A light microscope image shows the chromosomes, stained dark blue, in a dividing cell 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.

The illustration shows the capsid of human immunodeficiency virus (HIV) whose molecular features were resolved with cryo-electron microscopy (cryo-EM). On the left, the HIV capsid is "naked," a state in which it would be easily detected by and removed from cells. However, as shown on the right, when the viral capsid binds to and is covered with a host protein, called cyclophilin A (shown in red), it evades detection and enters and invades the human cell to use it to establish an infection. To learn more about how cyclophilin A helps HIV infect cells and how scientists used cryo-EM to find out the mechanism by which the HIV capsid attaches to cyclophilin A, see this news release by the University of Illinois. A study reporting these findings was published in the journal Nature Communications.

Ecteinascidin 743 (ET-743, brand name Yondelis), was discovered and isolated from a sea squirt, Ecteinascidia turbinata, by NIGMS grantee Kenneth Rinehart at the University of Illinois. It was synthesized by NIGMS grantees E.J. Corey and later by Samuel Danishefsky. Multiple versions of this structure are available as entries 2790-2797.

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

A section of mouse colon with gut bacteria (center, in green) residing within a protective pocket. Understanding how microorganisms colonize the gut could help devise ways to correct for abnormal changes in bacterial communities that are associated with disorders like inflammatory bowel disease.

Using an electrode, researchers apply an electrical pulse onto a piece of muscle tissue affected by Huntington's disease.

This time-lapse movie shows that bacterial communities called biofilms can create blockages that prevent fluid flow in devices such as stents and catheters over a period of about 56 hours. This video was featured in a news release from Princeton University.

Histone proteins loop together with double-stranded DNA to form a structure that resembles beads on a string. See image 2561 for a labeled version of this illustration. Featured in The New Genetics.

The small intestine is where most of our nutrients from the food we eat are absorbed into the bloodstream. The walls of the intestine contain small finger-like projections called villi which increase the organ's surface area, enhancing nutrient absorption. It consists of the duodenum, which connects to the stomach, the jejenum and the ileum, which connects with the large intestine. Related to image 3389.

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

Lysosomes (yellow) and detyrosinated microtubules (light blue). Lysosomes are bubblelike organelles that take in molecules and use enzymes to break them down. Microtubules are strong, hollow fibers that provide structural support to cells. The researchers who took this image found that in epithelial cells, detyrosinated microtubules are a small subset of fibers, and they concentrate lysosomes around themselves. This image was captured using Stochastic Optical Reconstruction Microscopy (STORM).

Related to images 6890, 6891, and 6892.

Human cells with the gene that codes for the protein FIT2 deleted. After an experimental intervention, they are expressing a nonfunctional version of FIT2, shown in green. The lack of functional FIT2 affected the structure of the endoplasmic reticulum (ER), and the nonfunctional protein clustered in ER membrane aggregates, seen as large bright-green spots. Lipid droplets are shown in red, and the nucleus is visible in gray. This image was captured using a confocal microscope. Related to image 6773.

Dynein (green) is a motor protein that “walks” along microtubules (red, part of the cytoskeleton) and carries its cargo along with it. This video was captured through fluorescence microscopy.

Three views of the entire nuclear lamina of a HeLa cell produced by tilted light sheet 3D single-molecule super-resolution imaging using a platform termed TILT3D.
See 6572 for a 3D view of this structure.

A computer model of the cell membrane, where the plasma membrane is red, endoplasmic reticulum is yellow, and mitochondria are blue. This image relates to a July 27, 2009 article in Computing Life.

These microscopic roundworms, called Caenorhabditis elegans, lack eyes and the opsin proteins used by visual systems to detect colors. However, researchers found that the worms can still sense the color of light in a way that enables them to avoid pigmented toxins made by bacteria. This image was captured using a stereo microscope.

The goal of the Protein Structure Initiative (PSI) is to determine the three-dimensional shapes of a wide range of proteins by solving the structures of representative members of each protein family found in nature. The collection of structures should serve as a valuable resource for biomedical research scientists.

Stereo triplet of a sea urchin embryo stained to reveal actin filaments (orange) and microtubules (blue). This image is part of a series of images: 1047, 1048, 1049, 1050 and 1052.

