Designing and Cloning of the Gene Sequence Encoding Silk Fibroin Amorphous Domain

To provide materials used in investigating the relationship between amino acid compositions of silk-like protein, structure, and functions, especially the biological functions, the motif genes encoding the silk fibroin amorphous domain, SGFGPVANGGSGEASSESDFGSSGFGPVANASSGEASSESDFAG(F) were designed and extended using a "head-to-tail" construction strategy. The designed genes were cloned into PSLFA1180FA and multimerized to form structures containing a two-timer, a four-timer, an eight-timer, and a twelve-timer. All the resulting plasmids were digested using the restriction enzyme BamHI and the double-enzymes BglII/HindIII. Restriction enzyme analysis and DNA sequencing revealed the motif was successfully cloned into PSLFA1180FA and multimerized to form a twelve-timer without gene deletion or mutation.

Study of Hydrophilic Properties of Polysaccharides

In this research,the structural characteristics,specific surface area,sorption of water vapor,and wetting enthalpy of various polysaccharides(cellulose,hemicelluloses,starch,pectin,chitin,and chitosan)have been studied.It was confirmed that crystallites are inaccessible for water,and therefore water molecules can interact only with polar groups in noncrystalline(amorphous)domains of biopolymers.The isotherms of water vapor sorption for various polysaccharides had sigmoid shapes,which can be explained by the absorption of water molecules in heterogeneous amorphous domains having clusters with different packing densities.The method of contributions of polar groups to sorption of water molecules was used,which allowed to derivate a simple calculating equation to describe the shape of sorption isotherms.The wetting of biopolymers with water was accompanied by a high exothermic thermal effect,in direct proportion to the amorphicity degree.The sorption values and wetting enthalpies of amorphous domains of biopolymers were calculated,which allowed to find the hydrophilicity index and compare the hydrophilicity of the various polysaccharides.

An atomistic model of silk protein network for studying the effect of pre-stretching on the mechanical performances of silks

Silk protein builds one of the strongest natural fibers based on its complex nanocomposite structures.However,the mechanical performance of silk protein,related to its molecular structure and packing is still elusive.In this study,we constructed an atomistic silk protein network model,which reproduces the extensive connection topology of silk protein with structure details of theβ-sheet crystallites and amorphous domains.With the silk protein network model,we investigated the structure evolution and stress distribution of silk protein under external loading.We found a pre-stretching treatment during the spinning process can improve the strength of silk protein.This treatment improves the properties of silk protein network,i.e.,increases the number of nodes and bridges,makes the nodes distributed homogeneously,and induces the bridges in the network well aligned to the loading direction,which is of great benefit to the mechanical performances of silk protein.Our study not only provides a realized atomistic model for silk protein network that well represents the structures and deformations of silk proteins under loading,but also gains deep insights into the mechanism how the pre-loading on silk proteins during spinning improves the mechanical properties of silk fibers.