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JoVE Science Education

A video library dedicated to teaching the practice and theory of scientific experiments through engaging and easy-to-understand visual demonstrations.

Education

An Introduction to the Centrifuge

The centrifuge is an instrument used in nearly every research lab across the globe. Centrifugation is the process by which a centrifuge is used to separate components of a complex mixture. By spinning laboratory samples at very high speeds, the components of a given mixture are subjected to centrifugal force, which causes more dense particles to migrate away from the axis of rotation and lighter ones to move toward it. These particles can sediment at the bottom of the tube into what&#x2019;s known as a pellet, and this isolated specimen, or the remaining solution, the supernatant, can be further processed or analyzed. This video is meant to introduce a student to some of the basic principles of centrifugation, as well as the instrument&#x2019;s basic operation. For example the speed of centrifugation in rotations per minute, or RPM, is contrasted with relative centrifugal force, or RCF, as a measurement of the magnitude of centrifugation, which is independent of rotor size. In addition to concepts and basic use, safety precautions relating to centrifugation are discussed, as well as the types of centrifuges and centrifuge rotors that exist.

Centrifuge: Principle, Instrumentation and Applications

The centrifuge is an instrument used in nearly every research lab across the globe.  Centrifugation is the process by which a centrifuge is used to ...

Introduction to the Microplate Reader

The microplate reader is a multimodal instrument that allows for a variety of experiments to be performed and measured simultaneously. Microplate readers can make absorbance, fluorescence and luminescence measurements. Multiwell plates are integral to the microplate reader and allow for many experiments to be performed at once. Regardless of the assay type, experiments on the plate reader utilize a standard curve to determine the experimental values. This curve uses samples of known concentration to generate a line of best fit or standard curve. Experimental values are then extrapolated to the curve or are calculated using the equation from the linear regression. Besides standards and samples being run on the multiwall plate, the blank along with positive and negative controls are also used in the assay to ensure it is working correctly. Multiplate readers are used to quantify protein, gene expression and various metabolic processes such as reactive oxygen species and calcium flux.

Microplate Reader: Principle, Data Interpretation, and Applications

The microplate reader is a multimodal instrument that allows for a variety of experiments to be performed and measured simultaneously.  Microplate readers ...

Understanding Concentration and Measuring Volumes

Solutions are utilized to some degree in almost all biological research applications. Therefore understanding how to measure and manipulate them is imperative to any experiment. In this video, concepts in preparing solutions are introduced. 

Solutions consist of a solute dissolved in solvent to yield a homogeneous mixture of molecular substances. Solutions are generally identified by their components and corresponding concentrations. Concentrated solutions are diluted through various methods, such as serial dilution.
 
This video also lays a foundation for the accurate preparation of solutions. For example, the video reviews how to measure volumes with precision through use of the appropriate volumetric container as well as how to read the volume when a meniscus is present. 

Some applications for measuring volumes are then presented. Gel electrophoresis is a commonly used laboratory procedure which requires preparation of a percent weight volume solution as well as parallel dilution of a concentrated stock solution. Use of a serial dilution to prepare standards for generating a standard curve in protein quantitation is also demonstrated.

Learning Concentration, Measuring Volumes, and Serial Dilutions

Solutions are utilized to some degree in almost all biological research applications.  Therefore understanding how to measure and manipulate them is ...

Making Solutions in the Laboratory

The ability to successfully make solutions is a basic laboratory skill performed in virtually all biological and chemical experiments. A solution is a homogenous mixture of solute dissolved in bulk liquid known as the solvent. Solutions can be described by their solute concentration, a measure of how much solute is present per unit of solution. 
 
In this video, a step-by-step procedure for how to make a water-based, or aqueous, solution for biological applications is presented. The video discusses how to calculate and measure the amount of solute needed for a given volume of solution. Methods for dissolving the solute in purified water and adjusting the pH of the solution are shown. Proper addition of the quantity sufficient (QS) to reach the desired volume is demonstrated with respect to the meniscus before discussing methods for sterilizing the solution. 

