Hippocampal cells in culture with a neuron in green, showing hundreds of the small protrusions known as dendritic spines. The dendrites of other neurons are labeled in blue, and adjacent glial cells are shown in red.

Structure of the bacterial antitoxin protein GhoS. GhoS inhibits the production of a bacterial toxin, GhoT, which can contribute to antibiotic resistance. GhoS is the first known bacterial antitoxin that works by cleaving the messenger RNA that carries the instructions for making the toxin. More information can be found in the paper: Wang X, Lord DM, Cheng HY, Osbourne DO, Hong SH, Sanchez-Torres V, Quiroga C, Zheng K, Herrmann T, Peti W, Benedik MJ, Page R, Wood TK. A new type V toxin-antitoxin system where mRNA for toxin GhoT is cleaved by antitoxin GhoS. Nat Chem Biol. 2012 Oct;8(10):855-61. Related to 3428.

2.5Å resolution reconstruction of rabbit muscle aldolase collected on a FEI/Thermo Fisher Titan Krios with energy filter and image corrector.

A zebrafish embryo showing its natural colors. Zebrafish have see-through eggs and embryos, making them ideal research organisms for studying the earliest stages of development. This image was taken in transmitted light under a polychromatic polarizing microscope.

Elastin is a fibrous protein in the extracellular matrix (ECM). It is abundant in artery walls like the one shown here. As its name indicates, elastin confers elasticity. Elastin fibers are at least five times stretchier than rubber bands of the same size. Tissues that expand, such as blood vessels and lungs, need to be both strong and elastic, so they contain both collagen (another ECM protein) and elastin. In this photo, the elastin-rich ECM is colored grayish brown and is most visible at the bottom of the photo. The curved red structures near the top of the image are red blood cells.

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.

Various views of a mouse brain that was genetically modified so that subpopulations of its neurons glow. Researchers often study mice because they share many genes with people and can shed light on biological processes, development, and diseases in humans.

This video was captured using a light sheet microscope.

Related to images 6929 and 6930.

The receptor is shown bound to an antagonist, JDTic.

Cell-like compartments that spontaneously emerged from scrambled frog eggs, with nuclei (blue) from frog sperm. Endoplasmic reticulum (red) and microtubules (green) are also visible. Image created using confocal microscopy.

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

For videos of cell-like compartments from frog eggs view: 6587, 6588, 6589, and 6590.

Atomic model of the membrane region of the mitochondrial ATP synthase built into a cryo-EM map at 3.6 Å resolution. ATP synthase is the primary producer of ATP in aerobic cells. Drugs that inhibit the bacterial ATP synthase, but not the human mitochondrial enzyme, can serve as antibiotics. This therapeutic approach was successfully demonstrated with the bedaquiline, an ATP synthase inhibitor now used in the treatment of extensively drug resistant tuberculosis.

More information about this structure can be found in the Science paper ”Atomic model for the dimeric F0 region of mitochondrial ATP synthase” by Guo et. al.

Cell-like compartments that spontaneously emerged from scrambled frog eggs, with nuclei (blue) from frog sperm. Endoplasmic reticulum (red) and microtubules (green) are also visible. Image created using confocal microscopy.

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

For videos of cell-like compartments from frog eggs view: 6587, 6588, 6589, and 6590.

From PDB entry 3c6k, Crystal structure of human spermine synthase in complex with spermidine and 5-methylthioadenosine.

Developing spermatids (precursors of mature sperm cells) begin as small, round cells and mature into long-tailed, tadpole-shaped ones. In the sperm cell's head is the cell nucleus; in its tail is the power to outswim thousands of competitors to fertilize an egg. As seen in this microscopy image, fruit fly spermatids start out as groups of interconnected cells. A small lipid molecule called PIP2 helps spermatids tell their heads from their tails. Here, PIP2 (red) marks the nuclei and a cell skeleton-building protein called tubulin (green) marks the tails. When PIP2 levels are too low, some spermatids get mixed up and grow with their heads at the wrong end. Because sperm development is similar across species, studies in fruit flies could help researchers understand male infertility in humans.

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

A cell nucleus (blue) surrounded by lipid droplets (yellow). Exogenously expressed, S-tagged UBXD8 (green) recruits endogenous p97/VCP (red) to the surface of lipid droplets in oleate-treated HeLa cells. Nucleus stained with DAPI.

In 2007, the FDA modified warfarin's label to indicate that genetic makeup may affect patient response to the drug. The widely used blood thinner is sold under the brand name Coumadin®. Scientists involved in the NIH Pharmacogenetics Research Network are investigating whether genetic information can be used to improve optimal dosage prediction for patients.

