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Biondetti E, Cho J, Lee H. Cerebral oxygen metabolism from MRI susceptibility. Neuroimage 2023; 276:120189. [PMID: 37230206 PMCID: PMC10335841 DOI: 10.1016/j.neuroimage.2023.120189] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Revised: 04/26/2023] [Accepted: 05/23/2023] [Indexed: 05/27/2023] Open
Abstract
This article provides an overview of MRI methods exploiting magnetic susceptibility properties of blood to assess cerebral oxygen metabolism, including the tissue oxygen extraction fraction (OEF) and the cerebral metabolic rate of oxygen (CMRO2). The first section is devoted to describing blood magnetic susceptibility and its effect on the MRI signal. Blood circulating in the vasculature can have diamagnetic (oxyhemoglobin) or paramagnetic properties (deoxyhemoglobin). The overall balance between oxygenated and deoxygenated hemoglobin determines the induced magnetic field which, in turn, modulates the transverse relaxation decay of the MRI signal via additional phase accumulation. The following sections of this review then illustrate the principles underpinning susceptibility-based techniques for quantifying OEF and CMRO2. Here, it is detailed whether these techniques provide global (OxFlow) or local (Quantitative Susceptibility Mapping - QSM, calibrated BOLD - cBOLD, quantitative BOLD - qBOLD, QSM+qBOLD) measurements of OEF or CMRO2, and what signal components (magnitude or phase) and tissue pools they consider (intravascular or extravascular). Validations studies and potential limitations of each method are also described. The latter include (but are not limited to) challenges in the experimental setup, the accuracy of signal modeling, and assumptions on the measured signal. The last section outlines the clinical uses of these techniques in healthy aging and neurodegenerative diseases and contextualizes these reports relative to results from gold-standard PET.
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Affiliation(s)
- Emma Biondetti
- Department of Neuroscience, Imaging and Clinical Sciences, "D'Annunzio University" of Chieti-Pescara, Chieti, Italy; Institute for Advanced Biomedical Technologies, "D'Annunzio University" of Chieti-Pescara, Chieti, Italy
| | - Junghun Cho
- Department of Biomedical Engineering, University at Buffalo, The State University of New York, New York, USA
| | - Hyunyeol Lee
- School of Electronic and Electrical Engineering, Kyungpook National University, Daegu, Republic of Korea; Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
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Theillet FX, Luchinat E. In-cell NMR: Why and how? PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2022; 132-133:1-112. [PMID: 36496255 DOI: 10.1016/j.pnmrs.2022.04.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 04/19/2022] [Accepted: 04/27/2022] [Indexed: 06/17/2023]
Abstract
NMR spectroscopy has been applied to cells and tissues analysis since its beginnings, as early as 1950. We have attempted to gather here in a didactic fashion the broad diversity of data and ideas that emerged from NMR investigations on living cells. Covering a large proportion of the periodic table, NMR spectroscopy permits scrutiny of a great variety of atomic nuclei in all living organisms non-invasively. It has thus provided quantitative information on cellular atoms and their chemical environment, dynamics, or interactions. We will show that NMR studies have generated valuable knowledge on a vast array of cellular molecules and events, from water, salts, metabolites, cell walls, proteins, nucleic acids, drugs and drug targets, to pH, redox equilibria and chemical reactions. The characterization of such a multitude of objects at the atomic scale has thus shaped our mental representation of cellular life at multiple levels, together with major techniques like mass-spectrometry or microscopies. NMR studies on cells has accompanied the developments of MRI and metabolomics, and various subfields have flourished, coined with appealing names: fluxomics, foodomics, MRI and MRS (i.e. imaging and localized spectroscopy of living tissues, respectively), whole-cell NMR, on-cell ligand-based NMR, systems NMR, cellular structural biology, in-cell NMR… All these have not grown separately, but rather by reinforcing each other like a braided trunk. Hence, we try here to provide an analytical account of a large ensemble of intricately linked approaches, whose integration has been and will be key to their success. We present extensive overviews, firstly on the various types of information provided by NMR in a cellular environment (the "why", oriented towards a broad readership), and secondly on the employed NMR techniques and setups (the "how", where we discuss the past, current and future methods). Each subsection is constructed as a historical anthology, showing how the intrinsic properties of NMR spectroscopy and its developments structured the accessible knowledge on cellular phenomena. Using this systematic approach, we sought i) to make this review accessible to the broadest audience and ii) to highlight some early techniques that may find renewed interest. Finally, we present a brief discussion on what may be potential and desirable developments in the context of integrative studies in biology.
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Affiliation(s)
- Francois-Xavier Theillet
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France.
