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Issue 7, 2015
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Transmission versus transflection mode in FTIR analysis of blood plasma: is the electric field standing wave effect the only reason for observed spectral distortions?

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Abstract

Fourier transform infrared (FTIR) microspectroscopy is assessed in terms of two techniques (i.e., transmission and transflection) as a method for rapid measurements of blood plasma. Apart from the expected effect of the electric field standing wave (EFSW), we also noticed that second-derivative IR spectra recorded in transflection mode exhibited a significant shift in the amide I band (up to 1667 cm−1) in comparison to the one recorded in transmission (1658 cm−1). This has not been reported thus far in studies of the EFSW distortion of IR spectra of biological material. The thinner the sample deposited on the low-e microscope slide, the lower the position of the amide I band found in FTIR spectra, suggesting various plasma compositions after stratification or certain changes in secondary protein conformations due to chemical and/or physical effects. There are potentially several phenomena that can occur at the surface of both IR substrates affecting the protein profile, including changes in optical properties (refractive index), variation in water content in the sample, and segregation of plasma components. All three hypotheses are discussed here, with the help of atomic force microscopy (AFM).

Graphical abstract: Transmission versus transflection mode in FTIR analysis of blood plasma: is the electric field standing wave effect the only reason for observed spectral distortions?

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Publication details

The article was received on 14 Oct 2014, accepted on 12 Dec 2014 and first published on 15 Dec 2014


Article type: Paper
DOI: 10.1039/C4AN01842G
Citation: Analyst, 2015,140, 2412-2421
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    Transmission versus transflection mode in FTIR analysis of blood plasma: is the electric field standing wave effect the only reason for observed spectral distortions?

    E. Staniszewska-Slezak, A. Rygula, K. Malek and M. Baranska, Analyst, 2015, 140, 2412
    DOI: 10.1039/C4AN01842G

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