This photograph shows a magnified view of a Drosophila melanogaster pupa in cross section. Compare this normal pupa to one that lacks an important receptor, shown in image 2759.

A zebrafish head with blood vessels shown in purple. Researchers often study zebrafish because they share many genes with humans, grow and reproduce quickly, and have see-through eggs and embryos, which make it easy to study early stages of development.

This image was captured using a light sheet microscope.

Related to video 6933.

The receptor is shown bound to an antagonist, JDTic.

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.

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.

Relapsing fever is caused by a bacterium and transmitted by certain soft-bodied ticks or body lice. The disease is seldom fatal in humans, but it can be very serious and prolonged. This scanning electron micrograph shows Borrelia hermsii (green), one of the bacterial species that causes the disease, interacting with red blood cells. Micrograph by Robert Fischer, NIAID. Related to image 3586.
For more information about relapsing fever, see https://www.cdc.gov/relapsing-fever/index.html.
This image is part of the Life: Magnified collection, which was displayed in the Gateway Gallery at Washington Dulles International Airport June 3, 2014, to January 21, 2015.

Here, a human HeLa cell (a type of immortal cell line used in laboratory experiments) is undergoing cell division. They come from cervical cancer cells that were obtained in 1951 from Henrietta Lacks, a patient at the Johns Hopkins Hospital. The final stage of division, called cytokinesis, occurs after the genomes—shown in yellow—have split into two new daughter cells. The myosin II is a motor protein shown in blue, and the actin filaments, which are types of protein that support cell structure, are shown in red.

Nerve cells have long, invisibly thin fibers that carry electrical impulses throughout the body. Some of these fibers extend about 3 feet from the spinal cord to the toes.

This time-lapse video shows the emergence of a flower-like pattern in a mixture of two bacterial species, motile Acinetobacter baylyi and non-motile Escherichia coli (green), that are grown together for 24 hours on 0.75% 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 6553 for a photo of this process at 48 hours on 1% 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.

Los ritmos circadianos son cambios físicos, mentales y conductuales que siguen un ciclo de 24 horas. Los ritmos circadianos típicos conducen a un nivel alto de energía durante la mitad del día (de 10 a.m. a 1 p.m.) y un bajón por la tarde. De noche, los ritmos circadianos hacen que la hormona melatonina aumente, lo que hace que la persona se sienta somnolienta.

Vea 6611 para la versión en inglés de esta infografía.

The microtubule severing protein, katanin, localizes to chromosomes and regulates anaphase A in mitosis. The movement of chromosomes on the mitotic spindle requires the depolymerization of microtubule ends. The figure shows the mitotic localization of the microtubule severing protein katanin (green) relative to spindle microtubules (red) and kinetochores/chromosomes (blue). Katanin targets to chromosomes during both metaphase (top) and anaphase (bottom) and is responsible for inducing the depolymerization of attached microtubule plus-ends. This image was a finalist in the 2008 Drosophila Image Award.

Proteins are long chains of amino acids. Each protein has a unique amino acid sequence. It is still a mystery how a protein folds into the proper shape based on its sequence. Scientists hope that one day they can "watch" this folding process for any given protein. The dream has been realized, at least partially, through the use of computer simulation.

A model of the molecule himastatin overlaid on an image of Bacillus subtilis bacteria. Scientists first isolated himastatin from the bacterium Streptomyces himastatinicus, and the molecule shows antibiotic activity. The researchers who created this image developed a new, more concise way to synthesize himastatin so it can be studied more easily. They also tested the effects of himastatin and derivatives of the molecule on B. subtilis.

More information about the research that produced this image can be found in the Science paper “Total synthesis of himastatin” by D’Angelo et al.

Related to image 6848 and video 6851.

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.

As an egg cell develops, a process called polarization controls what parts ultimately become the embryo's head and tail. This picture shows an egg of the fruit fly Drosophila. Red and green mark two types of signaling proteins involved in polarization. Disrupting these signals can scramble the body plan of the embryo, leading to severe developmental disorders.

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

The G switch allows our bodies to respond rapidly to hormones. G proteins act like relay batons to pass messages from circulating hormones into cells. A hormone (red) encounters a receptor (blue) in the membrane of a cell. Next, a G protein (green) becomes activated and makes contact with the receptor to which the hormone is attached. Finally, the G protein passes the hormone's message to the cell by switching on a cell enzyme (purple) that triggers a response. See image 2536 and 2537 for other versions of this image. Featured in Medicines By Design.

Luciferase-based imaging enables visualization and quantification of internal organs and transplanted cells in live adult zebrafish. In this image, a cardiac muscle-restricted promoter drives firefly luciferase expression. This is the lateral and overhead (Bottom) view.
For imagery of the overhead view go to 3557.
For imagery of the lateral view go to 3558.
For more information about the illumated area go to 3559.

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.

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

Cell-like compartments spontaneously emerge from scrambled frog eggs, with nuclei (blue) from frog sperm. Endoplasmic reticulum (red) and microtubules (green) are also 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: 6588, 6589, and 6590.

Spinal nerves are part of the peripheral nervous system. They run within the spinal column to carry nerve signals to and from all parts of the body. The spinal nerves enable all the movements we do, from turning our heads to wiggling our toes, control the movements of our internal organs, such as the colon and the bladder, as well as allow us to feel touch and the location of our limbs.

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.

