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Research has been conducted on ionotropic 5HT (sub)3 receptor. The expression of this receptor in mammalian cells has been carried out, and the results demonstrate the possibility of observing and distinguishing these receptors' appearance during their expression at different times on the cell surface.

Research has been conducted on the fluorescent antagonist bound to the purified detergent-solubilixed serotonin type 3 receptor. The fluorescence resonance energy transfer has been measured between this antagonist and a lipophilic acceptor probe partitioned into the micelle that surrounds the detergent-solubilized receptor and the results are described.

A study is conducted to show that the nuclear receptors initiate transcription, interacts with regulatory proteins, and are influenced by hormones, drugs and pollutants. The ligand-specific mobility patterns of human estrogen receptor-alpha (ER) in living cells are discussed using diffusion-time distribution analysis (DDA).

An attempt made to show monitoring cellular signaling reactions at an unreached miniaturization level is described. It is observed that cytochalasin induces mammalian cells to extrude from their plasma membrane submicrometer-sized native vesicles.

The secondary structures of 5-hydroxytryptamine (serotonin) receptor and nicotinic acetylcholine receptor are nearly identical with 36% of alpha-helix, 33% beta-strand, 15% Beta-turn, and 16% nonregular structures by curve fitting and 14% alpha-helix, 16% beta-strand, 26% beta-turn, and 14% nonregular structures by water-accessible part of the proteins as determined by high signal-to noise Fourier transform infrared spectroscopy.

Fluorescence spectroscopy was used to investigate the interaction between serotonin 5HT3 receptor and the ligand GR-flu. Results indicated that GR-flu is a high-affinity antagonist for the 5HT3 receptor displaying a pharmacological profile similar to that obtained with a radiolabeled ligand. Analysis of the kinetics of GR-flu binding with 5HT3 revealed that the binding site of the 5HT3 receptor has an acidic character. The moiety of GR-flu had a high mobility which suggested that the binding site has a wide opening.

A general procedure for the covalent labeling of cell surface fusion proteins with chemically different molecules is presented. The approach is definite and versatile and can be considered as an important tool for cell surface engineering.

Examines the monitoring expression and clustering of the ionotropic 5HT[sub3] receptor in plasma membranes of live biological cells. Use of fluorescence scanning confocal microscopy in observing receptor traffic in the plasma membrane of live cells; Critical size of individual clusters.

Skin problems are often overlooked due to a lack of robust and patient-friendly monitoring tools. Herein, we report a rapid, noninvasive, and high-throughput analytical chemical methodology, aiming at real-time monitoring of skin conditions and early detection of skin disorders. Within this methodology, adhesive sampling and laser desorption ionization mass spectrometry are coordinated to record skin surface molecular mass in minutes. Automated result interpretation is achieved by data learning, using similarity scoring and machine learning algorithms. Feasibility of the methodology has been demonstrated after testing a total of 117 healthy, benign-disordered, or malignant-disordered skins. Remarkably, skin malignancy, using melanoma as a proof of concept, was detected with 100% accuracy already at early stages when the lesions were submillimeter-sized, far beyond the detection limit of most existing noninvasive diagnosis tools. Moreover, the malignancy development over time has also been monitored successfully, showing the potential to predict skin disorder progression. Capable of detecting skin alterations at the molecular level in a nonsurgical and time-saving manner, this analytical chemistry platform is promising to build personalized skin care., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

The plasma membrane is of central importance for defining the closed volume of cells in contradistinction to the extracellular environment. The plasma membrane not only serves as a boundary, but it also mediates the exchange of physical and chemical information between the cell and its environment in order to maintain intra- and intercellular functions. Artificial lipid- and cell-derived membrane vesicles have been used as closed-volume containers, representing the simplest cell model systems to study transmembrane processes and intracellular biochemistry. Classical examples are studies of membrane translocation processes in plasma membrane vesicles and proteoliposomes mediated by transport proteins and ion channels. Liposomes and native membrane vesicles are widely used as model membranes for investigating the binding and bilayer insertion of proteins, the structure and function of membrane proteins, the intramembrane composition and distribution of lipids and proteins, and the intermembrane interactions during exo- and endocytosis. In addition, natural cell-released microvesicles have gained importance for early detection of diseases and for their use as nanoreactors and minimal protocells. Yet, in most studies, ensembles of vesicles have been employed. More recently, new micro- and nanotechnological tools as well as novel developments in both optical and electron microscopy have allowed the isolation and investigation of individual (sub)micrometer-sized vesicles. Such single-vesicle experiments have revealed large heterogeneities in the structure and function of membrane components of single vesicles, which were hidden in ensemble studies. These results have opened enormous possibilities for bioanalysis and biotechnological applications involving unprecedented miniaturization at the nanometer and attoliter range. This review will cover important developments toward single-vesicle analysis and the central discoveries made in this exciting field of research.

Scanning electrochemical microscopy (SECM) has been widely used for the electrochemical imaging of dynamic topographical and metabolic changes in alive adherent mammalian cells. However, extracting intracellular information by SECM is challenging, since it requires redox species to travel in and out the lipid cell membrane. Herein, we present cell fixation and permeabilization approaches as an alternative tool for visualizing cell properties by SECM. With this aim, adherent cells were analyzed in the SECM feedback mode in three different conditions: (i) alive; (ii) fixed, and (iii) fixed and permeabilized. The fixation was carried out with formaldehyde and does not damage lipid membranes. Therefore, this strategy can be used for the SECM investigation of cell topography or the passive transport of the redox mediator into the cells. Additional permeabilization of the cell membrane after fixation enables the analysis of the intracellular content through the coupling of SECM with immunoassay strategies for the detection of specific biomarkers. The latter was successfully applied as an easy and fast screening approach to detect the expression of the melanoma-associated marker tyrosinase in adherent melanoma cell lines corresponding to different cancer progression stages using the SECM substrate generation-tip collection mode. The present approach is simple, fast, and reliable and can open new ways to analyze cell cultures with electrochemically based scanning probe techniques.

Imaging samples on a surface by mass spectrometry (MS) requires the combination of MS detection with a scanning mode that enables localized desorption and ionization and/or detection of sample analytes with good spatial resolution. We have developed a new mass spectrometry imaging (MSI) method based on electrostatic spray ionization. It works under ambient conditions and can be applied to a wide range of molecules providing quantitative MS analysis even in the presence of salts in excess. 2D MS images of protein and peptide spots, inkjet-printed black dye patterns, and cells were obtained. The presented novel ambient ionization mass spectrometry imaging method can find many applications in analytical and bioanalytical chemistry.