Jerome Wenger NanoBioPhotonics

The natural autofluorescence of proteins in the UV is appealing to get the detailed information from single molecule data without requiring a potentially disturbing external fluorescent label. However, proteins feature significantly lower autofluorescence brightness and photostabilities than conventional fluorescent dyes. This issue has largely prevented so far the detection of label-free proteins in the ultraviolet.

In a recent article in the Journal of Physical Chemistry Letters, we use a dedicated combination of oxygen scavengers and reducing agents to promote the protein photostability, reduce the photobleaching probability and improve the net UV autofluorescence signal.

Significance:

- This is the first time that different photostability improvement strategies are reported and quantitatively assessed for label-free proteins in the ultraviolet range.

- We show that the underlying photochemical concepts initially derived for organic fluorescent dyes are still valid for protein autofluorescence in the UV, and therefore appear to be quite general.

- Fluorescence correlation spectroscopy (FCS) is demonstrated on label-free streptavidin proteins containing only 24 tryptophan residues, 6.5× less than the current state-of-the-art.

Also freely available on ArXiv 2002.09761

Zero-mode waveguide nanoapertures receive a large interest owing to their ability to confine light at the nanoscale and improve the detection of single fluorescent molecules. However, unwanted adhesion of the targeted molecules onto the metal surface can be a major issue.

In a recent article published in Scientific Reports, we highlight the role of the fluorescent dye in the surface adsorption phenomenon and we quantify the efficiency of different passivation approaches.

Significance:

- Despite its small size, we show that the fluorescent dye plays a key role in mediating the DNA molecule adsorption to the surface, with the dye’s surface charge and hydrophobicity being determining factors.

- We benchmark different surface passivation approaches and determine the most efficient approach to suppress nonspecific adhesion.

[Arcadia - Queen Emeraldas Revenge - Shadow Princess - Ebbesen's blade crew member]

Immediate evacuation order by emergency exits. This is not an exercise. Retreat with calm and discipline.

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Gentlemen, it's been an honour and a privilege to be your captain over these years. Good luck to all of you.

[End of transmission]

... and remember I expect your results and reports twice a week. There are things bigger and nastier than a virus that still exist...

Organic chemistry is gaining an increasing interest in the optics lab these days. According to WHO, here is a simple hanrub sanitizer recipe:

For a 1L solution, mix 833mL ethanol 96%, 4.2mL hydrogen peroxide 30%, 1.5mL glycerol and 161mL pure water. Shake well, avoid eye contact and do not even think of drinking it.

Even viruses have nightmares. So wash your hands and get results before he finds you...

Adhesion layers of chromium or titanium are widely used in plasmonics to ensure a proper adhesion between a gold film and a glass substrate. However, very little is known about their influence on the thermal response. As a result, the adhesion layer is often ignored while designing the experiments.

In a recent article published in Nanoscale, we demonstrate both experimentally and numerically that the adhesion layer can have a major impact on the thermal response of plasmonic structures.

Significance:

- We quantify the role of the adhesion layer in setting the local temperature around a single nanostructure milled in a gold film.  

- We show how to promote or avoid the temperature increase using different experimental designs. This further expands the plasmonic toolbox for heat-controlled experiments.

Also available (soon after the #!;/%# embargo) on HAL 02461519