title: Major Ampullate Spider Silk with Indistinguishable Spidroin Dope Conformations Leads to Different Fiber Molecular Structures.
abstract: To plentifully benefit from its properties (mechanical, optical, biological) and its potential to manufacture green materials, the structure of spider silk has to be known accurately. To this aim, the major ampullate (MA) silk of Araneus diadematus (AD) and Nephila clavipes (NC) has been compared quantitatively in the liquid and fiber states using Raman spectromicroscopy. The data show that the spidroin conformations of the two dopes are indistinguishable despite their specific amino acid composition. This result suggests that GlyGlyX and GlyProGlyXX amino acid motifs (X = Leu, Glu, Tyr, Ser, etc.) are conformationally equivalent due to the chain flexibility in the aqueous environment. Species-related sequence specificity is expressed more extensively in the fiber: the β-sheet content is lower and width of the orientation distribution of the carbonyl groups is broader for AD (29% and 58°, respectively) as compared to NC (37% and 51°, respectively). β-Sheet content values are close to the proportion of polyalanine segments, suggesting that β-sheet formation is mainly dictated by the spidroin sequence. The extent of molecular alignment seems to be related to the presence of proline (Pro) that may decrease conformational flexibility and inhibit chain extension and alignment upon drawing. It appears that besides the presence of Pro, secondary structure and molecular orientation contribute to the different mechanical properties of MA threads.
authors.affiliation: Regroupement québécois de Recherche sur la Fonction, l'Ingénierie et les Applications des Protéines (PROTEO), Centre de Recherche sur les Matériaux Avancés (CERMA), Centre Québécois sur les Matériaux Fonctionnels (CQMF), Département de Chimie, Université Laval, Pavillon Alexandre-Vachon, Ville de Québec, QC G1V 0A6, Canada. justine.dionne.1@ulaval.ca.
authors.forename: Justine
authors.initials: J
authors.lastname: Dionne
authors.affiliation: Regroupement québécois de Recherche sur la Fonction, l'Ingénierie et les Applications des Protéines (PROTEO), Centre de Recherche sur les Matériaux Avancés (CERMA), Centre Québécois sur les Matériaux Fonctionnels (CQMF), Département de Chimie, Université Laval, Pavillon Alexandre-Vachon, Ville de Québec, QC G1V 0A6, Canada. thierry.lefevre@chm.ulaval.ca.
authors.forename: Thierry
authors.initials: T
authors.lastname: Lefèvre
authors.affiliation: Regroupement québécois de Recherche sur la Fonction, l'Ingénierie et les Applications des Protéines (PROTEO), Centre de Recherche sur les Matériaux Avancés (CERMA), Centre Québécois sur les Matériaux Fonctionnels (CQMF), Département de Chimie, Université Laval, Pavillon Alexandre-Vachon, Ville de Québec, QC G1V 0A6, Canada. michele.auger@chm.ulaval.ca.
authors.forename: Michèle
authors.initials: M
authors.lastname: Auger
mesh_terms: D000818:Animals; D017433:Protein Structure, Secondary; D047011:Silk / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D013112:Spiders / Q000737:chemistry*
chemical_list: D047011:Silk
keywords: Raman spectromicroscopy; molecular orientation; orientation distribution function; silk protein structure; spider silk fibers; spinning dope