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 2519 for an unlabeled version of this illustration. Featured in The Chemistry of Health.

An image of the area of the mouse brain that serves as the 'master clock,' which houses the brain's time-keeping neurons. The nuclei of the clock cells are shown in blue. A small molecule called VIP, shown in green, enables neurons in the central clock in the mammalian brain to synchronize.

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.

Staphylococcus aureus bacteria (blue) on the porous coating of a femoral hip stem used in hip replacement surgery. The relatively rough surface of an implant is a favorable environment for bacteria to attach and grow. This can lead to the development of biofilms, which can cause infections. The researchers who took this image are working to understand where biofilms are likely to develop. This knowledge could support the prevention and treatment of infections. A scanning electron microscope was used to capture this image.

More information on the research that produced this image can be found in the Antibiotics paper "Free-floating aggregate and single-cell-initiated biofilms of Staphylococcus aureus" by Gupta et al.

Related to image 6803 and video 6805.

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 team of chemists and physicists used nanotechnology and DNA's ability to self-assemble with matching RNA to create a new kind of chip for measuring gene activity. When RNA of a gene of interest binds to a DNA tile (gold squares), it creates a raised surface (white areas) that can be detected by a powerful microscope. This nanochip approach offers manufacturing and usage advantages over existing gene chips and is a key step toward detecting gene activity in a single cell. Featured in the February 20, 2008, issue of Biomedical Beat.

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.

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

A 3D model of the human endoplasmic reticulum membrane protein complex (EMC) that identifies its nine essential subunits. The EMC plays an important role in making membrane proteins, which are essential for all cellular processes. This is the first atomic-level depiction of the EMC. Its structure was obtained using single-particle cryo-electron microscopy.

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).

Three C. elegans, tiny roundworms, with a ribosomal protein glowing red and muscle fibers glowing green. Researchers used these worms to study a molecular pathway that affects aging. The ribosomal protein is involved in protein translation and may play a role in dietary restriction-induced longevity. Image created using confocal microscopy.
View single roundworm here 6581.
View closeup of roundworms here 6583.

This fruit fly expresses green fluorescent protein (GFP) in the same pattern as the period gene, a gene that regulates circadian rhythm and is expressed in all sensory neurons on the surface of the fly.

A computer-generated sketch of a DNA origami folded into a flower-and-bird structure. See also related image 3690.

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.

The nucleus contains the DNA of eukaryotic cells. The double membrane that bounds the nucleus flows into the rough endoplasmic reticulum, an organelle studded with ribosomes that manufacture membrane-bound proteins for the rest of the cell.

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.

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.

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

On the left, a cross-section slice of a rat pancreas cell captured using cryo-electron tomography (cryo-ET). On the right, a 3D, color-coded version of the image highlighting cell structures. Visible features include the folded sacs of the Golgi apparatus (copper), transport vesicles (medium-sized dark-blue circles), microtubules (neon green), ribosomes (small pale-yellow circles), and lysosomes (large yellowish-green circles). Black line (bottom right of the left image) represents 200 nm. This image is a still from video 6609.

Multicellular yeast called snowflake yeast that researchers created through many generations of directed evolution from unicellular yeast. Here, the researchers visualized nuclei in orange to help them study changes in how the yeast cells divided. Cell walls are shown in blue. This image was captured using spinning disk confocal microscopy.

Related to images 6969 and 6970.

DNA consists of two long, twisted chains made up of nucleotides. Each nucleotide contains one base, one phosphate molecule, and the sugar molecule deoxyribose. The bases in DNA nucleotides are adenine, thymine, cytosine, and guanine. See image 2541 for an unlabeled version of this illustration. Featured in The New Genetics.

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.

Jellyfish are especially good models for studying the evolution of embryonic tissue layers. Despite being primitive, jellyfish have a nervous system (stained green here) and musculature (red). Cell nuclei are stained blue. By studying how tissues are distributed in this simple organism, scientists can learn about the evolution of the shapes and features of diverse animals.

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

A mouse's fat cells (red) are shown surrounded by a network of blood vessels (green). Fat cells store and release energy, protect organs and nerve tissues, insulate us from the cold, and help us absorb important vitamins.

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

An atomic force microscopy image shows DNA folded into an intricate, computer-designed structure. Image is featured on Biomedical Beat blog post Cool Image: DNA Origami. See also related image 3689 .

Colonies of bacteria growing despite high concentrations of antibiotics. These colonies are visible both by eye, as seen on the left, and by bioluminescence imaging, as seen on the right. The bioluminescent color indicates the metabolic activity of these bacteria, with their red centers indicating high metabolism.

More information about the research that produced this image can be found in the Antimicrobial Agents and Chemotherapy paper “Novel aminoglycoside-tolerant phoenix colony variants of Pseudomonas aeruginosa” by Sindeldecker et al.

Circadian rhythms are physical, mental, and behavioral changes that follow a 24-hour cycle. Circadian rhythms are influenced by light and regulated by the brain’s suprachiasmatic nucleus (SCN), sometimes referred to as a master clock. Learn more in NIGMS’ circadian rhythms fact sheet. See 6614 for the Spanish version of this infographic.

