This Maya animation depicts the process by which the translating ribosome is halted by the signal recognition particle (SRP). The ribosome is subsequently brought to the membrane and docked with a channel to translocate the nascent polypeptide chain. video by Eric Keller, Steve Davy / Stylus Visuals

Added by: sertan
Tags: srp
Date: 2008-01-05

a more in-depth look at the reovirus life cycle. This current version highlights each of the 8 proteins that make up the virus as well as its icosahedral symmetry. The virus is activated upon chymotrypsin 'attack' and cleavage of the outer protein layer. The virus then binds to and enters the cell via the JAM-1 receptor and clathrin-mediated endocytosis. video by Gael McGill, Janet Iwasa

Added by: sertan
Tags: reovirus
Date: 2008-01-05

A muscle contraction (also known as a muscle twitch or simply twitch) occurs when a muscle fiber generates tension through the action of actin and myosin cross-bridge cycling. While under tension, the muscle may lengthen, shorten or remain the same. Though the term 'contraction' implies a shortening or reduction, when used as a scientific term referring to the muscular system contraction refers to the generation of tension by muscle fibers with the help of motor neurons. Locomotion in most higher only through the repeated contraction of many muscles at the correct times. Contraction is controlled by the central nervous system (CNS), which comprises the brain and spinal cord. Voluntary muscle contractions are initiated in the brain, while the spinal cord initiates involuntary reflexes.

Added by: mnazirokur
Tags: contraction
Date: 2008-03-30

This video shows activated T cell which are shiny blue and attacting on the cancer cells and kill them. Video REf: http://www.hybridmedicalanimation.com

Added by: benchwork
Tags: ppar
Date: 2007-04-10

Antibiotic resistance genes can be shared between bacteria through a sex pilus. Video Ref: www.learner.org Video Reff: www.learner.org Bacterial Conjugation text info: Bacterial conjugation is the transfer of genetic material between bacteria through direct cell-to-cell contact. Discovered in 1946 by Joshua Lederberg and Edward Tatum, conjugation is a mechanism of horizontal gene transfer as are transformation and transductionalthough these mechanisms do not involve cell-to-cell contact. text reff: wikipedia

Added by: sana
Tags: Bacterial Conjugation
Date: 2007-04-06

An ATP synthase is a general term for an enzyme that can synthesize adenosine triphosphate (ATP) from adenosine diphosphate (ADP) and inorganic phosphate by utilizing some form of energy. The overall reaction sequence is: ADP + Pi → ATP Molecular model of ATP synthase by X-ray diffraction method ATP synthase in E. coliThese enzymes are of crucial importance in almost all organisms, because ATP is the common "energy currency" of cells. In mitochondria, the F1FO ATP synthase has a long history of scientific study. The F1 portion of the ATP synthase is above the membrane, the FO portion is within the membrane. It's easy to visualize the FOF1 particle as resembling the fruiting body of a common mushroom, with the head being the F1 particle, the stalk being the gamma subunit of F1, and the base and "roots" being the FO particle embedded in the membrane. The F1 particle was first isolated by Ephraim Racker in 1961. The nomenclature of the enzyme suffers from a long history. The F1 fraction derives it name from the term "Fraction 1" and FO (written as a subscript "O", not "zero") derives it name from being the oligomycine binding fraction. Taking as an example the nomenclature of subunits in the bovine enzyme, many subunits have Greek and Roman alphabet names (alpha, beta, gamma, delta, epsilon and a, b, c, d, e, f, g, h), while others have more complex names such as F6 (from "Fraction 6"), OSCP (the oligomycin sensitivity conferral protein), A6L (named for the gene that codes for it in the mitochondrial genome) and IF1 (inhibitory factor 1). The F1 particle is large and can be seen in the transmission electron microscope by negative staining (1962, Fernandez-Moran et al., Journal of Molecular Biology, Vol 22, p 63). These are particles of 9 nm diameter that pepper the inner mitochondrial membrane. They were originally called elementary particles and were thought to contain the entire respiratory apparatus of the mitochondrion, but through a long series of experiments, Ephraim Racker and his colleagues were able to show that this particle is correlated with ATPase activity in uncoupled mitochondria and with the ATPase activity in submitochondrial particles created by exposing mitochondria to ultrasound. This ATPase activity was further associated with the creation of ATP by yet another long series of experiments in many laboratories. The antibiotic oligomycin inhibits ATP synthase. Text Reff: http://en.wikipedia.org/wiki/ATP_synthase

