Table 1.

Magnetic Susceptibility of Common Biomolecules Encountered in SWI and QSM

Materials	Volume susc.1 (SI, unitless) χv, ppm	Molar Susc.2 (CGS, cm3/mol, emu/mol) χm, ppm	Conditions and references	Areas of relevance
Water (H2O)	−9.035	−12.98	20°C, Arrighini et al (47).
Hydroxyapatite (Ca2+)	−14.83		Room temperature; measured by NMR; χv = −1.18 in CGS. Hopkins and Wehrli (111).	Vascular calcification, Tumor
Phospholipid	χ̄ = −9.68	χ̄ = −5803	20°C, magneto-orientation method, phospholipid DPPC. Kawamura et al (63); phospholipid composes of stearic acids.	Myelination demyelination dysmyelination Multiple sclerosis
	χ|| = −10.43	χ|| = −6303
	χ⊥ = −9.30	χ⊥ = −560
	χa = −1.13	χa = −683
Stearic acid CH3(CH2)16COOH	χ̄ = −10.03	χ̄ = −218.4	20°C, Gouy method, powder stearic acid. ρ = 1.04 g/cm3, molar mass M = 284.4772 g/mol. Lonsdale 1939 (64).
	χ1 = −9.65	χ1 = −210.0
	χ2 = −10.83	χ2 = −235.7
	χ3 = −9.56	χ3 = −208.2
	χa = −1.22	χa = −26.6
Oxyhemoglobin (HbO2, Fe3+)4		−893	20°C, Gouy method. Pauling and Coryell (90); Coryell et al (91).	BOLD fMRI Cerebral vascular diseases
Deoxyhemoglobin (Hb, Fe2+)		11,910	25°C, Gouy method, Taylor and Coryell (92).
Methemoglobin (Hb+, Fe3+)		14,000	24°C, Gouy method, in solution, per heme. Coryell et al (91).	Methemoglobinemia Sickle cell disease
Hemosiderin (Fe2+ and Fe3+)		4,810	22°C, Gouy method, thick suspension. Michaelis et el (94).	Hemorrhage Hemochromatosis
Ferritin (Fe3+)		6,132	22°C, Gouy method, in solution, per heme. Michaelis et el (94).	Brain iron stores Mitochondrial disease Neurodegeneration
Ceruloplasmin (Cu2+)		550	20°C, susceptometer balance, in solution, Ehrenberg et al (108).	Wilson’s disease

Shaded volume susceptibility values were converted from reported experimental molar susceptibility values (unshaded) in the relevant literature. Not all values were converted due to the unknown sample mass density and molar mass at the time of the reported experiments. The molar susceptibilities of phospholipid and oxyhemoglobin are much larger than that of water because of the presence of many more contributing chemical bonds within a molecule, see, e.g., Lonsdale (64).

¹Magnetic susceptibility values are reported in the literature based on several different definitions (volume, mass, and molar susceptibility) and units (SI, CGS, CGS emu). Significant variations exist due to variations in measurement techniques and sample preparations.

²Conversion from molar to volume susceptibility follows ${\mathrm{\chi }}_v={\mathrm{\chi }}_m\frac{\mathrm{\rho }}{M}$ where ρ is the mass density (g/cm ³) and M is the molar mass (g/mol). Conversion from CGS to SI units follows χ_v (SI) = 4πχ_v (CGS).

³Mean susceptibility χ̄ = (χ₁ + χ₂ + χ₃)/3; parallel susceptibility χ_|| is the susceptibility along the long axis of the carbon chain; susceptibility anisotropy is χ_a = χ₂ − (χ₁ + χ₃)/2 or χ_a = χ_|| − χ_⊥.

⁴There are still debates on the iron state in oxyhemoglobin.