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Biomass Fundamentals(1)

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					          Biomass Fundamentals

Modules 6-11: Carbohydrates: a major building block for
                      biomass

                  A capstone course for

                           BioSUCCEED:
    Bioproducts Sustainability: a University Cooperative Center
                   of Excellence in EDucation




            The USDA Higher Education Challenge Grants program gratefully
                             acknowledged for support
This course would not be possible without
             support from:

                              USDA

  Higher Education Challenge (HEC) Grants Program

         www.csrees.usda.gov/funding/rfas/hep_challenge.html
                   Emil Fischer:
         Father of Carbohydrate Chemistry
                            (1852-1919)
• Prof. of Organic
  Chemistry University of
  Berlin
• Known for his
  monumental work on
  configuration of sugars

• Also worked on
  aminoacids, proteins,
  indoles &
  stereochemistry

• As a Grad. student he
  discovered
  phenylhydrazine              Nobel prize for Chemistry 1902
   What is a carbohydrate?
• Carbohydrates are
  polyhydroxyl compounds          Quiz M6/11.1
                                  1.
                general formula
     Cn(H2O)n
                  “Hydrates of
     Carbon”


• All contain hydroxyl groups
  -OH
  primary -CH2OH and
  secondary =CHOH
            What is a saccharide?

• A carbohydrate possessing
  the empirical formula,
  Cm(H2O)n, or hydrates of
  carbon analogous to
  inorganic hydrates (e.g., Fe2
  (SO4)3*6H2O)

• Shown at left is open chain
  form (Fischer Projection
  formula) of D-Glucose,            D-Glucose is a stereospecific
  isomer in which the hydroxy         form of glucose having the
  on C5 is RIGHT                  orientation specified by the Fisher
                                  Projection formula shown at left.
               Abundance
Quiz M6/11.2
1.                  • Carbohydrates are the most
                      abundant living biomaterial (a
                      substance derived from living
                      systems) on the planet

                    • They comprise the bulk of plants,
                      while constituting a significant
                      portion of the cellular membrane
                      of animals (yet, lesser than
                      proteins and lipids)

                    • They are however, a significant
                      source of stored energy
            Typical carbohydrates

• D-glucose, D-fructose

• Sucrose: common table
  sugar that is a disaccharide
  synthesized from
  dehydration of D-glucose &
  D-fructose

• Lactose: common milk
  sugar that is a disaccharide
  of D-glucose & D-galactose
        Structure of carbohydrates
Based on glyceraldehyde
                          Quiz M6/11.1
                           1.
Common carbohydrates

          ESSAY
            At this point, describe in a
            page or less, how XXX
            contributes to your lifestyle
            or how you would like it to
  Common carbohydrate: sucrose
• Dimer
• Disaccharide
• Indispensable to our
  way of life!
• Notice -acetal
  linkage
                         The linkage between glucose and fructose
                         responsible for the formation of this dimer
                         known as sucrose is known as a glycosidic
                         bond.
                            Nomenclature
                                           Quiz M6/11.4
Monosaccharides - characterized in terms
of the number of carbons
                                           1.


 Example          # of Carbons   Name
 glyceraldehyde        3         triose
                       4         tetrose
 xylose                5         pentose
 glucose               6         hexose
                      etc
             Nomenclature: part II

   CHO             CHO
 H    OH        HO    H
HO      H        H       OH
 H      OH      HO       H
 H      OH      HO       H

     CH2OH           CH2OH


 d-glucose       l-glucose
                              Shown above are two forms of a generic
                              amino acid (where R = carbon-containing
                              groups) that are said to be “enantiomeric.”
    Nomenclature: part III
       1
     CHO
       2
   H   OH                                      OH
       3                                   H
  HO           H                       4       6
                                                   5   H OH
       4
   H           OH                    HO        3
                                                        2
                                      HO                      O
       5
   H       OH                                      H   OH
                                                              1

       6                                       H              H
         CH2OH
 Fisher Projection                     D glucose

               H   OH                                                H   OH
           4       6                                                4    6       H O
                       5   H O                                               5
                                                                  HO             2
    HO                     2                                             3                  H
     HO            3                 OH                            HO
                       H         1                                           H         1
                            OH                                                   OH
                   H             H         Chair Conformation            H             OH
       -D glucopyranose                                           -D glucopyranose


• C1: Anomeric Carbon

• α : Axial configuration (vertical to the seat of
  the chair)

