<p><strong>A team from CEITEC Masaryk University (MUNI) in collaboration with researchers from two research institutes in Norway has, for the first time, captured how echovirus 18, a member of the enterovirus genus, releases its genetic material into cells to initiate infection. The study provides a structural view of an early stage of viral infection under near-native conditions. Using cryo-electron microscopy, the researchers discovered that the virus does not release its RNA through a small pore in its capsid, as had long been assumed. Instead, its protein shell partially disassembles, creating a large opening through which the viral genetic material escapes into the host cell. A detailed understanding of this genome release mechanism could eventually help develop compounds preventing enteroviruses from infecting cells.</strong></p><p>Enteroviruses are common human pathogens causing diseases ranging from the common cold and gastrointestinal infections to severe neurological disorders. Echovirus 18, the virus investigated in this study, is known primarily as a cause of meningitis and encephalitis in children. It belongs to the picornaviruses, a family of small, non-enveloped viruses whose genetic material is protected by a protein shell, the capsid, organized with icosahedral symmetry.</p><p>To replicate within a cell, the enteroviruses must release their RNA – the molecule that carries viral genetic information – from the capsid, into the cell cytoplasm. Although this step is crucial for initiating infection, it has never been observed in infected cells.</p><p><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/CEITEC_Vedci_z_CEITEC_jako_prvni_zachytili_jak_enteroviry_spousteji_infekci_bunek_71d553bb0e.jpg" alt="CEITEC/Plevka Lab: CEITEC Scientists Are the First to Capture How Enteroviruses Initiate Infection: View into a cell infected by echovirus 18. Echovirus 18 is shown in green and yellow, ribosomes in violet, and actin filaments in cyan. Scale 50 nm. " srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_CEITEC_Vedci_z_CEITEC_jako_prvni_zachytili_jak_enteroviry_spousteji_infekci_bunek_71d553bb0e.jpg 221w," sizes="100vw" width="1600" height="1128"></p><p><i>“For a long time, two main theories existed about how picornaviruses deliver their RNA genomes into cells. One proposed that the genome leaves the capsid through a small opening. The other, supported by earlier work from our laboratory, suggested that the genome escapes from partially disassembled capsids missing pentamers of capsid proteins. However, both models were based on experiments with virus particles outside cells. We wanted to go one step further and see what really happens during infection inside a cell,”</i> says <a target="_blank" rel="noopener noreferrer" href="https://www.ceitec.eu/liya-mukhamedova-ph-d/u89248?page=publication"><strong>Liya Mukhamedova</strong></a><strong>, the study’s first author from CEITEC MUNI</strong>.</p><p>Using cryo-electron microscopy, which allows scientists to visualize biological structures at exceptionally high resolution, the researchers observed individual echovirus 18 particles directly within infected cells. They discovered that empty virus particles in infected cells lack parts of their capsids. It is through these openings that the virus releases its RNA.</p><p>The study also revealed the role of the FcRn receptor, a cell-surface molecule that enteroviruses use to enter cells. The binding of the virus to the receptor triggers structural changes in the viral particle that prime it for subsequent genome release. The team showed that receptor binding causes the loss of the so-called pocket factor, a small molecule that normally helps stabilize the virus particle. The virus otherwise remains largely intact, suggesting that receptor binding is only the first step toward uncoating, while additional factors within the cell are required to complete the process and trigger genome release.</p><p><i>“Infection is a complex process, during which enterovirus particles sense various interactions with cell components. The binding of echovirus 18 to the FcRn host-cell receptor triggers conformational changes in the virus, priming it for genome release.”</i> – explains <a target="_blank" rel="noopener noreferrer" href="https://www.ceitec.eu/pavel-plevka-ph-d/u26854"><strong>Pavel Plevka</strong></a><strong>, head of the Structural Virology Research Group</strong>.</p><p>The researchers did not observe the so-called activated particles that are key intermediates in the enterovirus uncoating process. This suggests that genome release in cells occurs much faster than previous experiments had suggested.</p><p>By combining structural data obtained from studies of virus particles outside living cells with observations of infected cells, the study offers a picture of how enterovirus infection begins. Moving beyond simplified experiments with isolated virus particles, it brings scientists closer to understanding the earliest stages of enterovirus infection as they occur in living cells. The study, was published in the <a target="_blank" rel="noopener noreferrer" href="https://doi.org/10.1073/pnas.2601182123"><strong>PNAS journal</strong></a>.