| | - Enrico Luchinat
- Dipartimento di Scienze e Tecnologie Agro-Alimentari, Alma Mater Studiorum - Università di Bologna, Piazza Goidanich 60, 47521 Cesena, Italy; CERM - Magnetic Resonance Center, and Neurofarba Department, Università degli Studi di Firenze, 50019 Sesto Fiorentino, Italy
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Gardner PR. Ordered Motions in the Nitric-Oxide Dioxygenase Mechanism of Flavohemoglobin and Assorted Globins with Tightly Coupled Reductases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1414:45-96. [PMID: 36520413 DOI: 10.1007/5584_2022_751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Nitric-oxide dioxygenases (NODs) activate and combine O2 with NO to form nitrate. A variety of oxygen-binding hemoglobins with associated partner reductases or electron donors function as enzymatic NODs. Kinetic and structural investigations of the archetypal two-domain microbial flavohemoglobin-NOD have illuminated an allosteric mechanism that employs selective tunnels for O2 and NO, gates for NO and nitrate, transient O2 association with ferric heme, and an O2 and NO-triggered, ferric heme spin crossover-driven, motion-controlled, and dipole-regulated electron-transfer switch. The proposed mechanism facilitates radical-radical coupling of ferric-superoxide with NO to form nitrate while preventing suicidal ferrous-NO formation. Diverse globins display the structural and functional motifs necessary for a similar allosteric NOD mechanism. In silico docking simulations reveal monomeric erythrocyte hemoglobin alpha-chain and beta-chain intrinsically matched and tightly coupled with NADH-cytochrome b5 oxidoreductase and NADPH-cytochrome P450 oxidoreductase, respectively, forming membrane-bound flavohemoglobin-like mammalian NODs. The neuroprotective neuroglobin manifests a potential NOD role in a close-fitting ternary complex with membrane-bound NADH-cytochrome b5 oxidoreductase and cytochrome b5. Cytoglobin interfaces weakly with cytochrome b5 for O2 and NO-regulated electron-transfer and coupled NOD activity. The mechanistic model also provides insight into the evolution of O2 binding cooperativity in hemoglobin and a basis for the discovery of allosteric NOD inhibitors.
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Li W, van Zijl PC. Quantitative theory for the transverse relaxation time of blood water. NMR IN BIOMEDICINE 2020; 33:e4207. [PMID: 32022362 PMCID: PMC7322972 DOI: 10.1002/nbm.4207] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 09/19/2019] [Accepted: 10/01/2019] [Indexed: 05/08/2023]
Abstract
An integrative model is proposed to describe the dependence of the transverse relaxation rate of blood water protons (R2blood = 1/T2blood ) on hematocrit fraction and oxygenation fraction (Y). This unified model takes into account (a) the diamagnetic effects of albumin, hemoglobin and the cell membrane; (b) the paramagnetic effect of hemoglobin; (c) the effect of compartmental exchange between plasma and erythrocytes under both fast and slow exchange conditions that vary depending on field strength and compartmental relaxation rates and (d) the effect of diffusion through field gradients near the erythrocyte membrane. To validate the model, whole-blood and lysed-blood R2 data acquired previously using Carr-Purcell-Meiboom-Gill measurements as a function of inter-echo spacing τcp at magnetic fields of 3.0, 7.0, 9.4 and 11.7 T were fitted to determine the lifetimes (field-independent physiological constants) for water diffusion and exchange, as well as several physical constants, some of which are field-independent (magnetic susceptibilities) and some are field-dependent (relaxation rates for water protons in solutions of albumin and oxygenated and deoxygenated hemoglobin, ie, blood plasma and erythrocytes, respectively). This combined exchange-diffusion model allowed excellent fitting of the curve of the τcp -dependent relaxation rate dispersion at all four fields using a single average erythrocyte water lifetime, τery = 9.1 ± 1.4 ms, and an averaged diffusional correlation time, τD = 3.15 ± 0.43 ms. Using this model and the determined physiological time constants and relaxation parameters, blood T2 values published by multiple groups based on measurements at magnetic field strengths of 1.5 T and higher could be predicted correctly within error. Establishment of this theory is a fundamental step for quantitative modeling of the BOLD effect underlying functional MRI.
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Affiliation(s)
- Wenbo Li
- Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland
| | - Peter C.M. van Zijl
- Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland
- Correspondence: Peter C.M. van Zijl, PhD, F. M. Kirby Research Center for Functional Brain Imaging, The Kennedy Krieger Institute, 707 N. Broadway, Room G-25, Baltimore, MD, 21205, United States of America, , Tel: 443-923-9500, Fax: 443-923-9505
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Cho J, Kee Y, Spincemaille P, Nguyen TD, Zhang J, Gupta A, Zhang S, Wang Y. Cerebral metabolic rate of oxygen (CMRO 2 ) mapping by combining quantitative susceptibility mapping (QSM) and quantitative blood oxygenation level-dependent imaging (qBOLD). Magn Reson Med 2018. [PMID: 29516537 DOI: 10.1002/mrm.27135] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
PURPOSE To map the cerebral metabolic rate of oxygen (CMRO2 ) by estimating the oxygen extraction fraction (OEF) from gradient echo imaging (GRE) using phase and magnitude of the GRE data. THEORY AND METHODS 3D multi-echo gradient echo imaging and perfusion imaging with arterial spin labeling were performed in 11 healthy subjects. CMRO2 and OEF maps were reconstructed by joint quantitative susceptibility mapping (QSM) to process GRE phases and quantitative blood oxygen level-dependent (qBOLD) modeling to process GRE magnitudes. Comparisons with QSM and qBOLD alone were performed using ROI analysis, paired t-tests, and Bland-Altman plot. RESULTS The average CMRO2 value in cortical gray matter across subjects were 140.4 ± 14.9, 134.1 ± 12.5, and 184.6 ± 17.9 μmol/100 g/min, with corresponding OEFs of 30.9 ± 3.4%, 30.0 ± 1.8%, and 40.9 ± 2.4% for methods based on QSM, qBOLD, and QSM+qBOLD, respectively. QSM+qBOLD provided the highest CMRO2 contrast between gray and white matter, more uniform OEF than QSM, and less noisy OEF than qBOLD. CONCLUSION Quantitative CMRO2 mapping that fits the entire complex GRE data is feasible by combining QSM analysis of phase and qBOLD analysis of magnitude.
