Glukan

Glukan je polisaharid D-glukoznih monomera^[1] povezanih glikozidnim vezama. Među njima su mnogi i medicinski značajni, osobito beta-glukani.^[2]

Tipovi uredi

U glukane se ubrajaju: (α- i β- klarificiraju tip O-glikozidne veze.)

Alfa uredi

Dekstran, α-1,6-glukan sa α-1,3-granama;
Glikogen, α-1,4- i α-1,6-glukan;
Pululan, α-1,4- i α-1,6-glukan;
Skrob, α-1,4- i α-1,6-glukan;

Beta uredi

Celuloza, β-1,4-glukan;
Kurdlan, β-1,3-glukan;
Laminarin, β-1,3- and β-1,6-glukan;
Hrizolaminarin, β-1,3-glukan;
Lentinan, prečišćeni β-1,6:β-1,3-glukan iz Lentinus edodes;
Lihenin, β-1,3- and β-1,4-glukan;
Pleuran, β-1,3- and β-1,6-glukan izolovan iz Pleurotus ostreatus;
Zimozan, β-1,3-glukan.

Osobenost uredi

Svojstva glukana su otpornost na oralne kiseline i enzime i nerastvorljivost u vodi. Inače, rastvorljivost glukana koji su ekstrahovani iz žitarica može široko varirati.

Struktura uredi

Glukani su polisaharidi koji su izvedeni iz glukoznih monomera. Monomere su povezane glikozidnim vezama. Moguća su četiri tipa polisaharida na bazi glukoze: 1,6- (skrob), 1,4- (celuloza), 1,3- (laminarin) i 1,2-vezani glukani.

Prvi predstavnici nehidrolizirajućih linearnih polimera glavnog lanca, sastavljeni od jedinica levoglukozana, sintetizovani su 1985. anionskom polimerizacijom 2,3-epoksi derivata levoglukozana (1,6; 2,3-dianhidro-4-O-alkil -β- D-manopiranoze).^[3]

2,3-Polimer

Može se sintetizirati širok spektar jedinstvenih monomera sa različitim radikalima R.^[4] There were synthesized polymers with R= -CH₃,^[3] -CH₂CHCH₂,^[5] and -CH₂C₆H₅.^[6] Istraživanje kinetike polimerizacije tih derivata, molekulske težine i raspodjele molekulske težine pokazali su da polimerizacija ima značajke živog sistema polimerizacije. Proces se odvija bez prekida i prenosa polimernog lanca, sa stepenom polimerizacije jednakom molskom omjeru monomerama prema inicijatoru.^[7]^[8] U skladu s tim, polimer molekulske težine gornje vrijednosti određuje samo stepen sistema pročišćavanja, koji određuje prisustvo u sistemu nekontrolirane količine terminatora polimernih lanaca.

Poli (2-3)-D-glukoza sintetizirana je prelaskom transformacije benzila (R= -CH₂C₆H₅). koji je funkcionaliziran polimer.

Poliglukoza

Polimerizacija 3,4-epoksi levoglukozana (1,6; 3,4-dianhidro-2-O-alkil-β- D-galaktopiranoze)^[9] resultira formiranjem 3,4-vezanog levoglukozanskog polimera.

3,4-Polimer

Prisustvo 1,6-anhidro strukture u svakoj jedinici polimernih lanaca omogućava istraživačima da primijene sve spektre dobro razvijenih metoda hemije ugljikohidrata sa stvaranjem izuzetno intrigantnih bioloških polimera.

Polimeri su jedini poznati regularni polietri izgrađeni od ugljikohidratnih jedinica u glavnom polimernom lancu.^[10]^[11]

