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, two multivesicular bodies (with yellow membranes) contain tiny intralumenal vesicles (with a diameter of only 25 nanometers; shown in red) adjacent to the cell's vacuole (in orange).

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 microscopy photograph 5768 that was used to generate this illustration and a zoomed-out version 5769 of this illustration.

The green spots in this mouse brain are cells labeled with Calling Cards, a technology that records molecular events in brain cells as they mature. Understanding these processes during healthy development can guide further research into what goes wrong in cases of neuropsychiatric disorders. Also fluorescently labeled in this image are neurons (red) and nuclei (blue). Calling Cards and its application are described in the Cell paper “Self-Reporting Transposons Enable Simultaneous Readout of Gene Expression and Transcription Factor Binding in Single Cells” by Moudgil et al.; and the Proceedings of the National Academy of Sciences paper “A viral toolkit for recording transcription factor–DNA interactions in live mouse tissues” by Cammack et al. The technology was also featured in the NIH Director’s Blog post The Amazing Brain: Tracking Molecular Events with Calling Cards.

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A two-dimensional NMR spectrum of a protein, in this case a 2D 1H-15N HSQC NMR spectrum of a 228 amino acid DNA/RNA-binding protein.

The glial cells (black dots) and nerve cells (brown bands) in this developing fruit fly nerve cord formed normally despite the absence of the SPITZ protein, which blocks their impending suicide. The HID protein, which triggers suicide, is also lacking in this embryo.

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.

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.

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.

Actin is an essential protein in a cell's skeleton (cytoskeleton). It forms a dense network of thin filaments in the cell. Here, researchers have used a technique called stochastic optical reconstruction microscopy (STORM) to visualize the actin network in a cell in three dimensions. The actin strands were labeled with a dye called Alexa Fluor 647-phalloidin.  This image appears in a study published by Nature Methods, which reports how researchers use STORM to visualize the cytoskeleton.

Various views of 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 video was captured using a light sheet microscope.

Related to image 6934.

Ribonucleic acid (RNA) has a sugar-phosphate backbone and the bases adenine (A), cytosine (C), guanine (G), and uracil (U). Featured in The New Genetics.

See image 2554 for an unlabeled version of this illustration.

A crystal of bacterial alpha amylase protein created for X-ray crystallography, which can reveal detailed, three-dimensional protein structures.

Hippocampal neuron from rodent brain with dendrites shown in blue. The hundreds of tiny magenta, green and white dots are the dendritic spines of excitatory synapses.

The lubber grasshopper, found throughout the southern United States, is frequently used in biology classes to teach students about the respiratory system of insects. Unlike mammals, which have red blood cells that carry oxygen throughout the body, insects have breathing tubes that carry air through their exoskeleton directly to where it's needed. This image shows the breathing tubes embedded in the weblike sheath cells that cover developing egg chambers.

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

DNA encodes RNA, which encodes protein. DNA is transcribed to make messenger RNA (mRNA). The mRNA sequence (dark red strand) is complementary to the DNA sequence (blue strand). On ribosomes, transfer RNA (tRNA) reads three nucleotides at a time in mRNA to bring together the amino acids that link up to make a protein. See image 2548 for a version of this illustration that isn't numbered and 2547 for a an entirely unlabeled version. Featured in The New Genetics.

Colorized scanning electron micrographs progressively zoom in on the eye of a crab larva. In the higher-resolution frames, bacteria are visible on the eye.

Embryonic stem cells store pre-activated Bax (red) in the Golgi, near the nucleus (blue). Featured in the June 21, 2012, issue of Biomedical Beat.

This illustration shows, in simplified terms, how the CRISPR-Cas9 system can be used as a gene-editing tool. This is the first frame in a series of four. 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).

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

This image shows the hierarchical ontology of genes, cellular components and processes derived from large genomic datasets. From Dutkowski et al. A gene ontology inferred from molecular networks Nat Biotechnol. 2013 Jan;31(1):38-45. Related to 3436.

This network map shows the overlap (green) between the long QT syndrome (yellow) and epilepsy (blue) protein-interaction neighborhoods located within the human interactome. Researchers have learned to integrate genetic, cellular and clinical information to find out why certain medicines can trigger fatal heart arrhythmias. Featured in Computing Life magazine.

A segment of siRNA, shown in red, guides a "slicer" protein called Argonaute (multi-colored twists and corkscrews) to the target RNA molecules.

The fledgling field of X-ray microscopy lets researchers look inside whole cells rapidly frozen to capture their actions at that very moment. Here, a yeast cell buds before dividing into two. Colors show different parts of the cell. Seeing whole cells frozen in time will help scientists observe cells' complex structures and follow how molecules move inside them.