• β : Equatorial configuration (parallel to the seat
  of the chair)
Most Important Chemical Consideration of
                Sugars
   Consider the anomeric carbon! The aldehyde on the one
   position can be nucleophilically attacked by any of the hydroxyls!
Hemiacetalization Concept Key to
 Carbohydrate Ring Structures
    Nomenclature of Carbohydrates
• D, L Defines the configuration at C5
  D has the OH at Right in Fischer projection
  L has the OH at Left in Fischer projection
• Gluco defines the configuration of the OH at C2, C4, C5. These OH’s are
  on same side while the C3-OH is opposite to others
• α,β defines the configuration of the OH at C1, the anomeric
  carbon
• Pyran indicates 6 member ring size
• Furan indicates 5 member ring size



Examples follow
In Glucuronic acid C2, C4, C5 OH’s are on same
                     side

                H                  H
                C   O             C    O

            H       OH        H        OH
          HO        H        HO        H
            H       OH       HO        H
           H        OH        H        OH

                CO2H              CO2H
          glucuronic acid   galacturonic acid
                  Alditols
• In Mannitol C2, C4,
  C5 OH’s are not at         CH2OH         CH2OH

  same side in Fisher   HO     H     H          OH

  Projection            HO      H    HO         H

                        H       OH   H              OH

                        H       OH
                                           CH2OH

                             CH2OH

                         Mannitol         Xylitol
                 Conformations
                             Anomers
             CH2OH                             CH2OH
                 O OH                              O
             OH                                OH
           OH                                 OH       OH
                    OH                                OH
  -D glucopyranose                      -D glucopyranose
      25
[a]          +19o                                +112o      Rotations of
      D                                                     Fresh Solutions

                                         25
  For aged solutions [a]                       = +52.7o
                                        D
      Reason: Mutarotation is the best evidence for the cyclic
              hemiacetal structure of D-(+)-glucose
     Monosaccharides,Hemiacetal Formation II
      CH2OH
                                                    CH2OH
 H    C       O
              ..    H
                                            H       C         O
        H
 C    OH            C   O                             H                 OH
              H                             C       OH        H    C
HO    C       C     H                                                   H
                                           HO       C         C
      H       OH
                                                    H         OH
 C5 OH attacks aldehyde giving a pyranose ring (6 member structure)

     CH2OH                                  CH2OH
HO C H O H                           HO     C H O
        ..
                                                                   OH
   C         C O                            C
 H   OH    H                           H        OH            C
                                                          H        H
     C     C H                                  C         C
       H       OH                               H         OH
 C4 OH attacks aldehyde giving a furanose ring (5 member structure)
-D glucofuranose                                               -D glucopyranose
   CH2OH                         Mutarotation                      CH2OH
HO     O                                                               O
     OH        Ring closure between C1                             OH
            OH and C4 -OH            CHO                                 OH
                                                                  OH
          OH                       H     OH                            OH
                    CH2OH
                                  HO     H          CH2OH
                     OH
                        OH                              OH
                                   H     OH               CHO
                      OH   CHO                      OH
                                   H     OH
                                                   OH
                         OH            CH2OH             OH
                                   D glucose   Ring closure between    CH2OH
   CH2OH
HO     O OH                                    C1 and C5 -OH               O OH
     OH                                                                OH
                                                                      OH
          OH                                                               OH
-D glucofuranose                                               -D glucopyranose
Hemiacetalization Concept Key to
 Carbohydrate Ring Structures
• Oligosaccharides
  – consist of several monosaccharide residues
    joined together with glycosidic linkages


  – di, tri, tetrasaccharides
     (depending on the number of monosaccharides)


  – up to 10 - 20 monosaccharides (depending on
    analytical techniques i.e GC vs LC/MS)
• Polysaccharides
  – refer to polymers composed of a large number of
    monosaccharides linked by glycosidic linkages


  ex. Cellulose
                                 Cellobiose
          CH2OH                  OH           CH2OH                        OH
                  O    HO                             O       HO
   HO                                   O                                       OH
     HO               O                 HO                   O
                                 O                                      O
              OH                                    OH
                            CH2OH                                  CH2OH

                                                             n = 1 -5000
                          anhydro-         oxygen bridge
                        glucopyranose      (ether-type or
                            unit          glycosidic bond)
                               Cellulose
-D-anhydroglucopyranose units linked by
  (1,4)-glycosidic bonds

