Targeted elimination of Vancomycin resistance gene vanA by CRISPR-Cas9 system.

OBJECTIVE: The purpose of this study is to reduce the spread of the vanA gene by curing the vanA-harboring plasmid of vancomycin-resistant using the CRISPR-Cas9 system. METHODS: Two specific spacer sequence (sgRNAs) specific was designed to target the vanA gene and cloned into plasmid CRISPR-Cas9. The role of the CRISPR-Cas system in the plasmid elimination of drug-resistance genes was verified by chemically transformation and conjugation delivery methods. Moreover, the elimination efficiency in strains was evaluated by plate counting, PCR, and quantitative real-time PCR (qPCR). Susceptibility testing was performed by broth microdilution assay and by Etest strips (bioMérieux, France) to detect changes in bacterial drug resistance phenotype after drug resistance plasmid clearance. RESULTS: In the study, we constructed a specific prokaryotic CRISPR-Cas9 system plasmid targeting cleavage of the vanA gene. PCR and qPCR results indicated that recombinant pCas9-sgRNA plasmid can efficiently clear vanA-harboring plasmids. There was no significant correlation between sgRNA lengths and curing efficiency. In addition, the drug susceptibility test results showed that the bacterial resistance to vancomycin was significantly reduced after the vanA-containing drug-resistant plasmid was specifically cleaved by the CRISPR-Cas system. The CRISPR-Cas9 system can block the horizontal transfer of the conjugated plasmid pUC19-vanA. CONCLUSION: In conclusion, our study demonstrated that CRISPR-Cas9 achieved plasmid clearance and reduced antimicrobial resistance. The CRISPR-Cas9 system could block the horizontal transfer of plasmid carrying vanA. This strategy provided a great potential to counteract the ever-worsening spread of the vanA gene among bacterial pathogens and laid the foundation for subsequent research using the CRISPR-Cas9 system as adjuvant antibiotic therapy.

Effects of Tearing Conditions on the Crack Propagation in a Monolayer Graphene Sheet.

The path of crack propagation in a graphene sheet is significant for graphene patterning via the tearing approach. In this study, we evaluate the fracture properties of pre-cracked graphene during the tearing process, with consideration of the effects of the aspect ratio, loading speed, loading direction, and ambient temperatures on the crack propagation in the monolayer sheet. Some remarkable conclusions are drawn based on the molecular dynamic simulation results, i.e., a higher loading speed may result in a complicated path of crack propagation, and the propagation of an armchair crack may be accompanied by sp carbon links at high temperatures. The reason for this is that the stronger thermal vibration reduces the load stress difference near the crack tip and, therefore, the crack tip can pass through the sp link. A crack propagates more easily along the zigzag direction than along the armchair direction. The out-of-plane tearing is more suitable than the in-plane tearing for graphene patterning. The path of crack propagation can be adjusted by changing the loading direction, e.g., a rectangular graphene ribbon can be produced by oblique tearing. This new understanding will benefit the application of graphene patterning via the tearing approach.

Bonding few-layered graphene via collision with high-speed fullerenes.

Graphene, as a typical two-dimensional material, is popular in the design of nanodevices. The interlayer relative sliding of graphene sheets can significantly affect the effective bending stiffness of the few-layered graphene. For restricting the relative sliding, we adopted the atomic shot peening method to bond the graphene sheets together by ballistic C60 fullerenes from its two surfaces. Collision effects are evaluated via molecular dynamics simulations. Results obtained indicate that the fullerenes' incident velocity has an interval, in which the graphene sheet can be bonded after collision while no atoms on the fullerenes escaping from the graphene ribbon after collision. The limits of the interval increase with the layer number. Within a few picoseconds of collision, a stable carbon network is produced at an impacted area. The graphene sheets are bonded via the network and cannot slide relatively anymore. Conclusions are drawn to show the way of potential applications of the method in manufacturing a new graphene-based two-dimensional material that has a high out-of-plane bending stiffness.

Analogous Diamondene Nanotube Structure Prediction Based on Molecular Dynamics and First-Principle Calculations.

A concentric twin tube (CTT) can be built by placing a carbon nanotube (CNT) in another identical CNT. Different from diamondene nanotubes, a stable CTT has no inter-shell covalent bond. As a prestressed double-walled nanotube, CTT has a lower structural stability at a finite temperature. According to the molecular dynamics and first-principle calculations, (a) CTTs have three types of relaxed configurations. In a type III CTT, the inner tube buckles to produce a V-shaped cross-section, and the outer tube may be convex or concave. (b) The minimal radii of relaxed zigzag and armchair CTTs with concave outer tubes were found. (c) After relaxation, the circumferences and areas of the two tubes in a type III CTT are different from those of the corresponding ideal CNT. The area change rate (A-CR) and circumference change rate (C-CR) of the outer tube are the first-order Gaussian function of the radius of the ideal CNT (which forms the CTT), and tends to be 73.3% of A-CR or 95.3% of C-CR, respectively. For the inner tube of a CTT, the A-CR is between 29.3% and 37.0%, and the C-CR is close to 95.8%. (d) The temperature slightly influences the findings given above.

Recoverability of a gigahertz rotation-translation nanoconvertor with hydrogenated deformable rotor at room temperature.

To design a rotor with recoverable deformation for conversion between rotation and translation in a nanodevice, an internally hydrogenated deformable part (HDP) was introduced in the carbon nanotube-based rotor. Initially, under van der Waals (vdW) force, the hydrogenated areas on the HDP curved toward the rotating axis. When a rotational frequency was exerted on the rotor, the hydrogenated parts on the HDP were separated under strong centrifugal force. Translational motion of the free edge of the rotor was generated synchronously during deformation of the HDP. Once removing the input rotation, the rotor would stop rotating by friction from the stators, and the HDP shrank back by strong vdW force but weakening centrifugal force. Hence, the nanoconvertor has recoverability, which was verified by molecular dynamics simulations with considering the effects of hydrogenation schemes and input rotational frequency at room temperature. Conclusions were drawn for a design of a nanodevice based on the present rotation-translation nanoconvertor model.

[Effect of acupoint massage dominant early comprehensive intervention on the prognosis of premature infants with brain injury].

OBJECTIVE: To explore the effect of acupoint massage dominant early comprehensive intervention on the prognosis of premature infants with brain injury. METHODS: Totally 210 premature infants with brain injury were assigned to the intervention group (112 cases) and the control group (98 cases). All patients received routine therapy (medicinal + routine care instructions). Patients in the intervention group additionally received acupoint massage. Those with abnormal early motion received physical sports treatment. Those with upper limbs dysfunction or with fine movement disorders received occupational therapy. Premature infants' development quotient (DQ) was performed at corrected age of 6 and 12 months by using neuropsychological development examination table for 0 - 6 years old children. The incidence of cerebral palsy was statistically calculated. RESULTS: At corrected age of 6 months, DQ of gross motor, fine motor, language three functional areas was higher in the intervention group than in the control group with significant difference (P < 0.05). At corrected age of 12 months, DQ of gross motor, fine motor, language, social and adaptive capacities was higher in the intervention group than in the control groupwith significant difference (P < 0.05). The incidence of cerebral palsy was 4.46% (5/112) in the intervention group and 12.24% (12/98) in the control group (P < 0.05). CONCLUSION: Acupoint massage dominant early comprehensive intervention could obviously improve the intelligence development level and lower the incidence of cerebral palsy in premature infants with brain injury.