title: Solution structures of casein peptides: NMR, FTIR, CD, and molecular modeling studies of alphas1-casein, 1-23.
abstract: To determine its potential for interacting with other components of the casein micelle, the N-terminal section of bovine alphas1-casein-B, residues 1-23, was investigated with nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopies, and molecular modeling. NMR data were not consistent with conventional alpha-helical or beta-sheet structures, but changes in N-H proton chemical shifts suggested thermostable structures. Both CD and FTIR predicted a range of secondary structures for the peptide (30-40% turns, 25-30% extended) that were highly stable from 5 degrees C to 25 degrees C. Other conformational elements, such as loops and polyproline II helix, were indicated by FTIR only. Molecular dynamics simulation of the peptide predicted 32% turns and 27% extended, in agreement with FTIR and CD predictions and consistent with NMR data. This information is interpreted in accord with recent spectroscopic evidence regarding the nature of unordered conformations, leading to a possible role of alphas1-casein (1-23) in facilitating casein-casein interactions.
authors.affiliation: Eastern Regional Research Center, ARS, USDA, Wyndmoor, Pennsylvania 19038, USA. emalin@arserrc.gov
authors.forename: E L
authors.initials: EL
authors.lastname: Malin
authors.forename: M H
authors.initials: MH
authors.lastname: Alaimo
authors.forename: E M
authors.initials: EM
authors.lastname: Brown
authors.forename: J M
authors.initials: JM
authors.lastname: Aramini
authors.forename: M W
authors.initials: MW
authors.lastname: Germann
authors.forename: H M
authors.initials: HM
authors.lastname: Farrell
authors.forename: P L
authors.initials: PL
authors.lastname: McSweeney
authors.forename: P F
authors.initials: PF
authors.lastname: Fox
mesh_terms: D002364:Caseins / Q000737:chemistry*; D002942:Circular Dichroism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D010446:Peptide Fragments / Q000737:chemistry*; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D002364:Caseins; D010446:Peptide Fragments; C098970:isracidin