Transcript Slide 1
The Use of Self-Patterned Phospholipid Films for Directed Enzyme Lithography N.Y.-W. TANG and A. Badia, Department of Chemistry, University of Montreal, C.P. 6128, succursale Centre-ville Montreal, Qc, H3T 1J4, [email protected] Objectives Langmuir-Blodgett Monolayers of DPPC/DLPC Phospholipases Generate phospholipid-based surface patterns from phase-separated monolayers using the Langmuir-Blodgett technique PLA2, a calcium-dependent and interfacially-active enzyme, catalyzes the cleavage of the sn-2 acyl ester linkage of glycerophospholipids, yielding a fatty acid and lysophospholipid. Study the effect of lineactants on the pattern morphology Demonstrate that a striped phospholipid bilayer prepared by the Langmuir-Blodgett technique can be used for enzyme nanolithography 5 m 5 m 7.5 m The naturally occuring L form of the lipid is hydrolyzed, PLA2 binds but does not cleave the D form. Structures of Phospholipids and Lineactant cholesterol DPPC, C16; Tm = 41°C 20 μm 20 μm 20 μm PLA2 Degradation of a Striped D--DPPC/L--DLPC Bilayer Stripe Formation Mechanism DLPC, C12; Tm = -1 °C PLA2 hydrolysis Langmuir Monolayers of Phospholipids barrier 60 barrier Aqueous subphase 100% DLPC 0.25 DPPC 0.50 DPPC 100% DPPC 50 (mN/m) Wilhelmy balance 40 condensed 4.5 nm nm -5 -4.5 30 20 0 10 m 0 10 m DPPC 10 liquid 5 0 30 40 50 60 70 80 90 100 110 2 Area (Å /molecule) P. Moraille and A. Badia, Langmuir 2002, 18, 4414-4419 DLPC mica PLA2 Degradation of a Striped L--DPPC/ DEPC Bilayer Solid-Supported Phospholipid Films monolayer mica Effect of Cholesterol Lineactant on the Domain Morphology for a 50/50 DPPC/DLPC Mixture at = 32 mN/m Langmuir-Blodgett deposition bilayer 2% chol. 5% chol. PLA2 hydrolysis 10% chol. mica Mica substrate Langmuir-Schaeffer deposition Mica substrate 5 m monolayer 5 m mica 2% chol. Atomic Force Microscopy (AFM) Characterization of the Surface Morphology 5% chol. 5 m 10% chol. 5 m Conclusions and Future Work on Enzyme Nanolithography Enzyme Nanolithography Tapping Mode Enzymes make interesting nanolithographic tools due to their ability to catalyze chemical reactions with high efficiency and specificity under mild conditions and aqueous environment. The stereospecificity exhibited by certain enzymes can be exploited to spatially direct their activity to certain regions of a patterned surface, as shown herein. We have investigated the phospholipase A2 (PLA2 ) hydrolysis of stereochemically-differentiated DPPC/DLPC and chemically-differentiated DPPC/DEPC bilayers. PLA2 stereospecifically hydrolyzes the L--phospholipid enantiomer in bilayer templates. PLA2 only hydrolyzes dialkylphosphatidylcholines in bilayer templates. The regularity of the monolayer and bilayer stripe patterns will be improved. The PLA2 enzyme performance will be demonstrated for different enantiomer templates . Alkyl tail-functionalized phospholipids will be used to spatially direct the deposition of metal nanoparticles for the generation of 2D optical gratings.