Snl 10 probe

Surface roughness was determined by measuring the surface of the gel (n = 3) at 3 randomly selected positions (20×20 µm each measurement) before and after illumination (455 nm, 15 min) using an atomic force microscope (Bruker Bioscope Catalyst mounted on a Leica DMi6000B inverted optical microscope) in contact mode with a SNL‐10 probe (tip radius 2 nm, Bruker). Surface roughness (Rq) was calculated using the NanoScope Analysis software v150.

AFM images were acquired using JPKSPM (JPK Instruments AG, Berlin, Germany) with an SNL-10 probe (Bruker, Camarillo, CA) and a spring constant of 0.35 N/m in quantitative imaging (QI) mode at room temperature (25 °C). The AFM force vs. distance vs. time curves of entire cells were measured using a tipless cantilever (MIKROMASCH, Sofia, Bulgaria). The spring constant of the cantilever used here is 0.4 N/m. The deflection vs. displacement vs. time data were converted into force vs. relative distance vs. time graphs using the JPKSPM-data processing software.
Nanoscale images of random cells were captured by the AFM, while successful infection was confirmed in real time via Live/Dead staining. Fluorescent Live/Dead images of the samples on the substrates were captured by an epifluorescent microscope (Axio Zoom. V16, Zeiss, Germany) which is coupled with the AFM. Differently, infected cells were specifically chosen according to Live/Dead staining (appeared red) two hours since the addition of the T4 phages to determine the impact of T4 infection on the biomechanics of the cells.

The AFM topographs were collected on a Multimode 8 instrument equipped with a 15 μm scanner (E-scanner) coupled to a NanoScope V controller (Bruker). NanoScope software (v9.2, Bruker) was used for data collection and Gwyddion (v2.52, open-source software covered by GNU general public license, www.gwyddion.net) and OriginPro (v8.5.1, OriginLab Corp.) software packages were used for data processing and analysis. Proteoliposome samples were incubated on mica discs for 1 h at 4°C in adsorption buffer (20 mM MOPS pH 7.8, 20 mM NaCl and 5 mM MgCl₂), then imaged in imaging buffer (20 mM MOPS pH 7.8 and 20 mM NaCl). AFM images were recorded in peak-force tapping mode at a peak-force frequency of 2 kHz, using SNL-10 probes (56 kHz, k∼0.24 Nm⁻¹) (Bruker Nano). The peak-force amplitude was 10 nm and images were taken using either 256 × 256 or 512 × 512 pixel arrays. The peak-force set point varied between 50 and 1000 pN and the scan rate was between 0.5 and 1.0 Hz.

Samples were prepared on freshly cleaved mica and
dried at room temperature.
AFM images were acquired using a commercial AFM system (JPK NanoWizard
3 and 4). Measurements were performed in AC mode with SNL-10 probes
(Bruker) at 25 °C, 35–40% RH. AFM images were collected
with 1024 × 1024 pixels/frame. Each AFM tip was characterized
prior to usage. Analyses of AFM images were performed with JPK Data
Processing software. Note that for the height analyses of the AFM
images, the baseline height was leveled against the flat base plane
of the substrate. All AFM images were only subjected to the primary
first order flattening correction to remove sample tilt so that potential
artifacts induced by other image processing steps were avoided as
much as possible.

experiments were performed on a JPK NanoWizard 3 (JPK, Germany). The roughness and mechanical properties of the films were measured under QI Advanced Mode using SNL-10 probes (resonance frequency of ~65 kHz; spring constant of ~0.34 N/m; Bruker, Germany) with the exception of the PLL coated surface where a TAP525 probe (resonance frequency of ~525 kHz; spring constant of ~200 N/m, Bruker, Germany) was used. The Young modulus of the films were calculated by fitting the approach curves with the Hertz model, using a paraboloid tip shape (applying a very short indentation range, 0.5–1 nm – to eliminate contribution of the underlying substrate). All the probes were calibrated by contact with the underlying surfaces, from which sensitivity was determined, and by fitting the cantilever resonance frequency. All the experiments were performed in air, while the surfaces were humidified using a drop of water.