                           6
            OH     4       CH2OH                      3'          OH   1'            CH2OH
 HO                                    O                                                     O
                  O                             HO          5'              O
                               5   2                             2'
HO                HO                           O                             HO                    OH
              O                                        CH2OH O
      CH2OH            3           OH      1     4'                                         OH
                                                       6'                   n
                                                                                    Reducing
  Non-Reducing                                                                      End-Group
  End-Group
                                                                                (potential aldehyde)
             Polysaccharides
Polysaccharides are polymers composed of
 many monosaccharide units linked by
 glycosidic bonds
The glycosidic bond can can have either the α
 or a β-configuration and be joined to any of
 the hydroxyl groups at C-2, C-3, C-4 or C-6
The chain can either be Linear or Branched
  – branches can be single monosaccharide units,
    chains of two or more units, or chains of a
    variable number of units
              Polysaccharides
Polysaccharides can be divided into two classes
  – Homopolysaccharides
     • consist of only one kind of monosaccharide
           ex cellulose


  – Heteropolysaccharides
     • consist of two or more kinds of
       monosaccharides
           ex galactoglucomannans
         Homopolysaccharides
Homopolysaccharides can be further divided by the
type(s) of glycosidic linkages
  Homolinkages - either an α or a β configuration to
  a single position (exclusive of any branch
  linkages)
     •that is a single kind of monosaccharide linked
      by one type of bond α-14, β-14, and so on
  Heterolinkages - a mixture of a- and b-
  configurations and/or mixture of positions
     •usually have a definite pattern for the
      arrangement of the linkages
        Heteropolysaccharides
Heteropolysaccharides can have the same kind
of linkage diversity as with
homopolysaccharides, but now associated with
one or more of the different kinds of
monosaccharide units
  – infinite degree of diversity of structure
            Polysaccharides
Polysaccharides can not only have
different sequences of monosaccharide
units, but also different sequences of
glycosidic linkages and different kinds of
branching
  – a very high degree of diversity for
    polysaccharides and their structure-
    function relationships
               Plant Polysaccharides
The conformation of individual
monosaccharide residues in a polysaccharide
is relatively fixed, however, joined by
glycosidic linkages, they can rotate to give
different chain conformations.

               1,4 glycosidic                 OH
     OH        linkage                                       1,6 glycosidic
                                        HO          O        linkage
O          O
               
                                         HO                 
HO                     OH
                                                  HO
          HO                    O                       O
               O                                        
                HO                            HO                O
                            HO                 HO
                                    O                   HO
                                                                    O
          Plant Polysaccharides
The different kinds of primary structures that
result in secondary and tertiary structures give
different kinds of properties
  – water solubility, aggregation and crystallization,
    viscosity, gelation, etc.
Polysaccharides have a variety of functions
  – Storage of chemical energy in photosynthesis
  – Inducing Structural Integrity in plant cell walls
                                               Starch
Starch is composed completely of D-glucose
      – found in the leaves, stems, roots, seeds etc in higher plants
      – stores the chemical energy produced by photosynthesis
Most starches are composed of two types of polysaccharides - amylose and amylopectin
      – amylose - a mixture of linear polysaccharides of D-glucose units linked -(1-4) to each other
             • between 250-5,000 glucose residues
  The Components of Starch
            OH
              O
      O
       HO
             OH         OH
               O
                         O
                  HO
                         OH
                          O
                  (1-4)
                         HO        OH

Amylose                     HO
                                  O

                              O
                            OH


                       HO         OH
                             O
                       O
                    Amylopectin
– Amylopectin - a mixture of branched polysaccharides of D-
  glucose units linked -(1-4), with ~ 5% -(1-6) branch linkages
   • between 10,000-100,000 glucose residues


                         OH O
                                           OH
                                             O
                   OHO          OH O
                                   HO
                                OH O        OH
            OH O                              O (1-6)
                                    OHO
                   OH O HO            HO
                                                  O

          O HO                    (1-4)         OH
                                                   O
                                                 HO      OH
                                                         O
                                                   HO
                                                     O
        Starch Polymer Components



Amylose




Amylopectin (1 residue in every 20 is 16 linked to branch off)
          The Components of Starch
Amylose
                                              Amylopectin
        OH                                                     OH O
          O                                                                      OH
  O                                                                                O
   HO                                                    O            OH O
          OH        OH                                    HO             HO
            O                                                         OH O        OH
                     O                            OH O                              O (1-6)
              HO
                                                                          OHO
                     OH                                  OH O HO            HO
                                                                                        O
                      O
              (1-4)                            O HO                                   OH
                     HO        OH                                       (1-4)
                                                                                         O
                                                                                       HO      OH
                              O
                        HO
                                                                                               O
                          O                                                              HO
                        OH
                                                                                           O

