Human cardiac troponin I: A langmuir monolayer study

Jhony Orbulescu, Miodrag Micic, Mark Ensor, Sanja Trajkovic, Sylvia Daunert, Roger Leblanc

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Abstract

Human cardiac troponin I (cTnI) is the preferred biomarker in the assessment of myocardial infarction. It is known to interact with troponin C and T to form a trimeric complex. Whereas small amounts are found in the cytoplasm, most of cTnI is in the form of a complex with actin located in myofilaments. To understand these interactions of cTnI better, we first investigated the surface chemistry of cTnI as a Langmuir monolayer spread at the air-water interface. We investigated the optimal conditions for obtaining a stable Langmuir monolayer in terms of changing the ionic strength of the subphase using different concentrations of potassium chloride. Monolayer stability was investigated by compressing the cTnI monolayer to a specific surface pressure and keeping the surface pressure constant while measuring the decrease in the molecular area as a function of time. Aggregation and/or domain formation was investigated by using compression-decompression cycles, in situ UV-vis spectroscopy, Brewster angle microscopy (BAM), and epifluorescence microscopy. To ensure that the secondary structure is maintained, we used infrared reflection-absorption spectroscopy (IRRAS) directly at the air-subphase interface. It was found that cTnI forms a very stable monolayer (after more that 5000 s) that does not aggregate at the air-subphase interface. The cTnI molecules maintain their secondary structure and, on the basis of the low reflectivity observed, using BAM measurements and the low reflection-absorption intensities measured with IRRAS spectroscopy, lie flat on the subphase with the α-helices parallel to the air-subphase interface.

Original languageEnglish
Pages (from-to)3268-3274
Number of pages7
JournalLangmuir
Volume26
Issue number5
DOIs
StatePublished - Mar 2 2010

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ASJC Scopus subject areas

  • Electrochemistry
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Materials Science(all)
  • Spectroscopy

Cite this

Orbulescu, J., Micic, M., Ensor, M., Trajkovic, S., Daunert, S., & Leblanc, R. (2010). Human cardiac troponin I: A langmuir monolayer study. Langmuir, 26(5), 3268-3274. https://doi.org/10.1021/la903033x