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.

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.

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.

A biofilm is a highly organized community of microorganisms that develops naturally on certain surfaces. These communities are common in natural environments and generally do not pose any danger to humans. Many microbes in biofilms have a positive impact on the planet and our societies. Biofilms can be helpful in treatment of wastewater, for example. This dime-sized biofilm, however, was formed by the opportunistic pathogen Pseudomonas aeruginosa. Under some conditions, this bacterium can infect wounds that are caused by severe burns. The bacterial cells release a variety of materials to form an extracellular matrix, which is stained red in this photograph. The matrix holds the biofilm together and protects the bacteria from antibiotics and the immune system.

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.

A cross section of the measles virus in which six proteins (enlarged on the outside of the virus) 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. Portions of the proteins that have not been determined are shown with dots.

Learn more about the six proteins on PDB 101’s Molecule of the Month: Measles Virus Proteins. Structures are available for the ordered regions of nucleoprotein and phosphoprotein (PDB entries 5E4V, 3ZDO, 1T6O), but the remaining regions are thought to form a flexible, random tangle. For a larger look at the measles virus, see 6995.

Many researchers use the mouse (Mus musculus) as a model organism to study mammalian biology. Mice carry out practically all the same life processes as humans and, because of their small size and short generation times, are easily raised in labs. Scientists studying a certain cellular activity or disease can choose from tens of thousands of specially bred strains of mice to select those prone to developing certain tumors, neurological diseases, metabolic disorders, premature aging, or other conditions.

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.

A cropped image of a white poppy. View poppy uncropped here 3424.

C. elegans, a tiny roundworm, 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 group of roundworms here 6582.
View closeup of roundworms here 6583.

To splice a human gene (in this case, the one for insulin) into a plasmid, scientists take the plasmid out of an E. coli bacterium, cut the plasmid with a restriction enzyme, and splice in insulin-making human DNA. The resulting hybrid plasmid can be inserted into another E. coli bacterium, where it multiplies along with the bacterium. There, it can produce large quantities of insulin. See image 2564 for an unlabeled version of this illustration. Featured in The New Genetics.

The genetic code in DNA is transcribed into RNA, which is translated into proteins with specific sequences. During transcription, nucleotides in DNA are copied into RNA, where they are read three at a time to encode the amino acids in a protein. Many parts of a protein fold as the amino acids are strung together.

See image 2509 for an unlabeled version of this illustration.

Featured in The Structures of Life.

A scanning electron microscope picture of a nerve ending. It has been broken open to reveal vesicles (orange and blue) containing chemicals used to pass messages in the nervous system.

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.

This ACAPELLA robot for capillary protein crystallization grows protein crystals, freezes them, and centers them without manual intervention. The close-up is a view of one of the dispensers used for dispensing proteins and reagents.

Hepatocytes, like the one shown here, are the most abundant type of cell in the human liver. They play an important role in building proteins; producing bile, a liquid that aids in digesting fats; and chemically processing molecules found normally in the body, like hormones, as well as foreign substances like medicines and alcohol.

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

This fruit fly spermatid recycles various molecules, including malformed or damaged proteins. Actin filaments (red) in the cell draw unwanted proteins toward a barrel-shaped structure called the proteasome (green clusters), which degrades the molecules into their basic parts for re-use.

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.

Blood clots stop bleeding, but they also can cause heart attacks and strokes. A team led by computational biophysicist Klaus Schulten of the University of Illinois at Urbana-Champaign has revealed how a blood protein can give clots their lifesaving and life-threatening abilities. The researchers combined experimental and computational methods to animate fibrinogen, a protein that forms the elastic fibers that enable clots to withstand the force of blood pressure. This simulation shows that the protein, through a series of events, stretches up to three times its length. Adjusting this elasticity could improve how we manage healthful and harmful clots. NIH's National Center for Research Resources also supported this work. Featured in the March 19, 2008, issue of Biomedical Beat.

A Trigonium diatom imaged by a quantitative orientation-independent differential interference contrast (OI-DIC) microscope. Diatoms are single-celled photosynthetic algae with mineralized cell walls that contain silica and provide protection and support. These organisms form an important part of the plankton at the base of the marine and freshwater food chains. The width of this image is 90 μm.

More information about the microscopy that produced this image can be found in the Journal of Microscopy paper “An Orientation-Independent DIC Microscope Allows High Resolution Imaging of Epithelial Cell Migration and Wound Healing in a Cnidarian Model” by Malamy and Shribak.

X-ray co-crystal structure of Src kinase bound to a DNA-templated macrocycle inhibitor. Related to images 3413, 3414, 3415, 3416, 3417, and 3418.

Image of Streptococcus, a type (genus) of spherical bacteria that can colonize the throat and back of the mouth. Stroptococci often occur in pairs or in chains, as shown here.

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, two cells have formed after a round of mitosis.

Related to images 1010, 1011, 1012, 1013, 1014, 1015, 1016, 1017, 1018, and 1021.

This image shows the uncontrolled growth of cells in squamous cell carcinoma, the second most common form of skin cancer. If caught early, squamous cell carcinoma is usually not life-threatening.

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

A scanning electron microscope image of an activated mast cell. This image illustrates the interesting topography of the cell membrane, which is populated with receptors. The distribution of receptors may affect cell signaling. This image relates to a July 27, 2009 article in Computing Life.

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.

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