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Affiliation(s)
- Junghun Cho
- Department of Biomedical Engineering, Cornell University, Ithaca, New York, USA
| | - Youngwook Kee
- Department of Radiology, Weill Cornell Medical College, New York, New York, USA
| | - Pascal Spincemaille
- Department of Radiology, Weill Cornell Medical College, New York, New York, USA
| | - Thanh D Nguyen
- Department of Radiology, Weill Cornell Medical College, New York, New York, USA
| | - Jingwei Zhang
- Department of Biomedical Engineering, Cornell University, Ithaca, New York, USA
| | - Ajay Gupta
- Department of Radiology, Weill Cornell Medical College, New York, New York, USA
| | - Shun Zhang
- Department of Radiology, Weill Cornell Medical College, New York, New York, USA.,Department of Radiology, Tongji Hospital, Wuhan, China
| | - Yi Wang
- Department of Biomedical Engineering, Cornell University, Ithaca, New York, USA.,Department of Radiology, Weill Cornell Medical College, New York, New York, USA
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Kuchel PW, Kirk K, Shishmarev D. The NMR 'split peak effect' in cell suspensions: Historical perspective, explanation and applications. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2018; 104:1-11. [PMID: 29405979 DOI: 10.1016/j.pnmrs.2017.11.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 10/31/2017] [Accepted: 11/02/2017] [Indexed: 06/07/2023]
Abstract
The physicochemical environment inside cells is distinctly different from that immediately outside. The selective exchange of ions, water and other molecules across the cell membrane, mediated by integral, membrane-embedded proteins is a hallmark of living systems. There are various methodologies available to measure the selectivity and rates (kinetics) of such exchange processes, including several that take advantage of the non-invasive nature of NMR spectroscopy. A number of solutes, including particular inorganic ions, show distinctive NMR behaviour, in which separate resonances arise from the intra- and extracellular solute populations, without the addition of shift reagents, differences in pH, or selective binding partners. This 'split peak effect/phenomenon', discovered in 1984, has become a valuable tool, used in many NMR studies of cellular behaviour and function. The explanation for the phenomenon, based on the differential hydrogen bonding of the reporter solutes to water, and the various ways in which this phenomenon has been used to investigate aspects of cellular biochemistry and physiology, are the topics of this review.
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Affiliation(s)
- Philip W Kuchel
- The University of Sydney, School of Life and Environmental Sciences, Faculty of Science, Sydney, NSW 2006, Australia.
| | - Kiaran Kirk
- Australian National University, Research School of Biology, College of Science, Canberra, ACT 2601, Australia
| | - Dmitry Shishmarev
- The University of Sydney, School of Life and Environmental Sciences, Faculty of Science, Sydney, NSW 2006, Australia; Australian National University, John Curtin School of Medical Research, College of Health and Medicine, Canberra, ACT 2601, Australia
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Zhang J, Cho J, Zhou D, Nguyen TD, Spincemaille P, Gupta A, Wang Y. Quantitative susceptibility mapping-based cerebral metabolic rate of oxygen mapping with minimum local variance. Magn Reson Med 2017; 79:172-179. [PMID: 28295523 DOI: 10.1002/mrm.26657] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2016] [Revised: 01/05/2017] [Accepted: 02/03/2017] [Indexed: 12/14/2022]
Abstract
PURPOSE The objective of this study was to demonstrate the feasibility of a cerebral metabolic rate of oxygen (CMRO2 ) mapping method based on its minimum local variance (MLV) without vascular challenge using quantitative susceptibility mapping (QSM) and cerebral blood flow (CBF). METHODS Three-dimensional multi-echo gradient echo imaging and arterial spin labeling were performed in 11 healthy subjects to calculate QSM and CBF. Minimum local variance was used to compute whole-brain CMRO2 map from QSM and CBF. The MLV method was compared with a reference method using the caffeine challenge. Their agreement within the cortical gray matter (CGM) was assessed on CMRO2 and oxygen extraction fraction (OEF) maps at both baseline and challenge states. RESULTS Mean CMRO2 (in µmol/100 g/min) obtained in CGM using the caffeine challenge and MLV were 142 ± 16.5 and 139 ± 14.8 µmol/100 g/min, respectively; the corresponding baseline OEF were 33.0 ± 4.0% and 31.8 ± 3.2%, respectively. The MLV and caffeine challenge methods showed no statistically significant differences across subjects with small ( < 4%) biases in CMRO2 and OEF values. CONCLUSIONS Minimum local variance-based CMRO2 mapping without vascular challenge using QSM and arterial spin labeling is feasible in healthy subjects. Magn Reson Med 79:172-179, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Jingwei Zhang
- Department of Biomedical Engineering, Cornell University, Ithaca, New York, USA.,Department of Radiology, Weill Cornell Medical College, New York, New York, USA
