extraction of proteoglycans (pgs) and...
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Extraction of Proteoglycans (PGs) and Glycosaminoglycans (GAGs) from cells and tissues
PEG Trainee LectureJuly 9, 2012
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Development of Extraction Procedures
• Extraction of intact PGs at high yield– Disruptive Extraction
• High speed homogenization in low salt buffers– Dissociative Extraction
• Solvents of high ionic strength and strong denaturing effect (e.g., 4 M guanidine-HCl)
– Dissociative Extraction followed by Associative ionic strength
• 4 M guanidine-HCl followed by dialysis allows HA- binding PGs to re-form aggregate super-structures
Hascall & Kimura, PGs Isolation & characterization, Methods Enzymol. 82;769-800, 1982.
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Hyaluronan binding domain
Cartilage PG: Aggrecan
Monomer
500 nm
Aggrecan
Cartilage proteoglycan
~100 CS chains, ~100 KS chains (“bottle brush”)
Mr
~2.5 x 106
Da
Length ~ 0.5 m
PG preparation by isopycnic density gradient centrifugation in Cesium Chloride (CsCl) and 4 M GnHCl
Pucci M et al. J. Biol. Chem. 2001;276:4756-4765©2001 by American Society for Biochemistry and Molecular Biology
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Aggregate: 1 hyaluronan + ~180 aggrecan
monomersSupramacromolecular
complexes (5-8 m length)
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Aggrecan
Aggregate: 1 hyaluronan + ~100 aggrecan
monomersGlycerol spraying & rotary shadowing Electron Microscopy
Produced by Matthias Morgelin
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Dissociative Extraction followed by Associative ionic strength (0.5 M GnHCl)
4 M guanidine-HCl followed by dialysis allows HA-binding PGs to re- form aggregate super-structures
monomer
aggregate
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Development of Extraction Procedures
• Extraction of intact PGs at high yield– Low temperature extraction in the presence of
a combination of protease inhibitors– Use of select detergents to enhance the
yields of PGs having a higher hydrophobic content (e.g., cell membrane or intracellular PGs)
• Triton X-100, deoxycholate, CHAPS– SDS is not compatible with guanidine-HCl
Hascall & Kimura, PGs Isolation & characterization, Methods Enzymol. 82;769-800, 1982.
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Tissue Preparation
• Preference for freshly isolated tissue but rapidly frozen (liquid N2 ) tissue stored at ultra-low temperatures can be used– Frozen tissue should be pulverized and
thawed in the extraction solution• Larger tissues (> 1 cm3) can be
homogenized in the extraction solution at ice-cold temperature to yield smaller tissue pieces thereby increasing extraction yields
Hascall & Kimura, PGs Isolation & characterization, Methods Enzymol. 82;769-800, 1982.
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Tissue Preparation• Need to preserve protein’s primary structure
during extraction – pH of extraction solution should be 6.0
• Above acid protease and below neutral protease pH optima
– Add protease inhibitors to the extraction solution• 6-aminohexanoic acid inhibits cathepsin D• Benzamidine HCl inhibits trypsin class• EDTA inhibits metalloproteases• Phenylmethylsulfonyl fluoride (PMSF) inhibits serine-
dependent proteases (AEBSF can also be used)• N-ethylmaleimide inhibits thiol-dependent proteases and
prevents nonspecific disulfide exchange• Pepstatin inhibits cathepsin D
Hascall & Kimura, PGs Isolation & characterization, Methods Enzymol. 82;769-800, 1982.
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Tissue Preparation
• There may be the need to add inhibitors of other enzymes if one suspects the presence of other post-translational modifications– Any anticipated post-translational
modifications need to be preserved in native structure
• For example, inhibitors of phosphatases that will cleave organophosphate groups
Hascall & Kimura, PGs Isolation & characterization, Methods Enzymol. 82;769-800, 1982.
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Most Common Extraction Procedure for PGs
• 4 M Guanidine-HCl– Typically extracts 70-90% of total PG from tissues– Recovery of the remaining GAGs from the tissue
residue require exhaustive proteolysis or alkaline hydrolysis (at the cost of losing core protein structure)
• Chaotropic agents such as 6 M LiCl2 , 2 M CaCl2 , 3 M MgCl2 or 0.5 M LaCl2 can be used instead of 4 M GnHCl
• What are chaotropes?
