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.

Animation for the cisternae maturation model of Golgi transport.

Two highly stressed osteosarcoma cells are shown with a set of green droplet-like structures followed by a second set of magenta droplets. These droplets are composed of fluorescently labeled stress-response proteins, either G3BP or UBQLN2 (Ubiquilin-2). Each protein is undergoing a fascinating process, called phase separation, in which a non-membrane bound compartment of the cytoplasm emerges with a distinct environment from the surrounding cytoplasm. Subsequently, the proteins fuse with like proteins to form larger droplets, in much the same way that raindrops merge on a car’s windshield.

To better understand cell movements in developing embryos, researchers isolated cells from early zebrafish embryos and grew them as clusters. Provided with the right signals, the clusters replicated some cell movements seen in intact embryos. Each line in this image depicts the movement of a single cell. The image was created using time-lapse confocal microscopy. Related to video 6776.

CCD-1 is an enzyme produced by the bacterium Clostridioides difficile that helps it resist antibiotics. Here, researchers crystallized bound pairs of CCD-1 molecules and molecules of the antibiotic cefotaxime. This enabled their structure to be studied using X-ray crystallography.

Related to images 6765, 6766, and 6767.

Model of an enzyme, PanB, from Mycobacterium tuberculosis, the bacterium that causes most cases of tuberculosis. This enzyme is an attractive drug target.

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 red) have invaded the worm’s gut cells (the large blue dots are the cells' nuclei) 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 5777 and 5778.

This image captures the spiral-shaped ovary of an anglerfish in cross-section. Once matured, these eggs will be released in a gelatinous, floating mass. For some species of anglerfish, this egg mass can be up to 3 feet long and include nearly 200,000 eggs.

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

Cell-like compartments spontaneously emerge from scrambled frog eggs. Endoplasmic reticulum (red) and microtubules (green) are visible. Video created using epifluorescence microscopy.

For more photos of cell-like compartments from frog eggs view: 6584, 6585, 6586, 6591, 6592, and 6593.

For videos of cell-like compartments from frog eggs view: 6587, 6588, and 6590.

Yeast cells with nuclei shown in green and contractile rings shown in magenta. Nuclei store DNA, and contractile rings help cells divide. This image was captured using wide-field microscopy with deconvolution.

Related to images 6791, 6793, 6794, 6797, 6798, and videos 6795 and 6796.

Composite image of beta-galactosidase showing how cryo-EM’s resolution has improved dramatically in recent years. Older images to the left, more recent to the right. Related to image 5882. NIH Director Francis Collins featured this on his blog on January 14, 2016.

Trypanosoma brucei is a single-cell parasite that causes sleeping sickness in humans. Scientists have been studying trypanosomes for some time because of their negative effects on human and also animal health, especially in sub-Saharan Africa. Moreover, because these organisms evolved on a separate path from those of animals and plants more than a billion years ago, researchers study trypanosomes to find out what traits they may harbor that are common to or different from those of other eukaryotes (i.e., those organisms having a nucleus and mitochondria). This image shows the T. brucei cell membrane in red, the DNA in the nucleus and kinetoplast (a structure unique to protozoans, including trypanosomes, which contains mitochondrial DNA) in blue and nuclear pore complexes (which allow molecules to pass into or out of the nucleus) in green. Scientists have found that the trypanosome nuclear pore complex has a unique mechanism by which it attaches to the nuclear envelope. In addition, the trypanosome nuclear pore complex differs from those of other eukaryotes because its components have a near-complete symmetry, and it lacks almost all of the proteins that in other eukaryotes studied so far are required to assemble the pore.

Researchers use cluster analysis to study protein shape and function. Each green circle represents one potential shape of the protein mitoNEET. The longer the blue line between two circles, the greater the differences between the shapes. Most shapes are similar; they fall into three clusters that are represented by the three images of the protein. From a Rice University news release. Graduate student Elizabeth Baxter and Patricia Jennings, professor of chemistry and biochemistry at UCSD, collaborated with José Onuchic, a physicist at Rice University, on this work.

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.

The arrangement of identical molecular components can make a dramatic difference. For example, carbon atoms can be arranged into dull graphite (left) or sparkly diamonds (right). See image 2506 for an illustration without examples.

The structure of the endothelium, the thin layer of cells that line our arteries and veins, is visible here. The endothelium is like a gatekeeper, controlling the movement of materials into and out of the bloodstream. Endothelial cells are held tightly together by specialized proteins that function like strong ropes (red) and others that act like cement (blue).

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

Ionic and covalent bonds hold molecules, like sodium chloride and chlorine gas, together. Hydrogen bonds among molecules, notably involving water, also play an important role in biology. See image 2520 for a labeled version of this illustration. Featured in The Chemistry of Health.

