Preparation and characterization of adenine-based polyimide/nano-silica hybrid films

An efficient strategy with a synergistic effect of hydrophilic and electrostatic interactions for simultaneous enrichment of N- and O-glycopeptides

N- and O-glycosylation modifications of proteins are closely linked to the onset and development of many diseases and have gained widespread attention as potential targets for therapy and diagnosis. However, the low abundance and low ionization efficiency of glycopeptides as well as the high heterogeneity make glycosylation analysis challenging. Here, an enrichment strategy, using Knoevenagel copolymers modified with polydopamine-adenosine (denoted as PDA-ADE@KCP), was firstly proposed for simultaneous enrichment of N- and O-glycopeptides through the synergistic effects of hydrophilic and electrostatic interactions. The adjustable charged surface and hydrophilic properties endow the material with the capability to achieve effective enrichment of intact N- and O-glycopeptides. The experimental results exhibited excellent selectivity (1 : 5000) and sensitivity (0.1 fmol μL-1) of the prepared material for N-glycopeptides from standard protein digest samples. Moreover, it was further applied to simultaneous capturing of N- and O-glycopeptides from mouse liver protein digests. Compared to the commercially available zwitterionic hydrophilic interaction liquid chromatography (ZIC-HILIC) material, the number of glycoproteins corresponding to all N- and O-glycopeptides enriched with PDA-ADE@KCP was much more than that with ZIC-HILIC. Furthermore, PDA-ADE@KCP captured more O-glycopeptides than ZIC-HILIC, revealing its superior performance in O-glycopeptide enrichment. All these results indicated that the strategy holds immense potential in characterizing N- and O-intact glycopeptides in the field of proteomics.

Enhanced Mechanical and Thermal Properties of Polyimide Films Using Hydrophobic Fumed Silica Fillers

Polyimide (PI) composite films with enhanced mechanical properties were prepared by incorporating modified fumed silica (FS) particles while preserving their optical and thermal characteristics. The PI matrix was synthesized using a fluorinated diamine, a fluorinated dianhydride, and a rigid biphenyl dianhydride via chemical imidization. Commercially available FS particles, including unmodified FS particles (0-FS) and particles modified with dimethyl (2-FS), trimethyl (3-FS), octyl (8-FS), octamethylcyclotetrasiloxane (D4-FS), and polydimethylsiloxane (PDMS-FS) were used. Scanning electron microscope images and nitrogen adsorption-desorption isotherms revealed well-defined porous structures in the FS particles. The water contact angles on the composite films increased compared to those of the pristine PI films, indicating improved water resistance. The PI/0-FS films exhibited a typical trade-off relationship between tensile modulus and elongation at break, as observed in conventional composites. Owing to the poor compatibility and agglomeration of the PDMS-FS particles, the PI/PDMS-FS composite films exhibited poor mechanical performance and diminished optical characteristics. Although the longer-chained FS particles (8- and D4-FS) improved the tensile modulus of the PI film by up to 12%, a reduction of more than 20% in toughness was observed. The PI composite films containing the methylated FS particles (2- and 3-FS) outperformed 8- and D4-FS in terms of mechanical properties, with PI/3-FS films showing an over 10% increased tensile modulus (from 4.07 to 4.42 GPa) and 15% improved toughness (from 6.97 to 8.04 MJ/m3) at 7 wt. % silica loading. Except for the PI/PDMS-FS composites, all composite film samples exhibited more than 86% transmittance at 550 nm. Regarding thermal properties, the glass transition temperature (Tg) and thermal stability remained stable for most composite films. In addition, PI/3-FS films demonstrated enhanced dimensional stability with lower coefficients of thermal expansion (from 47.3 to 34.5 ppm/°C). Overall, this study highlights the potential of incorporating specific modified FS particles to tailor the mechanical, optical, and thermal properties of PI composite films.

Fine-Structure Analysis of Perhydropolysilazane-Derived Nano Layers in Deep-Buried Condition Using Polarized Neutron Reflectometry

A large background scattering originating from the sample matrix is a major obstacle for fine-structure analysis of a nanometric layer buried in a bulk material. As polarization analysis can decrease undesired scattering in a neutron reflectivity (NR) profile, we performed NR experiments with polarization analysis on a polypropylene (PP)/perhydropolysilazane-derived SiO₂ (PDS)/Si substrate sample, having a deep-buried layer of SiO₂ to elucidate the fine structure of the nano-PDS layer. This method offers unique possibilities for increasing the amplitude of the Kiessig fringes in the higher scattering vector (Q_z) region of the NR profiles in the sample by decreasing the undesired background scattering. Fitting and Fourier transform analysis results of the NR data indicated that the synthesized PDS layer remained between the PP plate and Si substrate with a thickness of approximately 109 Å. Furthermore, the scattering length density of the PDS layer, obtained from the background subtracted data appeared to be more accurate than that obtained from the raw data. Although the density of the PDS layer was lower than that of natural SiO₂, the PDS thin layer had adequate mechanical strength to maintain a uniform PDS layer in the depth-direction under the deep-buried condition.