Vertex 80 ftir

The constructs for pBAD24::plyC, pBAD24::plyCA, and pBAD24::plyCB were previously described (Nelson et al., 2006 (link)). Mutagenesis studies utilized the QuikChange II Site-Directed Mutagenesis Kit (Agilent Technologies, Santa Clara, CA) and were conducted per manufacturer’s instruction. All constructs were verified by DNA sequencing before being transformed into the expression strain BL21(DE3). The purifications of each construct were performed as previously described (McGowan et al., 2012 (link)). Mutants were characterized for proper folding by analytical gel filtration as previously described (Nelson et al., 2006 (link)) and by Fourier Transform Infrared Spectroscopy (FTIR) with an MCT detector in a Hyperion microscope (Nikon, Melville, NY) and a Vertex 80 FTIR (Bruker, Billerica, MA).

The morphologies of PPMs were observed by electron microscopy (FESEM, SU-8010), atomic force microscopy (AFM, SPM-9700), Ultra-Depth 3D Microscope (VHX-1000C) and Cryogenic scanning electron microscopy (Cryo-SEM, FEI Quanta 450). Fourier transform infrared spectroscopy (FT-IR) were obtained by a BRUKER Vertex 80 FT-IR (Germany). The interfacial tension of droplets and contact angle of films were measured by a contact angle meter (DATAPPHYSICS, OCA20). Element analyses (C, N, S, and H) were analyzed by an element analyzer (PerkinElmer, Optima 5300-DV). UV-Vis-NIR was conducted on a spectrophotometer (Lambda 750 S). Raman microscopy (LabRam HR Evolution) was recorded at 532 nm. X-ray photon spectroscopy (XPS) was recorded on ESCALAB Xi⁺ instrument (Thermo Fischer, Al Ka irradiation, 12.5 kV working voltage). For depth-dependent XPS measurements, PPM2.25 was etched using argon-ions (3000 eV) for different time. Differential scanning calorimeter (DSC) was done with DSC2500. Inductively coupled plasma emission (ICP-OES) was conducted with a PerkinElmer 8300 spectrometer. pH values were measured by a digital pH meter (SARTORIUS, pB-10).