This is the first structure of a protein derived from the metagenomic sequences collected during the Sorcerer II Global Ocean Sampling project. The crystal structure shows a barrel protein with a ferredoxin-like fold and a long chain fatty acid in a deep cleft (shaded red). Featured as one of the August 2007 Protein Structure Initiative Structures of the Month.

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.

The 46 human chromosomes are shown in blue, with the telomeres appearing as white pinpoints. The DNA has already been copied, so each chromosome is actually made up of two identical lengths of DNA, each with its own two telomeres.

This video shows a controlled outbreak of transmissible avian flu among people living in Thailand. Red indicates areas of infection while blue indicates areas where a combination of control measures were implemented. The video shows how control measures contained the infection in 90 days, before it spread elsewhere.

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 2507 for an illustration with examples.

Axolotls—a type of salamander—that have been genetically modified so that various parts of their nervous systems glow purple and green. Researchers often study axolotls for their extensive regenerative abilities. They can regrow tails, limbs, spinal cords, brains, and more. The researcher who took this image focuses on the role of the peripheral nervous system during limb regeneration.

This image was captured using a stereo microscope.

Related to images 6927 and 6932.

This image shows hundreds of human embryonic stem cells in various stages of differentiating into neurons. Some cells have become neurons (red), while others are still precursors of nerve cells (green). The yellow is an imaging artifact resulting when cells in both stages are on top of each other. Image and caption information courtesy of the California Institute for Regenerative Medicine.

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 pigment cells from pearl danio, a relative of the popular laboratory animal zebrafish. 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, 5757 and 5758.

An adult Hawaiian bobtail squid, Euprymna scolopes, (~4 cm) surrounded by newly hatched juveniles (~2 mm) in a bowl of seawater.

Related to image 7011 and video 7012.

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.

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 2513 and 2515 for other versions of this illustration. Featured in The Structures of Life.

This ribbon drawing of a protein hand drawn and colored by researcher Jane Richardson in 1981 helped originate the ribbon representation of proteins that is now ubiquitous in molecular graphics. The drawing shows the 3-dimensional structure of the protein triose phosphate isomerase. The green arrows represent the barrel of eight beta strands in this structure and the brown spirals show the protein's eight alpha helices. A black and white version of this drawing originally illustrated a review article in Advances in Protein Chemistry, volume 34, titled "Anatomy and Taxonomy of Protein Structures." The illustration was selected as Picture of The Day on the English Wikipedia for November 19, 2009. Other important and beautiful images of protein structures by Jane Richardson are available in her Wikimedia gallery.

Multiphoton fluorescence image of HeLa cells stained with the actin binding toxin phalloidin (red), microtubules (cyan) and cell nuclei (blue). Nikon RTS2000MP custom laser scanning microscope. See related images 3518, 3519, 3520, 3522.

To develop a system for studying cell motility in unnatrual conditions -- a microscope slide instead of the body -- Tom Roberts and Katsuya Shimabukuro at Florida State University disassembled and reconstituted the motility parts used by worm sperm cells.

A tomographic reconstruction of the colon shows the location of large pools of HIV-1 virus particles (in blue) located in the spaces between adjacent cells. The purple objects within each sphere represent the conical cores that are one of the structural hallmarks of the HIV virus.

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.

This image shows a computer-generated, three-dimensional map of the rotavirus structure. This virus infects humans and other animals and causes severe diarrhea in infants and young children. By the age of five, almost every child in the world has been infected with this virus at least once. Scientists have found a vaccine against rotavirus, so in the United States there are very few fatalities, but in developing countries and in places where the vaccine is unavailable, this virus is responsible for more than 200,000 deaths each year.

The rotavirus comprises three layers: the outer, middle and inner layers. On infection, the outer layer is removed, leaving behind a "double-layered particle." Researchers have studied the structure of this double-layered particle with a transmission electron microscope. Many images of the virus at a magnification of ~50,000x were acquired, and computational analysis was used to combine the individual particle images into a three-dimensional reconstruction.

The image was rendered by Melody Campbell (PhD student at TSRI). Work that led to the 3D map was published in Campbell et al. Movies of ice-embedded particles enhance resolution in electron cryo-microscopy. Structure. 2012;20(11):1823-8. PMCID: PMC3510009.

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.

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

Phenylalanine tRNA showing the anticodon (yellow) and the amino acid, phenylalanine (blue and red spheres).

Cross-section of skin anatomy shows layers and different tissue types.

Molecular model of the struture of heme. Heme is a small, flat molecule with an iron ion (dark red) at its center. Heme is an essential component of hemoglobin, the protein in blood that carries oxygen throughout our bodies. This image first appeared in the September 2013 issue of Findings Magazine. View side view of heme here 3539.

