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Chemia/Biochemia (858)

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! EN_90284221_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Vitamin C. Computer graphic depicting a molecule of vitamin C (ascorbic acid). The molecular formula is C6.H8.O6. Atoms are shown as spheres, joined by atomic bonds. Atoms are colour-coded: carbon (green), oxygen (red), hydrogen (white). Vitamin C is a water soluble vitamin which plays an essential role in the activity of many enzymes in the human body. It is necessary for the growth and maintenance of healthy bones, gums, teeth, ligaments, and blood vessels. It is also thought to stimulate the immune system against infection. Dietary sources of vitamin C are citrus fruits and green vegetables. Deficiency of vitamin C leads to scurvy, with swollen bleeding gums and anaemia.
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! EN_90268922_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Ribonuclease. Molecular computer graphic showing the structure of the enzyme ribonuclease. Here, the polypeptide (protein) skeleton of the molecule is represented. Coloured areas depict different sites on the molecule; chains of spherical atoms form linkages which hold the molecule in shape; at above centre (red) are rings of atoms. Ribo- nuclease is an enzyme involved in the breakdown or hydrolysis of RNA (mRNA) in the cell by breaking its phosphodiester bonds. RNA is involved in protein synthesis in all living cells. Enzymes are biological catalysts, proteins that speed up the rates of reactions within cells.
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! EN_90184810_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Miller-Urey experiment. Illustration showing the apparatus used in the Miller-Urey experiment to study the origin of life. In this experiment of the 1950s, American scientists Miller and Urey attempted to duplicate the conditions which would have existed on the primordial Earth. The apparatus contains a 'sea' of sterile water (at bottom) under an 'atmosphere' of hydrogen, methane and ammonia (upper right). Electrodes give off a spark to imitate either lightning or ultra- violet radiation from the Sun. After a week or so, the result is a tar-like residue containing amino acids, the basic building blocks of life.
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! EN_90227128_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Glycobiology research: computer graphics representation of the molecular structure of bi- antenarase, an oligosaccharide (short-chain sugar) complex of THY-1, a glycoprotein. THY-1 is the smallest member of the immunoglobulin superfamily (the group of glycoproteins that includes antibodies), and is a major cell-surface glycoprotein of thymocytes and brain cells. Colour coding: the sugar part is in yellow, protein in green. This image was produced at the Glycobiology Unit in the University of Oxford, where research is conducted into the body's sugar chemistry & its relationship to disease.
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! EN_90268892_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Illustration of the molecular structure of ice. Ice consists of, and is formed by, water molecules which have frozen into hexagonal crystals. Here, the three- dimensional hexagonal crystal structure of ice is shown. Each water molecule comprises one atom of oxygen (blue) and two hydrogen atoms (yellow) covalently bonded. In ice, hydrogen bonds (red and white) link the molecules of water into a lattice structure. Ice is seldom pure water, and other molecules may also infiltrate the crystal (seen at lower left, red). The freezing point at which ice forms is 0 degrees centigrade, adopted as a thermometric standard.
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! EN_90219249_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Computer graphics representation of haemoglobin, the oxygen-carrying molecule of blood, constructed during research for a blood substitute at the U.K. Medical Research Council (MRC) Laboratory of Molecular Biology, Cambridge. Haemoglobin's four protein chains are shown in blue & purple, with the four haem groups, the oxygen-binding sites, in red. MRC scientists used recombinant DNA techniques on the bacterium Escherichia coli, to synthesize human haemoglobin. The need to develop a blood substitute has arisen because of concern over contamination of stocks by pathogens such as HIV, the virus causing AIDS.
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! EN_90281055_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Superconducting fulleride: computer graphics representation of the surface of 'potassium buckide' (K3C60), a crystal produced by doping C60 (Buckminsterfullerene) with potassium. K3C60 consists of a face centred cubic structure of Buckyballs (blue), with potassium ions (yellow) filling the cavities between the 'balls. In 1991, researchers at AT & T Bell Labs discovered that potassium buckide became superconducting when cooled below 18 K. C60 films have also been grown on gallium arsenide crystals, indicating possible applications in fabricating microelectronic circuits.
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! EN_90268365_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Molecular graphics representation of methane diffusing through the zeolite catalyst ZSM-5. The image shows the channels through the zeolite's framework (in yellow & blue), with several methane molecules superimposed in sphere- and wire-drawn forms, to represent the path of the diffusing molecule. The series of channels or pores that comprises a zeolite presents an ideal environment for shape- selective catalysis. Industrial processes using zeolite catalysts include cracking of petroleum, isomerisation & hydrocarbon synthesis reactions.
