Using the intrinsic chirality of a molecule as a label-free probe to detect molecular adsorption to a surface by second harmonic generation.
Chiral second harmonic generation (C-SHG) has been used for the label-free detection of (R)-(+)-1,1'-bi-2-naphthol (RBN) and (S)-(+)-1,1'-bi-2-naphthol (SBN) binding to planar-supported lipid bilayers of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphotidylcholine (POPC) based on the intrinsic chirality of the molecules. C-SHG adsorption isotherms of RBN and SBN reveal Langmuir adsorption behavior with binding constants of 2.7 +/- 0.2 x 10(5) M(-1) and 3.0 +/- 0.1 x 10(5) M(-1), respectively. The kinetics of RBN binding to a POPC bilayer was also measured. It was determined that the adsorption rate for RBN was 5.7 +/- 0.4 x 10(3) s(-1)M(-1) and the desorption rate was 2.1 +/- 0.8 x 10(-2) s(-1). From the kinetic data a binding constant of 2.7 +/- 1.0 x 10(5) M(-1) was calculated, which agrees well with the thermodynamic measurement. The C-SHG technique was correlated with surface tension measurements in order to determine the RBN surface excess within the POPC membrane. The maximum surface excess of RBN in a monolayer of POPC was 4.3 +/- 0.5 x 10(-11) mol cm2. Using the maximum surface excess in conjunction with the C-SHG binding data a lower limit of detection of 1.5 +/- 0.1 x 10(-13) mols cm(-2) was calculated. The results of these studies show that C-SHG is a powerful tool for the study of chiral molecular interactions at surfaces.
Kriech
Matthew A
MA
Department of Chemistry, University of Utah, 315 S. 1400 E. RM 2020, Salt Lake City, Utah 84112, USA.
Conboy
John C
JC
D000327:Adsorption; D000465:Algorithms; D001665:Binding Sites; D007536:Isomerism; D007700:Kinetics; D008051:Lipid Bilayers / Q000032:analysis / Q000737:chemistry*; D015336:Molecular Probe Techniques; D009284:Naphthols / Q000032:analysis / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000032:analysis / Q000737:chemistry*; D012031:Refractometry / Q000379:methods*; D013057:Spectrum Analysis / Q000379:methods*
D008051:Lipid Bilayers; D009284:Naphthols; D010713:Phosphatidylcholines; C028694:1-palmitoyl-2-oleoylphosphatidylcholine