Kupffer cells appear in the liver during the early stages of mammalian development and stay put throughout life to protect liver cells, clean up old red blood cells, and regulate iron levels. Source article Replenishing the Liver’s Immune Protections. Posted on December 12th, 2019 by Dr. Francis Collins.

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

The beating of cilia on the outside of the Hawaiian bobtail squid’s light organ concentrates Vibrio fischeri cells (green) present in the seawater into aggregates near the pore-containing tissue (red). From there, the bacterial cells (~2 mm) swim to the pores and migrate through a bottleneck into the interior crypts where a population of symbionts grow and remain for the life of the host. This image was taken using confocal fluorescence microscopy.

Related to images 7016, 7017, 7018, and 7020.

A representation of a patient’s brain waves after receiving the anesthetic propofol. All anesthetics create brain wave changes that vary depending on the patient’s age and the type and dose of anesthetic used. These changes are visible in raw electroencephalogram (EEG) readings, but they’re easier to interpret using a spectrogram where the signals are broken down by time (x-axis), frequency (y-axis), and power (color scale). This spectrogram shows the changes in brain waves before, during, and after propofol-induced anesthesia. The patient is unconscious from minute 5, upon propofol administration, through minute 69 (change in power and frequency). But, between minutes 35 and 48, the patient fell into a profound state of unconsciousness (disappearance of dark red oscillations between 8 to 12 Hz), which required the anesthesiologist to adjust the rate of propofol administration. The propofol was stopped at minute 62 and the patient woke up around minute 69.

The green spots in this image are clumps of protein inside yeast cells that are deficient in both zinc and a protein called Tsa1 that prevents clumping. Protein clumping plays a role in many diseases, including Parkinson's and Alzheimer's, where proteins clump together in the brain. Zinc deficiency within a cell can cause proteins to mis-fold and eventually clump together. Normally, in yeast, Tsa1 codes for so-called "chaperone proteins" which help proteins in stressed cells, such as those with a zinc deficiency, fold correctly. The research behind this image was published in 2013 in the Journal of Biological Chemistry.

This is a magnified view of an Arabidopsis thaliana leaf a few days after being exposed to the pathogen Hyaloperonospora arabidopsidis. The plant from which this leaf was taken is genetically resistant to the pathogen. The spots in blue show areas of localized cell death where infection occurred, but it did not spread. Compare this response to that shown in Image 2782. Jeff Dangl has been funded by NIGMS to study the interactions between pathogens and hosts that allow or suppress infection.

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, 1050, 1051 and 1052.

The receptor is shown bound to an antagonist, ML056.

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.

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.

This computer algorithm plots all feasible small carbon-based molecules as though they were cities on a map and identifies huge, unexplored spaces that may help fuel research into new drug therapies. Featured in the May 16, 2013 issue of Biomedical Beat.

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.

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), Arp2 (green), and DAPI to visualize the nucleus (blue). Arp2, a subunit of the Arp2/3 complex, is absent in the filopodi-like structures based leading edge of ARPC3-/- fibroblasts cells. Related to images 3328, 3330, 3331, 3332, and 3333.

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

A colorized scanning electron micrograph of bacteria. Scanning electron microscopes allow scientists to see the three-dimensional surface of their samples.

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 (3 of 4), the Cas9 enzyme cuts both strands of the DNA.

For an explanation and overview of the CRISPR-Cas9 system, see the iBiology video, and find the full CRIPSR illustration here.

These neural precursor cells were derived from human embryonic stem cells. The neural cell bodies are stained red, and the nuclei are blue. Image and caption information courtesy of the California Institute for Regenerative Medicine.

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.

Network diagram showing a map of protein-protein interactions in a yeast (Saccharomyces cerevisiae) cell. This cluster includes 78 percent of the proteins in the yeast proteome. The color of a node represents the phenotypic effect of removing the corresponding protein (red, lethal; green, nonlethal; orange, slow growth; yellow, unknown).

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.

Neutrophil-like cells (blue) in a microfluidic chip preferentially migrating toward LTB4 over fMLP. A neutrophil is a type of white blood cell that is part of the immune system and helps the body fight infection. Both LTB4 and fMLP are molecules involved in immune response. Microfluidic chips are small devices containing microscopic channels, and they are used in a range of applications, from basic research on cells to pathogen detection. The scale bar in this video is 500μm.

Serum albumin (SA) is the most abundant protein in the blood plasma of mammals. SA has a characteristic heart-shape structure and is a highly versatile protein. It helps maintain normal water levels in our tissues and carries almost half of all calcium ions in human blood. SA also transports some hormones, nutrients and metals throughout the bloodstream. Despite being very similar to our own SA, those from other animals can cause some mild allergies in people. Therefore, some scientists study SAs from humans and other mammals to learn more about what subtle structural or other differences cause immune responses in the body.

Related to entries 3745 and 3746.

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.

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.

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 3390.

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.

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.

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.