| | - Junghun Cho
- Department of Biomedical Engineering, Cornell University, Ithaca, New York, USA.,Department of Radiology, Weill Cornell Medical College, New York, New York, USA
| | - Dong Zhou
- Department of Radiology, Weill Cornell Medical College, New York, New York, USA
| | - Thanh D Nguyen
- Department of Radiology, Weill Cornell Medical College, New York, New York, USA
| | - Pascal Spincemaille
- Department of Radiology, Weill Cornell Medical College, New York, New York, USA
| | - Ajay Gupta
- Department of Radiology, Weill Cornell Medical College, New York, New York, USA
| | - Yi Wang
- Department of Biomedical Engineering, Cornell University, Ithaca, New York, USA.,Department of Radiology, Weill Cornell Medical College, New York, New York, USA
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Zhang J, Zhou D, Nguyen TD, Spincemaille P, Gupta A, Wang Y. Cerebral metabolic rate of oxygen (CMRO2) mapping with hyperventilation challenge using quantitative susceptibility mapping (QSM). Magn Reson Med 2016; 77:1762-1773. [DOI: 10.1002/mrm.26253] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 03/06/2016] [Accepted: 03/31/2016] [Indexed: 11/09/2022]
Affiliation(s)
- Jingwei Zhang
- Department of Biomedical EngineeringCornell University301 Weill HallIthaca New York, USA
- Department of RadiologyWeill Cornell Medical College515 East 71st St, Suite 104New York, USA
| | - Dong Zhou
- Department of RadiologyWeill Cornell Medical College515 East 71st St, Suite 104New York, USA
| | - Thanh D. Nguyen
- Department of RadiologyWeill Cornell Medical College515 East 71st St, Suite 104New York, USA
| | - Pascal Spincemaille
- Department of RadiologyWeill Cornell Medical College515 East 71st St, Suite 104New York, USA
| | - Ajay Gupta
- Department of RadiologyWeill Cornell Medical College515 East 71st St, Suite 104New York, USA
| | - Yi Wang
- Department of Biomedical EngineeringCornell University301 Weill HallIthaca New York, USA
- Department of RadiologyWeill Cornell Medical College515 East 71st St, Suite 104New York, USA
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Discovery of the magnetic behavior of hemoglobin: A beginning of bioinorganic chemistry. Proc Natl Acad Sci U S A 2016; 112:13123-7. [PMID: 26508205 DOI: 10.1073/pnas.1515704112] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Two articles published by Pauling and Coryell in PNAS nearly 80 years ago described in detail the magnetic properties of oxy- and deoxyhemoglobin, as well as those of closely related compounds containing hemes. Their measurements revealed a large difference in magnetism between oxygenated and deoxygenated forms of the protein and, along with consideration of the observed diamagnetism of the carbonmonoxy derivative, led to an electronic structural formulation of oxyhemoglobin. The key role of hemoglobin as the main oxygen carrier in mammalian blood had been established earlier, and its allosteric behavior had been described in the 1920s. The Pauling-Coryell articles on hemoglobin represent truly seminal contributions to the field of bioinorganic chemistry because they are the first to make connections between active site electronic structure and the function of a metalloprotein.
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Zhang J, Liu T, Gupta A, Spincemaille P, Nguyen TD, Wang Y. Quantitative mapping of cerebral metabolic rate of oxygen (CMRO2 ) using quantitative susceptibility mapping (QSM). Magn Reson Med 2015; 74:945-52. [PMID: 25263499 PMCID: PMC4375095 DOI: 10.1002/mrm.25463] [Citation(s) in RCA: 113] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Revised: 08/17/2014] [Accepted: 08/20/2014] [Indexed: 12/29/2022]
Abstract
PURPOSE To quantitatively map cerebral metabolic rate of oxygen ( CMRO2) and oxygen extraction fraction ( OEF) in human brains using quantitative susceptibility mapping (QSM) and arterial spin labeling-measured cerebral blood flow (CBF) before and after caffeine vasoconstriction. METHODS Using the multiecho, three-dimensional gradient echo sequence and an oral bolus of 200 mg caffeine, whole brain CMRO2 and OEF were mapped at 3-mm isotropic resolution on 13 healthy subjects. The QSM-based CMRO2 was compared with an R2*-based CMRO2 to analyze the regional consistency within cortical gray matter (CGM) with the scaling in the R2* method set to provide same total CMRO2 as the QSM method for each subject. RESULTS Compared to precaffeine, susceptibility increased (5.1 ± 1.1 ppb; P < 0.01) and CBF decreased (-23.6 ± 6.7 ml/100 g/min; P < 0.01) at 25-min postcaffeine in CGM. This corresponded to a CMRO2 of 153.0 ± 26.4 μmol/100 g/min with an OEF of 33.9 ± 9.6% and 54.5 ± 13.2% (P < 0.01) pre- and postcaffeine, respectively, at CGM, and a CMRO2 of 58.0 ± 26.6 μmol/100 g/min at white matter. CMRO2 from both QSM- and R2*-based methods showed good regional consistency (P > 0.05), but quantitation of R2*-based CMRO2 required an additional scaling factor. CONCLUSION QSM can be used with perfusion measurements pre- and postcaffeine vascoconstriction to map CMRO2 and OEF.
