Model of a protein involved in cell division from Mycoplasma pneumoniae. This model, based on X-ray crystallography, revealed a structural domain not seen before. The protein is thought to be involved in cell division and cell wall biosynthesis.

Cells move forward with lamellipodia and filopodia supported by networks and bundles of actin filaments. Proper, controlled cell movement is a complex process. Recent research has shown that an actin-polymerizing factor called the Arp2/3 complex is the key component of the actin polymerization engine that drives amoeboid cell motility. ARPC3, a component of the Arp2/3 complex, plays a critical role in actin nucleation. In this photo, the ARPC3+/+ fibroblast cells were fixed and stained with Alexa 546 phalloidin for F-actin (red), mDia1 (green), and DAPI to visualize the nucleus (blue). mDia1 is localized at the lamellipodia of ARPC3+/+ fibroblast cells. Related to images 3328, 3329, 3331, 3332, and 3333.

In vivo vascular development in kdr:GFP frogs. Related to images 3403 and 3405.

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.

Learn how research organisms, such as fruit flies and mice, can help us understand and treat human diseases. Discover more resources from NIGMS’ Pathways collaboration with Scholastic. View the video on YouTube for closed captioning.

Wound healing requires the action of stem cells. In mice that lack the Sept2/ARTS gene, stem cells involved in wound healing live longer and wounds heal faster and more thoroughly than in normal mice. This confocal microscopy image from a mouse lacking the Sept2/ARTS gene shows a tail wound in the process of healing. See more information in the article in Science.

Related to images 3498 and 3500.

Three-dimensional image of misfolded proteins (green) within mitochondria (red). Related to image 5878. Learn more in this press release by The American Association for the Advancement of Science.

Influenza (flu) virus proteins in the act of self-replication. Viral nucleoprotein (blue) encapsidates [encapsulates] the RNA genome (green). The influenza virus polymerase (orange) reads and copies the RNA genome. In the background is an image of influenza virus ribonucleoprotein complexes observed using cryo-electron microscopy. This image is from a November 2012 News Release.

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.

A 3-D model of the alkaloid serratezomine A shows the molecule's complex ring structure.

An adult female Hawaiian bobtail squid, Euprymna scolopes, with its mantle cavity exposed from the underside. Some internal organs are visible, including the two lobes of the light organ that contains bioluminescent bacteria, Vibrio fischeri. The light organ includes accessory tissues like an ink sac (black) that serves as a shutter, and a silvery reflector that directs the light out of the underside of the animal.

The proteasome is a critical multiprotein complex in the cell that breaks down and recycles proteins that have become damaged or are no longer needed. This illustration shows a protein substrate (red) that is bound through its ubiquitin chain (blue) to one of the ubiquitin receptors of the proteasome (Rpn10, yellow). The substrate's flexible engagement region gets engaged by the AAA+ motor of the proteasome (cyan), which initiates mechanical pulling, unfolding and movement of the protein into the proteasome's interior for cleavage into small shorter protein pieces called peptides. During movement of the substrate, its ubiquitin modification gets cleaved off by the deubiquitinase Rpn11 (green), which sits directly above the entrance to the AAA+ motor pore and acts as a gatekeeper to ensure efficient ubiquitin removal, a prerequisite for fast protein breakdown by the 26S proteasome. Related to video 3764.

This image shows collagen, a fibrous protein that's the main component of the extracellular matrix (ECM). Collagen is a strong, ropelike molecule that forms stretch-resistant fibers. The most abundant protein in our bodies, collagen accounts for about a quarter of our total protein mass. Among its many functions is giving strength to our tendons, ligaments and bones and providing scaffolding for skin wounds to heal. There are about 20 different types of collagen in our bodies, each adapted to the needs of specific tissues.

A crystal of bacterial glucose isomerase protein created for X-ray crystallography, which can reveal detailed, three-dimensional protein structures.

The enzyme Dicer generates microRNAs by chopping larger RNA molecules into tiny Velcro^®-like pieces. MicroRNAs stick to mRNA molecules and prevent the mRNAs from being made into proteins. See image 2556 for an unlabeled version of this illustration. Featured in The New Genetics.

Thin, hair-like biological structures called cilia are tiny but mighty. Each one, made up of more than 600 different proteins, works together with hundreds of others in a tightly-packed layer to move like a crowd at a ball game doing "the wave." Their synchronized motion helps sweep mucus from the lungs and usher eggs from the ovaries into the uterus. By controlling how fluid flows around an embryo, cilia also help ensure that organs like the heart develop on the correct side of your body.

Learn about basic science, sometimes called “pure” or “fundamental” science, and how it contributes to the development of medical treatments. Discover more resources from NIGMS’ Pathways collaboration with Scholastic. View the video on YouTube for closed captioning.

Phenylalanine tRNA showing the anticodon (yellow) and the amino acid, phenylalanine (blue and red spheres).

