Significance: Glutamate transporters play a crucial role for the recovery of the neurotransmitter glutamate from the synaptic cleft. Thus far, studies of the transport dynamics and detailed information of the working mechanism of this family of transmembrane proteins have been sparse and indirect. Here, we used high-speed atomic force microscopy (HS-AFM) to characterize the transport mechanisms and dynamics of a prokaryotic glutamate transporter homolog Glt _Ph in lipid membranes. We assess transport dynamics as a function of substrate in the imaging buffer and provide direct visual evidence that Glt _Ph transport domains within the trimer are entirely independent.

Listeriolysin-O (LLO) plays a crucial role during infection by Listeria monocytogenes. It enables escape of bacteria from phagocytic vacuole, which is the basis for its spread to other cells and tissues. It is not clear how LLO acts at phagosomal membranes to allow bacterial escape. The mechanism of action of LLO remains poorly understood, probably due to unavailability of suitable experimental tools that could monitor LLO membrane disruptive activity in real time. Here, we used high-speed atomic force microscopy (HS-AFM) featuring high spatio-temporal resolution on model membranes and optical microscopy on giant unilamellar vesicles (GUVs) to investigate LLO activity. We analyze the assembly kinetics of toxin oligomers, the prepore-to-pore transition dynamics and the membrane disruption in real time. We reveal that LLO toxin efficiency and mode of action as a membrane-disrupting agent varies strongly depending on the membrane cholesterol concentration and the environmental pH. We discovered that LLO is able to form arc pores as well as damage lipid membranes as a lineactant, and this leads to large-scale membrane defects. These results altogether provide a mechanistic basis of how large-scale membrane disruption leads to release of Listeria from the phagocytic vacuole in the cellular context. Listeriolysin-O (LLO) plays a crucial role in Listeria monocytogenes infection by allowing bacteria to escape from intracellular phagosomes and cells via an unknown molecular mechanism. We used high-speed atomic force microscopy (HS-AFM) supported with giant unilamellar vesicles imaging (GUVs) to characterize the interaction and dynamics of LLO with the lipid membranes at the nano-and micro-scale. We show that LLO efficiency and mode of action as a membrane-disrupting agent is strongly dependent on membrane cholesterol content and environmental pH. LLO is able to form arc pores and damage membranes as a lineactant, which is crucial for the processive membrane disruption. The latter mechanism, a previously uncharacterized mode of action for this toxin, is strongly cholesterol dependent and may provide a novel angle of attack against listeriosis.

We present a marker-free microscope that records the phase, amplitude, and polarization state of the field diffracted by the sample for different illumination directions. The data are processed with an appropriate inversion method to yield the sample permittivity map. We observe that the full-polarized information ameliorates significantly the three-dimensional image of weakly scattering subdiffraction objects. A resolution about one-fourth of the illumination wavelength is experimentally demonstrated on complex samples.

Optically pumped magnetometers can provide functionality for bio-magnetic field detection and mapping. This has attracted widespread attention from researchers in the biomedical science field. Magnetocardiography has been proven to be an effective method for examining heart disease. Notably, vector magnetocardiography obtains more spatial information than the conventional method by only taking a component that is perpendicular to the chest surface. In this work, a spin-exchange-relaxation-free (SERF) magnetometer with a compact size of 14 mm × 25 mm × 90 mm was developed. The device has a high sensitivity of 25 fT/ $\sqrt{\text{Hz}}$. Meanwhile, in the multichannel working mode, synchronous sensor manipulation and data acquisition can be achieved through our control software without additional data acquisition boards. Since a typical SERF magnetometer only responds to dual-axis magnetic fields, two sensors are orthogonally arranged to form a vector detection channel. Our system consists of seven channels and allows 7 × 9 vector MCG mapping by scanning. High-quality heart vector signals are measured, and P peak, QRS peak, and T peak can be distinguished clearly. To better demonstrate the vectorial information, a vector scatter plot form is also provided. Through a basic bio-electric current model, it demonstrates that triaxial MCG measurements capture a richer spatial current information than traditional uniaxial MCG, offering substantial diagnostic potential for heart diseases and shedding more light on the inversion of cardiac issues.

We show experimentally that a resolution far beyond that of conventional far-field optical profilometers can be reached with optical diffraction tomography. This result is obtained in the presence of multiple scattering when using an adapted inverse scattering algorithm for profile reconstruction. This new profilometry technique, whose resolution can be compared to that of atomic microscopes, also gives access to the permittivity of the surface.

Magnetic particles (MPs), a group of engineered particles in the nanometer and microscale, are valuable tools for separation of chemical or biological substance in environmental research, for target delivery of antibodies or proteins in biomedical applications, and for quantification of cells or biomolecules in biological systems. Despite the estimation of the amount of magnetic nanoparticles that were realized by magnetic particle spectroscopy, accurate quantification of MPs at single-particle resolution is still a challenge. Here, we used an elliptically optically pumped M_x atomic magnetometer combined with a peristaltic pump system to perform magnetic field measurements to quantify magnetic particles at the single-particle level under aqueous solution condition. Quantitative analysis of cobalt micro-nanoparticles revealed the volume-field linear character of magnetic particles. From the measured intensity of the magnetic field generated by MPs, we calculated the geometric parameters and numbers of MPs and estimated the detection limit of our developed atomic magnetometer. Our work paves a way for the practical use of MPs in the biomedical field as well as other applications in industry.