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Affiliation(s)
- Jingwei Zhang
- Department of Biomedical Engineering, Cornell University, Ithaca, NY, United States Address: 301 Weill Hall, Cornell University, Ithaca, NY14853
- Department of Radiology, Weill Cornell Medical College, New York, NY, United States Address: 515 East 71 St, Suite 104, New York, NY, 10021
| | - Tian Liu
- Medimagemetric, LLC, New York, NY, NY, United States Address: 455 Main Street, New York, NY, 10044
| | - Ajay Gupta
- Department of Radiology, Weill Cornell Medical College, New York, NY, United States Address: 515 East 71 St, Suite 104, New York, NY, 10021
| | - Pascal Spincemaille
- Department of Radiology, Weill Cornell Medical College, New York, NY, United States Address: 515 East 71 St, Suite 104, New York, NY, 10021
| | - Thanh D. Nguyen
- Department of Radiology, Weill Cornell Medical College, New York, NY, United States Address: 515 East 71 St, Suite 104, New York, NY, 10021
| | - Yi Wang
- Department of Biomedical Engineering, Cornell University, Ithaca, NY, United States Address: 301 Weill Hall, Cornell University, Ithaca, NY14853
- Department of Radiology, Weill Cornell Medical College, New York, NY, United States Address: 515 East 71 St, Suite 104, New York, NY, 10021
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Song Y, Cho G, Chun SI, Baek JH, Cho H, Kim YR, Park SB, Kim JK. Oxygen-induced frequency shifts in hyperoxia: a significant component of BOLD signal. NMR IN BIOMEDICINE 2014; 27:835-842. [PMID: 24828299 DOI: 10.1002/nbm.3128] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Revised: 03/05/2014] [Accepted: 04/01/2014] [Indexed: 06/03/2023]
Abstract
In comparison to the well-documented significance of intravascular deoxyhemoglobin (deoxyHgb), the effects of dissolved oxygen on the blood-oxygen-level-dependent (BOLD) signal have not been widely reported. Based on the fact that the prolonged inspiration of high oxygen fraction gas can result in up to a sixfold increase of the baseline tissue oxygenation, the current study focused on the influence of dissolved oxygen on the BOLD signal during hyperoxia. As results, our in vitro study revealed that the r1 and r2 (relaxivities) of the oxygen-treated serum were 0.22 mM(-1) · s(-1) and 0.19 mM(-1) · s(-1) , respectively. In an in vivo experiment, hyperoxic respiration induced negative BOLD contrast (i.e. signal decrease) in 18-42% of measured brain regions, voxels with accompanying significant decreases in both the T(*)2 (-12.1% to -19.4%) and T1 (-5.8% to -3.3%) relaxation times. In contrast, the T(*)2 relaxation time significantly increased (11.2% to 14.0%) for the voxels displaying positive BOLD contrast (in 41-50% of the measured brain), which reflected a hyperoxygenation-induced reduction in tissue deoxyHgb concentration. These data imply that hyperoxia-driven BOLD signal changes are primarily determined by the counteracting effects of extravascular oxygen and intravascular deoxyHgb. Oxygen-induced magnetic susceptibility was further demonstrated by the study of 1 min hypoxia, which induced BOLD signal changes opposite to those under hyperoxia. Vasoconstriction was more common in voxels with negative BOLD contrast than in voxels with positive contrast (% change of blood volume, -9.8% to -12.8% versus 2.0% to 2.2%), which further suggests that negative BOLD contrast is mainly evoked by an increase in extravascular oxygen concentration. Conclusively, frequency shifts, which are induced by the accumulation of oxygen molecules and associated magnetic field inhomogeneity, are a significant source of the negative BOLD contrast during hyperoxia.
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Affiliation(s)
- Youngkyu Song
- Division of Magnetic Resonance, Korea Basic Science Institute, Cheongwon, Chungbuk, South Korea
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Jupin M, Michiels PJ, Girard FC, Wijmenga SS. Magnetic susceptibility to measure total protein concentration from NMR metabolite spectra: Demonstration on blood plasma. Magn Reson Med 2014; 73:459-68. [PMID: 24639074 DOI: 10.1002/mrm.25178] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 01/12/2014] [Accepted: 01/22/2014] [Indexed: 11/08/2022]
Abstract
PURPOSE Accurate metabolite and protein quantification in blood plasma and other body fluids from one single NMR measurement, allowing for improved quantitative metabolic profiling and better assessment of metabolite-protein interactions. THEORY AND METHODS The total protein concentration is derived from the common chemical-shift changes-caused by protein-induced bulk magnetic susceptibility (BMS)-measured on well-accessible and exchange-free metabolite resonances. These BMS shifts are simply obtained by external referencing with respect to 3-(trimethylsilyl)propionic-2,2,3,3-d4 acid, sodium salt in a coaxial insert. RESULTS Based on blood-plasma data from five volunteers, the estimated accuracy of the BMS method is ≤ 5% with respect and comparable to the 3.8% error of the standard colorimetric, Biuret, method. Valine, alanine, glucose, leucine, and lactate display no exchange-induced shift changes. Their well-accessible signals act as reliable probes for pure protein-induced BMS. The slopes and intercepts of their chemical-shift change versus protein concentration were derived from metabolite mixtures with (fatted) human and bovine albumin acting as blood-plasma mimics. CONCLUSION The BMS method, demonstrated on blood plasma, can also be used on other samples containing sufficient protein (> 10 g/L). Also, it allows measurement of the presence and sign of exchange-induced chemical-shift changes.
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Affiliation(s)
- Marc Jupin
- Biophysical Chemistry, Institute for Materials and Molecules, Radboud University, Nijmegen, The Netherlands
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Moore LR, Nehl F, Dorn J, Chalmers JJ, Zborowski M. Open Gradient Magnetic Red Blood Cell Sorter Evaluation on Model Cell Mixtures. IEEE TRANSACTIONS ON MAGNETICS 2013; 49:309-315. [PMID: 24910468 PMCID: PMC4047673 DOI: 10.1109/tmag.2012.2225098] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The emerging applications of biological cell separation to rare circulating tumor cell (CTC) detection and separation from blood rely on efficient methods of red blood cell (RBC) debulking. The two most widely used methods of centrifugation and RBC lysis have been associated with the concomitant significant losses of the cells of interest (such as progenitor cells or circulating tumor cells). Moreover, RBC centrifugation and lysis are not well adapted to the emerging diagnostic applications, relying on microfluidics and micro-scale total analytical systems. Therefore, magnetic RBC separation appears a logical alternative considering the high iron content of the RBC (normal mean 105 fg) as compared to the white blood cell iron content (normal mean 1.6 fg). The typical magnetic forces acting on a RBC are small, however, as compared to typical forces associated with centrifugation or the forces acting on synthetic magnetic nanoparticles used in current magnetic cell separations. This requires a significant effort in designing and fabricating a practical magnetic RBC separator. Applying advanced designs to the low cost, high power permanent magnets currently available, and building on the accumulated knowledge of the immunomagnetic cell separation methods and devices, an open gradient magnetic red blood cell (RBC) sorter was designed, fabricated and tested on label-free cell mixtures, with potential applications to RBC debulking from whole blood samples intended for diagnostic tests.
