Molecule‐Membrane Interactions in Biological Cells Studied with Second Harmonic Light Scattering

Abstract

The nonlinearo ptical phenomenon second harmonic light scattering (SHS) can be used for detecting molecules at the membrane surfaces of living biological cells. Over the last decade, SHS has been developed for quantitatively monitoring the adsorption and transport of smalla nd medium size molecules (both neutral and ionic) across membranes in living cells. SHS can be operated with both time and spatial resolution and is even capableo fisolating molecule-membrane interactions at specific membrane surfaces in multi-membrane cells, such as bacteria. In this review,w e discuss select examples from our lab employingt ime-resolved SHS to study real-time molecular interactions at the plasma membranes of biological cells. We first demonstrate the utility of this method for determining the transport rates at each membrane/interfacei naGram-negative bacterial cell. Next, we show how SHS can be used to characterize the molecular mechanism of the centuryo ld Gram stain protocol for classifyingb acteria. Additionally,w ee xamine how membrane structures and molecular charge and polarity affect adsorption and transport, as well as how antimicrobial compounds alter bacteria membrane permeability.F inally, we discuss adaptation of SHS as an imaging modality to quantify molecular adsorption and transport in sub-cellular regionso fi ndividual livingcells.[a] Prof.

Influence of Temperature on Molecular Adsorption and Transport at Liposome Surfaces Studied by Molecular Dynamics Simulations and Second Harmonic Generation Spectroscopy

“… 17 , 18 , 23 , 27 − 32 SHG has been used extensively to study the molecular adsorption and transport of small cationic molecules, such as malachite green (MG) 22 , 33 − 36 and malachite green isothiocyanate (MGITC), 12 at liposome surfaces in aqueous solution. The adsorption of these dye molecules to the outer lipid bilayer produces an enhanced SHG signal, 33 , 37 , 38 followed by a decrease in the SHG signal as the dye molecules transport through the membrane. 19 , 21 , 33 , 35 , 37 − 43 Since the lipid bilayer thickness, which is about 5 nm, is much smaller than the SHG coherence length, dye molecules adsorbed at the inner and outer liposome interface produce cancellation in the SHG signal, providing a time-resolved method for measuring molecular transport.…”

Determination of Bacterial Surface Charge Density Via Saturation of Adsorbed Ions

“…Over a series of prior studies, we have extensively quantified the molecular uptake kinetics of the molecular MG cation in the proto-typical Gram-negative bacteria, E. coli. (6) Using the surface sensitive time-resolved SHS technique, we have experimentally deduced the adsorption and transport kinetics for MG cations interacting with the bacterial OM, PM, and CM. As an extension of this work, we now examine the various molecular interactions of MG with a representative Gram-positive bacterium, L. rhamnosus.…”

“…We have previously demonstrated the use of time-resolved second-harmonic light scattering (SHS) for monitoring molecular interactions (e.g., surface adsorption and membrane transport) with living cells. (6) SHS is a nonlinear optical technique and is inherently surface sensitive. It is based upon the physical phenomenon, second-harmonic generation (SHG), whereby a portion of an incident light of frequency  is converted to 2 after interacting with a material.…”

Influence of Solvent on Dye‐Sensitized Solar Cell Efficiency: What is so Special About Acetonitrile?

“…[40,41,[57][58][59][60][61][62][63][64] Eisenthal and coworkers were the first to experimentally demonstrate that SHG can be detected from molecules, with strong nonlinear susceptibility, adsorbed on the surface of a colloidal particle. [62] The physics of SHG from colloidal particle surfaces is now well understood [50] and this technique has been widely used to characterize a variety of molecular processes on the surfaces of various colloidal objects, [41,53,60,65,66] including nanoparticles. [58,61,67] It is now known that the SHG signal intensity generated from molecules adsorbed on a particle surface displays an angular scattering pattern, which depends on the particle size and composition.…”