Application of Optical Tweezers in the Research of Molecular Interaction between Lymphocyte Function Associated Antigen-1 and Its Monoclonal Antibody

Lymphocyte function associated antigen-1 （CD11a/CD18, LFA-1） plays an important role in the structure of the immunological synapse and is required for efficient lysis of cytotoxic T lymphocytes （CTLs） and natural killer （NK） cells. To study the activation mode of LFA-1 on the NK cell surface, optical tweezers were used in the work. As an emerging technology, optical tweezers are widely used to manipulate microscopic objects and measure the forces of molecular interactions in the field of biological research. In our study, a new platform was constructed to study the single molecular behavior of receptor on cell surface using optical tweezers. Based on the platform, the interaction between an NK cell and a polystyrene microsphere coated with anti-LFA-1 antibody was observed. The result confirmed that the adhesion forces between an NK cell and a polystyrene bead were time-dependent. According to our findings, we propose that anti-LFA-1 antibody may cause the clustering of LFA-1 on NK cell surface. Cellular ＆ Molecular Immunology.

Application of BP neural networks in non-linearity correction of optical tweezers

The back-propagation(BP)neural network is proposed to correct nonlinearity and optimize the force measurement and calibration of an optical tweezer sys-tem.Considering the low convergence rate of the BP algo-rithm,the Levenberg-Marquardt(LM)algorithm is used to improve the BP network.The proposed method is experimentally studied for force calibration in a typical optical tweezer system using hydromechanics.The result shows that with the nonlinear correction using BP net-works,the range of force measurement of an optical tweezer system is enlarged by 30%and the precision is also improved compared with the polynomial fitting method.It is demonstrated that nonlinear correction by the neural network method effectively improves the per-formance of optical tweezers without adding or changing the measuring system.

Dynamic 3D holographic projection of vectorial images with a multimode fiber

An optical multimode fiber(MMF)is capable of delivering structured light modes or complex images with high flexibility.Here,we present a holographic approach to enable the MMF as a 3D holographic projector with the capability of complete polarization control.By harnessing the strong coupling of the spatial and polarization degrees of freedom of light propagating through MMFs,our approach realizes active control of the output intensity and polarization in 3D space by shaping only the wavefront of the incident light.In this manner,we demonstrate MMF-based holographic projection of vectorial images on multiple planes via a phase-only hologram.Particularly,dynamic projection of polarization-multiplexed grayscale images is presented with an averaged Pearson correlation coefficient of up to 0.91.Our work is expected to benefit fiber-based holographic displays,data transmission,optical imaging,and manipulation.

Aurora A orchestrates entosis by regulating a dynamic MCAK-TIP150 interaction

Entosis, a ceU-in-ceU process, has been implicated in the formation of aneuploidy associated with an aberrant cell division control. Microtubule plus-end-tracking protein TI P150 facilitates the loading of MCAK onto the microtubule plus ends and orchestrates micro- tubule plus-end dynamics during cell division. Here we show that TIP150 cooperates with MCAK to govern entosis via a regulatory cir- cuitry that involves Aurora A-mediated phosphorylation of MCAK. Our biochemical analyses show that MCAK forms an intra-molecular association, which is essential for TIP150 binding. Interestingly, Aurora A-mediated phosphorylation of MCAK modulates its intra-mo- lecular association, which perturbs the MCAK-TI P150 interaction in vitro and inhibits entosis in vivo. To probe if MCAK-TIP150 inter- action regulates microtubule plasticity to affect the mechanical properties of ceUs during entosis, we used an optical trap to measure the mechanical rigidity of live MCF7 ceils. We find that the MCAK cooperates with TIP150 to promote microtubule dynamics and modulate the mechanical rigidity of the cells during entosis. Our results show that a dynamic interaction of MCAK-TI P150 orchestrated by Aurora A-mediated phosphorylation governs entosis via regulating microtubule plus-end dynamics and cell rigidity. These data reveal a previously unknown mechanism of Aurora A regulation in the control of microtubule plasticity during ceU-in-ceU pro- cesses.

Measurement of dynamic membrane mechanosensation using optical tweezers

Many cellular processes are orchestrated by dynamic changes in the plasma membrane to form membrane projections and endocytic compartments in response to extracellular cue changes.Our previous studies show that post-translational modifications of ACAP4 regulate membrane dynamics and curvature in response to epidermal growth factor and chemokine(C−C motif)ligand 18 stimulation(Zhao et al.,2013;Song et al.,2018).