Stretching single polymer chains of donor-acceptor foldamers: toward the quantitative study on the extent of folding

Investigation of the interaction between MeCP2 methyl-CpG binding domain and methylated DNA by single molecule force spectroscopy

MeCP2 is an essential transcriptional repressor that mediates transcriptional inhibition by binding to methylated DNA. The binding specificity of MeCP2 protein to methylated DNA was considered to depend on its methyl-CpG binding domain (MBD). In this study, we used atomic force microscope based single-molecular force spectroscopy to investigate the interaction of MeCP2 MBD and methylated DNA. The specific interaction forces of the MeCP2 MBD-methylated DNA complexes were measured for the first time. The dynamics was also investigated by measuring the unbinding force of the complex at different loading rates. In addition, the distribution of unbinding forces and binding probabilities of MeCP2 MBD and different DNA were studied at the same loading rate. It was found that MeCP2 MBD had weak interaction with hemi-methylated and unmethylated DNA compared to methylated DNA. This work revealed the binding characteristics of MeCP2 MBD and methylated DNA at the single-molecule level. It provides a new idea for exploring the molecular mechanism of MeCP2 in regulating methylation signals.

Hydrangea-structured tumor microenvironment responsive degradable nanoplatform for hypoxic tumor multimodal imaging and therapy

Developing new strategies to alleviate tumor hypoxia and enhance the therapeutic efficacy towards solid tumors is of great significance to tumor therapy. Herein, to overcome tumor hypoxia, specifically designed aza-BODIPY photosensitizer is co-loaded with anti-cancer drug (doxorubicin, DOX) onto the hydrangea-structured MnO₂ nanoparticles, and a tumor microenvironment (TME) responsive degradable nanoplatform (MDSP NP) is established. MDSP NPs (∼54 nm), with near infrared absorption (∼853 nm), can be rapidly dissociated to generate oxygen in response to TME, whereby improving tumor hypoxia, in favor of effective drugs release and enhanced chemo/photodynamic therapy. Revealed by in vivo fluorescence and photoaccoustic imaging, MDSP NPs are preferential accumulated at tumor site. Confirmed by photothermal imaging, MDSP NPs can induce hyperthermia to relieve hypoxia, promote the uptake of therapeutic nanoparticles, and further reduce the resistance and improve the therapeutic efficiency. As a result, a remarkable synergistic tumor chemo/photodynamic/photothermal therapy with hydrangea-structured TME responsive oxygen-self-generation nanoplatform is confirmed by both in vitro and in vivo studies, testifying its great potential for hypoxic tumor treatment in clinical application.

Self-assembly of platinum(ii) 6-phenyl-2,2'-bipyridine complexes with solvato- and iono-chromic phenomena

Mono- and di-nuclear organoplatinum(ii) monomers with cyclometalated 6-phenyl-2,2'-bipyridine ligands have been successfully constructed. These systems are capable of displaying intriguing solvato- and iono-chromic phenomena by elaborately manipulating non-covalent PtPt metal-metal and π-π stacking interactions for their self-assembly processes.

Staphylokinase Displays Surprisingly Low Mechanical Stability

Single-molecule force spectroscopy (SMFS) and molecular dynamics (MD) simulations have revealed that shear topology is an important structural feature for mechanically stable proteins. Proteins containing a β-grasp fold display the typical shear topology and are generally of significant mechanical stability. In an effort to experimentally identify mechanically strong proteins using single-molecule atomic force microscopy, we found that staphylokinase (SAK), which has a typical β-grasp fold and was predicted to be mechanically stable in coarse-grained MD simulations, displays surprisingly low mechanical stability. At a pulling speed of 400 nm/s, SAK unfolds at ∼60 pN, making it the mechanically weakest protein among the β-grasp fold proteins that have been characterized experimentally. In contrast, its structural homologous protein streptokinase β domain displays significant mechanical stability under the same experimental condition. Our results showed that the large malleability of native-state SAK is largely responsible for its low mechanical stability. The molecular origin of this large malleability of SAK remains unknown. Our results reveal a hidden complexity in protein mechanics and call for a detailed investigation into the molecular determinants of the protein mechanical malleability.

Single-molecule study of the synergistic effects of positive charges and Dopa for wet adhesion

Using AFM based single-molecule force spectroscopy, we studied the synergy between Dopa and lysine for wet adhesion on titania (TiO₂) and mica surfaces.