                   HO         OH
                         O
                   O




                                    Starch tertiary structure (Helix)
Building Blocks of Life
Hemiacetalization Concept Key to
 Carbohydrate Ring Structures
Fructose is Bane of Our Civilization
                 •   Glycoproteins (biomaterial) from food
                     sugars are sticky – adhere to teeth enamel
                 •   Streptococcus mutans also adhere to
                     biomaterial
                 •   The glucose of the sucrose is polymerized
                     by glucosyl transferase (enzyme of
                     bacteria) to form plaque
                 •   Fructose from the above hydrolysis is
                     released
                 •   Bacteria needs anaerobic conditions
                     which are partially supprted by plaque to
                     hydrolyze fructose for energy
                 •   Ca3(PO4)2 + CH3CH2(OH)COOH 
                     CaHPO4 + Ca+2  loss of enamel
       Alditols: Reduction Products




Reduced aldehyde
end-group
                   D-Mannitol
   Aldaric Acids: Oxidation Products




• Above is oxidation product of D-galactose
• Galactaric acid
• Why is it not labeled as “D- ?”
               Sorbitol (D-Glucitol)




It is a polyol discovered in the berries of the mountain ash in 1872
commercially produced by the hydrogenation (reduction) of glucose).
It does not lead to tooth decay. WHY?
60% as sweet as sucrose with 1/3 fewer calories
Good sugar substitute
                  Relative Sweetness
COMPOUND                                 RELATIVE SWEETNESS
Lactose                                  0.2
D-Galactose                              0.3
Maltose                                  0.3
D-Glucose                                0.7
Sucrose                                  1.0 (Standard)
D-Fructose                               1.7
Sodium cyclamate (procarcinogen)         30
Aspartame                                190
Sodium saccharin (possible carcinogen)   500
Sucralose (brand name = Splenda)         600
Neohespiridin dihydrochalcone            1,000
5-nitro-2-propoxyaniline                 4,000
Glucose Derivative Spotlight: Glucosamine
       Nitrogen




• Found in mucin, a glycoprotein constituent of saliva
• Plays important role in production, maintenance, and repair of cartilage
  (prevents bone ends from rubbing)
• Used in Europe since 1980s to “offset” onset of osteoarthritis
• USA is now touting its benefits (perform search – 906K hits)
Most Important Chemical Consideration of
                Sugars
   Consider the anomeric carbon! The aldehyde on the one
   position can be nucleophilically attacked by any of the hydroxyls!
     Important Oligosaccharides
• ,-tetrahalose: glucose disaccharide found
  in the circulatory systems of insects; energy
  for insect eggs, larvae, and pupae. Found in
  fungi & yeasts
• Raffinose: widely distributed in plants at low
  concentration – 1:1:1 D-galactose:D-
  glucose:D-fructose (galactose+sucrose in
  which it is on C6 of glucose moiety)
              Starch (Amylose)
• High MW polyglucoside that is plant energy
• Can be hydrolyzed to specific oligosaccharides
• -Amylase (saliva & pancreatic juice) converts it to
  maltose and glucose
• -Amylase (in plants only) converts it to maltose –
  NOTE: malt from barley is its common source to
  BREW BEER
            Starch, Part Deux
• Noncrystalline
• Partially water soluble
• 25% amylose (linear polysaccharide), 75%
  amylopectin (branched polysaccharide)
          Starch Polymer Components



