The bouncing dynamics of inertial self-propelled particles reveals directional asymmetry

The paper is devoted to the study of experimental conditions for bound states in which active particles are forced by their environment to move forward and backward in a steady oscillatory mode. The realization of this idea in our proposal is carried out by means of a hexbug (a vibrating self-propelled toy robot) confined in a narrow channel bounded by a rigid moving end-wall. The motion modes were studied both experimentally and theoretically. In the theoretical framework, we investigated the one-dimensional single-particle approximation within the Brownian model of active particles with inertia using numerical simulations. The model includes the hexbug's contact with the base plate via tilted flexible legs that provide propulsion. At the same time, the tilting contributes to directional asymmetry of the system. The end-wall velocity was used as an external parameter to influence the bouncing process. After regressing the spatial and temporal statistical characteristics, the simulation satisfactorily reproduced the experimental properties of hexbug motion, mainly due to the considered directional asymmetry

Optically Trapped Surface-Enhanced Raman Probes Prepared by Silver Photoreduction to 3D Microstructures

3D microstructures partially covered by silver nanoparticles have been developed and tested for surface-enhanced Raman spectroscopy (SERS) in combination with optical tweezers. The microstructures made by two-photon polymerization of SU-8 photoresist were manipulated in a dual beam optical trap. The active area of the structures was covered by a SERS-active silver layer using chemically assisted photoreduction from silver nitrate solutions. Silver layers of different grain size distributions were created by changing the photoreduction parameters and characterized by scanning electron microscopy. The structures were tested by measuring the SERS spectra of emodin and hypericin. © 2015 American Chemical Society

Vectorisation de l'hypéricine par les lipoprotéines de faibles densités (étude dynamique du complexe et conséquences sur sa distribution intracellulaire et son activité photoinduite)

PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Interaction of a new antiviral and antitumor photosensitizer hypericin with human serum albumin: molecular modeling study

Molecular modeling has been employed to study the interaction of hypericin (Hyp) with human serum albumin (HSA). The structural model for Hyp/HSA complex is presented. Our results indicate that Hyp is bound in II A subdomain of HSA close to the tryptophan 214 (Trp214) (distance 5.12 Å between the centers of masses). In the presented model the carbonyl group of Hyp is hydrogen bonded to the Asn458. Another two candidates for hydrogen bonds have been identified between the bay-region hydroxyl group of Hyp and the carbonyl group of the Trp214 peptidic link and between the peri-region hydroxyl group of Hyp and Asn458 carbonyl group

Temperature and oxygen-concentration dependence of singlet oxygen production by RuPhen as induced by quasi-continuous excitation

Advanced Search Home > Journals > Photochemical & Photobi... > Temperature and oxygen-... For Authors & Referees | For Librarians | For Members Journal cover: Photochemical & Photobiological Sciences Photochemical & Photobiological Sciences Issue 12, 2014 A society-owned journal publishing high quality research on all aspects of photochemistry and photobiology. Impact Factor 2.939 12 Issues per Year Indexed in Medline Journal Home Previous Article | Next Article Paper Temperature and oxygen-concentration dependence of singlet oxygen production by RuPhen as induced by quasi-continuous excitation Jaroslav Varchola,a Veronika Huntosova,b Daniel Jancura,ab Georges Wagnières,c Pavol Miskovskyab and Gregor Bánó*ab Show Affiliations Photochem. Photobiol. Sci., 2014,13, 1781-1787 DOI: 10.1039/C4PP00202D Received 06 Jun 2014, Accepted 02 Oct 2014 First published online 06 Oct 2014 | | Share on citeulike | Share on facebook | Share on twitter | | More PDF Rich HTML Send PDF to Kindle Download Citation Help Request Permissions Abstract Cited by Related Content Assessment of partial pressure of oxygen (pO2) by luminescence lifetime measurements of ruthenium coordination complexes has been studied intensively during the last few decades. RuPhen (dichlorotris(1,10-phenanthroline) ruthenium(II) hydrate) is a water soluble molecule that has been tested previously for in vivo pO2 detection. In this work we intended to shed light on the production of singlet oxygen by RuPhen. The quantum yield of singlet oxygen production by RuPhen dissolved in 0.9% aqueous NaCl solution (pH = 6) was measured at physiological temperatures (285–310 K) and various concentrations of molecular oxygen. In order to minimize the bleaching of RuPhen, the samples were excited with low power (<2 mW) laser pulses (20 μs long), created by pulsing a cw laser beam with an acousto-optical modulator. We show that, whereas the RuPhen phosphorescence lifetime decreases rapidly with an increase of temperature (keeping the oxygenation level constant), the quantum yield of singlet oxygen production by RuPhen is almost identical in the temperature range of 285–310 K. For air-saturated conditions at 310 K the measured quantum yield is about 0.25. The depopulation rate constants of the RuPhen 3MLCT (metal-to-ligand charge-transfer) state are determined in the absence and in the presence of oxygen. We determined that the excitation energy for the RuPhen 3MLCT→d–d transition is 49 kJ mol−1 in the 0.9% NaCl solution (pH = 6)

Endosomes: Guardians Against [Ru(Phen)3]2+ Photo-action In Endothelial Cells During In Vivo pO2 Detection?

Phototoxicity is a side-effect of in vitro and in vivo oxygen partial pressure (pO(2)) detection by luminescence lifetime measurement methods. Dichlorotris(1,10-phenanthroline)-ruthenium(II) hydrate ([Ru(Phen)(3)](2+)) is a water soluble pO(2) probe associated with low phototoxicity, which we investigated in vivo in the chick's chorioallantoic membrane (CAM) after intravenous or topical administration and in vitro in normal human coronary artery endothelial cells (HCAEC). In vivo, the level of intravenously injected [Ru(Phen)(3)](2+) decreases within several minutes, whereas the maximum of its biodistribution is observed during the first 2 h after topical application. Both routes are followed by convergence to almost identical "intra/extra-vascular" levels of [Ru(Phen)(3)](2+). In vitro, we observed that [Ru(Phen)(3)](2+) enters cells via endocytosis and is then redistributed. None of the studied conditions induced modification of lysosomal or mitochondrial membranes without illumination. No nuclear accumulation was observed. Without illumination [Ru(Phen)(3)](2+) induces changes in endoplasmic reticulum (ER)-to-Golgi transport. The phototoxic effect of [Ru(Phen)(3)](2+) leads to more marked ultrastructural changes than administration of [Ru(Phen)(3)](2+) only (in the dark). These could lead to disruption of Ca2+ homeostasis accompanied by mitochondrial changes or to changes in secretory pathways. In conclusion, we have demonstrated that the intravenous injection of [Ru(Phen)(3)](2+) into the CAM model mostly leads to extracellular localization of [Ru(Phen)(3)](2+), while its topical application induces intracellular localization. We have shown in vivo that [Ru(Phen)(3)](2+) induces minimal photo-damage after illumination with light doses larger by two orders of magnitude than those used for pO(2) measurements. This low phototoxicity is due to the fact that [Ru(Phen)(3)](2+) enters endothelial cells via endocytosis and is then redistributed towards peroxisomes and other endosomal and secretory vesicles before it is eliminated via exocytosis. Cellular response to [Ru(Phen)(3)](2+), survival or death, depends on its intracellular concentration and oxidation-reduction properties