HIV is a retrovirus, a type of virus that carries its genetic material not as DNA but as RNA. Long before anyone had heard of HIV, researchers in labs all over the world studied retroviruses, tracing out their life cycle and identifying the key proteins the viruses use to infect cells. When HIV was identified as a retrovirus, these studies gave AIDS researchers an immediate jump-start. The previously identified viral proteins became initial drug targets. See images 2514 and 2515 for labeled versions of this illustration. Featured in The Structures of Life.

The white circle in this image is a Petri dish, named for its inventor, Julius Richard Petri. These dishes are one of the most common pieces of equipment in biology labs, where researchers use them to grow cells.

A combination of protein structures determined experimentally and computationally shows us the complete metabolic network of a heat-loving bacterium.

The nucleolinus is a cellular compartment that has been a lonely bystander in scientific endeavors. Although it's found in a range of species, its function has been mysterious—mainly because the structure is hard to visualize. An August 2010 study showed that the nucleolinus is crucial for cell division. When researchers zapped the structure with a laser, an egg cell didn't complete division. When the oocyte was fertilized after laser microsurgery (bottom right), the resulting zygote didn't form vital cell division structures (blue and yellow).

A color-coded, 3D model of a rat pancreatic β cell. This type of cell produces insulin, a hormone that helps regulate blood sugar. Visible are mitochondria (pink), insulin vesicles (yellow), the nucleus (dark blue), and the plasma membrane (teal). This model was created based on soft X-ray tomography (SXT) images.

Like tractor-trailers on a highway, small sacs called vesicles transport substances within cells. This image tracks the motion of vesicles in a living cell. The short red and yellow marks offer information on vesicle movement. The lines spanning the image show overall traffic trends. Typically, the sacs flow from the lower right (blue) to the upper left (red) corner of the picture. Such maps help researchers follow different kinds of cellular processes as they unfold.

To become products, reactants must overcome an energy hill. See image 2525 for an unlabeled version of this illustration. Featured in The Chemistry of Health.

Many disease-causing microbes manipulate their host’s metabolism and cells for their own ends. Microsporidia—which are parasites closely related to fungi—infect and multiply inside animal cells, and take the rearranging of cells’ interiors to a new level. They reprogram animal cells such that the cells start to fuse, causing them to form long, continuous tubes. As shown in this image of the roundworm Caenorhabditis elegans, microsporidia (shown in magenta) have invaded the worm’s gut cells (shown in yellow; the cells’ nuclei are shown in blue) and have instructed the cells to merge. The cell fusion enables the microsporidia to thrive and propagate in the expanded space. Scientists study microsporidia in worms to gain more insight into how these parasites manipulate their host cells. This knowledge might help researchers devise strategies to prevent or treat infections with microsporidia. For more on the research into microsporidia, see this news release from the University of California San Diego. Related to images 5778 and 5779.

During DNA replication, each strand of the original molecule acts as a template for the synthesis of a new, complementary DNA strand. See image 2544 for a labeled version of this illustration.

Floral pattern emerging as two bacterial species, motile Acinetobacter baylyi (red) and non-motile Escherichia coli (green), are grown together for 48 hours on 1% agar surface from a small inoculum in the center of a Petri dish.

See 6557 for a photo of this process at 24 hours on 0.75% agar surface.
See 6555 for another photo of this process at 48 hours on 1% agar surface.
See 6556 for a photo of this process at 72 hours on 0.5% agar surface.
See 6550 for a video of this process.

Fat tissue from the abdomen of a genetically mosaic adult fruit fly. Genetic mosaicism means that the fly has cells with different genotypes even though it formed from a single zygote. This specific mosaicism results in accumulation of a critical fly adipokine (blue-green) within the fat tissue cells that have reduced expression a key nutrient sensing gene (in left panel). The dotted line shows the cells lacking the gene that is present and functioning in the rest of the cells. Nuclei are labelled in magenta. This image was captured using a confocal microscope and shows a maximum intensity projection of many slices.

Related to images 6982, 6984, and 6985.

La sepsis o septicemia es la respuesta fulminante y extrema del cuerpo a una infección. En los Estados Unidos, más de 1.7 millones de personas contraen sepsis cada año. Sin un tratamiento rápido, la sepsis puede provocar daño de los tejidos, insuficiencia orgánica y muerte. El NIGMS apoya a muchos investigadores en su trabajo para mejorar el diagnóstico y el tratamiento de la sepsis.

Vea 6536 para la versión en inglés de esta infografía.

Shortly after a pregnant woman gives birth, her breasts start to secrete milk. This process is triggered by hormonal and genetic cues, including the protein Elf5. Scientists discovered that Elf5 also has another job--it staves off cancer. Early in the development of breast cancer, human breast cells often lose Elf5 proteins. Cells without Elf5 change shape and spread readily--properties associated with metastasis. This image shows cells in the mouse mammary gland that are lacking Elf5, leading to the overproduction of other proteins (red) that increase the likelihood of metastasis.

