Name: how tem reveals tiny structures
Uploaded: 2023-04-30T12:01:08.000Z
Duration: 1 min 15 s
Channel: JoVE

Se utiliza un microscopio electrónico de transmisión o TEM para estudiar la estructura y composición interna de una muestra.
El instrumento consiste en un cañón de electrones que emite un haz de electrones. A continuación, el haz se enfoca en la muestra utilizando dos o más lentes de condensador electromagnéticas.
Los electrones transmitidos a través de la muestra son recogidos y enfocados por lentes objetivo para formar la imagen intermedia. Esta imagen se amplía aún más con lentes intermedias y de proyector adicionales.
La imagen final se puede capturar utilizando dispositivos de imagen sensibles a los electrones, como una pantalla fosforescente o una cámara CCD.
TEM forma una imagen bidimensional en blanco y negro de una muestra. Las áreas más oscuras representan regiones densas que transmiten pocos o ningún electrón. Por el contrario, las áreas más claras indican las regiones a través de las cuales se transmiten más electrones.
TEM también se utiliza para analizar la composición de la muestra. La interacción haz de electrones-muestra genera rayos X característicos que se pueden utilizar para identificar y cuantificar diferentes elementos presentes en una muestra.

microscopio de transmisión por electrones

Transmission Electron Microscopy

En 1931, el físico Ernst Ruska, basándose en la idea de que los campos magnéticos pueden dirigir un haz de electrones del mismo modo que las lentes pueden dirigir un haz de luz en un microscopio óptico, desarrolló el primer prototipo de microscopio electrónico. Este desarrollo condujo al desarrollo del campo de la microscopía electrónica. En el microscopio electrónico de transmisión (TEM), los electrones son producidos por un elemento de tungsteno caliente y acelerados por una diferencia de potencial en un cañón de electrones, lo que les da hasta 400 keV de energía cinética. Después de salir del cañón de electrones, el haz de electrones se enfoca mediante lentes electromagnéticas (un sistema de lentes condensadoras) y se transmite a través de una muestra que se va a observar. La imagen de la muestra se reconstruye a partir del haz de electrones transmitido. La imagen ampliada se puede ver directamente en una pantalla fluorescente o indirectamente enviándola, por ejemplo, a una cámara digital o un monitor de computadora.

Todo el conjunto, que consta del cañón de electrones, las lentes, la muestra y la pantalla fluorescente, está encerrado en una cámara de vacío para evitar la pérdida de energía del haz. Los modelos modernos de alta resolución de un TEM pueden tener un poder de resolución superior a 0,5 Å y aumentos superiores a 50 millones de veces. A modo de comparación, el mejor poder de resolución obtenido con microscopía óptica es actualmente de unos 97 nm.

Una limitación del TEM es que las muestras deben tener aproximadamente 100 nm de espesor, y las muestras biológicas requieren una preparación especial que implique una "fijación" química para estabilizarlas para el corte ultrafino. Para superar las limitaciones, se han realizado varios avances en las técnicas TEM, como la crio-TEM, para eliminar artefactos y permitir la obtención de imágenes directas de la muestra sin las etapas dañinas de fijación y deshidratación de la muestra.

Microscopio de transmisión por electrones

En 1931, el físico Ernst Ruska, basándose en la idea de que los campos magnéticos pueden dirigir un haz de electrones al igual que las lentes pueden dirigir un haz de luz en un ...

Education

Educación

JoVE Core

Cell Biology

Biología Celular

Unit 1

Unidad 1

Visualizing Cells, Tissues, and Molecules

Visualización de células, tejidos y moléculas

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

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 up to 400 keV of kinetic energy. Electromagnetic lenses, arranged as condensing lenses, focus the beam before it passes through the sample.

The image is formed from the electrons that move through the specimen. That reconstructed image can be viewed on a fluorescent screen or sent to a digital camera or computer monitor. The full system, including the electron gun, lenses, specimen, and screen, sits inside a vacuum chamber to reduce energy loss from the beam.

Modern high-resolution TEM models can resolve details smaller than 0.5 Å and reach magnifications above 50 million times. By comparison, the best resolving power of light microscopy is about 97 nm. TEM does have limits, because samples must be about 100 nm thick, and biological samples need chemical fixing before ultrathin slicing.

To reduce these limits, researchers have developed newer TEM methods such as cryo-TEM. These approaches help remove artifacts and can allow direct imaging without the sample-damaging steps of fixation and dehydration.

How TEM Reveals Tiny Structures

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transmission electron microscopy

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...

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key terms and concepts

Learn how transmission electron microscopy uses electrons, magnetic lenses, and a vacuum to image ultra-thin samples at extreme magnification.

How TEM Reveals Tiny Structures | JoVE K12

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JoVE Core Biología Celular ilustra procesos celulares complejos mediante completos vídeos animados fáciles de entender. Esta colección se centra en los componentes esenciales de las células y su funcionamiento, incluyendo los orgánulos y las membranas, el transporte celular y el metabolismo energético celular. Todo este material se complementa con los vídeos de científicos en acción, que muestran la aplicación de la biología celular en experimentos reales de investigación.

How TEM Reveals Tiny Structures

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