title: Interaction between the natural lipopeptide [Glu1, Asp5)] surfactin-C15 and hemoglobin in aqueous solution.
abstract: The interaction between natural lipopeptide [Glu(1), Asp(5)] surfactin-C15 (surfactin) and hemoglobin (Hb) has been studied. Surface tension measurements show that the critical micelle concentration (cmc) of surfactin increases from 1.54 x 10(-5) to 3.86 x 10(-5) mol/L with Hb. The UV spectra display that the effect of surfactin on Hb exhibits strong concentration-dependent fashion and the aquometHb convert to hemichrome at high surfactin concentration. Small-angle neutron scattering (SANS) and freeze-fracture transmission electron microscopy (FF-TEM) measurements show that surfactin result in the formation of a fractal structure representing a "necklace model" of micelle-like clusters randomly distributed along the protein polypeptide chain at high surfactin concentration. Far-UV circular dichroism (CD) results confirmed that surfactin can disrupt the helical structure of protein at high concentrations, although the enhanced native-like behavior of protein by low concentration of surfactin was observed. The microenvironment change around Phe amino residues and disulfide bonds of Hb was obtained from near-UV CD spectra.
authors.affiliation: State Key Laboratory of Bioreactor Engineering and Institute of Applied Chemistry, East China University of Science and Technology, Shanghai 200237, PR China.
authors.forename: Aihua
authors.initials: A
authors.lastname: Zou
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
authors.forename: Vasil M
authors.initials: VM
authors.lastname: Garamus
authors.forename: Kai
authors.initials: K
authors.lastname: Zheng
authors.forename: Regine
authors.initials: R
authors.lastname: Willumeit
authors.forename: Bozhong
authors.initials: B
authors.lastname: Mu
mesh_terms: D001224:Aspartic Acid / Q000737:chemistry*; D018698:Glutamic Acid / Q000737:chemistry*; D006454:Hemoglobins / Q000737:chemistry*; D055666:Lipopeptides / Q000737:chemistry*; D012996:Solutions
chemical_list: D006454:Hemoglobins; D055666:Lipopeptides; D012996:Solutions; D001224:Aspartic Acid; D018698:Glutamic Acid