Applications of making solutions are presented through the discussion of several commonly used biological solutions, such as phosphate buffered saline (PBS), and their uses in biological research. These solutions are buffers that mimic physiological pH and osmolarity of cellular fluids.

The ability to successfully make solutions is a basic laboratory skill performed in virtually all biological and chemical experiments.  A solution is a ...

An Introduction to the Micropipettor

The micropipettor is a common laboratory instrument used for transferring microvolumes of liquid solutions. Micropipettors come in a range of sizes for the accurate movement of volumes between 0.5 and 5000 &#x03BC;l and each instrument requires one of three different sized disposable tips. Micropipettors work by displacing air from the pipette shaft, allowing the liquid to be drawn into the resulting vacuum. Their uses include transferring cell suspensions for a variety of cell-based assays, loading samples for different analytical techniques, and mechanically disrupting tissues into single cell suspensions. Micropipettors are an extremely helpful laboratory tools that are easy to use with a little bit of instruction and practice. In this video, JoVE shows the first-time user all the tips, tricks, and ins and outs of using a micropipettor in the lab.

Micropipettor: Operation and Applications

The micropipettor is a common laboratory instrument used for transferring microvolumes of liquid solutions. Micropipettors come in a range of sizes for ...

Introduction to Serological Pipettes and Pipettors

The serological pipette is frequently used in the laboratory for transferring milliliter volumes of liquid, from less than 1 ml to up to 50 ml. The pipettes can be sterile, plastic, and disposable or sterilizable, glass and reusable. Both kinds of pipettes use a pipet-aid, for the aspiration and dispensation of liquids. Different sizes of pipettes can be used with the same pipet-aid for a variety of experimental assays. For example, serological pipettes are useful for mixing chemical solutions or cell suspensions, transferring liquids between receptacles, or carefully layering reagents of different densities. With careful attention to the level of liquid being aspirated and dispensed, serological pipettes can be useful tools for transferring accurate milliliter volumes of solutions in the lab. This video discusses the way that volume can be read on a serological pipette, how a pipet aid works, and many different applications for using a serological pipette.

Serological Pipettes and Pipettors: Operation and Applications

The serological pipette is frequently used in the laboratory for transferring milliliter volumes of liquid, from less than 1 ml to up to 50 ml. The ...

Introduction to the Bunsen Burner

The Bunsen burner, named after and co-designed by Robert Bunsen in 1854, is a common laboratory instrument that produces a hot, sootless, non-luminous flame. The Bunsen Burner allows for precise regulation of the mixing of gas and oxygen in its central barrel before combustion, which ignites the flame. By manipulating the Bunsen burner, both the size and temperature of the flame can be controlled. Among other uses, the heat of a Bunsen burner flame can be used to create a convection current, which heats the space above the flame and lifts any particulates in the air up and away from the cooler air underneath it, keeping this work area sterile. Working with an open flame requires extra caution. Always remember to secure any loose hair, clothing, or accessories before lighting a Bunsen burner and to always have the proper safety equipment, like a fire extinguisher and/or a fire blanket, on hand. Taking the time to understand how to use a Bunsen burner and what safety equipment to have on hand will allow you to operate this useful laboratory tool with safety and confidence.

Bunsen Burner: Components, Operation and Flame Types

The Bunsen burner, named after and co-designed by Robert Bunsen in 1854, is a common laboratory instrument that produces a hot, sootless, non-luminous ...

An Introduction to Working in the Hood

Hoods are a common class of instrument, which act as a protective enclosure for various types of laboratory experiments. They serve to shield experimental samples from the environment, as well as to protect the researcher from hazardous or infectious samples. &#x201C;The Hood&#x201D; is a term that can include laminar flow benches, fume hoods, as well as tissue culture hoods or biosafety cabinets. 
All hoods operate based on the principle of laminar flow and have the same basic components, including a window sash and protective glass barrier, a non-porous work surface, and an air intake and exhaust. The type of hood used should be chosen based on the experiment. For example, fume hoods typically protect the user, and not the experimental environment. In contrast, laminar flow benches protect the experiment, but not the user, and therefore can but used to keep experimental samples sterile, when they pose no threat. If both the user and the experiment must be protected, a tissue culture hood or biosafety cabinet can be used. Tissue culture hoods maintain sterility of cell lines, while biosafety cabinets provide protection during procedures utilizing infectious agents
Once the appropriate unit is chosen for an experiment, the user should wear appropriate protective equipment, and follow all necessary safety procedures. This video discusses the principle of laminar flow, how the hood is used, and discusses the different types of procedures that should be carried out in each type of hood.

