As the indispensable oxygen-transporting cells, erythrocytes exhibit extreme deformability and amazing stability as they are subject to huge reversible shear stress and extrusion force during massive circulation in the body. The unique architecture of spectrin-actin-based membraneskeleton is considered to be responsible for such excellent mechanical properties of erythrocytes. Although erythrocytes have been recognized for more than 300 years, myriad questions about membrane-skeleton constantly attract people's attention. Here, we summarize the kinds of distinctive single-cell and single-molecule techniques that were used to investigate the structure and function of erythrocyte membrane-skeleton at macro and micro levels.

An ultrafast spectrum programmable femtosecond laser may enhance the performance of a wide variety of scientific applications, e.g., multi-photon imaging. In this paper, we report a digital micromirror device (DMD)-based ultrafast pulse shaper, i.e., DUPS, for femtosecond laser arbitrary amplitude shaping—the first time a programmable binary device reported to shape the amplitudes of ultrafast pulses spectrum at up to 32 kHz rate over a broad wavelength range. The DUPS is highly efficient, compact, and low cost based on the use of a DMD in combination with a transmission grating. Spatial and temporal dispersion introduced by the DUPS is compensated by a quasi-4-f setup and a grating pair, respectively. Femtosecond pulses with arbitrary spectrum shapes, including rectangular, sawtooth, triangular, double-pulse, and exponential profile, have been demonstrated in our experiments. A feedback operation process is implemented in the DUPS to ensure a robust and repeatable shaping process. The total efficiency of the DUPS for amplitude shaping is measured to be 27%.

α-catenin is an adhesion protein located at the cadherin-based cell–cell adherens junction. α-catenin cross-links β-catenin and actin fiber in the adhesion protein complex, and plays an important role in the formation and modulation of cell–cell adhesion. The central modulation domains can be unfolded to expose binding site of vinculin when stretching force is applied. Here, we studied the force-induced unfolding dynamics of α-catenin modulation domains under different loading rates from which the unfolding distance of M2 and M3 domains is determined to be 5–7 nm, and an unfolding intermediate state is identified. We also found that the folding process of M1–M3 domains goes through different pathways with cooperativity.

Enzymes are the major players for many biological processes. Fundamental studies of the enzymatic activity at the single-molecule level provides important information that is otherwise inaccessible at the ensemble level. Yet, these single-molecule experiments are technically difficult and generally require complicated experimental design. Here, we develop a Holliday junction (HJ)-based platform to study the activity of restriction endonucleases at the single-molecule level using single-molecule FRET (sm-FRET). We show that the intrinsic dynamics of HJ can be used as the reporter for both the enzyme-binding and the substrate-release events. Thanks to the multiple-arms structure of HJ, the fluorophore-labeled arms can be different from the surface anchoring arm and the substrate arm. Therefore, it is possible to independently change the substrate arm to study different enzymes with similar functions. Such a design is extremely useful for the systematic study of enzymes from the same family or enzymes bearing different pathologic mutations. Moreover, this method can be easily extended to study other types of DNA-binding enzymes without too much modification of the design. We anticipate it can find broad applications in single-molecule enzymology.

Coherent anti-Stokes Raman scattering (CARS) is able to enhance molecular signals by vibrational coherence compared to weak Raman signal. The surface or tip enhancement are successful technologies, which make it possible for Raman to detect single molecule with nanometer resolution. However, due to technical difficulties, tip-enhanced CARS (TECARS) is not as successful as expected. For single molecular detection, high sensitivity and resolution are two main challenges. Here, we reported the first single atom layer TECARS imaging on Graphene with the highest resolution about 20 nm, which has ever been reported. The highest EF_TECARS/CARS is about 10⁴, the similar order of magnitude with SECARS (EF of tip is usually smaller than that of substrates). Such resolution and sensitivity is promising for medical, biology and chemical applications in the future.

Luminescent properties of Er³⁺- and Yb³⁺- co-doped CaF₂ upconversion nanoparticles (UCNPs) were investigated in single particle and densely-packed states with a custom-built microscope. The single UCNPs exhibit linear dependency of luminescent intensity on excitation power while the densely-packed UCNPs exhibit a 2-order power law-dependency indicating a two-photon absorption process. Time-domain luminescence intensity measurements were performed and the curves were fitted to excitationnemission rate functions based on a simplified three-state model. The results indicate that the intermediates in single particles are much less and saturated in a short time, and there are strong couplings of the ground states and intermediate states between neighboring UCNPs in densely packed UCNPs.

Accepted 25 September 2018 Published 6 December 2018 Infrared neuron stimulation is regarded as an innovative approach for stimulating cochleae in animals while the exact mechanism still remains unknown. In this paper, we studied compound action potentials of guinea pig cochleae with chronic or acute deafness. We recorded optical compound action potentials and analyzed stretched cochlear preparations by fluorescence microscopy. Photoacoustic signals were measured by hydrophone and microphone, respectively. In our experiment, we observed a switch response effect in vitro and in vivo experiments. Therefore, we proposed photoacoustic effect could invoke auditory response in infrared neuron stimulation.

In this paper, we proposed a contrast-enhanced homemade spectral domain optical coherence tomography (SD-OCT) method for monitoring of brain microcirculation. We used the polyethylene glycol (PEG)-ylated gold nanorods (GNRs) as a contrast-enhanced agent, obtained clearly 2D and 3D OCT images of blood vessels and dynamic changes of probes in mouse blood vessels. Owing to high scattering of the PEG-GNRs, more tiny blood vessels can be imaged and the OCT signal can be enhanced by 5.87 dB after injection of PEG-GNRs for 20 min, the enhancement then declined gradually for 60 min. Our results demonstrate an effective technique for the enhanced imaging of blood vessels in vivo, especially for studies of the brain microcirculation, which could be serviced for disease mechanism research and therapeutic drug monitoring.