Name: immunogold labeling in electron microscopy
Uploaded: 2025-05-22T09:05:46.000Z
Duration: 1 min 20 s
Channel: JoVE

Na microscopia eletrônica imuno-ouro, uma molécula-alvo é marcada usando anticorpos conjugados com ouro.
O ouro aumenta o espalhamento de elétrons para dar manchas escuras de alto contraste. Essas manchas podem ser distinguidas das outras estruturas não marcadas e permitem a localização da molécula alvo.
A imunomarcação direta usa uma sonda de ouro ligada a um anticorpo primário que se liga diretamente à molécula alvo. 
A marcação indireta usa um anticorpo secundário marcado com ouro que se liga a um anticorpo primário não marcado. A rotulagem indireta é usada com mais frequência devido à sua maior sensibilidade.
A imunomarcação pode ser realizada usando várias técnicas diferentes - pós-incorporação, pré-incorporação ou montagem completa.
Na técnica de pós-incorporação, uma amostra é incorporada em resina e depois cortada em seções ultrafinas que são tratadas com anticorpos marcados com ouro.
Na técnica de pré-incorporação, uma amostra é primeiro incubada com os anticorpos marcados com ouro e, em seguida, incorporada em resina e seccionada transversalmente.
A técnica de montagem total não envolve incorporação de resina. As reações de anticorpos são realizadas diretamente em uma amostra colocada no suporte da amostra.

microscopia imunoeletrônica

Immunogold Electron Microscopy

A microscopia imunoeletrônica utiliza marcação imunogold de proteínas endógenas com anticorpos específicos para detectar e localizar essas proteínas em células e tecidos. O procedimento fornece insights sobre a distribuição e quantificação de proteínas sob diferentes condições de estimulação, oferecendo pistas sobre suas funções. A conjugação de partículas de ouro altamente eletrodensas com anticorpos primários ou secundários permite a detecção de antígenos nas células e dentro delas, com alta resolução e especificidade. A microscopia imunoeletrônica tem sido utilizada para identificar a localização celular e subcelular de proteínas envolvidas na neurotransmissão, componentes de proteínas nucleares e identificação de tipos de células imunes. Três abordagens são aplicadas para localizar antígenos celulares usando microscopia eletrônica de transmissão. Primeiro, ao estudar a localização de antígenos intracelulares, os protocolos envolvem marcação de anticorpos pós-incorporação em resinas acrílicas, marcação de anticorpos pré-incorporação na resina combinada com permeabilização da membrana celular,ou crio-ultramicrotomia sem incorporação. Em segundo lugar, quando as proteínas da superfície celular devem ser localizadas, o protocolo de pré-incorporação é usado, no qual a marcação com anticorpos imunogold é feita antes da incorporação na resina. A terceira técnica, a técnica de montagem completa, não envolve a incorporação de resina, e as reações dos anticorpos são realizadas diretamente em uma amostra para localizar as moléculas de superfície. Para microscopia eletrônica de varredura, a superfície de interesse deve necessariamente ser exposta. A amostra pode ser fixada e rotulada diretamente se a superfície externa da membrana plasmática for de interesse. No entanto, as células devem ser permeabilizadas com detergentes e imunomarcadas para estudar componentes intracelulares ou antígenos integrados a um tecido. Para visualização, a amostra é liofilizada (congelamento rápido e quebra com faca). Muitos componentes intracelulares, particularmente complexos macromoleculares, como cromatina, complexos proteicos ou vírus, podem ser isolados, fixados e imunomarcados para MEV. Finalmente, uma técnica de coloração imunonegativa é aplicada para antígenos de superfície em amostras pequenas, como vírus e bactérias, que se prestam à coloração negativa.

Microscopia Imunoeletrônica

A microscopia imunoeletrônica utiliza a marcação imuno-auricular de proteínas endógenas com anticorpos específicos para detectar e localizar essas proteínas nas células e ...

Education

JoVE Core

Cell Biology

Biologia Celular

Unit 1

Unidade 1

Visualizing Cells, Tissues, and Molecules

Visualizando Células, Tecidos e Moléculas

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

immunogold labeling in electron microscopy

Immunogold labeling in electron microscopy uses antibodies and tiny gold particles to find specific proteins in cells and tissues. The gold particles are very electron-dense, which means they show up clearly in electron microscope images. This gives researchers a high-resolution way to see where proteins are located and to compare their amounts under different stimulation conditions.

The method can reveal proteins on the cell surface and inside cells. It has been used to study proteins involved in neurotransmission, parts of the nucleus, and markers for immune cell types. The same labeling idea can be paired with different sample-preparation methods, depending on what needs to be seen.

For transmission electron microscopy, three main approaches are used to localize cell antigens. Intracellular antigens can be labeled after embedding in acrylic resin, before embedding with membrane permeabilization, or by cryo-ultramicrotomy without embedding. When cell-surface proteins are the target, pre-embedding labeling is used so the immunogold antibodies bind before the sample is placed in resin.