Amylose




Amylopectin (1 residue in every 20 is 16 linked to branch off)
         Homework Questions
• Draw structure of raffinose by only consulting
  these notes!
• Provide an explanation for the “sweetness” of
  saccharides – you may consult the literature
• Using your explanation, design a molecule that
  may compete with commercial sugars for
  market share!
    Article of Interest for Discussion
•   “Chemically modified chitin and chitosan as biomaterials” – Sashiwa, H.; Aiba, S.-I. Prog.
    Polym. Sci. 29 (2204) 887-908.
•   http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6TX2-4CNJ8S2-1-
    6&_cdi=5578&_user=290868&_orig=search&_coverDate=09%2F30%2F2004&_qd=1&_sk
    =999709990&view=c&wchp=dGLbVzb-
    zSkzS&md5=e9e66537b26f5f36324572d9f01635b8&ie=/sdarticle.pdf
•   Chitosan-derivatized -CD (2-position)
•   Slow radiative iodine release in blood of rats
•   Decontamination of textile dye-laden waters
•   Absorbent matrix
•   Positive cholesterol interaction
Structure of Starch
          • Unbranched chains
          • 500-20K -(14)-D-
            glucose units
          • Extended shape has
            possible 7-22 nm
            hydrodynamic radius
          • Usually forms stiff left-
            handed single helix
   Hydrogen Bonding in Amylose
• Single helical amylose has H-bonding between O2 
  O6 atoms on outside
• Syneresis (release of water) occurs
• Double-stranded crystallites formed resistant to
  amylase
• Fairly hydrophobic & low solubility
• Interior is like cyclodextrins – hydrophobic
            Cyclodextrins (CDs)
                                       • Cyclic oligomers of -D-
                                         glucopyranose
                                       • Glycosidic bonds
                                       • Discovered in 1891 by
                                         Villiers
                                       • Synthesized by the
                                         enzymatic conversion of
                                         amylose & selective
                                         precipitation



Cavity volume: 0.174, 0.262, & 0.472 nm2 for , , & -CDs, respectively
       CD Formation
        Precipitating   Yield (%)
        Agent
-CD    1-decanol       40


-CD    toluene         50-60


-CD    Cyclohexadec-   40-50
        8-en-1-ol
            Interesting Properties
• Formation of inclusion (host/guest) complexes with
  lipophilics
   – -CD: aliphatic chains
   – -CD: small aromatics (toluene)
   – -CD: larger molecules
• Low toxicity
• Biodegradable
From Frömming and Szejtli: Cyclodextrins in Pharmacy,
Kluwer, Acad. Press, Dordrecht, 1994.
Cyclodextrin Derivatives of
 Pharmaceutical Interest                               OR
                        HO       OH
                                             O                     OH
                                     O
                                                           O
                        O        OH                   OH
              HO                                                                 OR
                        O
         HO                                                RO                   OH
                            OR                                          O

                   O                                                        O
                                                           HO
                        O
              RO                 OH
                                             HO                O                OH

                                 O       O             O            OH
                   HO

                                      HO
                                                 OR



    Cyclodextrin                                               R                      DS

       HPCD                               CH2CHOHCH3                                 0.6
       SBECD                              (CH2)4SO3- Na+                             0.9
       RMCD                                           CH3                            1.8
   Also the CD derivative: HPCD
Some cyclodextrin-containing products
 Cyclodextrin       Product                 Trade name

 CD                PEG1 iv infusion        Prostavastin (Eur.), Caverject (USA)

 CD                Piroxicam tablets       Brexin (Eur.)

       HPCD        Intraconazole oral      Sporanox (Eur. and USA)
                    solution and iv soln.
    SBECD          Ziprasidone maleate     Zeldox (Eur.), Geodon (USA)
                    im solution
     RMCD          Estradiol nasal spray   Aerodiol (Eur.)

 CD                OP-1206 tablets         Opalmon (Japan)

       HPCD        Diclofenac sodium       Voltaren (EUR.)
                    eye drop solution

 World-wide there are close to 30 cyclodextrin containing pharmaceutical products
 on the market and most of them are marketed in more than one country. Almost
 half of them contain the natural CD.
   What are cyclodextrins used for?
• To increase aqueous solubility of drugs.
• To increase chemical stability of drugs.
• To enhance drug delivery to and through biological membranes.
• To increase physical stability of drugs.
• To convert liquid drugs to microcrystalline powders.
• To prevent drug-drug and drug-excipient interactions.
• To reduce local irritation after topical or oral administration.
• To prevent drug absorption into skin or after oral administration.
   And so on.
        Cyclodextrin complexation:
          conventional wisdom

-Cyclodextrin:
Seven -1,4-linked gluco-
pyranose units form a cone
with a hydrophilic outer
surface and a lipophilic
cavity in the center.
       Complex Formation




From Frömming and Szejtli:
Cyclodextrins in Pharmacy
Kluwer Acad. Press,
Dordrecht, 1994.
Cyclodextrin Complexes


         Doxorubicin-CD complex




         Aspirin-CD complex
  Why are cyclodextrins better
    than organic solvents?

• Frequently less irritating after iv
  and im injection.
• Frequently less toxic.
• The drug does not precipitate after
  iv injection.
• Can be used in solid dosage
  forms.
        Homework Questions
• Describe why CD is in “Fabreeze” (P&G
  product) and how you think it works.
• How do K1:3 complexes form? Give an
  example.

				
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