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Fluorescence correlation spectroscopy (FCS) is a quantitative single-molecule method that measures the concentration and rate of diffusion of fluorophore-tagged molecules, both large and small, in vitro and within live cells, and even within discrete cellular compartments. FCS is exceptionally well-suited to directly quantify the efficiency of intracellular protein delivery-specifically, how well different "cell-penetrating" proteins and peptides guide proteinaceous materials into the cytosol and nuclei of live mammalian cells. This article provides an overview of the procedures necessary to execute robust FCS experiments and evaluate endosomal escape efficiencies: preparation of fluorophore-tagged proteins, incubation with mammalian cells and preparation of FCS samples, setup and execution of an FCS experiment, and a detailed discussion of and custom MATLAB® script for analyzing the resulting autocorrelation curves in the context of appropriate diffusion models.
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http://dx.doi.org/10.1016/bs.mie.2020.05.007 | DOI Listing |
Methods
September 2025
Gynaecology and Obstetrics, The Second Affiliated Hospital of Harbin Medical University, Harbin Medical University, Heilongjiang 150081, PR China. Electronic address:
Single-cell surface-enhanced Raman scattering (SERS) has emerged as a powerful tool for precision medicine owing to its label-free detection, ultrasensitivity, and unique molecular fingerprinting. Unlike conventional bulk analysis, it enables detailed characterization of cellular heterogeneity, with particular promise in circulating tumor cell (CTC) identification, tumor microenvironment (TME) metabolic profiling, subcellular imaging, and drug sensitivity assessment. Coupled with microfluidic droplet systems, SERS supports high-throughput single-cell analysis and multiparametric screening, while integration with complementary modalities such as fluorescence microscopy and mass spectrometry enhances temporal and spatial resolution for monitoring live cells.
View Article and Find Full Text PDFStructure
September 2025
Institute of Anatomy, University of Bern, 3012 Bern, Switzerland. Electronic address:
Cryo-electron tomography (cryoET) provides 3D datasets of organelles and proteins at nanometer and sub-nanometer resolution. However, locating target proteins in live cells remains a significant challenge. Conventional labeling methods, such as fluorescent protein tagging and immunogold labeling, are unsuitable for small structures in vitrified samples at molecular resolution.
View Article and Find Full Text PDFPLoS Comput Biol
September 2025
Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland.
Ubiquity of cancer across the tree of life yields opportunities to understand variation in cancer defences across species. Peto's paradox, the finding that large-bodied species do not suffer from more cancer despite having more cells at risk of oncogenic mutations compared to small species, can be explained if large size selects for better cancer defences. Since birds live longer than non-flying mammals of equivalent size, and are descendants of moderate-sized dinosaurs, we ask whether ancestral cancer defences are retained if body size shrinks in a lineage.
View Article and Find Full Text PDFSTAR Protoc
September 2025
Laboratory of Genome Integrity, CCR, NCI, NIH, Bethesda, MD, USA. Electronic address:
Tracking the translocation of fluorescent-based reporters at the single-cell level in living mouse embryos requires specialized expertise in mouse embryology and deep computational skills. Here, we detail an approach to quantify cyclin-dependent kinase (CDK) activity levels in single cells throughout different stages of the pre-implantation embryo. We discuss in vitro culture strategies that enable efficient live fluorescent confocal image acquisition and subsequent cell tracking.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
September 2025
Department of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur 208016, India.
Agonist-induced interaction of G protein-coupled receptors (GPCRs) with β-arrestins (βarrs) is a critical mechanism that regulates the spatiotemporal pattern of receptor localization and signaling. While the underlying mechanism governing GPCR-βarr interaction is primarily conserved and involves receptor activation and phosphorylation, there are several examples of receptor-specific fine-tuning of βarr-mediated functional outcomes. Considering the key contribution of conformational plasticity of βarrs in driving receptor-specific functional responses, it is important to develop novel sensors capable of reporting distinct βarr conformations in cellular context.
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