Measuring proteins in H2O with 2D-IR spectroscopy

Samantha Hume, Gordon Hithell, Gregory M. Greetham, Paul M. Donaldson, Michael Towrie, Anthony W. Parker, Neil T. Hunt, Matthew Baker

Research output: Contribution to journalArticle

Abstract

The amide I infrared band of proteins is highly sensitive to secondary structure, but studies under physiological conditions are prevented by strong, overlapping water absorptions, motivating the widespread use of deuterated solutions. H/D exchange raises fundamental questions regarding the impact of increased mass on protein dynamics, while deuteration is impractical for biomedical or commercial applications of protein IR spectroscopy. We show that 2D-IR spectroscopy can avoid this problem because the 2D-IR amide I signature of proteins dominates that of water even at sub-millimolar protein concentrations. Using equine blood serum as a test system, we investigate the significant implications of being able to measure the spectroscopy and dynamics of proteins in water, demonstrating relevance in areas ranging from fundamental science to the clinic. Measurements of vibrational relaxation dynamics of serum proteins reveals that deuteration slows down the rate of amide I vibrational relaxation by > 10%, indicating a dynamic impact of isotopic exchange in some proteins. The unique link between protein secondary structure and 2D-IR amide I lineshape allows differentiation of signals due to albumin and globulin protein fractions in serum leading to measurements of the biomedically-important albumin to globulin ratio (AGR) with an accuracy of ±4% across a clinically-relevant range. Furthermore, we demonstrate that 2D-IR spectroscopy enables differentiation of the structurally-similar globulin proteins IgG, IgA and IgM, opening up a straightforward spectroscopic approach to measuring levels of serum proteins that are currently only accessible via biomedical laboratory testing.
LanguageEnglish
Pages6448-6456
Number of pages9
JournalChemical Science
Volume10
Issue number26
DOIs
Publication statusPublished - 14 May 2019

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Infrared spectroscopy
Proteins
Amides
Globulins
Blood Proteins
Albumins
Water
Water absorption
Immunoglobulin A
Immunoglobulin M
Ion exchange
Blood
Immunoglobulin G
Spectroscopy
Infrared radiation
Testing

Keywords

  • proteins
  • amide I infrared
  • spectrospcopy

Cite this

Hume, S., Hithell, G., Greetham, G. M., Donaldson, P. M., Towrie, M., Parker, A. W., ... Baker, M. (2019). Measuring proteins in H2O with 2D-IR spectroscopy. Chemical Science, 10(26), 6448-6456. https://doi.org/10.1039/C9SC01590F
Hume, Samantha ; Hithell, Gordon ; Greetham, Gregory M. ; Donaldson, Paul M. ; Towrie, Michael ; Parker, Anthony W. ; Hunt, Neil T. ; Baker, Matthew. / Measuring proteins in H2O with 2D-IR spectroscopy. In: Chemical Science. 2019 ; Vol. 10, No. 26. pp. 6448-6456.
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Hume, S, Hithell, G, Greetham, GM, Donaldson, PM, Towrie, M, Parker, AW, Hunt, NT & Baker, M 2019, 'Measuring proteins in H2O with 2D-IR spectroscopy' Chemical Science, vol. 10, no. 26, pp. 6448-6456. https://doi.org/10.1039/C9SC01590F

Measuring proteins in H2O with 2D-IR spectroscopy. / Hume, Samantha; Hithell, Gordon; Greetham, Gregory M.; Donaldson, Paul M.; Towrie, Michael; Parker, Anthony W.; Hunt, Neil T.; Baker, Matthew.

In: Chemical Science, Vol. 10, No. 26, 14.05.2019, p. 6448-6456.

Research output: Contribution to journalArticle

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AU - Hume, Samantha

AU - Hithell, Gordon

AU - Greetham, Gregory M.

AU - Donaldson, Paul M.

AU - Towrie, Michael

AU - Parker, Anthony W.

AU - Hunt, Neil T.

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Hume S, Hithell G, Greetham GM, Donaldson PM, Towrie M, Parker AW et al. Measuring proteins in H2O with 2D-IR spectroscopy. Chemical Science. 2019 May 14;10(26):6448-6456. https://doi.org/10.1039/C9SC01590F