Added by: benchwork
Tags: atpsynthase
Date: 2007-03-28

DNA fragment complexed with acridine derivative (a carcinogenic dye). Data source: Protein Data Bank code 2GB9. Wiki text info: Acridine, C13H9N, is an organic compound and a nitrogen heterocycle. Acridine is also used to describe compounds containing the C13N tricycle. Acridine is structurally related to anthracene with one of the central CH groups is replaced by nitrogen. Acridine, a colorless solid, was first isolated from coal tar. It is a raw material used for the production of dyes and some valuable drugs. Many acridines also have antiseptic properties such as Proflavine. Acridine and related derivatives bind to DNA and RNA due to their abilities to intercalate. Acridine Orange (3,6-dimethylaminoacridine) is a nucleic acid-selective metachromatic stain useful for cell cycle determination.

Added by: adamsan
Tags: acridine
Date: 2007-09-18

Stem cells serve as the source of all the other specialized cells in the body, both when it forms during embryogenesis and when it replaces cells that have been lost to aging, injury or disease. These videos are created by RIKEN CDB and they explain the different types of stem cell found in the embryonic body and the adult and illustrate the roles of these "master cells" in development and regeneration. Video REff: http://www.cdb.riken.go.jp I also uploaded other 3 parts. Search " stem cells" on DnaTube and most probably you will find other videos.

Added by: siere
Tags: stemcell
Date: 2007-04-02

How are proteins synthesized? This interactive animation will help you to understand the process. For more information about protein synthesis: Legend: Process whereby DNA encodes for the production of amino acids and proteins. This process can be divided into two parts: 1. Transcription Before the synthesis of a protein begins, the corresponding RNA molecule is produced by RNA transcription. One strand of the DNA double helix is used as a template by the RNA polymerase to synthesize a messenger RNA (mRNA). This mRNA migrates from the nucleus to the cytoplasm. During this step, mRNA goes through different types of maturation including one called splicing when the non-coding sequences are eliminated. The coding mRNA sequence can be described as a unit of three nucleotides called a codon. 2. Translation The ribosome binds to the mRNA at the start codon (AUG) that is recognized only by the initiator tRNA. The ribosome proceeds to the elongation phase of protein synthesis. During this stage, complexes, composed of an amino acid linked to tRNA, sequentially bind to the appropriate codon in mRNA by forming complementary base pairs with the tRNA anticodon. The ribosome moves from codon to codon along the mRNA. Amino acids are added one by one, translated into polypeptidic sequences dictated by DNA and represented by mRNA. At the end, a release factor binds to the stop codon, terminating translation and releasing the complete polypeptide from the ribosome Text Reff: http://www.accessexcellence.org/RC/VL/GG/protein_synthesis.html

Added by: tubeman
Tags: proteinsynthesis
Date: 2007-04-01

This 2-part Maya animation depicts the process of nucleic acid packing/assembly into the viral capsid. Part I shows the process simultaneous with the measured kinetics of packing and force (displayed on the right). Video by Eric Keller Stylus Visuals

Added by: sertan
Tags: viral
Date: 2008-01-05

This video shows the packaging of DNA in the nucleus.

