Recently, a de novo synthetic calcium-responsive self-assembly β-sheet peptide ID8 (Ile-Asp-Ile-Asp-Ile-Asp-Ile-Asp) has been developed to serve as the template inducing hydroxyapatite nucleation. The aim of this study was to evaluate the effect of ID8 on intrafibrillar mineralization of collagen making full use of its self-assembly ability. The mineralization experiments were carried out in vitro on both bare Type I collagen and fully demineralized dentin samples. The calcium-responsive self-assembly of ID8 was revealed by circular dichroism spectrum, 8-anilino-1-naphthalenesulfonic acid ammonium salt hydrate assay, attenuated total reflection Fourier transform infrared spectrum (ATR-FTIR) and transmission electron microscope (TEM). Polyacrylic acid (450 kDa) with a concentration of 100 μg ml−1 was selected as the nucleation inhibitor based on the determination of turbidimetry and TEM with selected area electron diffraction (TEM-SAED). The results showed that collagen intrafibrillar mineralization was significantly promoted with the pretreatment of self-assembly ID8 detected by TEM-SAED, SEM, X-ray diffraction and ATR-FTIR. The pretreatment of collagen utilizing self-assembly ID8 not only enhanced intermolecular hydrogen bonding but also contributed to calcium retention inside collagen and significantly increased the hydrophilicity of collagen. These results indicated that peptides with self-assembly properties like ID8 are expected to be potential tools for biomimetic mineralization of collagen.
Gang Zhou,Ying-si Wang,Hong Peng,Su-juan Li,Ting-li Sun,Cai-ling Li,Qing-shan Shi,Xiao-bao Xie
Citrobacter werkmanii , an aerobe and mesophilic Proteobacterium, is universal in industrial putrefaction, coastal water, and human blood. Our previous studies have discovered that outer membrane protein X (OmpX) of C. werkmanii is involved in calcium response, but the underlying mechanisms and its molecular characteristics remain elusive. To that end, the ompX gene was deleted from the genome of C. werkmanii and its phenotypic variations were thoroughly investigated in conjunction with the wild type (WT) and complementary strains using biochemical and molecular techniques such as RNA-Seq, respectively. The results demonstrated that deleting ompX reduces biofilm formation on polystyrene and glass surfaces. Meanwhile, Δ ompX ’s swimming ability but not for its twitching or swarming abilities, was also reduced on semi-solid plates compared with WT, which was caused by inhibition of flagellar assembly genes, such as flgC , flhB , and fliE , etc. Furthermore, ompX inactivation altered susceptibility to various bactericide classes, as well as responses to Ca 2+ and Mg 2+ stress. In addition, when compared to WT, Δ ompX captures a total of 1,357 deferentially expressed genes (DEGs), of which 465 were up-regulated and 892 were down-regulated, which can be enriched into various GO ontology and KEGG pathway terms. Furthermore, ompX , as well as ompD and ompW , can be modulated at the transcriptional levels by rbsR and tdcA . Overall, the ompX gene contributed to a variety of biological functions in C. werkmanii and could be served as a targeted site for controlling biofilm formation and developing new bactericides.
危险品化学品经营许可证（带存储）