scholarly journals Multiple Electron Ejection from Proteins Resulting from Single-Photon Excitation in the Valence Shell

2014 ◽  
Vol 5 (10) ◽  
pp. 1666-1671 ◽  
Author(s):  
Rodolphe Antoine ◽  
Quentin Enjalbert ◽  
Luke MacAleese ◽  
Philippe Dugourd ◽  
Alexandre Giuliani ◽  
...  
Keyword(s):  
Single Photon ◽  
Valence Shell ◽  
Photon Excitation ◽  
Electron Ejection

scholarly journals Assessment of Fluorochromes for Two-Photon Laser Scanning Microscopy of Biofilms

2002 ◽  
Vol 68 (2) ◽  
pp. 901-909 ◽  
Author(s):  
Thomas R. Neu ◽  
Ute Kuhlicke ◽  
John R. Lawrence
Keyword(s):  
Nucleic Acid ◽  
Laser Scanning ◽  
Single Photon ◽  
Selective Excitation ◽  
Laser Scanning Microscopy ◽  
Scanning Microscopy ◽  
Excitation Wavelength ◽  
Laser Microscopy ◽  
Two Photon ◽  
Photon Excitation

ABSTRACT A major limitation for the use of two-proton laser scanning microscopy (2P-LSM) in biofilm and other studies is the lack of a thorough understanding of the excitation-emission responses of potential fluorochromes. In order to use 2P-LSM, the utility of various fluorochromes and probes specific for a range of biofilm constituents must be evaluated. The fluorochromes tested in this study included classical nucleic acid-specific stains, such as acridine orange (AO) and 4",6"-diamidino-2-phenylindole (DAPI), as well as recently developed stains. In addition, stains specific for biofilm extracellular polymeric substances (EPS matrix components) were tested. Two-photon excitation with a Ti/Sapphire laser was carried out at wavelengths from 760 to 900 nm in 10-nm steps. It was found that autofluorescence of phototrophic organisms (cyanobacteria and green algae) resulted in strong signals for the entire excitation range. In addition, the coenzyme F420-related autofluorescence of methanogenic bacteria could be used to obtain images of dense aggregates (excitation wavelength, 780 nm). The intensities of the emission signals for the nucleic acid-specific fluorochromes varied. For example, the intensities were similar for excitation wavelengths ranging from 780 to 900 nm for AO but were higher for a narrower range, 780 to 810 nm, for DAPI. In selective excitation, fading, multiple staining, and combined single-photon-two-photon studies, the recently developed nucleic acid-specific fluorochromes proved to be more suitable regardless of whether they are intended for living or fixed samples. Probes specific for proteins and glycoconjugates allowed two-photon imaging of polymeric biofilm constituents. Selective excitation-emission was observed for Calcofluor White M2R (780 to 800 nm) and SyproOrange (880 to 900 nm). In addition, fluor-conjugated concanavalin A lectins were examined and provided acceptable two-photon emission signals at wavelengths ranging from 780 to 800 nm. Finally, CellTracker, a fluorochrome suitable for long-term labeling of microbial eucaryote cells, was found to give strong emission at wavelengths ranging from 770 to 810 nm. If fluorochromes have the same two-photon excitation cross section, they are suitable for multiple staining and multichannel recording. Generally, if an appropriate excitation wavelength and fluorochrome were used, it was possible to obtain more highly resolved images for thick biofilm samples with two-photon laser microscopy than with conventional single-photon laser microscopy. Due to its potential for higher resolution in light-scattering tissue-like material, such as biofilms, and extremely localized excitation, 2P-LSM is a valuable addition to conventional confocal laser scanning microscopy with single-photon excitation. However, further development of the method and basic research are necessary to take full advantage of nonlinear excitation in studies of interfacial microbial ecology.

