Chem120A+Notes+-+Biointerfaces+3

Chem120A+Notes+-+Biointerfaces+3 - Investigating...

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Investigating Biointerfaces Molecular Dynamics Simulation Nd:YAG OPG/OPA 1064nm ~20ps Sum Frequency Generation Vibrational Spectroscopy (SFG) ~ adsorbate PS / Silica gold electrode gold electrode quartz crystal driving ƒ decay recording data communicate Tunable IR 2800 - 3600 cm -1 Visible Beam 532 nm Sum Frequency (445 – 463 nm) Monochromator & PMT Detector Quartz Crystal Microbalance (QCM-D)
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Proteins at Surfaces
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Hen Egg Lysozyme Bovine Serum Albumin Fibrinogen Proteins MW pI Size (nm 3 ) Lysozyme 14,000 11.1 5 × 3 × 3 BSA 69,000 4.8 8 × 4 × 4 Fibrinogen 340,000 5.5 47 × × 5 Lysozyme: Antibacterial Activity BSA: Hydrocarbon Carrier Fibrinogen: Blood Clotting Model Proteins
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Wavenumber (cm -1 ) 2800 2900 3000 3100 S F G I n t e s i y ( A . U ) 0.0 0.2 0.4 0.6 0.8 1.0 Wavenumber (cm -1 ) 2800 2900 3000 3100 0.0 0.2 0.4 0.6 0.8 1.0 CH 3 (F) CH 3 (a) Hydrophobic Polystyrene Hydrophilic Silica CH 3 (s) Lysozyme adsorbed on hydrophilic silica and hydrophobic polystyrene surfaces J. Kim and G. A. Somorjai J. Am. Chem. Soc . 2003 , 125 , 3150 CD 2 CD H H H H H n ν 7b ν 7a ν 2 Polystyrene surface becomes less ordered by lysozyme adsorption Before adsorption Before adsorption Low surface coverage Low surface coverage High surface coverage High surface coverage
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Wavenumber (cm -1 ) 2800 2900 3000 3100 S F G I n t e s i y ( A . U ) 0.0 0.2 0.4 0.6 0.8 1.0 Wavenumber (cm -1 ) 2800 2900 3000 3100 SFG Intensity (A.U.) 0.0 0.2 0.4 0.6 0.8 1.0 CH 3 (F) CH 3 (a) Hydrophobic Polystyrene Hydrophilic Silica CH 3 (s) BSA orders better on hydrophilic silica than hydrophobic polystyrene surfaces J. Kim and G. A. Somorjai J. Am. Chem. Soc . 2003 , 125 , 3150 Before adsorption ν 7b ν 7a ν 2 Polystyrene surface reorders by BSA adsorption Before adsorption Low surface coverage High surface coverage CD 2 CD H H H H H n Low surface coverage High surface coverage
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Peptides Adsorbed on Polymer Surfaces
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Amino acids Nonpolar Polar Negative Charge Positive Charge
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β -strand sequence (7-mer ) Ac(XYXYXYX)NH 2 AR 7 solubility limit >2000 μ g/mL LK 7 solubility limit ~100 μ g/mL FR solubility limit <50 μ g/mL Peptide Sequence: Controlled 2 Peptide Sequence: Controlled 2 o Structure Structure MODEL AMPHIPHILIC PEPTIDES α -helical sequence (14-mer) Ac(XYYXXYXXYYXXYX)NH 2 X= Hydrophobic Side Chains (L, A, F) Y= + Hydrophilic (K, R) AR 14 solubility limit >6mg/mL LK 14 solubility limit ~1mg/mL FR 14 solubility limit ~0.13 mg/mL Random coil (14-mer) Homopeptide •A c ( K ) 14 NH 2 a Dr. David King HHMI, UC Berkeley L = leucine (nonpolar) N O K= Lysine (+) N O N + + L K N O N O N N N + A R N O N O N N N R = Arginine (+) + F R N O N + N O A K K= Lysine (+) A = Alanine (nonpolar) A = Alanine (nonpolar) F = Phenylalanine (nonpolar) R = Arginine (+)
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Experimental SFG Setup Visible (532 nm) IR (2800-3600 cm -1 ) SFG (445-463 nm) Biomolecule Solution in Petri Dish Quartz Prism ω I R ω VI S ω SF G Polystyrene
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L = Leucine N O K = Lysine N O N LK 14 (Leucine-Lysine) amphiphilic peptide 2.1 nm 1.4 nm Hydrophobic side Hydrophilic side
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Fused Silica N-H ν s C-H ν 2800 3000 3200 3400 3600 0.0 0.1 0.2 0.3 0.4 0.5 0.6 ssp SFG Intensity (a.u.) Wavenumber (cm -1 ) 2800 3000 3200 3400 3600 0 1 2 3 4 5 6 7 ssp Wavenumber (cm -1 ) Deuterated Polystyrene O-H ν NH 3 + CH 3 CH 3 Ac(LKKLLKLLKKLLKL)NH 2
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Water at Interfaces
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SFG Spectrum of the PBS Buffer/SiO 2 Interface O H H O H H O H H O
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Chem120A+Notes+-+Biointerfaces+3 - Investigating...

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