DNA (blue) and actin (red) in cultured fibroblast cells.

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.

The center cluster of cells, colored blue, shows a colony of human embryonic stem cells. These cells, which arise at the earliest stages of development, are capable of differentiating into any of the 220 types of cells in the human body and can provide access to cells for basic research and potential therapies. This image is from the lab of the University of Wisconsin-Madison's James Thomson.

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 lined up.

Related to images 1010, 1011, 1012, 1013, 1014, 1015, 1016, 1017, 1018, and 1019.

A mouse liver glows after being tagged with specially designed infrared-fluorescent protein (IFP). Since its discovery in 1962, green fluorescent protein (GFP) has become an invaluable resource in biomedical imaging. But because of its short wavelength, the light that makes GFP glow doesn't penetrate far in whole animals. So University of California, San Diego cell biologist Roger Tsien--who shared the 2008 Nobel Prize in chemistry for groundbreaking work with GFP--made infrared-fluorescent proteins (IFPs) that shine under longer-wavelength light, allowing whole-body imaging in small animals.

The receptor is shown bound to a small molecule peptide called CVX15.

Borrelia burgdorferi is a spirochete, a class of long, slender bacteria that typically take on a coiled shape. Infection with this bacterium causes Lyme disease.

Using techniques that took 4 years to design, a team of developmental biologists showed that certain proteins can direct the subdivision of fruit fly and chicken nervous system tissue into the regions depicted here in blue, green, and red. Molecules called bone morphogenetic proteins (BMPs) helped form this fruit fly embryo. While scientists knew that BMPs play a major role earlier in embryonic development, they didn't know how the proteins help organize nervous tissue. The findings suggest that BMPs are part of an evolutionarily conserved mechanism for organizing the nervous system. The National Institute of Neurological Disorders and Stroke also supported this work.

Kinases are enzymes that add phosphate groups (red-yellow structures) to proteins (green), assigning the proteins a code. In this reaction, an intermediate molecule called ATP (adenosine triphosphate) donates a phosphate group from itself, becoming ADP (adenosine diphosphate). See image 2534 for an unlabeled version of this illustration. Featured in Medicines By Design.

The plasma membrane is a cell's protective barrier. See image 2524 for a labeled version of this illustration. Featured in The Chemistry of Health.

In the absence of the engulfment receptor Draper, salivary gland cells (light blue) persist in the thorax of a developing Drosophila melanogaster pupa. See image 2758 for a cross section of a normal pupa that does express Draper.

A light microscope image of cells 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 separated into the opposite sides of a dividing cell.

Related to images 1010, 1012, 1013, 1014, 1015, 1016, 1017, 1018, 1019, and 1021.

Electron density maps such as this one are generated from the diffraction patterns of X-rays passing through protein crystals. These maps are then used to generate a model of the protein's structure by fitting the protein's amino acid sequence (yellow) into the observed electron density (blue).

Xenopus laevis, the African clawed frog, has long been used as a model organism for studying embryonic development. The frog embryo on the left lacks the developmental factor Sizzled. A normal embryo is shown on the right.

Genes are often interrupted by stretches of DNA (introns, blue) that do not contain instructions for making a protein. The DNA segments that do contain protein-making instructions are known as exons (green). See image 2551 for a labeled version of this illustration. Featured in The New Genetics.

The human skin cells pictured contain genetic modifications that make them pluripotent, essentially equivalent to embryonic stem cells. A scientific team from the University of Wisconsin-Madison including researchers Junying Yu, James Thomson, and their colleagues produced the transformation by introducing a set of four genes into human fibroblasts, skin cells that are easy to obtain and grow in culture.

This illustration represents the early life of a protein—specifically, apomyoglobin—as it is synthesized by a ribosome and emerges from the ribosomal tunnel, which contains the newly formed protein's conformation. The synthesis occurs in the complex swirl of the cell medium, filled with interactions among many molecules. Researchers in Silvia Cavagnero's laboratory are studying the structure and dynamics of newly made proteins and polypeptides using spectroscopic and biochemical techniques.