Autofluorescence of epithelial tissue: single-photon versus two-photon excitation

2008 ◽  
Vol 13 (5) ◽  
pp. 054010 ◽  
Author(s):  
Wei Zheng ◽  
Yicong Wu ◽  
Dong Li ◽  
Jianan Y. Qu
Keyword(s):  
Single Photon ◽  
Epithelial Tissue ◽  
Two Photon ◽  
Photon Excitation ◽  
Two Photon Excitation

scholarly journals Combination of PDT and NOPDT with a Tailored BODIPY Derivative

Antioxidants ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 531 ◽  
Author(s):  
Loretta Lazzarato ◽  
Elena Gazzano ◽  
Marco Blangetti ◽  
Aurore Fraix ◽  
Federica Sodano ◽  
...  
Keyword(s):  
Cancer Cell ◽  
Single Photon ◽  
Direct Detection ◽  
Green Light ◽  
Treatment Modalities ◽  
Suitable Model ◽  
Photon Excitation ◽  
Biological Studies ◽  
Key Species ◽  
Anticancer Treatment

The engineering of photosensitizers (PS) for photodynamic therapy (PDT) with nitric oxide (NO) photodonors (NOPD) is broadening the horizons for new and yet to be fully explored unconventional anticancer treatment modalities that are entirely controlled by light stimuli. In this work, we report a tailored boron-dipyrromethene (BODIPY) derivative that acts as a PS and a NOPD simultaneously upon single photon excitation with highly biocompatible green light. The photogeneration of the two key species for PDT and NOPDT, singlet oxygen (1O2) and NO, has been demonstrated by their direct detection, while the formation of NO is shown not to be dependent on the presence of oxygen. Biological studies carried out using A375 and SKMEL28 cancer cell lines, with the aid of suitable model compounds that are based on the same BODIPY light harvesting core, unambiguously reveal the combined action of 1O2 and NO in inducing amplified cancer cell mortality exclusively under irradiation with visible green light.

Photochemistry with high power ultraviolet lasers

1983 ◽  
Vol 61 (5) ◽  
pp. 1023-1026 ◽  
Author(s):  
R. J. Donovan ◽  
C. Fotakis ◽  
A. Hopkirk ◽  
C. B. McKendrick ◽  
A. Torre
Keyword(s):  
Energy Distribution ◽  
High Power ◽  
Single Photon ◽  
Laser Induced Fluorescence ◽  
Multiphoton Excitation ◽  
Dissociation Process ◽  
Two Photon ◽  
Photon Excitation ◽  
Ultraviolet Lasers ◽  
Two Photon Excitation

Rotationally resolved photofragment fluorescence from OH(A2Σ+) following the coherent two-photon excitation of H2O with a KrF laser (248 nm), is reported and the dynamics of the dissociation process are discussed. Fluorescence from CN(B2Σ+) following two-photon excitation of ICN is also described. In both cases the energy distribution in the photofragments is shown to differ significantly from that observed with single-photon excitation at closely similar energies.Two further examples of multiphoton excitation, involving CS2 and SO2, are briefly discussed. In these cases absorption of a further photon, by fragments produced in the primary step, gives rise to strong laser-induced fluorescence.

Fullerene ionization dynamics after single photon excitation with synchrotron radiation

1994 ◽  
Vol 29 (2) ◽  
pp. 81-83 ◽  
Author(s):  
H. Steger ◽  
M. Honka ◽  
W. Kamke ◽  
I. V. Hertel
Keyword(s):  
Synchrotron Radiation ◽  
Single Photon ◽  
Photon Excitation

scholarly journals Cardiovascular Imaging Using Two-Photon Microscopy

2008 ◽  
Vol 14 (6) ◽  
pp. 492-506 ◽  
Author(s):  
John A. Scherschel ◽  
Michael Rubart
Keyword(s):  
Laser Scanning ◽  
Single Photon ◽  
Second Harmonic ◽  
Multiphoton Microscopy ◽  
Cardiovascular Imaging ◽  
Laser Scanning Microscopy ◽  
Dye Transfer ◽  
Two Photon ◽  
Photon Excitation ◽  
Two Photon Excitation

