- Department of Chemistry, University of Toronto , Toronto, Ontario M5S 3H6, Canada
| | - Eric Reiner
- Ontario Ministry of the Environment , Toronto, Ontario M9P 3 V6, Canada
| | - André J Simpson
- Department of Chemistry, University of Toronto , Toronto, Ontario M5S 3H6, Canada
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13
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Masoom H, Courtier-Murias D, Farooq H, Soong R, Kelleher BP, Zhang C, Maas WE, Fey M, Kumar R, Monette M, Stronks HJ, Simpson MJ, Simpson AJ. Soil Organic Matter in Its Native State: Unravelling the Most Complex Biomaterial on Earth. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:1670-1680. [PMID: 26783947 DOI: 10.1021/acs.est.5b03410] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Since the isolation of soil organic matter in 1786, tens of thousands of publications have searched for its structure. Nuclear magnetic resonance (NMR) spectroscopy has played a critical role in defining soil organic matter but traditional approaches remove key information such as the distribution of components at the soil-water interface and conformational information. Here a novel form of NMR with capabilities to study all physical phases termed Comprehensive Multiphase NMR, is applied to analyze soil in its natural swollen-state. The key structural components in soil organic matter are identified to be largely composed of macromolecular inputs from degrading biomass. Polar lipid heads and carbohydrates dominate the soil-water interface while lignin and microbes are arranged in a more hydrophobic interior. Lignin domains cannot be penetrated by aqueous solvents even at extreme pH indicating they are the most hydrophobic environment in soil and are ideal for sequestering hydrophobic contaminants. Here, for the first time, a complete range of physical states of a whole soil can be studied. This provides a more detailed understanding of soil organic matter at the molecular level itself key to develop the most efficient soil remediation and agricultural techniques, and better predict carbon sequestration and climate change.
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Affiliation(s)
- Hussain Masoom
- Department of Chemistry, University of Toronto , Toronto, Ontario Canada , M1C 1A4
| | | | - Hashim Farooq
- Department of Chemistry, University of Toronto , Toronto, Ontario Canada , M1C 1A4
| | - Ronald Soong
- Department of Chemistry, University of Toronto , Toronto, Ontario Canada , M1C 1A4
| | - Brian P Kelleher
- School of Chemical Sciences, Dublin City University , Dublin, Ireland
| | - Chao Zhang
- Department of Chemistry, University of Toronto , Toronto, Ontario Canada , M1C 1A4
| | - Werner E Maas
- Bruker BioSpin Corp., Billerica, Massachusetts 01821-3991, United States
| | - Michael Fey
- Bruker BioSpin Corp., Billerica, Massachusetts 01821-3991, United States
| | - Rajeev Kumar
- Bruker BioSpin Canada, Milton, Ontario Canada , L9T 1Y6
| | | | | | - Myrna J Simpson
- Department of Chemistry, University of Toronto , Toronto, Ontario Canada , M1C 1A4
| | - André J Simpson
- Department of Chemistry, University of Toronto , Toronto, Ontario Canada , M1C 1A4
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14
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Mazzei P, Piccolo A. Interactions between natural organic matter and organic pollutants as revealed by NMR spectroscopy. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2015; 53:667-678. [PMID: 25783763 DOI: 10.1002/mrc.4209] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Revised: 12/13/2014] [Accepted: 12/16/2014] [Indexed: 06/04/2023]
Abstract
Natural organic matter (NOM) plays a critical role in regulating the transport and the fate of organic contaminants in the environment. NMR spectroscopy is a powerful technique for the investigation of the sorption and binding mechanisms between NOM and pollutants, as well as their mutual chemical transformations. Despite NMR relatively low sensibility but due to its wide versatility to investigating samples in the liquid, gel, and solid phases, NMR application to environmental NOM-pollutants relations enables the achievement of specific and complementary molecular information. This report is a brief outline of the potentialities of the different NMR techniques and pulse sequences to elucidate the interactions between NOM and organic pollutants, with and without their labeling with nuclei that enhance NMR sensitivity.