Enzymes convert substrates into products very quickly. See image 2521 for an unlabeled version of this illustration. Featured in The Chemistry of Health.

Skins cells were reprogrammed into heart muscle cells. The cells highlighted in green are remaining skin cells. Red indicates a protein that is unique to heart muscle. The technique used to reprogram the skin cells into heart cells could one day be used to mend heart muscle damaged by disease or heart attack. Image and caption information courtesy of the California Institute for Regenerative Medicine.

If a picture is worth a thousand words, what's a movie worth? For researchers studying cell migration, a "documentary" of fruit fly cells (bright green) traversing an egg chamber could answer longstanding questions about cell movement. Historically, researchers have been unable to watch this cell migration unfold in living ovarian tissue in real time. But by developing a culture medium that allows fly eggs to survive outside their ovarian homes, scientists can observe the nuances of cell migration as it happens. Such details may shed light on how immune cells move to a wound and why cancer cells spread to other sites. See 3594 for still image.

The feeding tube, or pharynx, of a planarian worm with cilia shown in red and muscle fibers shown in green

Yeast make bread, beer, and wine. And like us, yeast can reproduce sexually. A mother and father cell fuse and create one large cell that contains four offspring. When environmental conditions are favorable, the offspring are released, as shown here. Yeast are also a popular study subject for scientists. Research on yeast has yielded vast knowledge about basic cellular and molecular biology as well as about myriad human diseases, including colon cancer and various metabolic disorders.

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

Cell mopping up.

NMR solution structure of a plant protein that may function in host defense. This protein was expressed in a convenient and efficient wheat germ cell-free system. Featured as the June 2007 Protein Structure Initiative Structure of the Month.

This pig cell is in the process of dividing. The chromosomes (purple) have already replicated and the duplicates are being pulled apart by fibers of the cell skeleton known as microtubules (green). Studies of cell division yield knowledge that is critical to advancing understanding of many human diseases, including cancer and birth defects.

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

This image of laboratory-grown cells was taken with the help of a scanning electron microscope, which yields detailed images of cell surfaces.

Two mouse fibroblasts, one of the most common types of cells in mammalian connective tissue. They play a key role in wound healing and tissue repair. This image was captured using structured illumination microscopy.

Video of high-resolution confocal images depicting vimentin immunofluorescence (green) and nuclei (blue) at the edge of a quail embryo yolk. These images were obtained as part of a study to understand cell migration in embryos. An NIGMS grant to Professor Garcia was used to purchase the confocal microscope that collected these images. Related to images 2807 and 2808.

Sketch of an egg cell.

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.

Microtubules (magenta) and tau protein (light blue) in a cell model of tauopathy. Researchers believe that tauopathy—the aggregation of tau protein—plays a role in Alzheimer’s disease and other neurodegenerative diseases. This image was captured using Stochastic Optical Reconstruction Microscopy (STORM).

Related to images 6889, 6890, and 6891.

Stained kidney tissue. The kidney is an essential organ responsible for disposing wastes from the body and for maintaining healthy ion levels in the blood. It also secretes two hormones, erythropoietin (EPO) and calcitriol (a derivative of vitamin D), into the blood. It works like a purifier by pulling break-down products of metabolism, such as urea and ammonium, from the blood stream for excretion in urine. Related to image 3725.

The atomic structure of the morphine biosynthetic enzyme salutaridine reductase bound to the cofactor NADPH. The substrate salutaridine is shown entering the active site.

This image shows the structure of a synapse, or junction between two nerve cells in three dimensions. From the brain of a mouse.

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 complex between CCD-1 and the antibiotic cefotaxime (purple, yellow, and blue molecule). The structure revealed that CCD-1 provides extensive hydrogen bonding (shown as dotted lines) and stabilization of the antibiotic in the active site, leading to efficient degradation of the antibiotic.

Related to images 6764, 6765, and 6766.

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.

This human T cell (blue) is under attack by HIV (yellow), the virus that causes AIDS. The virus specifically targets T cells, which play a critical role in the body's immune response against invaders like bacteria and viruses.

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

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

The TRPA1 protein is responsible for the burn you feel when you taste a bite of sushi topped with wasabi. Known therefore informally as the "wasabi receptor," this protein forms pores in the membranes of nerve cells that sense tastes or odors. Pungent chemicals like wasabi or mustard oil cause the pores to open, which then triggers a tingling or burn on our tongue. This receptor also produces feelings of pain in response to chemicals produced within our own bodies when our tissues are damaged or inflamed. Researchers used cryo-EM to reveal the structure of the wasabi receptor at a resolution of about 4 angstroms (a credit card is about 8 million angstroms thick). This detailed structure can help scientists understand both how we feel pain and how we can limit it by developing therapies to block the receptor. For more on cryo-EM see the blog post Cryo-Electron Microscopy Reveals Molecules in Ever Greater Detail.

Time-lapse video of yeast cells undergoing cell division. Nuclear envelopes are shown in green, and spindle pole bodies, which help pull apart copied genetic information, are shown in magenta. This video was captured using wide-field microscopy with deconvolution.

Related to images 6791, 6792, 6793, 6794, 6797, 6798, and video 6796.