Investigation of the structure of alpha-lactalbumin protein nanotubes using optical spectroscopy

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Tarhan Ö., Tarhan E., Harsa Ş.

Journal of Dairy Research, vol.81, no.1, pp.98-106, 2014 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 81 Issue: 1
  • Publication Date: 2014
  • Doi Number: 10.1017/s0022029913000629
  • Journal Name: Journal of Dairy Research
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.98-106
  • Keywords: FTIR, Microscopy, Protein nanotubes, Raman, α-Lactalbumin
  • Uşak University Affiliated: No

Abstract

Alpha-lactalbumin (α-la) is one of the major proteins in whey. When partially hydrolysed with Bacillus licheniformis protease, it produces nanotubular structures in the presence of calcium ions by a self-assembly process. This study presents investigation of α-la protein structure during hydrolysis and nanotube formation using optical spectroscopy. Before spectroscopic measurements, nanotubes were examined with microscopy. The observed α-la nanotubes (α-LaNTs) were in the form of regular hollo strands with a diameter of about 20 nm and the average length of 1 μm. Amide and backbone vibration bands of the Raman spectra displayed remarkable conformational changes in α and β domains in the protein structure during nanotube growth. This was confirmed by the Fourier-transform infrared (FTIR) spectroscopy data. Also, FTIR analysis revealed certain bands at calcium (Ca++) binding sites of COO- groups in hydrolysed protein. These sites might be critical in nanotube elongation. © 2013 Proprietors of Journal of Dairy Research.