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Affiliation(s)
- Pierluigi Mazzei
- Centro Interdipartimentale per la Risonanza Magnetica Nucleare per l'Ambiente, l'Agro-Alimentare ed i Nuovi Materiali (CERMANU), Università di Napoli Federico II, Via Università 100, 80055, Portici, Italy
| | - Alessandro Piccolo
- Centro Interdipartimentale per la Risonanza Magnetica Nucleare per l'Ambiente, l'Agro-Alimentare ed i Nuovi Materiali (CERMANU), Università di Napoli Federico II, Via Università 100, 80055, Portici, Italy
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15
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Masoom H, Courtier-Murias D, Farooq H, Soong R, Simpson MJ, Maas W, Kumar R, Monette M, Stronks H, Simpson AJ. Rapid estimation of nuclear magnetic resonance experiment time in low-concentration environmental samples. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2013; 32:129-136. [PMID: 23065696 DOI: 10.1002/etc.2028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Revised: 07/28/2012] [Accepted: 08/23/2012] [Indexed: 06/01/2023]
Abstract
Nuclear magnetic resonance (NMR) spectroscopy is an essential tool for studying environmental samples but is often hindered by low sensitivity, especially for the direct detection of nuclei such as(13) C. In very heterogeneous samples with NMR nuclei at low abundance, such as soils, sediments, and air particulates, it can take days to acquire a conventional(13) C spectrum. The present study describes a prescreening method that permits the rapid prediction of experimental run time in natural samples. The approach focuses the NMR chemical shift dispersion into a single spike, and, even in samples with extremely low carbon content, the spike can be observed in two to three minutes, or less. The intensity of the spike is directly proportional to the total concentration of nuclei of interest in the sample. Consequently, the spike intensity can be used as a powerful prescreening method that answers two key questions: (1) Will this sample produce a conventional NMR spectrum? (2) How much instrument time is required to record a spectrum with a specific signal-to-noise (S/N) ratio? The approach identifies samples to avoid (or pretreat) and permits additional NMR experiments to be performed on samples producing high-quality NMR data. Applications in solid- and liquid-state(13) C NMR are demonstrated, and it is shown that the technique is applicable to a range of nuclei.
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Affiliation(s)
- Hussain Masoom
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
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16
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Simpson AJ, Simpson MJ, Soong R. Nuclear magnetic resonance spectroscopy and its key role in environmental research. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2012; 46:11488-11496. [PMID: 22909253 DOI: 10.1021/es302154w] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Nuclear magnetic resonance (NMR) is arguably the most powerful and versatile tool in modern science. It has the capability to solve complex structures and interactions in situ even in complex heterogeneous multiphase samples such as soil, plants, and tissues. NMR has vast potential in environmental research and can provide insight into a diverse range of environmental processes at the molecular level be it identifying the binding site in human blood for a specific contaminant or the compositional dynamics of soil with climate change. Modern NMR-based metabonomics is elucidating contaminant toxicity and toxic mode of action rapidly and at sub lethal concentrations. Combined modern NMR approaches provide a powerful framework to better understand carbon cycling and sustainable agriculture, as well as contaminant fate, bioavailability, toxicity, sequestration, and remediation.
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Affiliation(s)
- Andre J Simpson
- Environmental NMR Centre, Department of Chemistry, University of Toronto, Toronto, Canada.
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17
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Courtier-Murias D, Farooq H, Masoom H, Botana A, Soong R, Longstaffe JG, Simpson MJ, Maas WE, Fey M, Andrew B, Struppe J, Hutchins H, Krishnamurthy S, Kumar R, Monette M, Stronks HJ, Hume A, Simpson AJ. Comprehensive multiphase NMR spectroscopy: basic experimental approaches to differentiate phases in heterogeneous samples. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2012; 217:61-76. [PMID: 22425441 DOI: 10.1016/j.jmr.2012.02.009] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Accepted: 02/15/2012] [Indexed: 05/16/2023]
Abstract
Heterogeneous samples, such as soils, sediments, plants, tissues, foods and organisms, often contain liquid-, gel- and solid-like phases and it is the synergism between these phases that determine their environmental and biological properties. Studying each phase separately can perturb the sample, removing important structural information such as chemical interactions at the gel-solid interface, kinetics across boundaries and conformation in the natural state. In order to overcome these limitations a Comprehensive Multiphase-Nuclear Magnetic Resonance (CMP-NMR) probe has been developed, and is introduced here, that permits all bonds in all phases to be studied and differentiated in whole unaltered natural samples. The CMP-NMR probe is built with high power circuitry, Magic Angle Spinning (MAS), is fitted with a lock channel, pulse field gradients, and is fully susceptibility matched. Consequently, this novel NMR probe has to cover all HR-MAS aspects without compromising power handling to permit the full range of solution-, gel- and solid-state experiments available today. Using this technology, both structures and interactions can be studied independently in each phase as well as transfer/interactions between phases within a heterogeneous sample. This paper outlines some basic experimental approaches using a model heterogeneous multiphase sample containing liquid-, gel- and solid-like components in water, yielding separate (1)H and (13)C spectra for the different phases. In addition, (19)F performance is also addressed. To illustrate the capability of (19)F NMR soil samples, containing two different contaminants, are used, demonstrating a preliminary, but real-world application of this technology. This novel NMR approach possesses a great potential for the in situ study of natural samples in their native state.
