scholarly journals Connection of Jones and Mueller Tensors in Second Harmonic Generation and Multi-Photon Fluorescence Measurements

2016 ◽  
Vol 120 (13) ◽  
pp. 3281-3302 ◽  
Author(s):  
Garth J. Simpson
Keyword(s):  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
Second Harmonic ◽  
Fluorescence Measurements ◽  
Photon Fluorescence

scholarly journals Second Harmonic Generation Spectroscopy of Membrane Probe Dynamics in Gram-Positive Bacteria

2019 ◽  
Author(s):  
L. N. Miller ◽  
W. T. Brewer ◽  
J. D. Williams ◽  
E. M. Fozo ◽  
T. R. Calhoun
Keyword(s):  
Second Harmonic Generation ◽  
Small Molecules ◽  
Harmonic Generation ◽  
Second Harmonic ◽  
Bacterial Species ◽  
Gram Positive ◽  
Flip Flop ◽  
Bacterial Membranes ◽  
Gram Positive Bacteria ◽  
Fluorescence Measurements

ABSTRACTBacterial membranes are complex mixtures with dispersity that is dynamic over scales of both space and time. In order to capture adsorption onto and transport within these mixtures, we conduct simultaneous second harmonic generation (SHG) and two photon fluorescence measurements on two different gram-positive bacterial species as the cells uptake membrane-specific probe molecules. Our results show that SHG can not only monitor the movement of small molecules across membrane leaflets, but is also sensitive to higher-level ordering of the molecules within the membrane. Further, we show that the membranes of Staphylococcus aureus remain more dynamic after longer times at room temperature in comparison to Enterococcus faecalis. Our findings provide insight into the variability of activities seen between structurally similar molecules in gram-positive bacteria while also demonstrating the power of SHG to examine these dynamics.STATEMENT OF SIGNIFICANCEBacterial membranes are highly adept at discerning and modifying their interactions with different small molecules in their environment. Here we show how second harmonic generation (SHG) spectroscopy can track the dynamics of structurally similar membrane probes in two gram-positive bacterial species. Our results reveal behavior that is dependent on both the probe molecule and the membrane composition. Specifically, we observe flip-flop between leaflets for one molecule, while the other molecule produces a signal indicative of larger scale ordering in the membrane. These phenomena can all be explained by considering potential differences in the membrane fluidity and surface charge between the two bacterial species. Overall, our work highlights the dynamic differences between bacterial membranes and SHG’s sensitivity to probing these systems.

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