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Affiliation(s)
- Lee R Moore
- Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195 USA
| | - Franzisca Nehl
- Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195 USA ; Technische Universität Dresden, Fakultät Maschinenwesen/Bioverfahrenstechnik, Dresden, Germany
| | - Jenny Dorn
- Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195 USA ; Technische Universität Dresden, Fakultät Maschinenwesen/Bioverfahrenstechnik, Dresden, Germany
| | - Jeffrey J Chalmers
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH 43210 USA
| | - Maciej Zborowski
- Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195 USA
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Gutiérrez L, Vujić Spasić M, Muckenthaler MU, Lázaro FJ. Quantitative magnetic analysis reveals ferritin-like iron as the most predominant iron-containing species in the murine Hfe-haemochromatosis. Biochim Biophys Acta Mol Basis Dis 2012; 1822:1147-53. [PMID: 22465035 DOI: 10.1016/j.bbadis.2012.03.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Revised: 03/01/2012] [Accepted: 03/13/2012] [Indexed: 02/08/2023]
Abstract
Quantitative analysis of the temperature dependent AC magnetic susceptibility of freeze-dried mouse tissues from an Hfe hereditary haemochromatosis disease model indicates that iron predominantly appears biomineralised, like in the ferritin cores, in the liver, the spleen and duodenum. The distribution of the amount of ferritin-like iron between genders and genotypes coincides with that of elemental iron and nonheme iron. Importantly, the so-called paramagnetic iron, a quantity also determined from the magnetic data and indicative of nonmineralised iron forms, appears only marginally increased when iron overload takes place.
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Affiliation(s)
- Lucía Gutiérrez
- School of Physics, M013, The University of Western Australia, 6009, Crawley, Australia.
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15
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Luo J, He X, d'Avignon DA, Ackerman JJH, Yablonskiy DA. Protein-induced water 1H MR frequency shifts: contributions from magnetic susceptibility and exchange effects. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2010; 202:102-8. [PMID: 19879785 PMCID: PMC2818297 DOI: 10.1016/j.jmr.2009.10.005] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2009] [Revised: 10/07/2009] [Accepted: 10/12/2009] [Indexed: 05/06/2023]
Abstract
Defining the biophysics underlying the remarkable MRI phase contrast reported in high field MRI studies of human brain would lead to more quantitative image analysis and more informed pulse sequence development. Toward this end, the dependence of water (1)H resonance frequency on protein concentration was investigated using bovine serum albumin (BSA) as a model system. Two distinct mechanisms were found to underlie a water (1)H resonance frequency shift: (i) a protein-concentration-induced change in bulk magnetic susceptibility, causing a shift to lower frequency, and (ii) exchange of water between chemical-shift distinct environments, i.e., free (bulk water) and protein-associated ("bound") water, including freely exchangeable (1)H sites on proteins, causing a shift to higher frequency. At 37 degrees C the amplitude of the exchange effect is roughly half that of the susceptibility effect.
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Affiliation(s)
- Jie Luo
- Department of Chemistry, Washington University, Saint Louis, MO 63130, USA
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16
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Langham MC, Magland JF, Epstein CL, Floyd TF, Wehrli FW. Accuracy and precision of MR blood oximetry based on the long paramagnetic cylinder approximation of large vessels. Magn Reson Med 2009; 62:333-40. [PMID: 19526517 PMCID: PMC2753239 DOI: 10.1002/mrm.21981] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2008] [Accepted: 01/12/2009] [Indexed: 11/05/2022]
Abstract
An accurate noninvasive method to measure the hemoglobin oxygen saturation (%HbO(2)) of deep-lying vessels without catheterization would have many clinical applications. Quantitative MRI may be the only imaging modality that can address this difficult and important problem. MR susceptometry-based oximetry for measuring blood oxygen saturation in large vessels models the vessel as a long paramagnetic cylinder immersed in an external field. The intravascular magnetic susceptibility relative to surrounding muscle tissue is a function of oxygenated hemoglobin (HbO(2)) and can be quantified with a field-mapping pulse sequence. In this work, the method's accuracy and precision was investigated theoretically on the basis of an analytical expression for the arbitrarily oriented cylinder, as well as experimentally in phantoms and in vivo in the femoral artery and vein at 3T field strength. Errors resulting from vessel tilt, noncircularity of vessel cross-section, and induced magnetic field gradients were evaluated and methods for correction were designed and implemented. Hemoglobin saturation was measured at successive vessel segments, differing in geometry, such as eccentricity and vessel tilt, but constant blood oxygen saturation levels, as a means to evaluate measurement consistency. The average standard error and coefficient of variation of measurements in phantoms were <2% with tilt correction alone, in agreement with theory, suggesting that high accuracy and reproducibility can be achieved while ignoring noncircularity for tilt angles up to about 30 degrees . In vivo, repeated measurements of %HbO(2) in the femoral vessels yielded a coefficient of variation of less than 5%. In conclusion, the data suggest that %HbO(2) can be measured reproducibly in vivo in large vessels of the peripheral circulation on the basis of the paramagnetic cylinder approximation of the incremental field.
