Materials based on recombinantly produced spider silk proteins eADF4(Cx) have been established almost 2 decades ago.^[1] Responsible for their outstanding mechanical^[2] and biomedically relevant^[3] properties is the multiblockcopolymer-like character including hydrophilic amorphous and hydrophobic crystalline blocks. Aiming at a better understanding of folding and orientation processes in spider silk proteins, we report experimental work on both thin pure eADF4(Cx) films varying module number x (i.e. molecular weight) and thin blend films of corresponding amorphous and crystalline oligopeptides varying the mixing ratio.
Pure films of eADF4(Cx) ((GSSAAAAAAAASGPGGYGPENQGPSGPGGYGPGGP)x, x = 1–16) are cast from hexafluoroisopropanol solutions on silicon substrates (Si). Additionally, blend films of the crystalline (pep-c: GSSAAAAAAAAS) and amorphous peptide sequence (pep-a: GPGGYGPENQGPSGPGGYGPGGP) of eADF4(Cx) varying pep-c molar fraction (0 – 1) are cast. Both film types are characterized as-cast and after post treatment (pt) in methanol-vapor using dichroic attenuated total reflection (ATR-) FTIR spectroscopy, circular dichroism and SFM.^[4]
For as-cast eADF4(Cx) films, low ß-sheet (< 10 %) and high random coil content (> 80 %) is found.^{[4, 5]} The higher the module number x, the higher is the reached β-sheet content after pt until the theoretical crystalline fraction is reached. An out-of-plane orientation relative to the surface normal of β-sheets is found.
For pep-a/pep-c blend films correlations between pep-c molar fraction and reached β-sheet content after pt until saturation at around 60 % crystallinity is observed. Compared to eADF4(Cx) films, higher out-of-plane orientation of the β-sheets is found for blend films.

References
[1] D. Huemmerich et al. Biochemistry 2004, 43, 13604-13612.
[2] J. M. Gosline et al. J. Exp. Biol. 1999, 202, 3295.
[3] K. Spiess; A. Lammel; T. Scheibel Macromol. Biosci. 2010, 10, 998–1007.
[4] M. Hofmaier et al. JPC B 2021, 125, 1061 – 1071.
[5] C. Borkner et al. ACS Appl. Pol. Mat. 2019, 1, 3366 – 3374.