A whole-mount technique is also used. In this method, the sample is not embedded in resin, and the antibody reaction happens directly on the specimen to identify surface molecules. For scanning electron microscopy, the surface of interest must be exposed. The sample can be fixed and labeled directly if the outer surface of the plasma membrane is being studied.

If intracellular components or antigens within a tissue are being examined with SEM, the cells must be permeabilized with detergents and then immunolabeled. The sample is then freeze-fractured, which means it is rapidly frozen and broken with a knife for viewing. Many intracellular components, including chromatin, protein complexes, and viruses, can be isolated, fixed, and immunolabeled this way.

An immunonegative staining technique is used for small specimens such as viruses and bacteria. This method is suited to surface antigens on samples that work well with negative staining. Together, these approaches let scientists localize proteins and other antigens with strong specificity and fine structural detail.

Immunogold Labeling in Electron Microscopy

immunogold-labeling-in-electron-microscopy

imaging biological samples with optical microscopy

imaging-biological-samples-with-optical-microscopy

How Light Microscopes Bring Samples Into View

Optical microscopy uses light and lenses to make tiny biological samples visible. Antonie van Leeuwenhoek built the first compound optical microscope in the 17th century to view blood cells, bacteria, and yeast cells. In 1830, Joseph Jackson Lister developed an essentially modern light microscope. During the 20th century, microscopes gained better magnification and resolution. A sample is placed on a glass slide and clipped onto the stage, which is the flat platform of the microscope. The...

phase contrast and differential interference contrast microscopy

phase-contrast-and-differential-interference-contrast-microscopy

Microscope Contrast for Live, Unstained Cells

Phase-contrast and differential interference contrast microscopy help scientists see live cells without stains. Both methods boost contrast so thin, transparent structures become easier to study under the microscope. Phase-contrast microscopes use interference between light that passes straight through a cell and light that is refracted by cell parts. The microscope uses an annular stop in the condenser to make a hollow cone of light. The objective lens also contains a phase plate with a phase...

fixation and sectioning

Microscope Slide Prep and Staining

Microscope slide preparation includes wet mounts, fixation, and staining. These steps help make specimens easier to see under a light microscope. They also help preserve cells and highlight important structures. A wet mount is the simplest slide preparation. The specimen is placed in a drop of liquid on the slide. A liquid sample can be added directly with a dropper, and a solid sample, such as a skin scraping, can be placed on the slide before the liquid is added. The liquid is sometimes...

immunofluorescence microscopy

Fluorescent Antibody Staining in Cells

Fluorescent antibody staining uses a fluorescence microscope to make cells and microbes visible in bright colors against a dark background. The microscope works with fluorochromes, which are fluorescent dyes that absorb energy from a light source and then give off visible light. Some fluorochromes are natural, such as chlorophylls. Others are added to the specimen to improve contrast. Common examples of fluorochromes include Texas red and FITC. The method can also use nucleic acid dyes such as...

immunocytochemistry and immunohistochemistry

immunocytochemistry-and-immunohistochemistry

Antibody Staining in Cells and Tissues

Immunocytochemistry (ICC) and immunohistochemistry (IHC) use antibodies to detect specific proteins or antigens in samples. ICC focuses on individual cells, such as blood cells and stem cells. IHC is used for tissue samples. These methods were first published by Albert Coons in 1941, when they were used to detect pneumococcal antigen in mouse tissue sections from mice infected with Pneumococcus. Both techniques can produce either a colored signal or a fluorescent signal. Enzyme-conjugated...

confocal fluorescence microscopy

Confocal Microscopy for Sharp Cell Images

Confocal microscopy is an advanced imaging method used to capture sharp fluorescence images. Its main advantage is that it blocks out-of-focus light from the sample with pinholes. That helps produce high-resolution images with strong contrast. Unlike a standard optical microscope, a confocal microscope uses a focused laser beam to scan the sample surface at different z-planes. This makes it especially useful for thick specimens, such as biofilms. These samples can often be examined alive and...

protein dynamics in living cells

Fluorescent Methods for Protein Movement

Protein movement in living cells can be measured with fluorescence-based methods such as FRAP, FRET, and PET. These techniques help scientists track how proteins move, interact, and change distance inside the cell. Fluorescent recovery after photobleaching, or FRAP, measures protein movement rates within the cell. In this method, a small region is exposed to a strong laser beam. The beam permanently bleaches fluorophore-tagged proteins in that area. Over time, bleached proteins diffuse away...

total internal reflection fluorescence microscopy

total-internal-reflection-fluorescence-microscopy

Surface-Only Imaging with TIRF Microscopy

Total internal reflection fluorescence microscopy, or TIRF, is a microscope method used to view fluorophores near a solid surface with a higher refractive index, such as a glass coverslip. It is useful when scientists want to study signals close to the cell surface. TIRF works when light from a medium with a lower refractive index, such as air, hits the glass coverslip at a critical angle. Instead of entering the glass, the light undergoes total internal reflection. This reflection creates an...