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Affiliation(s)
- Michael C. Langham
- Laboratory for Structural NMR Imaging, Department of Radiology, University of Pennsylvania Medical Center, Philadelphia, PA, USA
| | - Jeremy F. Magland
- Laboratory for Structural NMR Imaging, Department of Radiology, University of Pennsylvania Medical Center, Philadelphia, PA, USA
| | - Charles L. Epstein
- Department of Mathematics, University of Pennsylvania, Philadelphia, PA, USA
| | - Thomas F. Floyd
- Department of Anesthesiology and Critical Care, Hospital of the University of Pennsylvania, Philadelphia, PA, USA
| | - Felix W. Wehrli
- Laboratory for Structural NMR Imaging, Department of Radiology, University of Pennsylvania Medical Center, Philadelphia, PA, USA
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17
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Magnetic susceptibility of iron in malaria-infected red blood cells. Biochim Biophys Acta Mol Basis Dis 2008; 1792:93-9. [PMID: 19056489 DOI: 10.1016/j.bbadis.2008.11.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2008] [Revised: 10/24/2008] [Accepted: 11/03/2008] [Indexed: 02/02/2023]
Abstract
During intra-erythrocytic maturation, malaria parasites catabolize up to 80% of cellular haemoglobin. Haem is liberated inside the parasite and converted to haemozoin, preventing haem iron from participating in cell-damaging reactions. Several experimental techniques exploit the relatively large paramagnetic susceptibility of malaria-infected cells as a means of sorting cells or investigating haemoglobin degradation, but the source of the dramatic increase in cellular magnetic susceptibility during parasite growth has not been unequivocally determined. Plasmodium falciparum cultures were enriched using high-gradient magnetic fractionation columns and the magnetic susceptibility of cell contents was directly measured. The forms of haem iron in the erythrocytes were quantified spectroscopically. In the 3D7 laboratory strain, the parasites converted approximately 60% of host cell haemoglobin to haemozoin and this product was the primary source of the increase in cell magnetic susceptibility. Haemozoin iron was found to have a magnetic susceptibility of (11.0+/-0.9)x10(-3) mL mol(-1). The calculated volumetric magnetic susceptibility (SI units) of the magnetically enriched cells was (1.88+/-0.60)x10(-6) relative to water while that of uninfected cells was not significantly different from water. Magnetic enrichment of parasitised cells can therefore be considered dependent primarily on the magnetic susceptibility of the parasitised cells.
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18
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Magnetic susceptibility. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/s0075-7535(06)32001-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2023]
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19
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Moore LR, Fujioka H, Williams PS, Chalmers JJ, Grimberg B, Zimmerman P, Zborowski M. Hemoglobin degradation in malaria-infected erythrocytes determined from live cell magnetophoresis. FASEB J 2006; 20:747-9. [PMID: 16461330 PMCID: PMC3728832 DOI: 10.1096/fj.05-5122fje] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
During intra-erythrocytic development, malaria trophozoites digest hemoglobin, which leads to parasite growth and asexual replication while accumulating toxic heme. To avoid death, the parasite synthesizes insoluble hemozoin crystals in the digestive vacuole through polymerization of beta-hematin dimers. In the process, the heme is converted to a high-spin ferriheme whose magnetic properties were studied as early as 1936 by Pauling et al. Here, by magnetophoretic cell motion analysis, we provide evidence for a graduated increase of live cell magnetic susceptibility with developing blood-stage parasites, compatible with the increase in hemozoin content and the mechanism used by P. falciparum to avoid heme toxicity. The measured magnetophoretic mobility of the erythrocyte infected with a late-stage schizont form was m = 2.94 x 10(-6) mm3 s/kg, corresponding to the net volume magnetic susceptibility (relative to water) of Deltachi = 1.80 x 10(-6), significantly higher than that of the oxygenated erythrocyte (-0.18x10(-6)) but lower than that of the fully deoxygenated erythrocyte (3.33x10(-6)). The corresponding fraction of hemoglobin converted to hemozoin, calculated based on the known magnetic susceptibilities of hemoglobin heme and hemozoin ferriheme, was 0.50, in agreement with the published biochemical and crystallography data. Magnetophoretic analysis of live erythrocytes could become significant for antimalarial drug susceptibility and resistance determination.
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Affiliation(s)
- Lee R. Moore
- Department of Biomedical Engineering Lerner Research Institute The Cleveland Clinic Foundation, Cleveland, Ohio
| | - Hisashi Fujioka
- Institute of Pathology Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - P. Stephen Williams
- Department of Biomedical Engineering Lerner Research Institute The Cleveland Clinic Foundation, Cleveland, Ohio
| | - Jeffrey J. Chalmers
- Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, Ohio
| | - Brian Grimberg
- The Center for Global Health & Diseases, Case Western Reserve University, Cleveland, Ohio
| | - Peter Zimmerman
- The Center for Global Health & Diseases, Case Western Reserve University, Cleveland, Ohio
| | - Maciej Zborowski
- Department of Biomedical Engineering Lerner Research Institute The Cleveland Clinic Foundation, Cleveland, Ohio
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20
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Kuchel P, Chapman B, Bubb W, Hansen P, Durrant C, Hertzberg M. Magnetic susceptibility: Solutions, emulsions, and cells. ACTA ACUST UNITED AC 2003. [DOI: 10.1002/cmr.a.10066] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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21
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Abstract
The existence of unpaired electrons in the four heme groups of deoxy and methemoglobin (metHb) gives these species paramagnetic properties as contrasted to the diamagnetic character of oxyhemoglobin. Based on the measured magnetic moments of hemoglobin and its compounds, and on the relatively high hemoglobin concentration of human erythrocytes, we hypothesized that differential migration of these cells was possible if exposed to a high magnetic field. With the development of a new technology, cell tracking velocimetry, we were able to measure the migration velocity of deoxygenated and metHb-containing erythrocytes, exposed to a mean magnetic field of 1.40 T and a mean gradient of 0.131 T/mm, in a process we call cell magnetophoresis. Our results show a similar magnetophoretic mobility of 3.86 x 10(-6) mm(3) s/kg for erythrocytes with 100% deoxygenated hemoglobin and 3.66 x 10(-6) mm(3) s/kg for erythrocytes containing 100% metHb. Oxygenated erythrocytes had a magnetophoretic mobility of from -0.2 x 10(-6) mm(3) s/kg to +0.30 x 10(-6) mm(3) s/kg, indicating a significant diamagnetic component relative to the suspension medium, in agreement with previous studies on the hemoglobin magnetic susceptibility. Magnetophoresis may open up an approach to characterize and separate cells for biochemical analysis based on intrinsic and extrinsic magnetic properties of biological macromolecules.