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

Motor neuron progenitors (green) were derived from human embryonic stem cells. Image and caption information courtesy of the California Institute for Regenerative Medicine.

A light microscope image of a cell from the endosperm of an African globe lily (Scadoxus katherinae). This is one frame of a time-lapse sequence that shows cell division in action. The lily is considered a good organism for studying cell division because its chromosomes are much thicker and easier to see than human ones. Staining shows microtubules in red and chromosomes in blue. Here, condensed chromosomes are clearly visible and have lined up in the middle of the dividing cell.

Related to images 1010, 1011, 1012, 1013, 1014, 1015, 1016, 1018, 1019, and 1021.

The extracellular matrix (ECM) is most prevalent in connective tissues but also is present between the stems (axons) of nerve cells. The axons of nerve cells are surrounded by the ECM encasing myelin-supplying Schwann cells, which insulate the axons to help speed the transmission of electric nerve impulses along the axons.

Cross-section of skin anatomy shows layers and different tissue types.

The signal is obtained by allowing proteins in human serum to interact with glycan (polysaccharide) arrays. The arrays are shown in replicate so the pattern is clear. Each spot contains a specific type of glycan. Proteins have bound to the spots highlighted in green.

Researchers doing behavioral experiments with honeybees sometimes use paint or enamel to give individual bees distinguishing marks. The elaborate social structure and impressive learning and navigation abilities of bees make them good models for behavioral and neurobiological research. Since the sequencing of the honeybee genome, published in 2006, bees have been used increasingly for research into the molecular basis for social interaction and other complex behaviors.

The nucleolus is a small but very important protein complex located in the cell's nucleus. It forms on the chromosomes at the location where the genes for the RNAs are that make up the structure of the ribosome, the indispensable cellular machine that makes proteins from messenger RNAs.

However, how the nucleolus grows and maintains its structure has puzzled scientists for some time. It turns out that even though it looks like a simple liquid blob, it's rather well-organized, consisting of three distinct layers: the fibrillar center, where the RNA polymerase is active; the dense fibrillar component, which is enriched in the protein fibrillarin; and the granular component, which contains a protein called nucleophosmin. Researchers have now discovered that this multilayer structure of the nucleolus arises from differences in how the proteins in each compartment mix with water and with each other. These differences let the proteins readily separate from each other into the three nucleolus compartments.

This video of nucleoli in the eggs of a commonly used lab animal, the frog Xenopus laevis, shows how each of the compartments (the granular component is shown in red, the fibrillarin in yellow-green, and the fibrillar center in blue) spontaneously fuse with each other on encounter without mixing with the other compartments.

For more details on this research, see this press release from Princeton. Related to video 3789, image 3792 and image 3793.

Human cells with the gene that codes for the protein FIT2 deleted. Green indicates an endoplasmic reticulum (ER) resident protein. The lack of FIT2 affected the structure of the ER and caused the resident protein to cluster in ER membrane aggregates, seen as large, bright-green spots. Red shows where the degradation of cell parts—called autophagy—is taking place, and the nucleus is visible in blue. This image was captured using a confocal microscope.

Myelinated axons in a rat spinal root. Myelin is a type of fat that forms a sheath around and thus insulates the axon to protect it from losing the electrical current needed to transmit signals along the axon. The axoplasm inside the axon is shown in pink. Related to 3397.

Neurons (green) and glial cells from isolated dorsal root ganglia express COX-2 (red) after exposure to an inflammatory stimulus (cell nuclei are blue). Lawrence Marnett and colleagues have demonstrated that certain drugs selectively block COX-2 metabolism of endocannabinoids -- naturally occurring analgesic molecules -- in stimulated dorsal root ganglia. Featured in the October 20, 2011 issue of Biomedical Beat.

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

Model of a protein, antigen 85B, that is the most abundant protein exported by Mycobacterium tuberculosis, which causes most cases of tuberculosis. Antigen 85B is involved in building the bacterial cell wall and is an attractive drug target. Based on its structure, scientists have suggested a new class of antituberculous drugs.

A light organ (~0.5 mm across) of a juvenile Hawaiian bobtail squid, Euprymna scolopes. Movement of cilia on the surface of the organ aggregates bacterial symbionts (green) into two areas above sets of pores that lead to interior crypts. This image was taken using a confocal fluorescence microscope.

Related to images 7016, 7017, 7019, and 7020.

Body organs such as the liver and kidneys process chemicals and toxins. These "target" organs are susceptible to damage caused by these substances. See image 2496 for an unlabeled version of this illustration.

This eerily glowing blob isn't an alien or a creature from the deep sea--it's a mouse embryo just eight and a half days old. The green shell and core show a protein called Smad4. In the center, Smad4 is telling certain cells to begin forming the mouse's liver and pancreas. Researchers identified a trio of signaling pathways that help switch on Smad4-making genes, starting immature cells on the path to becoming organs. The research could help biologists learn how to grow human liver and pancreas tissue for research, drug testing and regenerative medicine. In addition to NIGMS, NIH's National Institute of Diabetes and Digestive and Kidney Diseases also supported this work.