atomic force microscopy

Atomic Force Microscopy for Surface Mapping

Atomic force microscopy is used to map the surface details of materials. It can examine ceramics, glass, polymers, and biological samples. The method gives far more resolution than an optical imaging system and produces three-dimensional surface profiles instead of flat 2D images. The probe is the key part of an AFM setup. It includes the cantilever and tip assembly, and it is also the part that is replaced most often. Constant contact with samples wears down the tip, so probe choice depends...

super-resolution fluorescence microscopy

Sharper Cell Images with Fluorescence Microscopy

Super-resolution fluorescence microscopy gives sharper images than standard fluorescence microscopy by reducing the point spread function, or PSF. The PSF is the light pattern from a point source that makes it look blurred. Because of this blur, each fluorescent spot appears larger than it really is. Nearby fluorophores can also overlap through their PSFs and make the image less clear. Several super-resolution methods have been developed to improve image detail. Photoactivated localization...

overview of electron microscopy

Electron Microscopy: TEM vs SEM

Electron microscopy uses electrons instead of visible light to make images with much higher detail than a light microscope. Visible light limits the resolution of light microscopes, which usually magnify up to 1000X, and sometimes up to 1500X. Electrons have a much shorter wavelength, about 0.005 nm, so they can produce resolution as fine as 0.05 nm. An electron microscope can also magnify images up to 2,000,000X and reveal subcellular structures and some molecular structures, including single...

scanning electron microscopy

How SEM Reveals Surface Details

A scanning electron microscope (SEM) reveals the surface details of a sample with an electron beam. The beam scans across the sample in a two-dimensional pattern. SEM can image areas from about 1 centimeter down to 5 micrometers wide. SEM is useful for studying bacteria, viruses, tissues, and larger samples such as insects. Conventional SEM can produce magnification from 20X to 30,000X. It also offers spatial resolution of about 50 to 100 nanometers. The process starts when the electron gun...

transmission electron microscopy

How TEM Reveals Tiny Structures

Transmission electron microscopy uses electrons to reveal very small structures inside a specimen. The technique grew from the first electron microscope prototype developed in 1931 by physicist Ernst Ruska. He built on the idea that magnetic fields can direct an electron beam, just as lenses direct light in an optical microscope. In a transmission electron microscope, a hot tungsten element produces electrons. An electron gun then accelerates them with a potential difference, giving the beam...

preparation of samples for electron microscopy

preparation-of-samples-for-electron-microscopy

Electron Microscopy Sample Prep Methods

Electron microscopy sample prep methods help biological samples survive imaging in TEM and SEM. Before a specimen can be viewed, it must be fixed, or stabilized, so the electron beam does not damage it. It also must be dried well, or desiccated, because the microscope uses a vacuum. Fixation should happen as quickly as possible. Once a sample leaves its natural environment, its properties begin to change. In tissue samples, oxygen levels can drop and change the appearance of mitochondria. That...

immunogold electron microscopy

Immunogold labeling in electron microscopy uses antibodies and tiny gold particles to find specific proteins in cells and tissues. The gold particles are very electron-dense, which means they show up clearly in electron microscope images. This gives researchers a high-resolution way to see where proteins are located and to compare their amounts under different stimulation conditions. The method can reveal proteins on the cell surface and inside cells. It has been used to study proteins...

cryo-electron microscopy

Cryo-EM for Native Biomolecule Imaging

Cryo-EM, or cryo-electron microscopy, lets scientists image biomolecules in their frozen, native state. It avoids the dehydration, fixation, and staining used in conventional electron microscopy, which can distort samples and create artifacts. It also reduces damage from the electron beam by using gentler imaging conditions. This method is useful when other structure tools have limits. X-ray diffraction needs a molecule to form a crystal, and that is not always possible. Even when...

electron microscope tomography and single-particle reconstruction

electron-microscope-tomography-and-single-particle-reconstruction

3D Imaging with Electron Microscopy

Transmission electron microscopy (TEM) can build 3D images of biological samples. It does this with electron microscope tomography and single-particle reconstruction. Tomography can show cell parts or small cells in vivo, while single-particle reconstruction is used for macromolecules and macromolecular complexes in vitro only. Electron tomography can be done in TEM or in STEM, which stands for scanning transmission electron microscopy. STEM is mainly used for thick biological specimens. It...

key terms and concepts

Learn how immunogold labeling uses antibody-bound gold particles to map proteins in cells and tissues with transmission and scanning electron microscopy.

Immunogold Labeling in Electron Microscopy | JoVE K12

cell biology

JoVE Core - Biologia Celular ilustra processos celulares complexos em vídeos de animação fáceis de entender e, ao mesmo tempo, abrangentes. Esta coleção foca nos componentes e funções essenciais das células, incluindo organelas e membranas, transporte celular e energia celular. É complementado por vídeos de Cientistas em ação que demonstram a aplicação da biologia celular em experimentos de pesquisa do mundo real.

Immunogold Labeling in Electron Microscopy

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