NIGMS staff are located in the Natcher Building on the NIH campus.

The G switch allows our bodies to respond rapidly to hormones. G proteins act like relay batons to pass messages from circulating hormones into cells. A hormone (red) encounters a receptor (blue) in the membrane of a cell. Next, a G protein (green) becomes activated and makes contact with the receptor to which the hormone is attached. Finally, the G protein passes the hormone's message to the cell by switching on a cell enzyme (purple) that triggers a response. See image 2536 and 2537 for other versions of this image. Featured in Medicines By Design.

The structure of the pore-forming protein VDAC-1 from humans. This molecule mediates the flow of products needed for metabolism--in particular the export of ATP--across the outer membrane of mitochondria, the power plants for eukaryotic cells. VDAC-1 is involved in metabolism and the self-destruction of cells--two biological processes central to health.

Related to images 2491, 2494, and 2495.

Reactivating telomerase in our cells does not appear to be a good way to extend the human lifespan. Cancer cells reactivate telomerase.

Duplicated pair of chromosomes lined up and ready to cross over.

Nodes of Ranvier are short gaps in the myelin sheath surrounding myelinated nerve cells (axons). Myelin insulates axons, and the node of Ranvier is where the axon is exposed to the extracellular environment, allowing for the transmission of action potentials at these nodes via ion flows between the inside and outside of the axon. The image shows a cross-section through the node, with the surrounding extracellular matrix encasing and supporting the axon shown in cyan.

Early on, this Arabidopsis plant embryo picks sides: While one end will form the shoot, the other will take root underground. Short pieces of RNA in the bottom half (blue) make sure that shoot-forming genes are expressed only in the embryo's top half (green), eventually allowing a seedling to emerge with stems and leaves. Like animals, plants follow a carefully orchestrated polarization plan and errors can lead to major developmental defects, such as shoots above and below ground. Because the complex gene networks that coordinate this development in plants and animals share important similarities, studying polarity in Arabidopsis--a model organism--could also help us better understand human development.

The molecule on the left is an electrostatic potential map of the van der Waals surface of the transition state for human purine nucleoside phosphorylase. The colors indicate the electron density at any position of the molecule. Red indicates electron-rich regions with negative charge and blue indicates electron-poor regions with positive charge. The molecule on the right is called DADMe-ImmH. It is a chemically stable analogue of the transition state on the left. It binds to the enzyme millions of times tighter than the substrate. This inhibitor is in human clinical trials for treating patients with gout. This image appears in Figure 4, Schramm, V.L. (2011) Annu. Rev. Biochem. 80:703-732.

Cilia (cilium in singular) are complex molecular machines found on many of our cells. One component of cilia is the doublet microtubule, a major part of cilia’s skeletons that give them support and shape. This animated image is a partial model of a doublet microtubule’s structure based on cryo-electron microscopy images. Video can be found here 6549.

This illustration shows, in simplified terms, how the CRISPR-Cas9 system can be used as a gene-editing tool. The CRISPR system has two components joined together: a finely tuned targeting device (a small strand of RNA programmed to look for a specific DNA sequence) and a strong cutting device (an enzyme called Cas9 that can cut through a double strand of DNA). In this frame (2 of 4), the CRISPR machine locates the target DNA sequence once inserted into a cell.

For an explanation and overview of the CRISPR-Cas9 system, see the iBiology video, and find the full CRIPSR illustration here.

Vibrio fischeri (2 mm in length) is the exclusive symbiotic partner of the Hawaiian bobtail squid, Euprymna scolopes. After this bacterium uses its flagella to swim from the seawater into the light organ of a newly hatched juvenile, it colonizes the host and loses the appendages. This image was taken using a scanning electron microscope.

Glide across an icy canyon, where you see smiling snowmen and waddling penguins. Toss a snowball, hear it smash against an igloo, and then watch it explode in bright colors. Psychologists David Patterson and Hunter Hoffman of the University of Washington in Seattle developed this virtual "Snow World" to test whether immersing someone in a pretend reality could ease pain during burn treatment and other medical procedures. They found that people fully engaged in the virtual reality experience reported 60 percent less pain. The technology offers a promising way to manage pain.

Both instruments shown were developed by CellFree Sciences of Yokohama, Japan. The instrument on the left, the GeneDecoder 1000, can generate 384 proteins from their corresponding genes, or gene fragments, overnight. It is used to screen for properties such as level of protein production and degree of solubility. The instrument on the right, the Protemist Protein Synthesizer, is used to generate the larger amounts of protein needed for protein structure determinations.

