الأواكس
15-05-2007, 09:16 PM
هذا الموضوع بعنوان الchitin مختصر لمحاضرة الدكتور جميل
لمن يرغبون الاستفادة من هذا الموضوع راح تحصلون أغلب مواضيعي بالانجليزي لانه مهم في التخصص والله يعيننا عليه
وبالتوفيق للجميع ................
Chitin
Chitin is the second most abundant polysaccharide in nature (after cellulose). At least 10 gigatons of chitin are synthesised and degraded each year in the biosphere. Chitin mainly consists of the aminosugar N-acetylglucosamine, which is partially deacetylated. The mostly deacetylated form of chitin is called chitosan. Chitin (javascript:abb01e()) is present in nature usually complexed with other polysaccharides and with proteins. Chitin is a renewable resource and is isolated from crab and shrimp waste. It is used for waste water clearing, for cosmetics and for medical and verterinary applications.
The following projects are investigated in our group:
1. Hormonal regulation of chitin metabolism (http://www.uni-ulm.de/biologie1/Forschung/Chitin/chitine.html#Hormonal regulation of chitin metabolism#Hormonal regulation of chitin metabolism)
2. Insecticides interfering with the chitin metabolism (http://www.uni-ulm.de/biologie1/Forschung/Chitin/chitine.html#Insecticides interfering with the chitin metabolism#Insecticides interfering with the chitin metabolism)
3. Detection of chitin (http://www.uni-ulm.de/biologie1/Forschung/Chitin/chitine.html#Detection of chitin#Detection of chitin)
4. Repair mechanisms of insect cuticula (http://www.uni-ulm.de/biologie1/Forschung/Chitin/chitine.html#Repair mechanisms of insect cuticula#Repair mechanisms of insect cuticula)
1) Hormonal regulation of chitin metabolism
Scientific:
Chitin has to be degraded and synthesized regularly during a moulting cycle. Therefore, a regulation of these processes is obvious ® (javascript:Literatur1()).
Actual
We study the hormonal regulation of chitin degradation and synthesis in an insect epithelial cell line from Chironomus tentans. We have cloned a cDNA for chitinase and expressed the enzyme in a functional state in the baculovirus/Spodoptera system ® (javascript:Literatur2()). The chromosomal localisation of the chitinase gene (javascript:abb1e()) is determined by in situ hybridisation. The structure of the chitinase gene is currently elucidated. The influence of hormone on enzymatic activity, secretion, RNA expression, RNA stability etc are investigated.
2) Insecticides interfering with the chitin metabolism
We have developed test systems, which allow the screening for compounds, interfering with chitin synthesis and degradation ® (javascript:Literatur3()). Chitin synthesis is studied by incorporation of radio-labelled precursors into chitin, chitinolytic enzymes are determined by microfluorimetric assays ® (javascript:Literatur4()). A lead structure for inhibition of chitinase is the pseudotrisaccharide allosamidin. By comparison of chitinases from bacteria, fungi, plants, crustaceans and insects and various allosamidin (javascript:abb2e()) derivatives we established information on structure activity relationships ® (javascript:Literatur5()). The elucidation of the three-dimensional structure of the catalytic domain enables directed drug design. Chitin metabolism is appreciated as target for insecticides and fungicides since this molecule does not occur in vertebrates.
3) Detection of chitin
Our methods, designed to detect chitin in very small amounts are currently used for the following projects: We use an immuno-histochemical method to localise chitin in biological samples. With the same techniques, chitosan and chitin can be detected after topical application on skin. This allows to monitor the fate of applied chitin/chitosan. ng amounts of chitin and related substances are quantified by an ELISA ® (javascript:Literatur6()).
لمن يرغبون الاستفادة من هذا الموضوع راح تحصلون أغلب مواضيعي بالانجليزي لانه مهم في التخصص والله يعيننا عليه
وبالتوفيق للجميع ................
Chitin
Chitin is the second most abundant polysaccharide in nature (after cellulose). At least 10 gigatons of chitin are synthesised and degraded each year in the biosphere. Chitin mainly consists of the aminosugar N-acetylglucosamine, which is partially deacetylated. The mostly deacetylated form of chitin is called chitosan. Chitin (javascript:abb01e()) is present in nature usually complexed with other polysaccharides and with proteins. Chitin is a renewable resource and is isolated from crab and shrimp waste. It is used for waste water clearing, for cosmetics and for medical and verterinary applications.
The following projects are investigated in our group:
1. Hormonal regulation of chitin metabolism (http://www.uni-ulm.de/biologie1/Forschung/Chitin/chitine.html#Hormonal regulation of chitin metabolism#Hormonal regulation of chitin metabolism)
2. Insecticides interfering with the chitin metabolism (http://www.uni-ulm.de/biologie1/Forschung/Chitin/chitine.html#Insecticides interfering with the chitin metabolism#Insecticides interfering with the chitin metabolism)
3. Detection of chitin (http://www.uni-ulm.de/biologie1/Forschung/Chitin/chitine.html#Detection of chitin#Detection of chitin)
4. Repair mechanisms of insect cuticula (http://www.uni-ulm.de/biologie1/Forschung/Chitin/chitine.html#Repair mechanisms of insect cuticula#Repair mechanisms of insect cuticula)
1) Hormonal regulation of chitin metabolism
Scientific:
Chitin has to be degraded and synthesized regularly during a moulting cycle. Therefore, a regulation of these processes is obvious ® (javascript:Literatur1()).
Actual
We study the hormonal regulation of chitin degradation and synthesis in an insect epithelial cell line from Chironomus tentans. We have cloned a cDNA for chitinase and expressed the enzyme in a functional state in the baculovirus/Spodoptera system ® (javascript:Literatur2()). The chromosomal localisation of the chitinase gene (javascript:abb1e()) is determined by in situ hybridisation. The structure of the chitinase gene is currently elucidated. The influence of hormone on enzymatic activity, secretion, RNA expression, RNA stability etc are investigated.
2) Insecticides interfering with the chitin metabolism
We have developed test systems, which allow the screening for compounds, interfering with chitin synthesis and degradation ® (javascript:Literatur3()). Chitin synthesis is studied by incorporation of radio-labelled precursors into chitin, chitinolytic enzymes are determined by microfluorimetric assays ® (javascript:Literatur4()). A lead structure for inhibition of chitinase is the pseudotrisaccharide allosamidin. By comparison of chitinases from bacteria, fungi, plants, crustaceans and insects and various allosamidin (javascript:abb2e()) derivatives we established information on structure activity relationships ® (javascript:Literatur5()). The elucidation of the three-dimensional structure of the catalytic domain enables directed drug design. Chitin metabolism is appreciated as target for insecticides and fungicides since this molecule does not occur in vertebrates.
3) Detection of chitin
Our methods, designed to detect chitin in very small amounts are currently used for the following projects: We use an immuno-histochemical method to localise chitin in biological samples. With the same techniques, chitosan and chitin can be detected after topical application on skin. This allows to monitor the fate of applied chitin/chitosan. ng amounts of chitin and related substances are quantified by an ELISA ® (javascript:Literatur6()).