Added by: benchwork
Tags: 3D struct of nuc chroms
Date: 2007-03-22

This video shows how rnai works in the cells. Video reference: Nature.com Info: RNA interference (also called "RNA-mediated interference", abbreviated RNAi) is a mechanism for RNA-guided regulation of gene expression in which double-stranded ribonucleic acid inhibits the expression of genes with complementary nucleotide sequences. Conserved in most eukaryotic organisms, the RNAi pathway is thought to have evolved as a form of innate immunity against viruses and also plays a major role in regulating development and genome maintenance. The RNAi pathway is initiated by the enzyme dicer, which cleaves double-stranded RNA (dsRNA) to short double-stranded fragments of 20–25 base pairs. One of the two strands of each fragment, known as the guide strand, is then incorporated into the RNA-induced silencing complex (RISC) and base-pairs with complementary sequences. The most well-studied outcome of this recognition event is a form of post-transcriptional gene silencing. This occurs when the guide strand base pairs with a messenger RNA (mRNA) molecule and induces degradation of the mRNA by argonaute, the catalytic component of the RISC complex. The short RNA fragments are known as small interfering RNA (siRNA) when they derive from exogenous sources and microRNA (miRNA) when they are produced from RNA-coding genes in the cell's own genome. The RNAi pathway has been particularly well-studied in certain model organisms such as the nematode worm Caenorhabditis elegans, the fruit fly Drosophila melanogaster, and the flowering plant Arabidopsis thaliana. The selective and robust effect of RNAi on gene expression makes it a valuable research tool, both in cell culture and in living organisms; synthetic dsRNA introduced into cells can induce suppression of specific genes of interest. RNAi may also be used for large-scale screens that systematically shut down each gene in the cell, which can help identify the components necessary for a particular cellular process or an event such as cell division. Exploitation of the pathway is also a promising tool in biotechnology and medicine. Historically, RNA interference was known by other names, including post transcriptional gene silencing, transgene silencing, and quelling. Only after these apparently-unrelated processes were fully understood did it become clear that they all described the RNAi phenomenon. RNAi has also been confused with antisense suppression of gene expression, which does not act catalytically to degrade mRNA but instead involves single-stranded RNA fragments physically binding to mRNA and blocking translation. info ref: http://en.wikipedia.org/wiki/RNAi

Added by: benchwork
Tags: rnai
Date: 2007-03-26

The primase/helicase from the T7 bacteriophage is required for unwinding duplex DNA and the production of short RNA primers called Okazaki fragments during DNA replication. The RNA primers are synthesized in the primase domain of the molecule via a two metal-ion mechanism of catalysis that is facilitated by the zinc-binding domain. During primer synthesis the zinc-binding domain closes over the active site of the primase domain. The helicase domain unwinds DNA by shuttling the 3'-end of the duplex DNA away from the molecule by pulling the 5'-strand through the enzyme. The mechanism of unwinding is facilitated by DNA binding loops present in the helicase domain. This movie is based on the X-ray crystal structure of the primase and helicase domains. Zinc binding domains have been modeled in. The first half of the animation highlights the possible mechanism of DNA unwinding by the helicase domain. The motion of each domain has been inferred from the crystal structure. The second portion of the movie highlights the mechanism of RNA primer synthesis by the primase/zinc binding domain. Synthesis of short RNA primers of a defined sequence (5'-ACCC-3') are utilized by the replicative polymerases during lagging strand DNA synthesis. Finally, the new primer/template is presented to the replication machinery by the zinc binding domain. www.scianafilms.com

Added by: sertan
Tags: primase
Date: 2008-01-05

Helicases are a class of enzymes vital to all living organisms. They are motor proteins that move directionally along a nucleic acid phosphodiester backbone, separating two annealed nucleic acid strands (i.e. DNA, RNA, or RNA-DNA hybrid) using energy derived from nucleotide hydrolysis. Many cellular processes (DNA replication, RNA transcription, DNA recombination, DNA repair, Ribosome biogenesis) involve the separation of nucleic acid strands. Helicases are often utilized to separate strands of a DNA double helix or a self-annealed RNA molecule using the energy from ATP or GTP hydrolysis. They move incrementally along one nucleic acid strand of the duplex with a directionality specific to each particular enzyme. There are many helicases (14 confirmed in E. coli, 24 in human cells) resulting from the great variety of processes in which strand separation must be catalyzed.[citation needed] Helicases adopt different structures and oligomerization states. Whereas DnaB-like helicases unwind DNA as donut shaped hexamers, other enzymes have been shown to be active as monomers or dimers. Their precise mechanisms of action remain unclear. Text Reff: http://en.wikipedia.org/wiki/Helicase

Added by: benchwork
Tags: 06.2-DNA_helicase
Date: 2007-03-25

The lac operon is an operon required for the transport and metabolism of lactose in Escherichia coli and some other enteric bacteria. It consists of three adjacent structural genes, a promoter, a terminator, and an operator. The lac operon is regulated by several factors including the availability of glucose and of lactose. Gene regulation of the lac operon was the first genetic regulatory mechanism to be elucidated and is often used as the canonical example of prokaryotic gene regulation.

