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Chlorophyll |
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German chemist Wells Tate. In the early 1900s, using the most advanced chromatography to extract the green leaves of the material. After 10 years of hard work, Wells Tate with tons of green leaves, and finally captured the mysterious substance leaves - chlorophyll, chlorophyll in plants, it is precisely because of the peculiar role played, it makes us humans to survive . Due to the successful extraction of chlorophyll, 1915, Wells Tate was awarded the Nobel Prize in Chemistry. Chemical structure Molecular structure of chlorophyll early 19th century, the Russian chemist, founder chromatography MC Ciwei Te adsorption chromatography with proof of chlorophyll in the leaves of higher plants, there are two ingredients. Germany H. Fischer, etc. After years of efforts, made clear the complexity of the chemical structure of chlorophyll. 1960 U.S. laboratory led by RB Woodward synthesis of chlorophyll a. Thus, the molecular structure of chlorophyll get conclusive.Chlorophyll molecule is composed of two parts: the core part is a porphyrin ring (porphyrin ring), its function is to absorb light; other part is a long aliphatic hydrocarbon side chains known as phytol (phytol), chlorophyll a This side chain is inserted into the thylakoid membrane. And heme iron group is different, chlorophyll porphyrin ring containing one magnesium atom. Chlorophyll molecules porphyrin ring via a single bond and a double bond to absorb changes in visible light. Structural differences between the various chlorophyll small. Such as chlorophyll a and b only on the pyrrole ring Ⅱ additional groups there are differences: the former is a methyl group, which is a formaldehyde-based. Bacterial chlorophyll and chlorophyll a different point also lies in the porphyrin ring Ⅰ replaced on vinyl ketone and ring Ⅱ a pair of double bonds are hydrogenated. Chemical properties The chlorophyll in chloroplasts of higher plants are mainly two kinds of chlorophyll a and chlorophyll b. They do not dissolve in water, but soluble in organic solvents, such as ethanol, acetone, ether, chloroform and the like. Chlorophyll a formula: C55H72O5N4Mg; chlorophyll b formula: C55H70O6N4Mg. In color, chlorophyll a bluish-green and yellow-green chlorophyll b. According to the chemical nature, chlorophyll chlorophyllin ester saponification reaction can occur. Chlorophyllin is a dicarboxylic acid, in which a carboxyl group is esterified with methanol, and the other is esterified with phytol. Chlorophyll molecule contains a porphyrin ring of the "head" and a phytol "tail." Magnesium atoms residing in the center of the porphyrin ring, biased with a positive charge associated with the nitrogen atom is biased at a negative charge, which porphyrin polar, hydrophilic, and can be combined with protein. Leaf alcohol is composed of four isoprene units diterpene is a lipophilic fatty chain, which determines the soluble chlorophyll. Chlorophyll does not participate in the transfer of hydrogen or hydrogen oxidation-reduction, while only electron transfer (ie, gains and losses arising from electron redox) and conjugated transfer (direct energy transfer) way to participate in the energy transfer. Magnesium porphyrin ring atoms may be a hydrogen ion, copper ion, zinc ion is replaced. Leaves treated with acid, hydrogen ions are easy to enter the chloroplast, the replacement of magnesium atoms form pheophytin, so that leaves brown. Pheophytin Yi then with copper ions combine to form copper behalf of chlorophyll, the color is more stable than the original. According to this principle that people often use to save the green copper acetate treated specimens. Phytol are lipophilic aliphatic chain, because it determines the presence of soluble chlorophyll molecules, so soluble in acetone, alcohol, ether and other organic solvents. Because the difference in the structure of chlorophyll a bluish green, b yellow green. Susceptible to oxidation and to the light fade. Chlorophyll is an ester of dicarboxylic acid, with an alkali saponification reaction occurs. Chlorophyll is not very stable, light, acid, alkali, oxygen, oxidants, etc. are to decomposition. Under acidic conditions, it is easy to lose chlorophyll molecules of magnesium porphyrin ring as pheophytin. Chlorophyll solution can be part of a similar reaction of photosynthesis, the light so that some compounds oxidation or reduction. Chlorophyll film artificially prepared to produce light and optical position photocurrent can also be some catalytic redox reactions. Photosynthesis Photosynthesis is the chloroplasts of green plants, the use of solar energy, carbon dioxide and water into organic matter storage of energy, and release of oxygen in the process. The first step in photosynthesis light energy is absorbed by the chlorophyll and chlorophyll ionized. The chemical can be temporarily stored in adenosine triphosphate (ATP) in, and eventually carbon dioxide and water into carbohydrates and oxygen. In 1864, German scientist sax made such an experiment: the green leaves on the dark hours, the purpose is to let the leaves of nutrients consumed. Then half of the blade exposure, the other semi-shade. Over a period of time after treatment with iodine vapor leaves the half leaf shading found no color change, that half of the blade exposure is dark blue. This experiment proved successful green leaf starch produced in photosynthesis. In 1880, German scientist Hermann engi photosynthesis carried out with water sponge experiment: containing Spirogyra and aerobic bacteria temporary mounts on no air and is a dark environment, and then use a very fine beam irradiation Spirogyra . Observed through a microscope, the aerobic bacteria are concentrated in the chloroplast by the beam irradiated to the vicinity of the site; if the temporary mounts completely exposed to the light, the aerobic bacteria are concentrated in the chloroplast light all around the area. Engi Mann proved: Oxygen is released from the chloroplast, the chloroplast is the site of photosynthesis of green plants. The one off the starch violet leaves in the sun for several hours after the