Hoods: Principle, Types and Components, Operation

Hoods are a common class of instrument, which act as a protective enclosure for various types of laboratory experiments. They serve to shield experimental ...

Measuring Mass in the Laboratory

The analytical balance is the common piece of equipment in the scientific laboratory. These highly precise instruments can measure down to ten thousandths or even hundred thousandths of a gram. The triple beam balance is a type of scale that uses counterweights on a three rider beams to counterbalance the sample in the pan. On the other hand, modern analytical balances use a complex system of electronic sensors to accurately mass a substance. The analytical balance is so sensitive that it often has a draft shield to prevent air currents from interfering with the measurement. When weighing, a weigh boat or weigh paper is used to hold the substance being weighed and protect the weighing pan. Before weighing a substance, analytical balances are tarred to subtract the weigh boat or weigh paper and re-zero the scale. Tarring refers to setting the scale back to read zero and allows for a substance to be accurately weighed. Aside from weighing chemical substances, analytical balances are used to animals or insects, and centrifuge tubes in ultracentrifugation experiments.

Measuring Mass in the Laboratory Using Analytical Balance

The analytical balance is the common piece of equipment in the scientific laboratory. These highly precise instruments can measure down to ten thousandths ...

Introduction to the Spectrophotometer

The spectrophotometer is a routinely used instrument in scientific research. Spectrophotometry is the quantitative measurement of how much a chemical substance absorbs light by passing a beam of light through the sample using a spectrophotometer. 

In this video, basic concepts in spectrophotometry, including transmittance, absorbance and the Beer-Lambert Law are reviewed in addition to the components of the spectrophotometer. These concepts provide a foundation for how to determine the concentration of a solute in solution that is capable of absorbing light in the ultraviolet and visible range. 

Furthermore, a procedure for how to operate the spectrophotometer is demonstrated, including instructions on how to blank and measure the absorbance of a sample at the desired wavelength. The video also covers how to make a standard curve for determination of analyte concentration. 

Several applications of the spectrophotometer in biological research are discussed, such as measurement of cell density and determination of chemical reaction rates. Finally, the microvolume spectrophotometer is introduced, as well as its advantage in measuring the quality and quantity of protein and nucleic acids.

Spectrophotometer: Principle, Instrumentation and Applications

The spectrophotometer is a routinely used instrument in scientific research.  Spectrophotometry is the quantitative measurement of how much a chemical ...

Histological Sample Preparation for Light Microscopy

Histology is the study of cells and tissues, which is typically aided by the use of a light microscope. The preparation of histological samples can vary greatly based on the inherent properties of the samples such as size and hardness as well as expected post-processing which includes planned staining techniques or other down-stream applications. As described in this video, specimen preparation typically begins with a fixation procedure to prevent degradation of the sample by naturally occurring enzymes that are released by the cells upon death. Once fixed, samples are placed into an embedding medium that is able to sufficiently support the sample. Most commonly this is paraffin wax, but other materials such as a glycerin based freezing medium and agars are also used to surround the sample during sectioning. Sectioning then takes place on a microtome or other cutting device that allows the user to shave the sample into thin slices ranging from a few microns to a few millimeters in thickness. Once cut, sections are mounted on a glass slide and stained to bring out specific features of the sample before being imaged on a microscope.

Histological Sample Prep for a Light Microscope

Histology is the study of cells and tissues, which is typically aided by the use of a light microscope.  The preparation of histological samples can vary ...