Također pogledajte uredi

Reference uredi

^ Glucans na US National Library of Medicine Medical Subject Headings (MeSH)
^ Yudkin J., Edelman J., Hough L. (1973): Sugar - Chemical, biological and nutritional aspects of sucrose. The Butterworth Group, ISBN 0-408-70172-2.
^ ^a ^b Berman, E.L., Gorkovenko A.A., Zubov, V.P., and Ponomarenko, V.A.,"Regio and Stereospecific Synthesis of Polyglucose with Novel Type BondSoviet J.Bioorg. Chem. 11 (1985), 1125-1129
^ Carlson, LJ (November 1965). "Preparation of 2- and 4-Substituted D-Glucose Derivatives from 1,6-Anhydro-β-D- glucopyranose". The Journal of Organic Chemistry. 30 (11): 3953–3955. doi:10.1021/jo01022a517.
^ Gorkovenko, A.A., Berman, E.L., and Ponomarenko, V.A. Polymerization of 1, 6;2,3 dianhydro 4 O allyl β D manno¬pyranose" Vysocomol. Soed., Ser. B, 1987, 29, 134 137
^ Gorkovenko, A.A., Berman, E.L., and Ponomarenko, V.A. "A New Polymer of Glucose. Poly(2 3) D glucose" Soviet J. Bioorg. Chem., 1987, 13, 218 222
^ Berman, E.L., Gorkovenko, A.A., Rogozhkina, E.D., Izumnikov, A.A., and Ponomarenko, V.A. “Kinetics and Mechanism of Epoxy Ring-Opening Polymerization of 1,6;2,3-Dianhydro-4-O-alkyl-b-D-mannopyranoses” Polymer Sci. USSR, 1988, 413-418
^ Berman E.L. Gorkovenko, A.A., Rogozhkina, E.D., Izyumnikov, A.L., and Ponomarenko, V.A. "Synthesis of Chiral Derivatives of Poly(Ethylene Oxide)" Bull. Acad. Sci. USSR, Div. Chem. Sci., 1988, 705 707
^ Gorkovenko A. A., Berman, E.L., and Ponomarenko, V.A., Poly(3 4) 2 O methyl 1,6 anhydro b D glucopyranose. The First Example of (3 4) linked Polymer Carbohydrates" Soviet J. Bioorg. Chem. 12 (1986), 514-520
^ Berman E.L., Gorkovenko, A.A., and Ponomarenko, V.A. "Structure and Polymerizability of 1,6;2,3 and 1,6;3,4¬ Dianhydrohexapyranoses" Polymer Sci. USSR, 1988, 30, 497¬-502
^ Berman, E.L., “New Glucose Polymers” in “Levoglucosenone and Levoglucosanes: Symposium: 204th National meeting”, Zbigniew J. Witczak (editor), American Chemical Society. Division of Carbohydrate Chemistry, 189-214. Publisher: A T L Press, Scientific Publishers ISBN 978-1-882360-13-0 ISBN 1882360133

Vanjski linkovi uredi

[1] Glucans na US National Library of Medicine Medical Subject Headings (MeSH)

[2] Yudkin J., Edelman J., Hough L. (1973): Sugar - Chemical, biological and nutritional aspects of sucrose. The Butterworth Group, ISBN 0-408-70172-2.

[Berman-3] Berman, E.L., Gorkovenko A.A., Zubov, V.P., and Ponomarenko, V.A.,"Regio and Stereospecific Synthesis of Polyglucose with Novel Type BondSoviet J.Bioorg. Chem. 11 (1985), 1125-1129

[4] Carlson, LJ (November 1965). "Preparation of 2- and 4-Substituted D-Glucose Derivatives from 1,6-Anhydro-β-D- glucopyranose". The Journal of Organic Chemistry. 30 (11): 3953–3955. doi:10.1021/jo01022a517.

[5] Gorkovenko, A.A., Berman, E.L., and Ponomarenko, V.A. Polymerization of 1, 6;2,3 dianhydro 4 O allyl β D manno¬pyranose" Vysocomol. Soed., Ser. B, 1987, 29, 134 137

[newpolymer-6] Gorkovenko, A.A., Berman, E.L., and Ponomarenko, V.A. "A New Polymer of Glucose. Poly(2 3) D glucose" Soviet J. Bioorg. Chem., 1987, 13, 218 222

[7] Berman, E.L., Gorkovenko, A.A., Rogozhkina, E.D., Izumnikov, A.A., and Ponomarenko, V.A. “Kinetics and Mechanism of Epoxy Ring-Opening Polymerization of 1,6;2,3-Dianhydro-4-O-alkyl-b-D-mannopyranoses” Polymer Sci. USSR, 1988, 413-418

[8] Berman E.L. Gorkovenko, A.A., Rogozhkina, E.D., Izyumnikov, A.L., and Ponomarenko, V.A. "Synthesis of Chiral Derivatives of Poly(Ethylene Oxide)" Bull. Acad. Sci. USSR, Div. Chem. Sci., 1988, 705 707

[9] Gorkovenko A. A., Berman, E.L., and Ponomarenko, V.A., Poly(3 4) 2 O methyl 1,6 anhydro b D glucopyranose. The First Example of (3 4) linked Polymer Carbohydrates" Soviet J. Bioorg. Chem. 12 (1986), 514-520

[10] Berman E.L., Gorkovenko, A.A., and Ponomarenko, V.A. "Structure and Polymerizability of 1,6;2,3 and 1,6;3,4¬ Dianhydrohexapyranoses" Polymer Sci. USSR, 1988, 30, 497¬-502

[11] Berman, E.L., “New Glucose Polymers” in “Levoglucosenone and Levoglucosanes: Symposium: 204th National meeting”, Zbigniew J. Witczak (editor), American Chemical Society. Division of Carbohydrate Chemistry, 189-214. Publisher: A T L Press, Scientific Publishers ISBN 978-1-882360-13-0 ISBN 1882360133

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