To investigate the anti-tumor activity of dry Gekko swinhonis freeze-dried powder (DGFP) and fresh G. swinhonis freeze-dried powder (FGFP) on mice sarcoma S180 and acute toxicity testing of the two powders.Mice xenotransplant model of sarcoma S180 was established. Eighty mice were randomly divided into 8 groups. Control group were orally administrated by saline, another intraperitoneally injected with 5-Fu, the other six groups were orally administrated by DGFP and FGFP, each at three different doses (low, moderate and high). Rate of restraining tumor, index of thymus and spleen were calculated after 10 days' treatment. Acute toxicity testing tried to figure out LDs and LD, of DGFP and FGFP.The restraining tumor rates of DGFP and FGFP each at three doses were 31.4%, 50.8%, 37.7% and 14.8%, 19.1%, 54.7%. DGFP and FGFP elevated the thymic weight and thymic index of the mice to different extent. There were no significant differences among the eight groups in their spleen weight and spleen index. Acute toxicity testing did not figure out LD50 of DGFP and FGFP. In LD0 test, the administrating dosages of DGFP and FGFP given to the mice were both more than 2000 times than those given to patients on clinic. The result showed nothing abnormal in DGFP group. Compared with the DGFP and control group there was only a significant body weight decrease (P < 0.01) in the FGFP group in the first three days. However, on the fifth day and the seventh day there was no significant difference.DGFP and FGFP have conspicuous anti-tumor effects in vivo. The mechanism may be related to the elevated cellular immune function. Acute toxicity testing reveals that DGFP and FGFP are quite safe for conventional oral use on clinic.
Three different types of experiments, quiescent stress relaxation, delayed rate-switching during stress relaxation, and elastic recovery after step strain, are carried out in this work to elucidate the existence of a finite cohesion barrier against free chain retraction in entangled polymers. Our experiments show that there is little hastened stress relaxation from step-wise shear up to γ = 0.7 and step-wise extension up to the stretching ratio λ = 1.5 at any time before or after the Rouse time. In contrast, a noticeable stress drop stemming from the built-in barrier-free chain retraction is predicted using the GLaMM model. In other words, the experiment reveals a threshold magnitude of step-wise deformation below which the stress relaxation follows identical dynamics whereas the GLaMM or Doi-Edwards model indicates a monotonic acceleration of the stress relaxation dynamics as a function of the magnitude of the step-wise deformation. Furthermore, a sudden application of startup extension during different stages of stress relaxation after a step-wise extension, i.e. the delayed rate-switching experiment, shows that the geometric condensation of entanglement strands in the cross-sectional area survives beyond the reptation time τd that is over 100 times the Rouse time τR. Our results point to the existence of a cohesion barrier that can prevent free chain retraction upon moderate deformation in well-entangled polymer melts.
Coarse-grained three-dimensional (3D) architectured polymers, namely, soft-clusters, exhibit a glassy yet melt state even at temperatures much higher than their glass transition temperature. In this study, we systematically modulated the number of beads and manipulated the 3D architectures of these soft-clusters. We unveiled the distinct decoupling of translational and rotational relaxation and identified three distinct types of viscoelasticity. Remarkably, the center-of-mass dynamics of soft-clusters are less sensitive to pressure and density, with the critical determinants being the compactness of the architecture and the number of beads, which collectively dictate a predefined level of cooperation. We established direct correlations between the divergent relaxation time, growth of dynamic heterogeneity, and the activation energy of the center of mass. Our findings underscore the essential role of predefined cooperativeness, introduced via chemical bonds (springs), in the behavior of soft-clusters. This novel realization of glassiness suggests a fruitful future for 3D-architectured polymers.
This work studies the transient rheological responses of different entangled melts to startup deformation at unconventionally high rates, which can be accessed by working at sufficiently low temperature, e.g., at and below 130 °C for polystyrene. When the rate is as high as the second crossover frequency ωe observed from the small amplitude oscillatory shear (SAOS) data for storage and loss modulus G′ and G″, there is sizable viscous stress that dominates the initial mechanical response. It is shown based on the various polymer melts including PS, PMMA, SBR, PC, and PS mixtures that this viscous component of the stress cannot be neglected when characterizing such fast deformation in either extension or shear. This sizable frictional addition to the rubber elasticity component of the initial stress is founded to be preceded by solid-like deformation. The remarkable transient elasticity can be characterized by a modulus Ginterseg that grows well beyond the magnitude of the melt plateau modulus GN0 as the temperature lowers toward the glass transition temperature Tg. In the case of PS, Ginterseg reaches a level of 300 MPa at 110 °C and reduces to 2.0 MPa, i.e., 10GN0, at 130 °C. The initial elasticity is short-lived because the melts quickly transition to a state of viscous flow at a strain of just a few percent. The magnitude of the viscous stress at the solid-to-liquid transition defines a yield stress. This yield stress is found to scale with the applied rate in a power law, agreeing with the dependence of G″ on frequency ω from the SAOS data. Moreover, the intersegmental effect, i.e., the transient elasticity, is shown to also take place in unentangled and barely entangled PS melts as well as branched polyisoprene melts.