Hascall & Kimura, PGs Isolation & characterization, Methods Enzymol. 82;769-800, 1982.
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Chaotropes• ‘Chaotropes’ (disorder-maker) unfold proteins,
destabilize hydrophobic aggregates and increase the solubility of hydrophobes– Guanidinium chloride; Urea; Sodium dodecyl sulfate; Phenol;
Butanol; Ethanol; Propanol; Lithium perchlorate; Magnesium chloride; Thiourea
Urea FormamideGuanidine HCl
Sodium dodecyl sulfate
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Water Structure• Water forms liquid-crystal lattices at room
temperature and pressure– Extensive H-bonding between water molecules
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Water Structure• Water solvates ionic groups in proteins,
nucleic acids and carbohydrates
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Solute Interaction with Water Molecules
• Miscible solutes interact with the liquid crystal water lattice – ‘Kosmotropes' (order-maker) stabilize proteins and
hydrophobic aggregates in solution and reduce the solubility of hydrophobes
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Solute Interaction with Water Molecules
• Miscible solutes interact with the liquid crystal water lattice – Chaotropes decrease the polar nature of a water
lattice
Urea – H2 O Guanidinium – H2 O
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• The Hofmeister mechanism involves specific interactions between ions and proteins and ions and the water molecules directly contacting the proteins– Anions appear to have a larger effect than cations, and are usually
ordered:
• Early members of the series increase solvent surface tension and decrease the solubility of nonpolar molecules ("salting out")– they strengthen the hydrophobic interaction.
• Later salts in the series increase the solubility of nonpolar molecules ("salting in") & decrease the order in water– they weaken the hydrophobic effect
• Ions that have a strong 'salting in' effect such as guanidinium and SCN- are strong denaturants and interact much more strongly with the unfolded form of a protein than with its native form. – Consequently, they shift the chemical equilibrium of the unfolding
reaction towards unfolded protein.
Hofmeister series
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Hydrophilicity vs. Hydrophobicity• Water organizes an interface boundary
with lipids
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Hydrophobicity• Hydrophobic (‘water fearing’) molecules
self organize to exclude water molecules– Triacylglycerols (TAGs) vs. Phospholipids (PLs)
Triacylglycerols (‘triglycerides’)
Schematic diagram of a phospholipid bilayer vesicle with bound nanoparticles.
Wang B et al. PNAS 2008;105:18171-18175
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Critical Micelle Concentration (CMC)
• Phospholipids self-organize in water and physiological solutions– Concentration dependent phenomenonPhospholipid monomers Phospholipid multimers
Lower concentration Higher concentration
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Critical Micelle Concentration (CMC)
• Detergents self-organize in physiological solutions– Concentration dependent
phenomenon
Lower
Higher
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Triton X-100
Sodium dodecyl sulfate
Detergents• Detergents are polar lipids that are soluble in
water and increase the solubility of hydrophobes– Triton X-100; Sodium dodecyl sulfate; CHAPS; CHAPSO;
Deoxycholate
Deoxycholate
CHAPS
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Detergent Micelle Size
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Gel Filtration Chromatography• Simple column-based means to separate
varying sized molecules in solution
29Midura & Yanagishita, Chaotropes increase CMC of Detergents, Anal Biochem, 228;318-322, 1995
Vo Vt
Triton X-100
Phenyl ring absorbs light at 280 nm wavelength
M.W., Da
90,000
650
Vo: Void Volume (totally excluded)Vt: Totally included volume
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Centrifugal Ultrafiltration
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90,000 Da
650 Da
TX-10018,000 Da
288 Da
SDS
6,150 Da
615 Da
CHAPS
Midura & Yanagishita, Chaotropes increase CMC of Detergents, Anal Biochem, 228;318-322, 1995
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NaClin H2 O
GnHClUrea
Formamidein H2 O
Midura & Yanagishita, Chaotropes increase CMC of Detergents, Anal Biochem, 228;318-322, 1995
33Midura & Yanagishita, Chaotropes increase CMC of Detergents, Anal Biochem, 228;318-322, 1995
34Midura & Yanagishita, Chaotropes increase CMC of Detergents, Anal Biochem, 228;318-322, 1995
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Sodium dodecyl sulfate
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PG Migration Behavior in SDS-PAGE
MW Standards stained with Coomaisse Blue
Corneal PGs