An RNA molecule dynamically refolds itself as it is being synthesized. When the RNA is short, it ties itself into a “knot” (dark purple). For this domain to slip its knot, about 5 seconds into the video, another newly forming region (fuchsia) wiggles down to gain a “toehold.” About 9 seconds in, the temporarily knotted domain untangles and unwinds. Finally, at about 23 seconds, the strand starts to be reconfigured into the shape it needs to do its job in the cell.

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.

Muscles stretch and contract when we walk, and skin splits open and knits back together when we get a paper cut. To study these contractile forces, researchers built a three-dimensional scaffold that mimics tissue in an organism. Researchers poured a mixture of cells and elastic collagen over microscopic posts in a dish. Then they studied how the cells pulled and released the posts as they formed a web of tissue. To measure forces between posts, the researchers developed a computer model. Their findings--which show that contractile forces vary throughout the tissue--could have a wide range of medical applications.

This image represents the structure of TrpRS, a novel member of the tryptophanyl tRNA-synthetase family of enzymes. By helping to link the amino acid tryptophan to a tRNA molecule, TrpRS primes the amino acid for use in protein synthesis. A cluster of iron and sulfur atoms (orange and red spheres) was unexpectedly found in the anti-codon domain, a key part of the molecule, and appears to be critical for the function of the enzyme. TrpRS was discovered in Thermotoga maritima, a rod-shaped bacterium that flourishes in high temperatures.

Misfolded proteins (green) within mitochondria (red). Related to video 5877.

X-ray co-crystal structure of Src kinase bound to a DNA-templated macrocycle inhibitor. Related to 3413, 3414, 3415, 3417, 3418, and 3419.

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).

Arranging exons in different patterns, called alternative splicing, enables cells to make different proteins from a single gene. See image 2553 for a labeled version of this illustration. Featured in The New Genetics.

During mitosis, spindle microtubules (red) attach to chromosome pairs (blue), directing them to the spindle equator. This midline alignment is critical for equal distribution of chromosomes in the dividing cell. Scientists are interested in how the protein kinase Plk1 (green) regulates this activity in human cells. 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. Related to image 5766.

The research that led to this image was funded by NIGMS.

Cdc42, a member of the Rho family of small guanosine triphosphatase (GTPase) proteins, regulates multiple cell functions, including motility, proliferation, apoptosis, and cell morphology. In order to fulfill these diverse roles, the timing and location of Cdc42 activation must be tightly controlled. Klaus Hahn and his research group use special dyes designed to report protein conformational changes and interactions, here in living neutrophil cells. Warmer colors in this image indicate higher levels of activation. Cdc42 looks to be activated at cell protrusions.

Related to images 2451, 2453, and 2454.

A model of a Geobacter sulfurreducens nanowire created from cryo-electron microscopy images. The bacterium conducts electricity through these nanowires, which are made up of protein and iron-containing molecules.

A 20-µm thick section of mouse midbrain. The nerve cells are transparent and weren’t stained. Instead, the color is generated by interaction of white polarized light with the molecules in the cells and indicates their orientation.

The image was obtained with a polychromatic polarizing microscope that shows the polychromatic birefringent image with hue corresponding to the slow axis orientation. More information about the microscopy that produced this image can be found in the Scientific Reports paper “Polychromatic Polarization Microscope: Bringing Colors to a Colorless World” by Shribak.

Mitosis creates cells, and apoptosis kills them. The processes often work together to keep us healthy.

Pigment cells are cells that give skin its color. In fishes and amphibians, like frogs and salamanders, pigment cells are responsible for the characteristic skin patterns that help these organisms to blend into their surroundings or attract mates. The pigment cells are derived from neural crest cells, which are cells originating from the neural tube in the early embryo. Investigating pigment cell formation and migration in animals helps answer important fundamental questions about the factors that control pigmentation in the skin of animals, including humans. This image shows a pigment cell from zebrafish at high resolution. Related to images 5755, 5756, 5757 and 5758.

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.

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.

This image shows how the CRISPR surveillance complex is disabled by two copies of anti-CRISPR protein AcrF1 (red) and one AcrF2 (light green). These anti-CRISPRs block access to the CRISPR RNA (green tube) preventing the surveillance complex from scanning and targeting invading viral DNA for destruction.

The world's smallest motor, ATP synthase, generates energy for the cell. See image 2518 for a labeled version of this illustration. Featured in The Chemistry of Health.