Bacillus anthracis (anthrax) cells being killed by a fluorescent trans-translation inhibitor, which disrupts bacterial protein synthesis. The inhibitor is naturally fluorescent and looks blue when it is excited by ultraviolet light in the microscope. This is a black-and-white version of Image 3525.

Model of the enzyme aminopeptidase N from the human pathogen Neisseria meningitidis, which can cause meningitis epidemics. The structure provides insight on the active site of this important molecule.

Disassembly of vasculature in kdr:GFP frogs following addition of 250 µM TBZ. Related to images 3404 and 3505.

A computer model shows how the endoplasmic reticulum is close to and almost wraps around mitochondria in the cell. The endoplasmic reticulum is lime green and the mitochondria are yellow. This image relates to a July 27, 2009 article in Computing Life.

In the top snapshots, the brain of a sleep-deprived fruit fly glows orange, marking high concentrations of a synaptic protein called Bruchpilot (BRP) involved in communication between neurons. The color particularly lights up brain areas associated with learning. By contrast, the bottom images from a well-rested fly show lower levels of the protein. These pictures illustrate the results of an April 2009 study showing that sleep reduces the protein's levels, suggesting that such "downscaling" resets the brain to normal levels of synaptic activity and makes it ready to learn after a restful night.

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.

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.

A protein called kinesin (blue) is in charge of moving cargo around inside cells and helping them divide. It's powered by biological fuel called ATP (bright yellow) as it scoots along tube-like cellular tracks called microtubules (gray).

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.

The new highly efficient parallelized DelPhi software was used to calculate the potential map distribution of an entire virus, the adeno-associated virus, which is made up of more than 484,000 atoms. Despite the relatively large dimension of this biological system, resulting in 815x815x815 mesh points, the parallelized DelPhi, utilizing 100 CPUs, completed the calculations within less than three minutes. Related to image 3374.

Bean-shaped mitochondria are cells' power plants. These organelles have their own DNA and replicate independently. The highly folded inner membranes are the site of energy generation.

This video condenses 6.5 minutes into less than a minute to show how the toxin in bee venom, called melittin, destroys an animal or bacterial cell. What looks like a red balloon is an artificial cell filled with red dye. Melittin molecules are colored green and float on the cell's surface like twigs on a pond. As melittin accumulates on the cell's membrane, the membrane expands to accommodate it. In the video, the membrane stretches into a column on the left. When melittin levels reach a critical threshold, countless pinhole leaks burst open in the membrane. The cell's vital fluids (red dye in the video) leak out through these pores. Within minutes, the cell collapses.

Crystal structure of the beta2-adrenergic receptor protein. This is the first known structure of a human G protein-coupled receptor, a large family of proteins that control critical bodily functions and the action of about half of today's pharmaceuticals. Featured as one of the November 2007 Protein Structure Initiative Structures of the Month.

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.

These smooth muscle cells were derived from human embryonic stem cells. The nuclei are stained blue, and the proteins of the cytoskeleton are stained green. Image and caption information courtesy of the California Institute for Regenerative Medicine.

This lab space was designed for work on the induced pluripotent stem (iPS) cell collection, part of the NIGMS Human Genetic Cell Repository at the Coriell Institute for Medical Research.

In the gene-editing tool CRISPR, a small strand of RNA identifies a specific chunk of DNA. Then the enzyme Cas9 (green) swoops in and cuts the double-stranded DNA (blue/purple) in two places, removing the specific chunk.

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.

Sugars light up the cells in this jaw of a 3-day-old zebrafish embryo and highlight a scientific first: labeling and tracking the movements of sugar chains called glycans in a living organism. Here, recently produced glycans (red) are on the cell surface while those made earlier in development (green) have migrated into the cells. In some areas, old and new glycans mingle (yellow). A better understanding of such traffic patterns could shed light on how organisms develop and may uncover markers for disease, such as cancer. Featured in the May 21, 2008 of Biomedical Beat.

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.

Inside the fertilized egg cell of a fruit fly, we see a type of myosin (related to the protein that helps muscles contract) made to glow by attaching a fluorescent protein. After fertilization, the myosin proteins are distributed relatively evenly near the surface of the embryo. The proteins temporarily vanish each time the cells' nuclei--initially buried deep in the cytoplasm--divide. When the multiplying nuclei move to the surface, they shift the myosin, producing darkened holes. The glowing myosin proteins then gather, contract, and start separating the nuclei into their own compartments.