Three-dimensional reconstruction of a tubular matrix in a thin section of the peripheral endoplasmic reticulum between the plasma membranes of the cell.
The endoplasmic reticulum (ER) is a continuous membrane that extends like a net from the envelope of the nucleus outward to the cell membrane. The ER plays several roles within the cell, such as in protein and lipid synthesis and transport of materials between organelles.
Shown here are super-resolution microscopic images of the peripheral ER showing the structure of an ER tubular matrix between the plasma membranes of the cell. See image 5857 for a more detailed view of the area outlined in white in this image. For another view of the ER tubular matrix see image 5855

On the left, a cross-section slice of a rat pancreas cell captured using cryo-electron tomography (cryo-ET). On the right, a color-coded, 3D version of the image highlighting cell structures. Visible features include insulin vesicles (purple rings), insulin crystals (gray circles), microtubules (green rods), ribosomes (small yellow circles). The black line at the bottom right of the left image represents 200 nm. Related to image 6608.

Featured in the March 15, 2012 issue of Biomedical Beat. Related to Hsp33 Figure 1, image 3354.

It has been said that gastrulation is the most important event in a person's life. This part of early embryonic development transforms a simple ball of cells and begins to define cell fate and the body axis. In a study published in Science magazine, NIGMS grantee Bob Goldstein and his research group studied how contractions of actomyosin filaments in C. elegans and Drosophila embryos lead to dramatic rearrangements of cell and embryonic structure. In these images, myosin (green) and plasma membrane (red) are highlighted at four timepoints in gastrulation in the roundworm C. elegans. The blue highlights in the top three frames show how cells are internalized, and the site of closure around the involuting cells is marked with an arrow in the last frame. See related image 3297.

At the root tips of the mustard plant Arabidopsis thaliana (red), two proteins work together to control the uptake of water and nutrients. When the cell division-promoting protein called Short-root moves from the center of the tip outward, it triggers the production of another protein (green) that confines Short-root to the nutrient-filtering endodermis. The mechanism sheds light on how genes and proteins interact in a model organism and also could inform the engineering of plants.

Viral RNA (red) in an RSV-infected cell. More information about the research behind this image can be found in a Biomedical Beat Blog posting from January 2014.

These neurons are derived from mouse embryonic stem cells. Red shows cells making a protein called TH that is characteristic of the neurons that degenerate in Parkinson's disease. Green indicates a protein that's found in all neurons. Blue indicates the nuclei of all cells. Studying dopaminergic neurons can help researchers understand the origins of Parkinson's disease and could be used to screen potential new drugs. Image and caption information courtesy of the California Institute for Regenerative Medicine. Related to images 3270 and 3285.

Like a map showing heavily traveled roads, this mathematical model of metabolic activity inside an E. coli cell shows the busiest pathway in white. Reaction pathways used less frequently by the cell are marked in red (moderate activity) and green (even less activity). Visualizations like this one may help scientists identify drug targets that block key metabolic pathways in bacteria.

Serum albumin (SA) is the most abundant protein in the blood plasma of mammals. SA has a characteristic heart-shape structure and is a highly versatile protein. It helps maintain normal water levels in our tissues and carries almost half of all calcium ions in human blood. SA also transports some hormones, nutrients and metals throughout the bloodstream. Despite being very similar to our own SA, those from other animals can cause some mild allergies in people. Therefore, some scientists study SAs from humans and other mammals to learn more about what subtle structural or other differences cause immune responses in the body.

Related to entries 3745 and 3746.

An adult Hawaiian bobtail squid, Euprymna scolopes, swimming next to a submerged hand.

Related to image 7010 and video 7012.

Some nerve cells (neurons) in the brain keep track of the daily cycle. This time-keeping mechanism, called the circadian clock, is found in all animals including us. The circadian clock controls our daily activities such as sleep and wakefulness. Researchers are interested in finding the neuron circuits involved in this time keeping and how the information about daily time in the brain is relayed to the rest of the body. In this image of a brain of the fruit fly Drosophila the time-of-day information flowing through the brain has been visualized by staining the neurons involved: clock neurons (shown in blue) function as "pacemakers" by communicating with neurons that produce a short protein called leucokinin (LK) (red), which, in turn, relays the time signal to other neurons, called LK-R neurons (green). This signaling cascade set in motion by the pacemaker neurons helps synchronize the fly's daily activity with the 24-hour cycle. To learn more about what scientists have found out about circadian pacemaker neurons in the fruit fly see this news release by New York University. This work was featured in the Biomedical Beat blog post Cool Image: A Circadian Circuit.

