Measuring, in solution, multiple-fluorophore labeling by combining Fluorescence Correlation Spectroscopy and photobleaching

Laser-induced fluorescence quenching of red fluorescent dyes with green excitation: avoiding artifacts in PIE-FRET and FCCS analysis

Multicolor excitation is at the core of many fluorescence spectroscopy techniques such as PIE-FRET, ALEX-FRET, or FCCS. However, the influence of the multiple laser excitations on the dye photophysics is often overlooked. Here, we show that green laser pulses can surprisingly quench the fluorescence of common red dyes Alexa Fluor 647 and Atto 647N, even when the conditions leading to photobleaching are avoided. The physical origin of this phenomenon is discussed via a long-lived dark state and/or photorefractive effects. These observations are important to avoid measurement artifacts as both t…

Benchmarking the performance of DFT functionals for absorption and fluorescence spectra of EGFR inhibitor AG-1478 using TD-DFT

Optical spectra (UV-vis and fluorescence) are sensitive to the chemical environment and conformation of fluorophores and therefore, are ideal probes for their conformation and solvent responses. Tyrosine kinase inhibitors (TKI) such as AG-1478 of epidermal growth factor receptor (EGFR) when containing a quinazolinamine scaffold are fluorophores. Conformers of AG-1478 have been confirmed by both experiment and theory. It is, however, very important to benchmark computational methods such as DFT functionals against optical spectral measurements, when time-dependent density functional theory (TD-…

Barium Selective Chemosensing by Diazacrown Ether Naphthalimide Turn-on Fluorophores for Single Ion Barium Tagging

Single molecule fluorescence detection of barium is investigated for enhancing the sensitivity and robustness of a neutrinoless double beta decay ($0νββ$) search in $^{136}$Xe, the discovery of which would alter our understanding of the nature of neutrinos and the early history of the Universe. A key developmental step is the synthesis of barium-selective chemosensors capable of incorporation into ongoing experiments in high-pressure $^{136}$Xe gas. Here we report turn-on fluorescent naphthalimide chemosensors containing monoaza- and diaza-crown ethers as agents for single Ba$^{2+}$ detection.…

Ultraviolet Photostability Improvement for Autofluorescence Correlation Spectroscopy on Label-Free Proteins

The poor photostability and low brightness of protein autofluorescence have been major limitations preventing the detection of label-free proteins at the single molecule level. Overcoming these issues, we report here a strategy to promote the photostability of proteins and use their natural tryptophan autofluorescence in the ultraviolet (UV) for fluorescence correlation spectroscopy (FCS). Combining enzymatic oxygen scavengers with antioxidants and triplet state quenchers greatly promotes the protein photostability, reduces the photobleaching probability and improves the net autofluorescence d…

Laser-Induced Fluorescence Spectroscopy (LIFS) of Trapped Molecular Ions in Gas-phase

This review presents the Laser-Induced Fluorescence Spectroscopy (LIFS) of trapped gas-phase molecular ions. A brief description of the theory and experimental approaches involved in fluorescence spectroscopy, together with state-of-the-art LIFS experiments employing ion traps, is presented. Quadrupole ion traps are commonly used for spatial confinement of ions. One of the main challenges involved in such experiments is poor Signal-to-Noise Ratio (SNR) arising due to weak gas-phase fluorescence emission, high background noise, and small solid angle for the fluorescence collection optics. The e…

速率分布形式体系在描述存在扩散时的发光猝灭中的局限性

Limitations of the rate-distribution formalism in describing luminescence quenching in the presence of diffusion

该研究指出速率分布形式体系仅在固态等荧光团和猝灭剂不可移动的情况下对双分子发光猝灭有明确物理解释，存在相对扩散运动时使用该体系描述实验结果并不合适。

花青素定向近红外双光子荧光探针的合理设计

Rational Designing of Anthocyanidins-Directed Near-Infrared Two-Photon Fluorescence Probes

本文研究了不同骨架花青素的光物理性质，通过烷基环化、氮丁环和扩展π共轭抑制TICT效应，设计了新型双光子荧光探针2a-n，其中2a-3展现出长发射波长、大TPA截面和Stokes位移，适用于高分辨率NTR检测。