title: Structural transformation of apocytochrome c induced by alternating copolymers of maleic acid and alkene.
abstract: Apocytochrome c interacts with two copolymers: poly(isobutylene-alt-maleic acid) (PIMA) and poly(1-tetradecene-alt-maleic acid) (PTMA). The interaction leads to apocytochrome c, a conformational change from random coil to alpha-helical structure. The alpha-helix content is influenced by the copolymer concentration, the length of alkyl chain of the copolymers, and pH of the medium. The electrostatic attraction between the copolymer and protein is an indispensable factor for the folding of the protein at acid pH. The hydrophobic interaction is an important factor over the entire pH range, especially when both the copolymer and protein carry negative charges at alkaline pH. The electrostatic and hydrophobic attractions between the copolymer and protein exclude water molecules, promoting the formation of hydrogen bonds within the helical structure. On the other hand, the hydrogen bonds formed between the ionized carboxyl of the copolymer and the amide of the protein partly restrain the formation of hydrogen bonds within the helical structure when the copolymer concentration is higher at pH 6.5 and 10.5.
authors.affiliation: Department of Macromolecular Science and Key Laboratory of Molecular Engineering of Polymer, Fudan University, Shanghai 200433, China.
authors.forename: Li
authors.initials: L
authors.lastname: Liang
authors.forename: Ping
authors.initials: P
authors.lastname: Yao
authors.forename: Ming
authors.initials: M
authors.lastname: Jiang
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D000818:Animals; D002244:Carbon / Q000737:chemistry; D002942:Circular Dichroism; D045304:Cytochromes c / Q000737:chemistry* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006736:Horses; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D007477:Ions; D008298:Maleates / Q000737:chemistry*; D008956:Models, Chemical; D011108:Polymers / Q000737:chemistry*; D011199:Potentiometry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry; D055672:Static Electricity; D014364:Tryptophan / Q000737:chemistry; D014466:Ultraviolet Rays
chemical_list: D000475:Alkenes; D007477:Ions; D008298:Maleates; D011108:Polymers; D000644:Quaternary Ammonium Compounds; C002189:polyelectrolyte 60; C001420:3-hydroxyphenyltrimethylammonium; D002244:Carbon; D014364:Tryptophan; D045304:Cytochromes c; C030272:maleic acid