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Affiliation(s)
- Denis Courtier-Murias
- Department of Chemistry, University of Toronto, 1265 Military Trail, Toronto, ON, Canada M1C 1A4
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18
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Longstaffe JG, Simpson AJ. Understanding solution-state noncovalent interactions between xenobiotics and natural organic matter using 19F/1H heteronuclear saturation transfer difference nuclear magnetic resonance spectroscopy. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2011; 30:1745-1753. [PMID: 21538490 DOI: 10.1002/etc.560] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Revised: 03/03/2011] [Accepted: 04/07/2011] [Indexed: 05/30/2023]
Abstract
A combination of forward and reverse heteronuclear ((19)F/(1)H) saturation transfer difference (STD) nuclear magnetic resonance (NMR) spectroscopic techniques were applied to characterize the noncovalent interactions between perfluorinated aromatic xenobiotics and dissolved humic acid. These NMR techniques produce detailed molecular-level descriptions of weak noncovalent associations between components in complex environmental mixtures, allowing the mechanisms underlying these interactions to be explored; (19)F observed heteronuclear STD (H-STD) is used to describe the average molecular orientation of the xenobiotics during their interactions with humic acid, whereas (1)H observed reverse-heteronuclear STD (RH-STD) is used to both identify and quantify preferences exhibited by xenobiotics for interactions at different types of humic acid moieties. First, by using H-STD, it is shown that selected aromatic organofluorides orient with their nonfluorine functional groups (OH, NH(2), and COOH) directed away from humic acid during the interactions, suggesting that these functional groups are not specifically involved. Second, the RH-STD experiment is shown to be sensitive to subtle differences in preferred interaction sites in humic acid and is used here to demonstrate preferential interactions at aromatic humic acid sites for selected aromatic xenobiotics, C(10)F(7)OH, and C(6)F(4)X(2), (where X = F, OH, NH(2), NO(2), or COOH), that can be predicted from the electrostatic potential density maps of the xenobiotic.
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19
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Simpson AJ, McNally DJ, Simpson MJ. NMR spectroscopy in environmental research: from molecular interactions to global processes. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2011; 58:97-175. [PMID: 21397118 DOI: 10.1016/j.pnmrs.2010.09.001] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2010] [Accepted: 09/17/2010] [Indexed: 05/30/2023]
Affiliation(s)
- André J Simpson
- Environmental NMR Center, Department of Chemistry, University of Toronto, Ontario, Canada.
