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81.
Wiktor Kemula Barbara Behr Joanna Taraszewska 《Journal of Electroanalytical Chemistry》1975,65(2):651-659
It has been shown that a hanging mercury drop electrode of the Kemula type is a very convenient tool for studying the redox processes of organic substances in the positive potential range. Conditions influencing the oxidation process are discussed. The method described may prove to be an analytical tool for the determination of some aromatic amines. 相似文献
82.
Ilse M. Welleman Mark W. H. Hoorens Ben L. Feringa Hendrikus H. Boersma Wiktor Szymaski 《Chemical science》2020,11(43):11672
Light-based therapeutic and imaging modalities, which emerge in clinical applications, rely on molecular tools, such as photocleavable protecting groups and photoswitches that respond to photonic stimulus and translate it into a biological effect. However, optimisation of their key parameters (activation wavelength, band separation, fatigue resistance and half-life) is necessary to enable application in the medical field. In this perspective, we describe the applications scenarios that can be envisioned in clinical practice and then we use those scenarios to explain the necessary properties that the photoresponsive tools used to control biological function should possess, highlighted by examples from medical imaging, drug delivery and photopharmacology. We then present how the (photo)chemical parameters are currently being optimized and an outlook is given on pharmacological aspects (toxicity, solubility, and stability) of light-responsive molecules. With these interdisciplinary insights, we aim to inspire the future directions for the development of photocontrolled tools that will empower clinical applications of light.This perspective article explores the current state of light-controlled molecular tools for medical therapy and imaging and offers an outlook on clinical application scenarios and optimisation strategies. 相似文献
83.
Tailoring the optical and dynamic properties of iminothioindoxyl photoswitches through acidochromism
Miroslav Medved' Mark W. H. Hoorens Mariangela Di Donato Adle D. Laurent Jiayun Fan Maria Taddei Michiel Hilbers Ben L. Feringa Wybren Jan Buma Wiktor Szymanski 《Chemical science》2021,12(12):4588
Multi-responsive functional molecules are key for obtaining user-defined control of the properties and functions of chemical and biological systems. In this respect, pH-responsive photochromes, whose switching can be directed with light and acid–base equilibria, have emerged as highly attractive molecular units. The challenge in their design comes from the need to accommodate application-defined boundary conditions for both light- and protonation-responsivity. Here we combine time-resolved spectroscopic studies, on time scales ranging from femtoseconds to seconds, with density functional theory (DFT) calculations to elucidate and apply the acidochromism of a recently designed iminothioindoxyl (ITI) photoswitch. We show that protonation of the thermally stable Z isomer leads to a strong batochromically-shifted absorption band, allowing for fast isomerization to the metastable E isomer with light in the 500–600 nm region. Theoretical studies of the reaction mechanism reveal the crucial role of the acid–base equilibrium which controls the populations of the protonated and neutral forms of the E isomer. Since the former is thermally stable, while the latter re-isomerizes on a millisecond time scale, we are able to modulate the half-life of ITIs over three orders of magnitude by shifting this equilibrium. Finally, stable bidirectional switching of protonated ITI with green and red light is demonstrated with a half-life in the range of tens of seconds. Altogether, we designed a new type of multi-responsive molecular switch in which protonation red-shifts the activation wavelength by over 100 nm and enables efficient tuning of the half-life in the millisecond–second range.Protonation of an ITI molecular photoswitch shifts its absorption to the orange/red part of the spectrum and allows for manipulation of the thermal half-life of the photogenerated E-isomer over three orders of magnitude. 相似文献
84.
Wiktor I. Owtscharenko Wolfgang Huber Karl E. Schwarzhans 《Monatshefte für Chemie / Chemical Monthly》1987,118(8-9):955-957
The first spinlabelled ferrocene has been prepared by interaction of ferrocenealdehyde and 1-oximino-2-hydroxylamino-1-phenyl-2-methylpropane followed by oxidation with lead(IV) oxide in methanol. 相似文献
85.