Drosophila adult brain showing that an adipokine (fat hormone) generates a response from neurons (aqua) and regulates insulin-producing neurons (red).

Related to images 6982, 6983, and 6984.

Yeast cells entering mitosis, also known as cell division. The green and magenta dots are two proteins that play important roles in mitosis. They show where the cells will split. This image was captured using wide-field microscopy with deconvolution.

Related to images 6792, 6793, 6794, 6797, 6798, and videos 6795 and 6796.

The parasitic worm that causes schistosomiasis hatches in water and grows up in a freshwater snail, as shown here. Once mature, the worm swims back into the water, where it can infect people through skin contact. Initially, an infected person might have a rash, itchy skin, or flu-like symptoms, but the real damage is done over time to internal organs.

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

Blood vessels at the back of the eye (retina) are used to diagnose glaucoma and diabetic eye disease. They also display characteristic changes in people with high blood pressure. In the image, the vessels appear green. It's not actually the vessels that are stained green, but rather filaments of a protein called actin that wraps around the vessels. Most of the red blood cells were replaced by fluid as the tissue was prepared for the microscope. The tiny red dots are red blood cells that remain in the vessels. The image was captured using confocal and 2-photon excitation microscopy for a project related to neurofibromatosis.

Model of the mandelate racemase enzyme from Bacillus subtilis, a bacterium commonly found in soil.

Fruit flies are a common model organism for basic medical research.

A microtubule, part of the cell's skeleton, builds and deconstructs.

A crystal of porcine trypsin protein created for X-ray crystallography, which can reveal detailed, three-dimensional protein structures.

Those of us who get sneezy and itchy-eyed every spring or fall may have pollen grains, like those shown here, to blame. Pollen grains are the male germ cells of plants, released to fertilize the corresponding female plant parts. When they are instead inhaled into human nasal passages, they can trigger allergies.

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

Proteins are 3D structures made up of smaller units. DNA is transcribed to RNA, which in turn is translated into amino acids. Amino acids form a protein strand, which has sections of corkscrew-like coils, called alpha helices, and other sections that fold flat, called beta sheets. The protein then goes through complex folding to produce the 3D structure.

This delicate, birdlike projection is an immature seed of the Arabidopsis plant. The part in blue shows the cell that gives rise to the endosperm, the tissue that nourishes the embryo. The cell is expressing only the maternal copy of a gene called MEDEA. This phenomenon, in which the activity of a gene can depend on the parent that contributed it, is called genetic imprinting. In Arabidopsis, the maternal copy of MEDEA makes a protein that keeps the paternal copy silent and reduces the size of the endosperm. In flowering plants and mammals, this sort of genetic imprinting is thought to be a way for the mother to protect herself by limiting the resources she gives to any one embryo. Featured in the May 16, 2006, issue of Biomedical Beat.

Meiosis is used to make sperm and egg cells. During meiosis, a cell's chromosomes are copied once, but the cell divides twice. During mitosis, the chromosomes are copied once, and the cell divides once. For simplicity, cells are illustrated with only three pairs of chromosomes.

See image 1333 for an unlabeled version of this illustration.

Endocytosis is the process by which cells are able to take up membrane and extracellular materials through the formation of a small intracellular bubble, called a vesicle. This process, called membrane budding, is generally by a coating of proteins. This protein coat helps both to deform the membrane and to concentrate specific proteins inside the newly forming vesicle. Clathrin is a coat protein that functions in receptor-mediated endocytosis events at the plasma membrane. This animation shows the process of clathrin-mediated endocytosis. An iron-transport protein called transferrin (blue) is bound to its receptor (purple) on the exterior cell membrane.  Inside the cell, a clathrin cage (shown in white/beige) assembles through interactions with membrane-bound adaptor proteins (green), causing the cell membrane to begin bending. The adaptor proteins also bind to receptors for transferrin, capturing them in the growing vesicle. Molecules of a protein called dynamin (purple) are then recruited to the neck of the vesicle and are involved in separating the membranes of the cell and the vesicle. Soon after the vesicle has budded off the membrane, the clathrin cage is disassembled. This disassembly is mediated by another protein called HSC70 (yellow), and its cofactor protein auxilin (orange).

Cells function within organs and tissues, such as the lungs, heart, intestines, and kidney.

Speckle microscopy analysis of actin cytoskeleton force. This is an example of NIH-supported research on single-cell analysis. Images in related series; Related to 2799, 2800, 2801, 2802 and 2803.

X-ray structure of a DNA repair enzyme superfamily representative from the human gastrointestinal bacterium Enterococcus faecalis. European scientists used this structure to generate homologous structures. Featured as the May 2007 Protein Structure Initiative Structure of the Month.