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D'eon JC, Simpson AJ, Kumar R, Baer AJ, Mabury SA. Determining the molecular interactions of perfluorinated carboxylic acids with human sera and isolated human serum albumin using nuclear magnetic resonance spectroscopy. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2010; 29:1678-88. [PMID: 20821619 DOI: 10.1002/etc.204] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Perfluorooctanoate (PFOA) is ubiquitous in North American human sera and has a serum half-life of 3.5 years in humans. The molecular interactions that lead to the bioaccumulation of these hydrophobic and lipophobic molecules in human blood are not well understood. Perfluorohexanoic acid (PFHxA) and PFOA were used as model perfluorinated carboxylic acids (PFCAs) to characterize the major site of PFCA interaction in human sera. Using novel heteronuclear saturation transfer difference nuclear magnetic resonance spectroscopy experiments, human serum albumin (HSA) was identified as the major site of interaction for both PFHxA and PFOA in human sera. Heteronuclear single quantum coherence nuclear magnetic resonance experiments were then performed to interrogate site-specific interactions of PFHxA and PFOA with isolated HSA. Perfluorohexanoic acid was found to bind specifically to Sudlow's drug-binding site II, whereas PFOA interacted preferentially with Sudlow's drug-binding site I at the lower concentration, with additional interactions developing at the higher concentration. These experiments highlight the utility of nuclear magnetic resonance spectrometry as a tool to observe the in situ interactions of chemical contaminants with biological systems. Both PFCAs displaced the endogenous HSA ligand oleic acid at concentrations lower than observed for the drugs ibuprofen and phenylbutazone, which are established HSA ligands. Interactions between PFCAs and HSA may affect the pharmacokinetics and distribution of fatty acids and certain drugs in the human body and warrant further investigation.
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Affiliation(s)
- Jessica C D'eon
- Department of Chemistry, University of Toronto, Toronto, Ontario, M5S 3H6 Canada
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21
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Longstaffe JG, Simpson MJ, Maas W, Simpson AJ. Identifying components in dissolved humic acid that bind organofluorine contaminants using (1)H{(19)F} reverse heteronuclear saturation transfer difference NMR spectroscopy. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2010; 44:5476-5482. [PMID: 20568693 DOI: 10.1021/es101100s] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Interactions between dissolved peat humic acid and two structurally dissimilar organofluorine compounds, perfluoro-2-naphthol and perfluoro-octanoic acid, are probed using a novel (1)H{(19)F} Nuclear Magnetic Resonance (NMR) Spectroscopy technique based on the Saturation Transfer Difference (STD) experiment. This technique is used here to show selectively only those regions of the (1)H NMR spectrum of humic acid that arise from chemical constituents interacting with perfluorinated organic compounds. This approach provides a tool for high-resolution analysis of interactions between contaminants and soil organic matter (SOM) directly at the molecular level. Soil organic matter is a chemically heterogeneous mixture, and traditional techniques used to study sorption or binding phenomenon are unable to resolve multiple processes occurring simultaneously at distinct chemical moieties. Here, multiple interaction domains are identified based on known chemical constituents of humic acid, most notably from lignin- and protein-derived material. Specifically, perfluoro-2-naphthol is shown to interact with lignin, protein, and aliphatic material; however, preference is exhibited for lignin-derived domains, while perfluoro-octanoic acid exhibits near exclusive preference for the protein-derived domains of humic acid.
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Affiliation(s)
- James G Longstaffe
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
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22
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Keiluweit M, Kleber M. Molecular-level interactions in soils and sediments: the role of aromatic pi-systems. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2009; 43:3421-3429. [PMID: 19544834 DOI: 10.1021/es8033044] [Citation(s) in RCA: 284] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
This review intends to deepen our understanding of mechanisms by which molecules with aromatic moieties attach to organic and mineral components of terrestrial environments. We present published evidence for the existence of specific, sorptive interactions of aromatic moieties with environmental sorbents. We find that aromatic pi-systems within organic compounds have the capacity to adsorb to minerals and organic soil and sediment components such as natural organic matter (NOM) and fire-derived black carbon (BC) through specific sorptive forces other than hydrophobic interactions. Polar interactions of aromatic pi-donor and -acceptor compounds show adsorption energies between 4 and 167 kJ mol(-1). Bonding strengths of cation-pi interactions and pi-pi electron donor-acceptor (EDA) interactions appear to be larger than H bonding strengths and comparable to inner- and outer-sphere complex formation. We conclude that, in analogy to polar and ionizable functional groups, components with aromatic pi-donor and -acceptor systems equip organic molecules with a substantial sorptive potential. This observation has important implications for the fate and transport of aromatic contaminants. The resulting sorptive interactions might also play a yet-overlooked functional role in the complex chain of processes which preserve NOM against decomposition.
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Affiliation(s)
- Marco Keiluweit
- Department of Crop and Soil Science, Soils Division, Oregon State University, Corvallis, Oregon 97331, USA.
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