</p><p><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/CEITEC_Vedci_z_CEITEC_jako_prvni_zachytili_jak_enteroviry_spousteji_infekci_bunek_2_3601bf1df9.jpg" alt="CEITEC/Plevka Lab: CEITEC Scientists Are the First to Capture How Enteroviruses Initiate Infection: Reconstructions of E18 particles from infected cells. The particles are rainbow-colored based on the distance from the particle center. Scale 10 nm." srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_CEITEC_Vedci_z_CEITEC_jako_prvni_zachytili_jak_enteroviry_spousteji_infekci_bunek_2_3601bf1df9.jpg 245w," sizes="100vw" width="1600" height="906"></p><blockquote><h4><strong>Article</strong></h4><h4><a target="_blank" rel="noopener noreferrer" href="https://www.pnas.org/doi/10.1073/pnas.2601182123"><strong>Particles of echovirus 18 open to release their genomes in vivo</strong></a></h4><p>Liya Mukhamedova, David Buchta, Zuzana Trebichalská, Yevgen Levdansky, Jana Moravcová, David Potěšil, Zbyněk Zdráhal, Dominik Hřebík, Lucie Nepovímová, Torleif Tollefsrud Gjølberg, Jan Terje Andersen, Jiří Nováček, Tibor Füzik, and Pavel Plevka</p><p><i><strong>Proc. Natl. Acad. Sci. U.S.A.</strong></i>, 2026, <strong>123</strong>, e2601182123</p><div>&nbsp;</div><div><a target="_blank" rel="noopener noreferrer" href="https://doi.org/10.1073/pnas.2601182123">https://doi.org/10.1073/pnas.2601182123</a></div><h6>licenced under <a target="_blank" rel="noopener noreferrer" href="https://creativecommons.org/licenses/by/4.0/"><strong>CC-BY 4.0</strong></a></h6></blockquote><h4><strong>Abstract</strong></h4><p>Enteroviruses cause a broad spectrum of human diseases, ranging from mild respiratory or gastrointestinal infections to severe neurological disorders such as aseptic meningitis and encephalitis. Enterovirus cell entry involves receptor-mediated endocytosis followed by destabilizing rearrangements of the virus capsid that enable genome release. However, the mechanism of enterovirus genome release has not been visualized in infected cells. Here, we used cryoelectron tomography and microscopy to image echovirus 18 (E18) entry into host cells and its interaction with the neonatal Fc receptor (FcRn). 30 min postinfection, endosomes and cytoplasm contained empty capsids missing one or several pentamers of capsid proteins, providing evidence that in vivo E18 releases its genome through capsid opening. In vitro, FcRn binding induced the expulsion of pocket factors from hydrophobic pockets in VP1, priming the virus for uncoating. The cryoelectron microscopy reconstruction of genome-containing particles of E18 inside infected cells did not reveal pocket factors, indicating that receptor binding triggers the same priming process during infection. We did not detect activated particles in infected cells, suggesting that these intermediates are short-lived and rapidly release their genomes in vivo. Our results identify capsid opening as the in vivo mechanism of echovirus 18 genome release, providing structural evidence for a process previously only inferred from in vitro experiments.</p>

CEITEC Scientists Are the First to Capture How Enteroviruses Initiate Infection 

<p><strong>Gas chromatography (GC) is a powerful analytical technique used to separate and analyze compounds in a mixture. Whether you're working in pharmaceuticals, environmental testing, or food safety, understanding the key components of a gas chromatograph is essential for accurate and efficient results.</strong></p><p>In this article, we will delve into the primary components of gas chromatography, including the injector, column, detector, and carrier gas—and explain how each plays a critical role in the separation and analysis process.</p><p>By mastering these elements, you can optimize your GC setup for precise and reliable outcomes. Let's explore each component in detail:</p><h3><strong>Sample Injector</strong></h3><p>The injector is the starting point in the <a target="_blank" rel="noopener noreferrer" href="https://www.phenomenex.com/techniques/gc"><strong>gas chromatography process</strong></a>, where the sample is introduced into the system. In GC, the sample must be vaporized into a gas before it enters the column. The injector serves this purpose by heating the sample to its gaseous state. There are many types of injectors, Split/Splitless, PTV, on column.</p><p>The most common injector is the Split/Splitless injector that can be used in split mode or in splitless mode:</p><ul><li><strong>Split Injection:</strong> This mode allows a portion of the sample to be sent to the column while the remainder is vented. It is useful for high-concentration samples to prevent system overload.</li><li><strong>Splitless Injection:</strong> In this mode, the entire sample is introduced into the column, making it ideal for trace analysis where even minute quantities need detection.</li></ul><p>Proper choice of injector type and proper control of injection conditions, such as temperature, sample size, injection mode are crucial for achieving reproducible and reliable results.</p><h3><strong>Carrier Gas</strong></h3><p>In gas chromatography, the mobile phase is represented by carrier gas, which transports the vaporized sample through the column. The carrier gas is an inert gas, such as helium, nitrogen, or hydrogen. The choice of carrier gas can influence the efficiency of the separation process.</p><ul><li><strong>Helium</strong> is the most used carrier gas due to its inertness and high flow rate.</li><li><strong>Hydrogen</strong> offers faster analysis times but requires careful handling due to its flammability.</li><li><strong>Nitrogen</strong> provides a cheaper solution compared to Helium, although it's slower than helium or hydrogen.</li></ul><p>The flow rate and pressure of the carrier gas need to be carefully controlled to ensure that the sample moves smoothly through the system and adequate efficiency is generated.