Salk researchers captured the structure of a protein complex called an intasome (center) that lets viruses similar to HIV establish permanent infection in their hosts. The intasome hijacks host genomic material, DNA (white) and histones (beige), and irreversibly inserts viral DNA (blue). The image was created by Jamie Simon and Dmitry Lyumkis. Work that led to the 3D map was published in: Ballandras-Colas A, Brown M, Cook NJ, Dewdney TG, Demeler B, Cherepanov P, Lyumkis D, & Engelman AN. (2016). Cryo-EM reveals a novel octameric integrase structure for ?-retroviral intasome function. Nature, 530(7590), 358—361

Two fruit fly (Drosophila melanogaster) egg cells, one on each side of the central black line. The colorful swirls show the circular movement of cytoplasm—called ooplasmic streaming—that occurs in late egg cell development in wild-type (right) and mutant (left) oocytes. This image was captured using confocal microscopy.

More information on the research that produced this image can be found in the Journal of Cell Biology paper “Ooplasmic flow cooperates with transport and anchorage in Drosophila oocyte posterior determination” by Lu et al.

Cells walk along body surfaces via tiny "feet," called focal adhesions, that connect with the extracellular matrix. See image 2502 for an unlabeled version of this illustration.

Each of the tiny colored specs in this image is a cell on the surface of a fish scale. To better understand how wounds heal, scientists have inserted genes that make cells brightly glow in different colors into the skin cells of zebrafish, a fish often used in laboratory research. The colors enable the researchers to track each individual cell, for example, as it moves to the location of a cut or scrape over the course of several days. These technicolor fish endowed with glowing skin cells dubbed "skinbow" provide important insight into how tissues recover and regenerate after an injury.

For more information on skinbow fish, see the Biomedical Beat blog post Visualizing Skin Regeneration in Real Time and a press release from Duke University highlighting this research. Related to image 3782.

In many animals, the egg cell develops alongside sister cells. These sister cells are called nurse cells in the fruit fly (Drosophila melanogaster), and their job is to “nurse” an immature egg cell, or oocyte. Toward the end of oocyte development, the nurse cells transfer all their contents into the oocyte in a process called nurse cell dumping. This video captures this transfer, showing significant shape changes on the part of the nurse cells (blue), which are powered by wavelike activity of the protein myosin (red). Researchers created the video using a confocal laser scanning microscope. Related to image 6753.

Microtubules (magenta) in neurons of the hippocampus, a part of the brain involved in learning and memory. Microtubules are strong, hollow fibers that provide structural support to cells. This image was captured using Stochastic Optical Reconstruction Microscopy (STORM).

Related to images 6889, 6891, and 6892.

This is a magnified view of an Arabidopsis thaliana leaf eight days after being infected with the pathogen Hyaloperonospora arabidopsidis, which is closely related to crop pathogens that cause 'downy mildew' diseases. It is also more distantly related to the agent that caused the Irish potato famine. The veins of the leaf are light blue; in darker blue are the pathogen's hyphae growing through the leaf. The small round blobs along the length of the hyphae are called haustoria; each is invading a single plant cell to suck nutrients from the cell. Jeff Dangl and other NIGMS-supported researchers investigate how this pathogen and other like it use virulence mechanisms to suppress host defense and help the pathogens grow.

Actin gliding powered by myosin 1D. Note the counterclockwise motion of the gliding actin filaments.

A number of environmental factors cause DNA mutations that can lead to cancer: toxins in cigarette smoke, sunlight and other radiation, and some viruses.

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.

Hydra magnipapillata is an invertebrate animal used as a model organism to study developmental questions, for example the formation of the body axis.

Microarrays, also called gene chips, are tools that let scientists track the activity of hundreds or thousands of genes simultaneously. For example, researchers can compare the activities of genes in healthy and diseased cells, allowing the scientists to pinpoint which genes and cell processes might be involved in the development of a disease.

On top, the brain of a sleep-deprived fly glows orange because of Bruchpilot, a communication protein between brain cells. These bright orange brain areas are associated with learning. On the bottom, a well-rested fly shows lower levels of Bruchpilot, which might make the fly ready to learn after a good night's rest.

These images model the molecular structures of three enzymes with critical roles in the life cycle of the human immunodeficiency virus (HIV). At the top, reverse transcriptase (orange) creates a DNA copy (yellow) of the virus's RNA genome (blue). In the middle image, integrase (magenta) inserts this DNA copy in the DNA genome (green) of the infected cell. At the bottom, much later in the viral life cycle, protease (turquoise) chops up a chain of HIV structural protein (purple) to generate the building blocks for making new viruses. See these enzymes in action on PDB 101’s video A Molecular View of HIV Therapy.

Cdc42, a member of the Rho family of small guanosine triphosphatase (GTPase) proteins, regulates multiple cell functions, including motility, proliferation, apoptosis, and cell morphology. In order to fulfill these diverse roles, the timing and location of Cdc42 activation must be tightly controlled. Klaus Hahn and his research group use special dyes designed to report protein conformational changes and interactions, here in living neutrophil cells. Warmer colors in this image indicate higher levels of activation. Cdc42 looks to be activated at cell protrusions.

Related to images 2452, 2453, and 2454.