title: Investigation of the structure of alpha-lactalbumin protein nanotubes using optical spectroscopy.
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 hollow 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.
authors.affiliation: Department of Food Engineering, Faculty of Engineering, Izmir Institute of Technology, Urla, Izmir TR-35430, Turkey.
authors.forename: Ozgür
authors.initials: O
authors.lastname: Tarhan
authors.affiliation: Department of Physics, Faculty of Science, Izmir Institute of Technology, Urla, Izmir TR-35430, Turkey.
authors.forename: Enver
authors.initials: E
authors.lastname: Tarhan
authors.affiliation: Department of Food Engineering, Faculty of Engineering, Izmir Institute of Technology, Urla, Izmir TR-35430, Turkey.
authors.forename: Sebnem
authors.initials: S
authors.lastname: Harsa
mesh_terms: D001407:Bacillus / Q000201:enzymology; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D006868:Hydrolysis; D007768:Lactalbumin / Q000737:chemistry* / Q000378:metabolism; D008854:Microscopy, Electron; D043942:Nanotubes / Q000737:chemistry*; D010447:Peptide Hydrolases / Q000378:metabolism; D011487:Protein Conformation; D017550:Spectroscopy, Fourier Transform Infrared; D013057:Spectrum Analysis / Q000379:methods*; D013059:Spectrum Analysis, Raman
chemical_list: D007768:Lactalbumin; D010447:Peptide Hydrolases; D002118:Calcium