</p><h3><strong>Column/Stationary Phase</strong></h3><p>The column is the heart of the gas chromatograph, where the actual separation of compounds occurs. <a target="_blank" rel="noopener noreferrer" href="https://labrulez.com/en-us/gcms/products?category=7&amp;manufacturerItems=50"><strong>GC columns</strong></a> are typically long, thin tubes made from stainless steel or fused silica. They are coated with a stationary phase, which interacts with the components of the sample as they pass through.</p><ul><li><strong>Packed Columns:</strong> These contain small particles of stationary phase material and generally have a larger volume. While they are less efficient than capillary columns, they can be suitable for specific applications.</li><li><strong>Capillary Columns:</strong> These thin tubes are coated with a stationary phase, offering higher resolution and faster analysis times due to their smaller diameter.</li></ul><p>The length, diameter, and type of stationary phase of the column are important factors that affect the efficiency and selectivity of the separation. The choice of stationary phase (polar or non-polar; liquid-coated or solid) affects how different compounds interact with it.</p><p>As the sample moves through the column, compounds separate based on volatility and their affinity for the stationary phase, resulting in distinct peaks in the chromatogram.</p><h3><strong>Detector</strong></h3><p>Once the sample has passed through the column, it reaches the detector, where individual components are identified and measured. There are several types of detectors, each suited to different applications:</p><ul><li><span><strong>Flame Ionization Detector (FID):</strong> One of the most commonly used detectors in GC. It measures ions produced when organic compounds are burned in a hydrogen-air flame. FID is highly sensitive to a wide range of organic compounds and offers a broad linear dynamic range.</span></li><li><span><strong>Thermal Conductivity Detector (TCD):</strong> Detects changes in the thermal conductivity of the gas stream as analytes elute from the column. It is a universal, non-destructive detector, but is generally less sensitive than FID.</span></li><li><strong>Electron capture detector (ECD):</strong> A very sensitive and selective detector used to detect chlorinated compounds it is easily contaminated and requires very pure and dry carrier and makeup gases and difficult maintenance.</li><li><strong>Mass Spectrometer (MS):</strong> Provides structural information, aiding in both identification and quantification. Requires advanced and trained users and it’s difficult to maintain.</li></ul><p>The choice of detector depends on the type of analysis being performed and the sensitivity required. Each detector converts physical or chemical changes associated with the analytes into a measurable signal, producing a chromatogram that reflects concentration and retention time.</p><h3><strong>Data System</strong></h3><p>Although not a physical part of the chromatograph, the data system plays an integral role in processing and interpreting the signals generated by the detector. Modern gas chromatographs are equipped with software that converts detector signals into chromatograms—visual representations of the separation process. The software allows users to quantify and identify the components of the sample based on retention times and peak areas.</p><h3><strong>How to Read a Gas Chromatogram?</strong></h3><p>Interpreting a gas chromatogram involves understanding its essential elements, such as peaks, retention times, and the overall data for qualitative and quantitative analysis.</p><h4><strong>The Nature of the Sample</strong></h4><p>Begin by considering the sample's characteristics; different samples, such as environmental pollutants or food components, may exhibit distinct peak patterns. Recognizing the baseline (the flat line representing the signal without analytes) is crucial for identifying peaks accurately. While well-defined peaks indicate successful separation of components, poorly shaped or broad peaks may suggest issues with the separation process. For instance, if a mixture is injected and three peaks are observed, it indicates the presence of three different compounds in the sample. Conversely, when evaluating the purity of a sample, one would anticipate observing a single peak. Ideally, the chromatogram should reflect this expectation, confirming the sample's purity.</p><h4><strong>The Identity of the Sample</strong></h4><p>Retention time (Rt) is a critical factor in identifying the compounds present in the sample. Each analyte has a characteristic retention time that can be compared to known standards or literature. To confirm identities, a standard mixture should run alongside the sample; this allows to correlate retention times with specific compounds. If available, utilizing MS in conjunction with gas chromatography (GC-MS) can provide additional structural information, enhancing identification accuracy. With HR-MS or MS-MS detectors, unknown compounds can be identified by matching perfectly the Molecular weight or by matching the fragmentation pattern.</p><h4><strong>The Amount of Sample</strong></h4><p>Quantifying analytes involves analyzing peak area or height, which is directly proportional to the concentration of the analyte in the sample. A calibration curve constructed from known concentrations can help relate peak areas to actual concentrations. It is essential to consider the detector’s sensitivity and the limits of detection, as peaks below a certain threshold may not provide reliable quantification.</p>

Basic Principles of Gas Chromatography - Separation and Analysis

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