When the heat shock protein hsp33 is folded, it is inactive and contains a zinc ion, stabilizing the redox sensitive domain (orange). In the presence of an environmental stressor, the protein releases the zinc ion, which leads to the unfolding of the redox domain. This unfolding causes the chaperone to activate by reaching out its "arm" (green) to protect other proteins.

Like a world of its own, this sphere represents all the known chemical reactions in the E. coli bacterium. The colorful circles on the surface symbolize sets of densely interconnected reactions. The lines between the circles show additional connecting reactions. The shapes inside the circles are landmark molecules, like capital cities on a map, that either act as hubs for many groups of reactions, are highly conserved among species, or both. Molecules that connect far-flung reactions on the sphere are much more conserved during evolution than molecules that connect reactions within a single circle. This statistical cartography could reveal insights about other complex systems, such as protein interactions and gene regulation networks.

RNA polymerase (purple) is a complex enzyme at the heart of transcription. During this process, the enzyme unwinds the DNA double helix and uses one strand (darker orange) as a template to create the single-stranded messenger RNA (green), later used by ribosomes for protein synthesis.

From the RNA polymerase II elongation complex of Saccharomyces cerevisiae (PDB entry 1I6H) as seen in PDB-101's What is a Protein? video.

Haplotypes are combinations of gene variants that are likely to be inherited together within the same chromosomal region. In this example, an original haplotype (top) evolved over time to create three newer haplotypes that each differ by a few nucleotides (red). See image 2566 for an unlabeled version of this illustration. Featured in The New Genetics.

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

Gene transcription is a process by which the genetic information encoded in DNA is transcribed into RNA. It's essential for all life and requires the activity of proteins, called transcription factors, that detect where in a DNA strand transcription should start. In eukaryotes (i.e., those that have a nucleus and mitochondria), a protein complex comprising 14 different proteins is responsible for sniffing out transcription start sites and starting the process. This complex, called TFIID, represents the core machinery to which an enzyme, named RNA polymerase, can bind to and read the DNA and transcribe it to RNA. Scientists have used cryo-electron microscopy (cryo-EM) to visualize the TFIID-RNA polymerase-DNA complex in unprecedented detail. In this illustration, TFIID (blue) contacts the DNA and recruits the RNA polymerase (gray) for gene transcription. The start of the transcribed gene is shown with a flash of light. To learn more about the research that has shed new light on gene transcription, see this news release from Berkeley Lab. Related to video 5730.

Planarians are freshwater flatworms that have powerful abilities to regenerate their bodies, which would seem to make them natural model organisms in which to study stem cells. But until recently, scientists had not been able to efficiently find the genes that regulate the planarian stem cell system. In this image, a single stem cell has given rise to a colony of stem cells in a planarian. Proliferating cells are red, and differentiating cells are blue. Quantitatively measuring the size and ratios of these two cell types provides a powerful framework for studying the roles of stem cell regulatory genes in planarians.

Superconducting magnet for NMR research, from the February 2003 profile of Dorothee Kern in Findings.

Mitochondria are the powerhouses of the cells, generating the energy the cells need to do their tasks and to stay alive. Researchers have studied mitochondria for some time because when these cell organelles don't work as well as they should, several diseases develop. In this photograph of cow cells taken with a microscope, the mitochondria were stained in bright yellow to visualize them in the cell. The large blue dots are the cell nuclei and the gray web is the cytoskeleton of the cells.

This image results from a research project to visualize which regions of the adult fruit fly (Drosophila) brain derive from each neural stem cell. First, researchers collected several thousand fruit fly larvae and fluorescently stained a random stem cell in the brain of each. The idea was to create a population of larvae in which each of the 100 or so neural stem cells was labeled at least once. When the larvae grew to adults, the researchers examined the flies’ brains using confocal microscopy. With this technique, the part of a fly’s brain that derived from a single, labeled stem cell “lights up. The scientists photographed each brain and digitally colorized its lit-up area. By combining thousands of such photos, they created a three-dimensional, color-coded map that shows which part of the Drosophila brain comes from each of its ~100 neural stem cells. In other words, each colored region shows which neurons are the progeny or “clones” of a single stem cell. This work established a hierarchical structure as well as nomenclature for the neurons in the Drosophila brain. Further research will relate functions to structures of the brain.

Related to image 5868 and video 5843

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.

CCD-1 is an enzyme produced by the bacterium Clostridioides difficile that helps it resist antibiotics. Using X-ray crystallography, researchers determined the structure of a CCD-1 molecule and a molecule of the antibiotic cefotaxime bound together. The structure revealed that CCD-1 provides extensive hydrogen bonding and stabilization of the antibiotic in the active site, leading to efficient degradation of the antibiotic.

Related to images 6764, 6765, and 6767.

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.