The Center for Eukaryotic Structural Genomics protein purification facility is responsible for purifying all recombinant proteins produced by the center. The facility performs several purification steps, monitors the quality of the processes, and stores information about the biochemical properties of the purified proteins in the facility database.

Xenopus laevis, the African clawed frog, has long been used as a research organism for studying embryonic development. The abnormal presence of RNA encoding the signaling molecule plakoglobin causes atypical signaling, giving rise to a two-headed tadpole.

This crystal structure shows a conserved hypothetical protein from Mycobacterium tuberculosis. Only 12 other proteins share its sequence homology, and none has a known function. This structure indicates the protein may play a role in metabolic pathways. Featured as one of the August 2007 Protein Structure Initiative Structures of the Month.

Closeup of 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 group of roundworms here 6582.

Bacteria engineered to act as genetic clocks flash in synchrony. Here, a "supernova" burst in a colony of coupled genetic clocks just after reaching critical cell density. Superimposed: A diagram from the notebook of Christiaan Huygens, who first characterized synchronized oscillators in the 17th century.

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 3744 and 3746

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.

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.

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.

The body uses a variety of ion channels to transport small molecules across cell membranes.

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

This map paints a colorful portrait of human genetic variation around the world. Researchers analyzed the DNA of 485 people and tinted the genetic types in different colors to produce one of the most detailed maps of its kind ever made. The map shows that genetic variation decreases with increasing distance from Africa, which supports the idea that humans originated in Africa, spread to the Middle East, then to Asia and Europe, and finally to the Americas. The data also offers a rich resource that scientists could use to pinpoint the genetic basis of diseases prevalent in diverse populations. Featured in the March 19, 2008, issue of Biomedical Beat.

Cilia (cilium in singular) are complex molecular machines found on many of our cells. One component of cilia is the doublet microtubule, a major part of cilia’s skeletons that give them support and shape. This animated image is a partial model of a doublet microtubule’s structure based on cryo-electron microscopy images. Video can be found here 6549.

The human immunodeficiency virus (HIV), shown here as tiny purple spheres, causes the disease known as AIDS (for acquired immunodeficiency syndrome). HIV can infect multiple cells in your body, including brain cells, but its main target is a cell in the immune system called the CD4 lymphocyte (also called a T-cell or CD4 cell).

Genome editing using CRISPR/Cas9 is a rapidly expanding field of scientific research with emerging applications in disease treatment, medical therapeutics and bioenergy, just to name a few. This technology is now being used in laboratories all over the world to enhance our understanding of how living biological systems work, how to improve treatments for genetic diseases and how to develop energy solutions for a better future.

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

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.

CCD-1 is an enzyme produced by the bacterium Clostridioides difficile that helps it resist antibiotics. Here, researchers crystallized bound pairs of CCD-1 molecules and molecules of the antibiotic cefotaxime. This enabled their structure to be studied using X-ray crystallography.

Related to images 6765, 6766, and 6767.

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

Sketch of an egg cell.

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.

Zinc is required for the function of more than 300 enzymes, including those that help regulate gene expression, in various organisms including humans. Researchers study how plants acquire, sequester and distribute zinc to find ways to increase the zinc content of crops to improve human health. Using synchrotron X-ray fluorescence technology, they created this heat map of zinc levels in an Arabidopsis thaliana plant leaf. This image is a winner of the 2015 FASEB Bioart contest and was featured in the NIH Director's blog.

The cytoskeleton (green) and DNA (purple) are highlighed in these cells by immunofluorescence.

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.

Animation for the cisternae maturation model of Golgi transport.

An adult female Hawaiian bobtail squid, Euprymna scolopes, with its mantle cavity exposed from the underside. Some internal organs are visible, including the two lobes of the light organ that contains bioluminescent bacteria, Vibrio fischeri. The light organ includes accessory tissues like an ink sac (black) that serves as a shutter, and a silvery reflector that directs the light out of the underside of the animal.

Researchers doing behavioral experiments with honeybees sometimes use paint or enamel to give individual bees distinguishing marks. The elaborate social structure and impressive learning and navigation abilities of bees make them good models for behavioral and neurobiological research. Since the sequencing of the honeybee genome, published in 2006, bees have been used increasingly for research into the molecular basis for social interaction and other complex behaviors.

These cells are induced stem cells made from human adult skin cells that were genetically reprogrammed to mimic embryonic stem cells. The induced stem cells were made potentially safer by removing the introduced genes and the viral vector used to ferry genes into the cells, a loop of DNA called a plasmid. The work was accomplished by geneticist Junying Yu in the laboratory of James Thomson, a University of Wisconsin-Madison School of Medicine and Public Health professor and the director of regenerative biology for the Morgridge Institute for Research.

Fruit flies are a common model organism for basic medical research.