A representation of a patient’s brain waves after receiving the anesthetic propofol. All anesthetics create brain wave changes that vary depending on the patient’s age and the type and dose of anesthetic used. These changes are visible in raw electroencephalogram (EEG) readings, but they’re easier to interpret using a spectrogram where the signals are broken down by time (x-axis), frequency (y-axis), and power (color scale). This spectrogram shows the changes in brain waves before, during, and after propofol-induced anesthesia. The patient is unconscious from minute 5, upon propofol administration, through minute 69 (change in power and frequency). But, between minutes 35 and 48, the patient fell into a profound state of unconsciousness (disappearance of dark red oscillations between 8 to 12 Hz), which required the anesthesiologist to adjust the rate of propofol administration. The propofol was stopped at minute 62 and the patient woke up around minute 69.

Anaphase is the critical step during mitosis when sister chromosomes are disjoined and directed to opposite spindle poles, ensuring equal distribution of the genome during cell division. In this image, one pair of sister chromosomes at the top was lost and failed to divide after chemical inhibition of polo-like kinase 1. This image depicts chromosomes (blue) separating away from the spindle mid-zone (red). Kinetochores (green) highlight impaired movement of some chromosomes away from the mid-zone or the failure of sister chromatid separation (top). Scientists are interested in detailing the signaling events that are disrupted to produce this effect. The image is a volume projection of multiple deconvolved z-planes acquired with a Nikon widefield fluorescence microscope.

This image was chosen as a winner of the 2016 NIH-funded research image call. The research that led to this image was funded by NIGMS.

Related to image 5765.

X-ray co-crystal structure of Src kinase bound to a DNA-templated macrocycle inhibitor. Related to 3413, 3415, 3416, 3417, 3418, and 3419.

DNA doesn't leave a fossil record in stone, the way bones do. Instead, the DNA code itself holds the best evidence for organisms' genetic history. Some of the most telling evidence about genetic history comes from retroviruses, the remnants of ancient viral infections.

This normal human skin cell was treated with a growth factor that triggered the formation of specialized protein structures that enable the cell to move. We depend on cell movement for such basic functions as wound healing and launching an immune response.

This image was part of the Life: Magnified exhibit that ran from June 3, 2014, to January 21, 2015, at Dulles International Airport.

The Golgi complex, also called the Golgi apparatus or, simply, the Golgi. This organelle receives newly made proteins and lipids from the ER, puts the finishing touches on them, addresses them, and sends them to their final destinations.

Collecting and transporting cellular waste and sorting it into recylable and nonrecylable pieces is a complex business in the cell. One key player in that process is the endosome, which helps collect, sort and transport worn-out or leftover proteins with the help of a protein assembly called the endosomal sorting complexes for transport (or ESCRT for short). These complexes help package proteins marked for breakdown into intralumenal vesicles, which, in turn, are enclosed in multivesicular bodies for transport to the places where the proteins are recycled or dumped. In this image, a multivesicular body (the round structure slightly to the right of center) contain tiny intralumenal vesicles (with a diameter of only 25 nanometers; the round specks inside the larger round structure) adjacent to the cell's vacuole (below the multivesicular body, shown in darker and more uniform gray).

Scientists working with baker's yeast (Saccharomyces cerevisiae) study the budding inward of the limiting membrane (green lines on top of the yellow lines) into the intralumenal vesicles. This tomogram was shot with a Tecnai F-20 high-energy electron microscope, at 29,000x magnification, with a 0.7-nm pixel, ~4-nm resolution.

To learn more about endosomes, see the Biomedical Beat blog post The Cell’s Mailroom. Related to a color-enhanced version 5767 and image 5769.

A nanometer-sized biosensor can detect a single deadly bacterium in tainted ground beef. How? Researchers attached nanoparticles, each packed with thousands of dye molecules, to an antibody that recognizes the microbe E. coli O157:H7. When the nanoball-antibody combo comes into contact with the E. coli bacterium, it glows. Here is the transition, a single bacterial cell glows brightly when it encounters nanoparticle-antibody biosensors, each packed with thousands of dye molecules.

This video shows the structure of the pore-forming protein VDAC-1 from humans. This molecule mediates the flow of products needed for metabolism--in particular the export of ATP--across the outer membrane of mitochondria, the power plants for eukaryotic cells. VDAC-1 is involved in metabolism and the self-destruction of cells--two biological processes central to health.

Related to videos 2570 and 2571.

A shell from the venomous cone snail Conus omaria, which lives in the Pacific and Indian oceans and eats other snails. University of Utah scientists discovered a new toxin in this snail species' venom, and say it will be a useful tool in designing new medicines for a variety of brain disorders, including Alzheimer's and Parkinson's diseases, depression, nicotine addiction and perhaps schizophrenia.

A cross section of the measles virus in which six proteins work together to infect cells. The measles virus is extremely infectious; 9 out of 10 people exposed will contract the disease. Fortunately, an effective vaccine protects against infection.

For a zoomed-in look at the six important proteins, see Measles Virus Proteins.

The three fibers of the cytoskeleton--microtubules in blue, intermediate filaments in red, and actin in green--play countless roles in the cell.