Introduction to Fluorescence Microscopy

Fluorescence microscopy is a very powerful analytical tool that combines the magnifying properties of light microscopy with visualization of fluorescence. Fluorescence is a phenomenon that involves absorbance and emission of a small range of light wavelengths by a fluorescent molecule known as a fluorophore. Fluorescence microscopy is accomplished in conjunction with the basic light microscope by the addition of a powerful light source, specialized filters, and a means of fluorescently labeling a sample. This video describes the basic principles behind fluorescence microscopy including the mechanism of fluorescence, the Stoke&#x2019;s shift, and photobleaching. It also gives examples of the numerous ways to fluorescently label a sample including the use of fluorescently tagged antibodies and proteins, nucleic acid fluorescent dyes with, and the addition of naturally fluorescent proteins to a specimen. The major components of the fluorescence microscope including a xenon or mercury light source, light filters, the dichroic mirror, and use of the shutter to illuminate the sample are all described. Finally, examples of some of the many applications for fluorescence microscopy are shown.

Fluorescence Microscopy: Concept, Instrumentation, and Applications

Fluorescence microscopy is a very powerful analytical tool that combines the magnifying properties of light microscopy with visualization of fluorescence. ...

Introduction to Light Microscopy

The light microscope is an instrument used by researchers in many different fields to magnify specimens to as much as a thousand times their original size. In its simplest form, it is composed of a clear lens that magnifies the sample and a light source to illuminate it. However, most light microscopes are much more complex and house numerous fine-tuned lenses with tightly controlled dimensions all within the body of the microscope itself and in components such as the objectives and eyepieces. In this video, the major components of the light microscope are described and their uses and functions are explained in detail. The basic principles of magnification, focus, and resolution are also introduced. Basic light microscope operation begins with bringing light to the sample and ensuring that the light source is of the correct intensity, directionality, and shape in order to produce the best quality image. Next, the sample must be magnified properly and brought into focus to view the region of interest. There are many practical applications for light microscopy including the viewing of stained or unstained cells and tissues, resolving small details of specimens, and even magnifying a region of interest during surgery to assist with complex procedures on the micron scale.

Light Microscopy: Principle, Instrumentation, and Applications

The light microscope is an instrument used by researchers in many different fields to magnify specimens to as much as a thousand times their original ...

Regulating Temperature in the Lab: Preserving Samples Using Cold

Preservation of laboratory samples, specimens, and reagents using extreme cold is routinely performed in biomedical research labs. This video will discuss some of the methods for keeping laboratory samples cold and will explain the correct cooling method to use for each experimental requirement.
For example, cooling agents, such as ice and dry ice, are typically used when keeping samples cold during experiments. This video discusses the physical properties of the most commonly used cooling agents, as well as safety precautions for working with them.
When it comes to keeping samples cold in between experiments, cooling equipment, including laboratory grade refrigerators and freezers can be used to preserve samples for extended period of time. Also discussed in this video are types of samples and reagents that can be stored in the commonly-available laboratory cooling equipment.
Finally, the concept of cryopreservation is introduced as a process through which tissues, cells, and biomolecules are cooled to sub-zero temperatures, thereby effectively stopping all sample-degrading biological activity. Several methods of cryopreservation are discussed that minimize or eliminate the formation of damaging ice crystals.

Preserving Samples Using Cold: Cooling Agents and Instruments, and Cryopreservation

Preservation of laboratory samples, specimens, and reagents using extreme cold is routinely performed in biomedical research labs.  This video will ...

Regulating Temperature in the Lab: Applying Heat

Although many experimental assays are performed at room temperature (RT; ~20-25&#176;C), it is not uncommon for experiments, or parts of experiments, to require some type of temperature regulation. This video discusses the different reasons for and temperatures at which a scientist may want to &#x201C;keep things warm&#x201D;. For example, sometime, cells need to be cultured in an environment close to body temperature (~37&#176;C), protein structure needs to be modified (>56&#176;C), or reagents and solutions need to be heated (~100&#176;C). Also discussed, is the proper way to handle a thermometer and measure the temperature in stirring liquids. Since it is not always obvious how to regulate temperatures in the laboratory, this video will also talk about what types of equipment one might choose in each situation.

Although many experimental assays are performed at room temperature (RT; ~20-25&#176;C), it is not uncommon for experiments, or parts of experiments, to ...

Science Education - Basic Biology

General Laboratory Techniques