Added by: mnazirokur
Tags: DEAS
Date: 2007-03-17

This This 3D animation provided courtesy of Rosetta Genomics shows how microrna works. In genetics, microRNAs (miRNA) are single-stranded RNA molecules of about 21-23 nucleotides in length thought to regulate the expression of other genes. miRNAs are encoded by genes that are transcribed from DNA but not translated into protein (non-coding RNA); instead they are processed from primary transcripts known as pri-miRNA to short stem-loop structures called pre-miRNA and finally to functional miRNA. Mature miRNA molecules are partially complementary to one or more messenger RNA (mRNA) molecules, and they function to downregulate gene expression. More info: The genes encoding miRNAs are much longer than the processed miRNA molecule; miRNAs are first transcribed as primary transcripts or pri-miRNA and processed to short, 70-nucleotide stem-loop structures known as pre-miRNA in the cell nucleus. This processing is performed in animals by a protein complex known as the Microprocessor complex, consisting of the nuclease Drosha and the double-stranded RNA binding protein Pasha.[2] These pre-miRNAs are then processed to mature miRNAs in the cytoplasm by interaction with the endonuclease Dicer, which also initiates the formation of the RNA-induced silencing complex (RISC).[3] This complex is responsible for the gene silencing observed due to miRNA expression and RNA interference. The pathway in plants varies slightly due to their lack of Drosha homologs; instead, Dicer homologs alone effect several processing steps.[4] Zeng et al. have shown that efficient processing of pre-miRNA by Drosha requires presence of extended single-stranded RNA on both 3'- and 5'-ends of hairpin molecule. They demonstrated that these motifs could be of different composition while their length is of high importance if processing is to take place at all. Their findings were confirmed in another work by Han et al. Using bioinformatical tools Han et al. analysed folding of 321 human and 68 fly pri-miRNAs. 280 human and 55 fly pri-miRNAs were selected for further study, excluding those molecules which folding showed presence of multiple loops. All human and fly pri-miRNA contained very similar structural regions, which authors called 'basal segments', 'lower stem', 'upper stem' and 'terminal loop'. Based on the encoding position of miRNA, i.e. in the 5'-strand (5'-donors) or 3'-strand (3'-donors), thermodynamical profiles of pri-miRNA was determined. Following experiments have shown that Drosha complex cleaves RNA molecule ~2 helical turns away from the terminal loop and ~1 turn away from basal segments. In most analysed molecules this region contain unpaired nucleotides and the free energy of the duplex is relatively high compared to lower and upper stem regions. Most pre-miRNAs don't have a perfect double-stranded RNA (dsRNA) structure topped by a terminal loop. There are few possible explanations for such selectivity. One could be that dsRNAs longer than 11 base pairs activate interferon response and anti-viral machinery in the cell. Another plausible explanation could be that thermodynamical profile of pre-miRNA determines which strand will be incorporated into Dicer complex. Indeed, aforementioned study by Han et al. demonstrated very clear similarities between pri-miRNAs encoded in respective (5'- or 3'-) strands. When Dicer cleaves the pre-miRNA stem-loop, two complementary short RNA molecules are formed, but only one is integrated into the RISC complex. This strand is known as the guide strand and is selected by the argonaute protein, the catalytically active RNase in the RISC complex, on the basis of the stability of the 5' end.[5] The remaining strand, known as the anti-guide or passenger strand, is degraded as a RISC complex substrate.[6] After integration into the active RISC complex, miRNAs base pair with their complementary mRNA molecules and induce mRNA degradation by argonaute proteins, the catalytically active members of the RISC complex. It is as yet unclear how the activated RISC complex locates the mRNA targets in the cell, though it has been shown that the process is not coupled to ongoing protein translation from the mRNA.[7] REf: http://en.wikipedia.org/wiki/Micro_RNA

Added by: benchwork
Tags: dsadsa
Date: 2007-03-26

A sperm's tale.

Added by: siere
Tags: sperm
Date: 2007-06-22

Vascular endothelial growth factor (VEGF) is an important signaling protein involved in both vasculogenesis (the de novo formation of the embryonic circulatory system) and angiogenesis (the growth of blood vessels from pre-existing vasculature). Text reff: wiki Video reff:

Added by: asteri
Tags: vegf
Date: 2007-12-05

Receptor tyrosine kinase is activated when a growth factor binds to one of the receptors and recruits the second receptor molecule. This is called

Added by: Samuray
Tags: receptor tyrosine kinase activation phosphorylation
Date: 2007-07-14

Mitochondrian structure. Data is obtained by using tomogram

Added by: benchwork
Tags: 14.1-mitochondion
Date: 2007-03-28