AbstractTwo-photon excitation microscopy has become the standard technique for high resolution deep tissue and intravital imaging. It provides intrinsic three-dimensional resolution in combination with increased penetration depth compared to single-photon confocal microscopy. This article will describe the basic physical principles of two-photon excitation and will review its multiple applications to cardiovascular imaging, including second harmonic generation and fluorescence laser scanning microscopy. In particular, the capability and limitations of multiphoton microscopy to assess functional heterogeneity on a cellular scale deep within intact, Langendorff-perfused hearts are demonstrated. It will also discuss the use of two-photon excitation-induced release of caged compounds for the study of intracellular calcium signaling and intercellular dye transfer.

scholarly journals Non-linear Simultaneous Two-Photon Excitation Energy Transfer in the Wrong Direction

1997 ◽  
Vol 17 (3) ◽  
pp. 161-174 ◽  
Author(s):  
M. Nickoleit ◽  
A. Uhl ◽  
J. Bendig
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
Single Photon ◽  
Energy Levels ◽  
Excitation Energy Transfer ◽  
Laser Exposure ◽  
Two Photon ◽  
Photon Excitation ◽  
Covalently Linked ◽  
Two Photon Excitation

The simultaneous two-photon excitation energy transfer (SEET) was demonstrated for the first time using trichromophoric model compounds. Two identical donors (A–antenna) were covalently linked to an energy acceptor unit (T–target) with different energy levels preventing energy transfer of a single photon. At high intensity illumination (laser exposure) of a trichromophoric system A∼T∼A (A–fluorescein, erythrosin; T-Estilbene), sufficient to excite both of the appended donor subunits, population of the target excited state may occur via simultaneous energy transfer of two photons, one from each donor. In order to restrict reverse energy transfer from the higher energy target to the lower energy donor(s) it is necessary that the excited target unit undergoes an efficient photoreaction. In the investigated case this was achieved by photoisomerization of the stilbene unit used for monitoring of the SEET.

Multi-photon Fluorescence Micro-spectroscopy of Plant Tissues

2000 ◽  
Vol 6 (S2) ◽  
pp. 808-809
Author(s):  
F. J. Kao ◽  
B. L. Lin ◽  
P. C. Cheng
Keyword(s):  
Single Photon ◽  
Second Harmonic ◽  
Spectral Response ◽  
Broad Band ◽  
Small Contribution ◽  
Two Photon ◽  
Photon Excitation ◽  
Photon Spectra ◽  
Photon Fluorescence ◽  
Two Photon Excitation

Considering its non-linear nature, two-photon excitation may generate very different spectral response in samples when compared with single photon excitation. It is thus necessary to measure the two-photon spectra of samples, so that the two-photon fluorescence microscopic images can be properly interpreted. Fluorescence spectra obtained from bulk samples may not provide useful information for microscopy. For instance, due to the relatively small contribution to the total fluorescence intensity, a small number of fluorescent particles in a generally fluorescing specimen may escape detection when the spectrum of the specimen as a whole is obtained. Under two-photon excitation, the background noise can be greatly reduced due to the naturally limited excitation volume of focused laser beam. In addition, signals resulted from second harmonic generation (SHG) may be mixed with low level broad-band background autofluorescence which is commonly found in biological specimen. Therefore, measuring fluorescence spectrum from a micro-focused volume is essential for the proper interpretation of multi-photon fluorescence images.

Investigation of the luminescence properties of ZnO clusters induced by single-photon and two-photon excitation

2021 ◽  
Vol 18 (10) ◽  
pp. 106003
Author(s):  
Jun Dai ◽  
Zhengguo Li ◽  
Yi Zhang ◽  
Yongzhu Chen ◽  
Xing Zhu ◽  
...  
Keyword(s):  
Single Photon ◽  
Luminescence Properties ◽  
Two Photon ◽  
Photon Excitation ◽  
Zno Clusters ◽  
Two Photon Excitation
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