Melatonin and serotonin are important phytochemicals enabling plants to redirect growth in response to environmental stresses. Despite much research on their biosynthetic routes, localization of their biosynthetic enzymes and recent identification of a phytomelatonin receptor, localization of the molecules themselves has to date not been possible. Elucidation of their locations in living tissues can provide an effective tool to facilitate indolamine research across systems including both plants and animals. In this study, we employed a novel technique, quantum dot nanoparticles, to directly visualize melatonin and serotonin in axenic roots. Melatonin was absorbed through epidermal cells, travelled laterally, and accumulated in endodermal and rapidly dividing pericycle cells. Serotonin was absorbed by cells proximal to the crown with rapid polar movement toward the root tip. Thermal stress disrupted localizationand dispersed melatonin and serotonin across cells. These data demonstrate the natural movement of melatonin and serotonin in roots directing cell growth and suggest that plants have a mechanism to disperse the indolamines throughout tissues as antioxidants in response to environmental stresses. K E Y W O R D Sabiotic stress, indolamine, localization, melatonin, quantum dot, serotonin, transport 2 of 10 | ERLAND Et AL.

Molecular force sensors (MFSs) have grown to become an important tool to study the mechanobiology of cells and tissues. They provide a minimally invasive means to optically report mechanical interactions at the molecular level. One of the challenges in molecular force sensor studies is the interpretation of the fluorescence readout. In this review, we divide existing MFSs into three classes based on the force-sensing mechanism (reversibility) and the signal output (analog/digital). From single-molecule force spectroscopy (SMFS) perspectives, we provided a critical discussion on how the sensors respond to force and how the different sensor designs affect the interpretation of their fluorescence readout. Lastly, the review focuses on the limitations and attention one must pay in designing MFSs and biological experiments using them; in terms of their tunability, signal-to-noise ratio (SNR), and perturbation of the biological system under investigation.

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Epidermal growth factor receptor (EGFR) is a membrane protein that controls critical cellular functions including adhesion, invasion and proliferation. Gene amplification in the EGFR or overexpression of the receptor in cell surface has been implicated in various neurodegenerative diseases and cancers. Binding of a ligand in the extracellular domain dictates vast and varied conformational changes in each part of the intracellular domain. The domain interactions and time sequence of these conformational changes which collectively influence cellular response have been largely unexplored, due to the challenge associated with isolating full-length EGFR in near native environment and difficulties associated with isolating individual conformational states. In this project, we isolate functional full-length monomeric EGFR within membrane nanodisc, a lipid bilayer encircled by an ApoA1 belting protein by employing cell-free expression. Using single-molecule Forster resonance energy transfer (FRET), we measure conformational states of individual full-length EGFR upon extracellular ligand binding. Our results provide mechanistic picture of signal transduction mechanism across the full-length EGFR protein with single-protein resolution.

Rolling adhesion is a unique process in which the adhesion events are short-lived and operate under highly non-equilibrium conditions. These characteristics pose a challenge in molecular force quantification, where in situ measurement of such forces cannot be achieved with most molecular force sensors that probe near equilibrium. In this report, we demonstrated a quantitative adhesion footprint assay combining DNA-based non-equilibrium force probes and modelling to measure the molecular force involved in fast rolling adhesion. We were able to directly profile the ensemble molecular force distribution during rolling adhesion with a dynamic range between 0 – 18 pN. Our results showed that the shear stress driving bead rolling motility directly controls the molecular tension on the probe-conjugated adhesion complex. Furthermore, the shear stress can steer the dissociation bias of components within the molecular force probe complex, favouring either DNA probe dissociation or receptor-ligand dissociation.

Rolling adhesion is a unique process in which the adhesion events are short-lived and operate under highly nonequilibrium conditions. These characteristics pose a challenge in molecular force quantification, where in situ measurement of these forces cannot be achieved with molecular force sensors that probe near equilibrium. Here, we demonstrated a quantitative adhesion footprint assay combining DNA-based nonequilibrium force probes and modeling to measure the molecular force involved in fast rolling adhesion. We were able to directly profile the ensemble molecular force distribution in our system during rolling adhesion with a dynamic range between 0 and 18 pN. Our results showed that the shear stress driving bead rolling motility directly controls the molecular tension on the probe-conjugated adhesion complex. Furthermore, the shear stress can steer the dissociation bias of components within the molecular force probe complex, favoring either DNA probe dissociation or receptor-ligand dissociation.

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Objective Type 2 diabetes mellitus (T2D) is the result of a dysregulation of insulin production and signalling, leading to an increase in both glucose concentration and pro-inflammatory cytokines such as interleukin (IL)-6 and tumour necrosis factor (TNF)-α. Previous work showed that T2D patients exhibited immune dysfunction associated with increased adhesion molecule expression on endothelial cell surfaces, accompanied by decreased neutrophil rolling velocity on the endothelial cell surface. Changes in cell rolling adhesion have direct vascular and immune complications such as atherosclerosis and reduced healing time in T2D patients. While previous studies focused primarily on how endothelial cells affect neutrophil rolling under T2D conditions, little is known about changes to neutrophils that affect their rolling. In this study, we aim to show how the rolling behaviour of neutrophils is affected by T2D conditions on a controlled substrate. Results We found that neutrophils cultured in T2D-serum mimicking media increased cell rolling velocity compared to neutrophils under normal conditions. Specifically, glucose alone is responsible for higher rolling velocity. While cytokines further increase the rolling velocity, they also reduce the cell size. Both glucose and cytokines likely reduce the function of P-selectin Glycoprotein Ligand-1 (PSGL-1) on neutrophils.