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! EN_90285715_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Computer graphics space-filling representation of the m- (left) and p- (right) isomers of xylene in the zeolite catalyst ZSM-5. Zeolites are a group of materials, based on silicon, aluminium, phosphorus & oxygen, that have structures based on interconnecting cavities & channels which form an ideal environment for shape-selective catalysis. Industrial applications include the cracking of petroleum, isomerisation & hydrocarbon synthesis reactions. In this image, the proximity of methyl groups in m-xylene (left), prevent its free diffusion along ZSM-5's straight channel. In contrast p-xylene (left) is able to move freely.
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! EN_90268374_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Computer graphics representation of a molecule of methanol (green carbon atom) passing through a channel in the synthetic zeolite catalyst ZS 5. Zeolite minerals containing a silica-alumina crystalline structure are used as catalysts in the cracking process by which petroleum is refined. ZSM-5 forms the basis of the conversion of methanol to gasoline - an alternative to petroleum. A MOBIL commercial plant is in operation in New Zealand in 1991. Environmental pressure will undoubtedly ensure that this & similar processes continue to evolve commercially. This image was prepared using BIOSYM fsoftware.
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! EN_90219250_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Computer graphic representation of part of the haemoglobin molecule, the oxygen-carrying substance of human blood, showing its four polypeptide (protein) chains. The protein component of haemoglobin combines with four haem groups (iron-containing porphyrin substances), shown here in green & red. Haemoglobin has the ability to combine reversibly with oxygen, taking it up in the lungs and releasing it through the tissues. Red blood cells (erythrocytes) are literally packed with haemoglobin, containing only very small amounts of other substances.
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! EN_90263541_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Computer graphics representation of the structures of four different hydrocarbon molecules found in diesel fuel. Modelled using Chemical Design's Chem-X software.
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! EN_90259568_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Computer graphics representation of a molecule of fructose (also called laevulose or fruit sugar), a simple sugar isomeric with glucose. Saccharides or sugars are comprised of rings of 4 or 5 carbon atoms (green) and one oxygen atom (red). Attached around the ring are hydroxy (OH) groups. Glucose & fructose are monosaccharides - single rings. Sucrose (cane sugar) consists of two rings joined together. Polysaccharides such as starch and cellulose consist of hundreds of glucose rings joined in a chain. Cellulose, the structural material of plants, is one of the most abundant naturally-occurring polymers. The image was modelled using Chemical Design's Chem-X software.
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! EN_90219246_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Computer graphics space-filling representation of the haem group of the protein haemoglobin, the oxygen- and carbon dioxide-transporting pigment in blood. The site of interraction between oxygen or carbon dioxide and haemoglobin is an atom of iron (the central purple sphere), held in the centre of a perfectly flat porphyrin ring. The flat shape of the porphyrin allows oxygen and carbon dioxide access to the central iron atom to bind, be carried and ultimately be released without undergoing any chemical change. Image modelled using Chemical Design's Chem-X software.
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! EN_90219242_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Computer graphics model of the protein haemoglobin, the oxygen-transporting pigment in blood. The site of interraction between oxygen and haemoglobin is an atom of Iron (Fe++ - yellow ball), which is held in the centre of a haem ring (represented by the green balls). The protein environment and the geometry of atoms surrounding the Iron atom permits oxygen to be bound, carried and ultimately given up without having been oxidised or otherwise changed chemically. The image was produced using Chemical Design's Chem-X software.
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! EN_90271224_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Computer graphics image of an organometallic gold cluster compound, modelled using Chemical Design's Chem-X software.
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! EN_90227127_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Computer graphic image of the molecular structure of Immunoglobin G (IgG) with the notational name 'DOB'. Immunoglobins are a group of structurally related proteins that act as antibodies. Antibodies are special blood proteins. They are synthesised in lymphoid tissue in response to the presence of a particular antigen (foreign material) & circulated in the blood plasma to the troubled site. A huge range of antibodies are produced each with some slight structural difference. All immunoglobins contain a binding site, which fits, binds & inactivates foreign materials entering the body.
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! EN_90256829_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Computer graphics of the enzyme-substrate complex of serine proteases, one of the enzymes used in the digestion of proteins in human food.
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