The present rheological study reveals for the first time that entangled polymer solutions made of linear polystyrene or poly(methyl methacrylate) can exhibit strain hardening due to non-Gaussian stretching during startup shear at sufficiently high rates and temperatures well above their overall glass transition temperatures: Tg,solute > Texp > Tg,solution. The solutions made of high-Tg polymers only show partial yielding in the sense that both shear and normal stresses grow monotonically in time until a point of rupture, signified by an emergent cusp in the stress vs strain curve and macroscopic breakup along a shear plane. The shear softening-to-hardening transition, which occurs as a function of the applied shear rate, happens at lower equivalent rate with decreasing temperature, violating the time–temperature superposition principle.
Entangled proteins have attracted significant research interest. Herein, we report the first rationally designed lasso proteins, or protein [1]rotaxanes, by using a p53dim-entwined dimer for intramolecular entanglement and a SpyTag-SpyCatcher reaction for side-chain ring closure. The lasso structures were confirmed by proteolytic digestion, mutation, NMR spectrometry, and controlled ligation. Their dynamic properties were probed by experiments such as end-capping, proteolytic digestion, and heating/cooling. As a versatile topological intermediate, a lasso protein could be converted to a rotaxane, a heterocatenane, and a "slide-ring" network. Being entirely genetically encoded, this robust and modular lasso-protein motif is a valuable addition to the topological protein repertoire and a promising candidate for protein-based biomaterials.
Objective To investigate the difference of mitochondrial DNA(mtDNA) deletions,respiratory chain enzyme complexes and ATP synthesis in rat heart of various ages.Methods Wistar rats were divided into three groups.namely infant rats(1 month),young rats(6 months) and aged rats(24 months). mtDNA deletions , respiratory chain enzyme complexes and ATP synthesis were divided determined with polymerase chain reaction(PCR),enzyme kinetics and bioluminescence technique.Results The deletion of mtDNA was present at different leveles in 3 groups. the relative deletion of mtDNA in heart of aged group(2.09 ±1.62) increased as comparde with infant group(0.77±1.16) (P0.05). the activities of mitochondrial respiratory enzyme chain complexesⅣ in heart of aged group (2347.21±623.33)decreased as comparde with infant group(4776.90±548.63) and young group(3859.12±703.53) (P 0.01).the ATP synthes in heart of aged group (196.95±33.26)also decreased as comparde with young group(337.53±62.18) (P 0.01). the activities of mitochondrial respiratory chain enzyme complexesⅠis no significant difference in three group(P0.05).Conclusions The study demonstrates relative relation between oxidative damage of mitochondrial DNA and aging.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Radiotherapy is a common method to treat gastric cancer (GC). However, the clinical outcomes of GC radiotherapy face challenges, and the mechanisms of GC radioresistance remain unclear. Our study aimed to investigate the role and mechanism of miR-4537 in the radiation sensitivity of GC cells. Cell viability was determined by Cell Counting Kit-8. The proliferation of HGC27 and KATO III cells was measured using a colony formation assay. Flow cytometry was performed to examine the changes in cell apoptosis. Western blotting was conducted to detect the expression of zinc finger protein 587 (ZNF587) protein in HGC27 and KATO III cells. To confirm the relationship between miR-4537 and ZNF587, a luciferase reporter assay was performed. MiR-4537 was downregulated in GC tumors and cells and suppressed cell proliferation, while promoting cell apoptosis in GC. Importantly, we found that miR-4537 reduced the radioresistance of GC cells. In addition, we also confirmed that miR-4537 expression is negatively correlated with ZNF587 expression in GC tissues. MiR-4537 bound to ZNF587 and suppressed the expression level of ZNF587. Overexpression of ZNF587 partially counteracted the effects of miR-4537 on cell proliferation and apoptosis. In conclusion, in GC cells, miR-4537 inhibited the ability of cell proliferation, but on the contrary, it promoted the ability of cell apoptosis and improved radiosensitivity of the cells.
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