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Affiliation(s)
- Maciej Zborowski
- Department of Biomedical Engineering/ND20, Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, Ohio 44915, USA.
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22
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Spees WM, Yablonskiy DA, Oswood MC, Ackerman JJ. Water proton MR properties of human blood at 1.5 Tesla: magnetic susceptibility, T(1), T(2), T*(2), and non-Lorentzian signal behavior. Magn Reson Med 2001; 45:533-42. [PMID: 11283978 DOI: 10.1002/mrm.1072] [Citation(s) in RCA: 372] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Accurate knowledge of the magnetic properties of human blood is required for the precise modeling of functional and vascular flow-related MRI. Herein are reported determinations of the relaxation parameters of blood, employing in vitro samples that are well representative of human blood in situ. The envelope of the blood (1)H(2)O free-induction decay signal magnitude during the first 100 msec following a spin echo at time TE is well- described empirically by an expression of the form, S(t) = S(o). exp[-R(*)(2). (t - TE) - AR*. (t - TE)(2)]. The relaxation parameters AR* and R(*)(2) increase as a function of the square of the susceptibility difference between red blood cell and plasma and depend on the spin-echo time. The Gaussian component, AR*, should be recognized in accurate modeling of MRI phenomena that depend upon the magnetic state of blood. The magnetic susceptibility difference between fully deoxygenated and fully oxygenated red blood cells at 37 degrees C is 0.27 ppm, as determined independently by MR and superconducting quantum interference device (SQUID) measurements. This value agrees well with the 1936 report of Pauling and Coryell (Proc Natl Acad Sci USA 1936;22:210-216), but is substantially larger than that frequently used in MRI literature. Magn Reson Med 45:533-542, 2001.
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Affiliation(s)
- W M Spees
- Department of Radiology, Washington University, St. Louis, Missouri, USA
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23
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Affiliation(s)
- P W Kuchel
- Department of Biochemistry, University of Sydney, NSW, Australia
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24
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The use of a superconducting magnetometer to measure spin equilibria in hemoglobin. J Mol Liq 1989. [DOI: 10.1016/0167-7322(89)80032-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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25
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26
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Noble RW, De Young A, Vitale S, Morante S, Cerdonio M. Studies on the linkage between spin equilibria and protein structure in carp ferric hemoglobin. EUROPEAN JOURNAL OF BIOCHEMISTRY 1987; 168:563-7. [PMID: 2822419 DOI: 10.1111/j.1432-1033.1987.tb13454.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The effects of protein conformation on the spin-state equilibria of several derivatives of carp hemoglobin have been examined. This has been done by measuring the pH dependence of the paramagnetic susceptibilities of these derivatives in the presence and absence of inositol hexakisphosphate, P6-inositol. In all cases the addition of P6-inositol at low pH and the lowering of the pH in the presence of P6-inositol shift the spin-state equilibrium in favor of the high-spin electronic configuration. The P6-inositol and pH dependence of these magnetic properties parallels the pH and P6-inositol dependence of the conformational state of the hemoglobin as determined in earlier studies and further supports a thermodynamic linkage between the electronic state of the iron atoms and the quaternary structure of the hemoglobin molecule.
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Affiliation(s)
- R W Noble
- Veteran's Administration Medical Center, New York City, New York
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27
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28
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Cordone L, Cupane A, Leone M, Vitrano E. Optical absorption spectra of deoxy- and oxyhemoglobin in the temperature range 300-20 K. Relation with protein dynamics. Biophys Chem 1986; 24:259-75. [PMID: 3768470 DOI: 10.1016/0301-4622(86)85031-1] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
We have studied the optical absorption spectra of human deoxy- and oxyhemoglobin in the temperature range 300-20 K and in the wavelength range 350-1350 nm. By lowering the temperature, a narrowing and a shift of all bands were observed together with a sizeable increase of the integrated intensities of the charge-transfer bands of deoxyhemoglobin. At all temperatures the spectra are in full agreement with the band assignment previously suggested in the literature and no new relevant bands have been detected for both deoxy- and oxyhemoglobin. Analysis of the first and second moment of the bands, within the framework of the harmonic Franck-Condon approximation, gave information on the dynamic properties of the heme in the heme pocket.
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29
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Neya S, Funasaki N. Proton nuclear magnetic resonance investigation of the spin-state equilibrium of the alpha and beta subunits in intact azidomethemoglobin. Biochemistry 1986; 25:1221-6. [PMID: 3964673 DOI: 10.1021/bi00354a005] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The hyperfine-shifted proton NMR spectra of human azidomethemoglobin were examined at 300 MHz in the 2-60 degree C range. From analysis of the temperature-dependent heme methyl shifts, the thermal spin-state equilibria of the alpha and beta subunits were independently analyzed in the intact tetramer. The thermodynamic values of the spin equilibrium of the alpha and beta subunits were comparable, suggesting that the spin equilibrium properties of the constituent subunits are similar to each other. Examination of the azidomethemoglobins reconstituted with deutero- or mesohemin further shows that the alpha and beta subunit difference is still small in these hemoglobins probably due to the smallness of the steric and electronic difference of the heme 2,4-substituents of the examined porphyrins. The similarity of the spin equilibrium profiles of the subunits indicates that the strain imposed from the globin to the heme iron is of comparable magnitude for the alpha and beta subunits within the azidomethemoglobins.
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