A macrophage—a type of immune cell that engulfs invaders—“eats” and is activated by a “two-faced” Janus particle. The particle is called “two-faced” because each of its two hemispheres is coated with a different type of molecule, shown here in red and cyan. During macrophage activation, a transcription factor tagged with a green fluorescence protein (NF-κB) gradually moves from the cell’s cytoplasm into its nucleus and causes DNA transcription. The distribution of molecules on “two-faced” Janus particles can be altered to control the activation of immune cells. Details on this “geometric manipulation” strategy can be found in the Proceedings of the National Academy of Sciences paper "Geometrical reorganization of Dectin-1 and TLR2 on single phagosomes alters their synergistic immune signaling" by Li et al. and the Scientific Reports paper "Spatial organization of FcγR and TLR2/1 on phagosome membranes differentially regulates their synergistic and inhibitory receptor crosstalk" by Li et al. This video was captured using epi-fluorescence microscopy.

Related to video 6800.

Cell-like compartments spontaneously emerge from scrambled frog eggs, with nuclei (blue) from frog sperm. Endoplasmic reticulum (red) and microtubules (green) are also visible. Regions without nuclei formed smaller compartments. 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, 6589, and 6590.

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.

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

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

T cells are white blood cells that are important in defending the body against bacteria, viruses and other pathogens. Each T cell carries proteins, called T-cell receptors, on its surface that are activated when they come in contact with an invader. This activation sets in motion a cascade of biochemical changes inside the T cell to mount a defense against the invasion. Scientists have been interested for some time what happens after a T-cell receptor is activated. One obstacle has been to study how this signaling cascade, or pathway, proceeds inside T cells.

In this image, researchers have created a T-cell receptor pathway consisting of 12 proteins outside the cell on an artificial membrane. The image shows two key steps during the signaling process: clustering of a protein called linker for activation of T cells (LAT) (blue) and polymerization of the cytoskeleton protein actin (red). The findings show that the T-cell receptor signaling proteins self-organize into separate physical and biochemical compartments. This new system of studying molecular pathways outside the cells will enable scientists to better understand how the immune system combats microbes or other agents that cause infection.

To learn more how researchers assembled this T-cell receptor pathway, see this press release from HHMI's Marine Biological Laboratory Whitman Center. Related to video 3786.

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.

A rendering of an activity biosensor image overlaid with a cell-centered frame of reference used for image analysis of signal transduction. This is an example of NIH-supported research on single-cell analysis. Related to 2798 , 2799, 2800, 2801 and 2803.

Ribbon diagram showing the structure of Ribonuclease P with tRNA.

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.

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) and DAPI to visualize the nucleus (blue). In the absence of functional Arp2/3 complex, ARPC3-/- fibroblast cells' leading edge morphology is significantly altered with filopodia-like structures. Related to images 3328, 3329, 3330, 3331, and 3332.

This image of the hippocampus was taken with an ultra-widefield high-speed multiphoton laser microscope. Tissue was stained to reveal the organization of glial cells (cyan), neurofilaments (green) and DNA (yellow). The microscope Deerinck used was developed in conjunction with Roger Tsien (2008 Nobel laureate in Chemistry) and remains a powerful and unique tool today.

Catalases are some of the most efficient enzymes found in cells. Each catalase molecule can decompose millions of hydrogen peroxide molecules every second—working as an antioxidant to protect cells from the dangerous form of reactive oxygen. Different cells build different types of catalases. The human catalase that protects our red blood cells, shown on the left from PDB entry 1QQW, is composed of four identical subunits and uses a heme/iron group to perform the reaction. Many bacteria scavenge hydrogen peroxide with a larger catalase, shown in the center from PDB entry 1IPH, that uses a similar arrangement of iron and heme. Other bacteria protect themselves with an entirely different catalase that uses manganese ions instead of heme, as shown at the right from PDB entry 1JKU.

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. This image shows neural crest cell-derived, migrating pigment cells in a salamander. 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. Related to images 5754, 5755, 5756 and 5757.

Trajectories of single molecule labeled cell surface receptors. This is an example of NIH-supported research on single-cell analysis. Related to 2798 , 2799, 2800, 2802 and 2803.