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Image and data processing algorithms for identifying cell-bound membrane vesicle trajectories and movement information
摘要： This DIB article provides details about the trajectory identification and data processing algorithms used in the article "Dynamic single-vesicle tracking of cell-bound membrane vesicles on resting, activated, and cytoskeleton-disrupted cells" (Zhang et al.) [1]. The algorithm identifies vesicles on cell membranes from series of undyed grayscale images captured by the confocal microscope based on contrast differences and then trajectories of vesicles are obtained by analyzing their positions in consecutive images. Once the trajectories have been obtained, other quantitative movement information, such as moving speed, direction and acceleration, are derived by standard dynamic relations.
关键词： MATLAB algorithms,Vesicle tracking,Trajectory tracing,Confocal microscopy,Image processing
更新于2025-09-23 15:22:29
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Thermodynamic Analysis of the Transition of Liquid Crystals from Lamellar to Vesicular Phase
摘要： Here, we report the results of thermodynamic analyses on the lamellar-vesicular transition for a cationic amphiphilic species, namely 2-hydroxyethyl di(alkanol)oxyethyl methylammonium methylsulfate (DEAE). Previously, we have shown that spontaneous vesicle formation from a Lα-lamellar liquid crystal (LC) phase only occurs on the addition of a quantitative amount of additives to the DEAE LC at certain temperatures and that this change occurs without the input of any extra mechanical energy. These lamellar-vesicular transitions occur in two steps: the first step is the formation of an excited state, caused by the solubilization of organic substances in the bilayer structure. The second step, induced by the addition of a small amount of inorganic salt to the excited LC state, is the transition from lamellar to vesicular phase. From our experimental data, the change in the Gibbs free energy was estimated by assuming an ideal electrical chemical potential. As a result, the thermodynamic parameters at 303 K for the lamellar-vesicular transition from the initial state (lamellar) to the final state (vesicle) were found to be approximately －2.7 kJ/mol for the Gibbs free energy, －14.6 kJ/mol for the enthalpy change, and －11.9 kJ/mol for the entropy change. Each state change was due to structural changes not only in the LC bilayers but also in the hydration structure of the surrounding water. Moreover, the most significant finding is that the free energy change in lamellar-vesicular transition is negative, which may be explained based on the stabilization of solubilized vesicles with respect to the unsolubilized lamellar phases.
关键词： electrochemical potential,lamellar liquid crystal,chemical potential,vesicle,transition energy
更新于2025-09-23 15:21:01
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Maintenance of Rhodopsin levels in <i>Drosophila</i> photoreceptor and phototransduction requires Protein Kinase D
摘要： During Drosophila phototransduction, the G protein coupled receptor (GPCR) Rhodopsin (Rh1) transduces photon absorption into electrical signal via G-protein coupled activation of phospholipase C (PLC). Rh1 levels in the plasma membrane are critical for normal sensitivity to light. In this study, we report that Protein kinase D (dPKD) regulates Rh1 homeostasis in adult photoreceptors. Although eye development and retinal structure are unaffected in the dPKD hypomorph (dPKDH), it exhibited elevated levels of Rh1. Surprisingly, despite having elevated levels of Rh1, no defect was observed in the electrical response to light in these flies. By contrast the levels of another transmembrane protein of the photoreceptor plasma membrane, Transient receptor potential (TRP) was not altered in dPKDH. Our results indicate that dPKD is dispensable for eye development but is required for maintaining Rh1 levels in adult photoreceptors.
关键词： Electroretinogram (ERG),Phototransduction,Retinal degeneration,Rhodopsin,Drosophila,Rhodopsin loaded vesicle (RLVs),Protein Kinase D
更新于2025-09-19 17:15:36
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Frequency-Modulated Wave Dielectrophoresis of Vesicles And Cells: Periodic U-Turns at the Crossover Frequency
摘要： We have formulated the dielectrophoretic force exerted on micro/nanoparticles upon the application of frequency-modulated (FM) electric fields. By adjusting the frequency range of an FM wave to cover the crossover frequency fX in the real part of the Clausius-Mossotti factor, our theory predicts the reversal of the dielectrophoretic force each time the instantaneous frequency periodically traverses fX. In fact, we observed periodic U-turns of vesicles, leukemia cells, and red blood cells that undergo FM wave dielectrophoresis (FM-DEP). It is also suggested by our theory that the video tracking of the U-turns due to FM-DEP is available for the agile and accurate measurement of fX. The FM-DEP method requires a short duration, less than 30 s, while applying the FM wave to observe several U-turns, and the agility in measuring fX is of much use for not only salty cell suspensions but also nanoparticles because the electric-field-induced solvent flow is suppressed as much as possible. The accuracy of fX has been verified using two types of experiment. First, we measured the attractive force exerted on a single vesicle experiencing alternating-current dielectrophoresis (AC-DEP) at various frequencies of sinusoidal electric fields. The frequency dependence of the dielectrophoretic force yields fX as a characteristic frequency at which the force vanishes. Comparing the AC-DEP result of fX with that obtained from the FM-DEP method, both results of fX were found to coincide with each other. Second, we investigated the conductivity dependencies of fX for three kinds of cell by changing the surrounding electrolytes. From the experimental results, we evaluated simultaneously both of the cytoplasmic conductivities and the membrane capacitances using an elaborate theory on the single-shell model of biological cells. While the cytoplasmic conductivities, similar for these cells, were slightly lower than the range of previous reports, the membrane capacitances obtained were in good agreement with those previously reported in the literature.
关键词： Cell,Frequency-modulated wave,Crossover frequency,The Clausius-Mossotti factor,Spectroscopy,Dielectrophoresis,Vesicle
更新于2025-09-04 15:30:14
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Exosome-like Nanozyme Vesicles for H2O2-responsive Catalytic Photoacoustic Imaging of Xenograft Nasopharyngeal Carcinoma
摘要： Photoacoustic imaging (PAI) is an attractive imaging modality, which is promising for clinical cancer diagnosis due to its advantages on deep tissue penetration and fine spatial resolution. However, few tumor catalytic/responsive PAI strategies are developed. Here, we design an exosome-like nanozyme vesicle for in vivo H2O2-responsive PAI of nasopharyngeal carcinoma (NPC). The intrinsic peroxidase-like activity of graphene quantum dot nanozyme (GQDzyme) effectively converts the 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) into its oxidized form in the presence of H2O2. The oxidized ABTS exhibits strong near-infrared (NIR) absorbance, rendering it to be an ideal contrast agent for PAI. Thus, GQDzyme/ABTS nanoparticle is a novel type of catalytic PAI contrast agent which is sensitive to H2O2 produced from NPC cells. Furthermore, we develop an approach to construct exosome-like nanozyme vesicle via biomimetic functionalization of GQDzyme/ABTS nanoparticle with natural erythrocyte membrane modified with folate acid. In vivo animal experiments demonstrated that, this exosome-like nanozyme vesicle effectively accumulated in NPC and selectively triggered catalytic PAI for NPC. In addition, our nanozyme vesicle exhibits excellent biocompatibility and stealth ability for long blood circulation. Together, we demonstrate that GQDzyme/ABTS based exosome-like nanozyme vesicle is an ideal nanoplatform for developing deep-tissue tumor-targeted catalytic PAI in vivo.
关键词： photoacoustic imaging,nasopharyngeal carcinoma,H2O2-responsive,graphene quantum dot nanozyme,exosome-like vesicle,erythrocyte membranes
更新于2025-09-04 15:30:14