iodine reagent, can be found only on the green leaf area and the white area is not discolored, that only the green areas the presence of starch. This shows a lack of chlorophyll in photosynthesis can not be the case, the presence of chlorophyll is a necessary condition for photosynthesis. Phenomenon of fluorescence and phosphorescence phenomena Chlorophyll absorption spectrum of visible light in the blue and red light at each have a significant absorption peaks. The peak position and the extinction values with the size of the different types of chlorophyll vary. Chlorophyll a maximum absorption wavelength of 420-663nm, the maximum absorption wavelength of chlorophyll b in the range 460-645nm. When the chlorophyll molecules in chloroplast membrane, since the chlorophyll protein interactions with the membrane, the light absorption characteristics will change slightly. Alcohol solution of chlorophyll in transmitted light is emerald green, and the reflected light is brownish red. The red light is the light of chlorophyll fluorescence emitted after excitation. This phenomenon is the phenomenon of fluorescence. The main principle is to have two different due chlorophyll absorption peak. Chlorophyll absorbs light ability, if the acetone extract chlorophyll placed between the light source and the beam splitter, you can see some of the wavelength spectrum of the light is absorbed. Thus, in the spectrum appeared black lines or dark band, this is called absorption spectrum. The strongest absorption spectrum of chlorophyll two areas: one at the wavelength of 640nm-660nm red light portion, and the other at a wavelength of 430nm-450nm blue-violet light-receiving section. Absorb less light on the other, in which the green light absorbed at least, at least as chlorophyll absorbs green, so green chlorophyll solution. Acetone extract chlorophyll in transmitted light is emerald green, and in the reflected light is reddish brown. Solution of chlorophyll fluorescence of up to about 10% of light absorption. The low level of fluorescence leaf, means of its absorption of about 0.1% -1%. Fluorescence effects in plant physiology in a wide range of applications. This effect can be studied with the resilience of plant physiology. Because in the face of adversity, transformation will occur chlorophyll in plants to study the fluorescence can be used as plant affected by the degree of adversity stress indicators. In addition, there is a phosphorescent effect. That is, when the fluorescence appeared immediately after the interrupt source, using sensitive optical instrument can also see the faint red light in a short time, this is the phosphorescence. Biosynthesis and metabolism Chlorophyll a biosynthetic pathway, succinyl coenzyme A by the condensation and synthesis of glycine δ-aminolevulinic acid, δ-aminolevulinic acid two condensed to porphobilinogen pyrrole derivatives, and then by polymerization of 4 porphobilinogen into a porphyrin ring ─ ─ protoporphyrin Ⅳ, protoporphyrin Ⅳ is the formation of chlorophyll and heme precursors together with ferrous heme binding on into, and combine it into a magnesium magnesium protoporphyrin. Magnesium protoporphyrin longer accept a methyl group, cyclization has become the first ring of the original off Ⅴ alcohol plant chlorophyll, the latter by photoreduction, esterification step and the formation of chlorophyll a. Defoliation In vivo chlorophyll and other substances are also the same as the state is constantly updated. It is chlorophyll enzymes break down, or by photo-oxidation and bleaching. Many trees in late autumn when the leaves were beautiful red, because when speed is greater than the degradation of chlorophyll synthesis rate, content decreased, the original masked by chlorophyll carotenoids, anthocyanins color display's sake. Chlorophyll-containing N, Mg, carotenoids contain N, Mg. In plant senescence and storage process, the enzyme can cause the decomposition of chlorophyll destruction. This enzymatic changes can be divided into direct and indirect effects of two types of action. Directly to the substrate only chlorophyll chlorophyll enzyme, catalytic chlorophyll phytol ester bond hydrolysis and removal of chlorophyll phytol. Pheophytin also its substrate, the product is water-soluble magnesium removal removal plant chlorophyll, which is olive green. The optimum temperature of the enzyme chlorophyll 60-82 ℃, 100 ℃ when completely inactivated. Indirect effects of a protease, lipase, lipoxygenase, peroxidase, pectin esterase and so on. Protease and lipase protein complex through the decomposition of chlorophyll, chlorophyll loss protection to make it easier destroyed. Lipoxygenase and peroxidase to catalyze oxidation of the corresponding substrate, resulting material therebetween causes oxidative decomposition of chlorophyll. Pectin esterase is the role of pectin hydrolysis of pectic acid, thereby increasing the proton concentration, the chlorophyll is broken off and magnesium. Green plants in vivo chlorophyll photosynthesis can play, it will not happen photolysis. But in the course of processing and storage, chlorophyll often subject to light and oxygen effect, be photolysis as a series of small molecules and fade. Photolysis products are lactic acid, citric acid, succinic acid, maleic acid, and a small amount of alanine. Therefore, the correct choice of packaging materials and methods, and appropriate use of antioxidants to prevent photooxidation fading. Extract Chlorophyll extract preparation is in a semi-dark room, the room temperature maintained at 25 ℃. Extracting the following steps: (1) Take 1000 grams of fresh green leaves, stir in Webster Cutter pulverized. (2) 1000g of the pulverized leaves into a small amount of calcium carbonate added acetone (temperature 20 ℃) for extraction until the filter after cleaning the leaves as a colorless fragments. (3) the filtered extract was placed in acetone containing 1 l of petroleum ether and acetone 100ml funnel, and then gently rotated while until layering plus put up with distilled water. Most of the aqueous layer is discarded acetone and water soluble impurities, only petroleum ether was added. |
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