2D NMR studies demonstrate that the residence lifetime of 15NH4+ ions within the bimolecular G-quadruplex adopted by d(G4T4G4) is reduced from 270 ms in the presence of ammonium ions alone to 36 ms in the presence of Na+ ions. 相似文献
86.
Synthetic routes to twenty six crown ether compounds with pendent amide, N-alkylamide, or N,N-dialkyl-amide groups are reported. The new crown ether compounds are based on sym-dibenzo-16-crown-5-oxyacetamide and sym-(propyl)-dibenzo-16-crown-5-oxyacetamide and are obtained in high yields. 相似文献
87.
A general scheme of constructing a canonical structure (i.e. Poisson bracket, canonical fields) in classical field theories is proposed. The theory is manifestly independent of the particular choice of an initial space-like surface in space-time. The connection between dynamics and canonical structure is established. Applications to theories with a gauge and constraints are of special interest. Several physical examples are given. 相似文献
88.
Dr. Adèle D. Laurent Dr. Miroslav Medved' Dr. Alessandro Iagatti Dr. Laura Bussotti Dr. Andrea Lapini Prof. Dr. Wybren Jan Buma Prof. Dr. Paolo Foggi Dr. Wiktor Szymański Prof. Dr. Ben L. Feringa 《Angewandte Chemie (International ed. in English)》2018,57(27):8063-8068
Donor–acceptor Stenhouse adducts (DASAs) are negative photochromes that switch with visible light and are highly promising for applications ranging from smart materials to biological systems. However, the strong solvent dependence of the photoswitching kinetics limits their application. The nature of the photoswitching mechanism in different solvents is key for addressing the solvatochromism of DASAs, but as yet has remained elusive. Here, we employ spectroscopic analyses and TD‐DFT calculations to reveal changing solvatochromic shifts and energies of the species involved in DASA photoswitching. Time‐resolved visible pump‐probe spectroscopy suggests that the primary photochemical step remains the same, irrespective of the polarity and protic nature of the solvent. Disentangling the different factors determining the solvent‐dependence of DASA photoswitching, presented here, is crucial for the rational development of applications in a wide range of different media. 相似文献
89.
Orthoconic Antiferroelectric Liquid Crystals (OAFLC) are recognised as a promising medium for display and photonic applications due to their unique electrooptical properties. The application of OAFLC is still hampered by a number of parasitic effects deteriorating the electrooptical performance of contemporary available materials. An attempt elaborating of a working OAFLC mixture with the helical pitch longer than the typical cell gap is reported. Using this mixture, near-perfect optical uniformity and excellent dark state at the zero electric field applied were obtained. Basic OAFLC mixture was doped with two homostructural analogues to study the influence of the molecular polarity and chirality on the electrooptical performance and chosen physical parameters. The physical and structural properties of admixtures and their electrooptical performance are presented and discussed. 相似文献
90.
Emilia Miszczyk Rafał Mazur Przemysław Morawiak Mateusz Mrukiewicz Wiktor Piecek Zbigniew Raszewski 《Liquid crystals》2018,45(11):1690-1698
There exists a problem in advanced numerically controlled automatic laser metrology. Reported study is related to minimising the system generating three or more coherent laser measuring beams. These rays, generated in a proper rangefinder, are necessary to determine the spatial coordinates and spatial orientation of the measured details. The simplest solution is to generate laser coherent light beams of wavelength λ = 0.6328 µm with a given light polarisation plane and then to direct them along three or more independent optical paths. To form these optical paths, a special refractive index matched liquid crystal cell (MLCC) might be applied. To ensure a stable laser operation during the measurement process, the back reflection of the laser beam from MLCC should not exceed 0.7%. The main task of this work is developing such a MLCC transducer. To reach the critical back reflection low enough, the MLCC is constructed as multilayer structure. MLCC operates in positive twisted nematic (TN) mode. Owing to the high-birefringence nematic liquid crystal mixture used and rather big cell gap, the elaborated low reflective MLCC (with R < 0.7%) works at TN mode above the sixth interference maximum of transmitting linearly polarised light. 相似文献