Asymmetric growth of Au-core/Ag-shell nanorods with a strong octupolar plasmon resonance and an efficient second-harmonic generation

Colloidal Au-core/Ag-shell nanorods with an asymmetric transverse cross- section and a strong octupolar plasmon resonance are synthesized by the controlled growth of Ag shells on one side of the Au cores. A largely enhanced second harmonic generation （SHG） from these asymmetric core-shell nanorods is demonstrated for the first time by tuning the dipolar and the octupolar plasmon modes to make them resonant with the fundamental and harmonic frequencies, respectively. The SHG intensity of the Au-Ag nanorods with dual-frequency resonances is enhanced by 21 times compared to that of the bare Au nanorods. The co-existence of the dipolar, quadrupolar, and octupolar radiations in the SHG is revealed. Additionally, the cellular uptake of the Au-Ag nanorods is monitored and the evolution of the membrane bleb is successfully observed by the SHG imaging. Our observations provide a strategy for enhancing the SHG of the colloidal metal nanoparticles and can have applications in chemical process monitoring and biological sensing.

Monte Carlo simulation of asymmetrical growth of cube-shaped nanoparticles

We simulated the asymmetrical growth of cube-shaped nanoparticles by applying the Monte Carlo method.The influence of the specific mechanisms on the crystal growth of nanoparticles has been phenomenologically described by efficient growth possibilities along different directions（or crystal faces）.The roles of the thermodynamic and kinetic factors have been evaluated in three phenomenological models.The simulation results would benefit the understanding about the cause and manner of the asymmetrical growth of nanoparticles.

A positive feedback circuit for ROP-mediated polar growth

Tip growth is a special type of polarized growth in which a single and unique polarization site is established and maintained.Rho of Plants(ROP)proteins,which represent the only class of Rho GTPases in plants,regulate tip growth.The dynamic and asymmetric distribution of ROPs is critical for the establishment and maintenance of tip growth,and requires at least one positive feedback loop,which is still elusive.Here,we report a positive feedback circuit essential for tip growth of root hairs,in which ROPs,ROP activators and effectors,and AGC1.5 subfamily kinases are interconnected by sequential oligomerization and phosphorylation.AGC1.5 subfamily kinases interact with and phosphorylate two guanine nucleotide exchange factors(GEFs)of ROPs,RopGEF4 and RopGEF10.They also interact with two ROP effectors,ICR2/RIP3 and MIDD1/RIP4,which bridge active ROPs with AGC1.5.Functional loss of the AGC1.5 subfamily kinases or ICR2 and MIDD1 compromised root hair growth due to reduced ROP signaling.We found that asymmetric targeting of RopGEF4 and RopGEF10 is controlled by AGC1.5-dependent phosphorylation.Interestingly,we discovered that the ROP effectors recruit AGC1.5 to active ROP domains at the plasma membrane during root hair growth and are critical for AGC1.5-dependent phosphorylation of RopGEFs.Given the large number of AGC kinases in plants,this positive feedback circuit may be a universal theme for plant cell polar growth.

Lumbar Scoliosis Induction in Juvenile Dogs by Three？dimensional Modulation of Spinal Growth Using Nickel？Titanium Coil Springs

Background： Current treatments for scoliosis have some defects and complications. To study spinal deformities and test novel scoliosis treatments, many animal models of scoliosis have been developed. These models applied a single load to the spine and could not precisely modulate the spinal growth in different dimensions. In this study, we applied posterior tethering in various directions with the application of nickel-titanium （NT） coil springs in dog＇s spine to modulate spinal growth in the coronal, sagittal, and transverse planes and create a scoliosis model possess curves that mimic adolescent idiopathic scoliosis （AIS） three dimensionally. Methods： Scoliosis was surgically induced in eight 8-week-old female dogs （weight： 1.95–2.30 kg） using bone screws and NT coil springs. The deformity was induced through the placement of posterior NT coil springs that tethered the spine by bone screw fixation. All dogs were monitored with serial radiographs to document changes in deformities. Results： All experimental animals developed scoliotic curves convex to the left in the lumbar segment. The mean coronal Cobb angle was 18.0° immediately postoperatively and 54.5° at 22 weeks. The mean lordosis increased from 6.2° postoperatively to 35.0° at final follow-up. Apical axial rotation increased from 4.5° postoperatively to 31.2° at 22 weeks. Conclusions： With the application of NT springs in dogs that allowed posterior tethering in various directions, lumbar spinal deformity was achieved in three planes： coronal, sagittal, and transverse planes. Notably, the lumbar spine in surgically treated dogs developed lordoscoliosis with obvious rotation and the curves mimic AIS three dimensionally well. This method allows lumbar scoliosis to develop without deep dissection of muscle and maintains the essential anatomical elements along the spinal curve. Moreover, the spinal growth modulation technique could yield information that would provide a basis for developing novel early-stage treatments for children with scoliosis.