Journal articles: 'Time dependent fluorescence shift'

1

Harju, Timo O., A. Herbert Huizer, Cyril A. G. O. Varma, and Jon Songstad. "Reconstructing the Solvation Time Correlation Function from the Time-Dependent Fluorescence Stokes Shift." Acta Chemica Scandinavica 49 (1995): 829–33. http://dx.doi.org/10.3891/acta.chem.scand.49-0829.

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Gakamsky, Dmitry M., Alexander A. Goldin, Eugene P. Petrov, and Anatoly N. Rubinov. "Fluorescence decay time distribution for polar dye solutions with time-dependent fluorescent shift." Biophysical Chemistry 44, no. 1 (August 1992): 47–60. http://dx.doi.org/10.1016/0301-4622(92)85034-2.

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Li, Tanping, and Revati Kumar. "Role of excited state solvent fluctuations on time-dependent fluorescence Stokes shift." Journal of Chemical Physics 143, no. 17 (November 7, 2015): 174501. http://dx.doi.org/10.1063/1.4934661.

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Dandapat, Manika, and Debabrata Mandal. "Time-dependent fluorescence Stokes shift and molecular-scale dynamics in alginate solutions and hydrogels." Chemical Physics Letters 627 (May 2015): 67–72. http://dx.doi.org/10.1016/j.cplett.2015.03.027.

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5

Tröscher, Anna R., Barbara Werner, Nadia Kaouane, and Wulf Haubensak. "Spectral recording of gene expression history by fluorescent timer protein." BioTechniques 67, no. 4 (October 2019): 154–64. http://dx.doi.org/10.2144/btn-2019-0050.

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Monitoring spatio-temporal patterns of gene expression by fluorescent proteins requires longitudinal observation, which is often difficult to implement. Here, we fuse a fluorescent timer (FT) protein with an immediate early gene (IEG) promoter to track live gene expression in single cells. This results in a stimulus- and time-dependent spectral shift from blue to red for subsequent monitoring with fluorescence activated cell sorting (FACS) and live cell imaging. This spectral shift enables imputing the time point of activity post-hoc to dissociate early and late responders from a single snapshot in time. Thus, we provide a tool for tracking stimulus-driven IEG expression and demonstrate proof of concept exploiting promoter::FT fusions, adding new dimensions to experiments that require reconstructing spatio-temporal patterns of gene expression in cells, tissues or living organisms.

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Nilsson, L., and B. Halle. "Molecular origin of time-dependent fluorescence shifts in proteins." Proceedings of the National Academy of Sciences 102, no. 39 (September 14, 2005): 13867–72. http://dx.doi.org/10.1073/pnas.0504181102.

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Sakai, Hisashi, Akira Itaya, and Hiroshi Masuhara. "Time-dependent fluorescence spectral shift and unusual slow decay of exciplex in poly(N-vinylcarbazole) films." Journal of Physical Chemistry 93, no. 14 (July 1989): 5351–53. http://dx.doi.org/10.1021/j100351a010.

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Toptygin, Dmitri, Thomas B. Woolf, and Ludwig Brand. "MD Simulations of the Time-Dependent Red Shift in the Fluorescence of Trp in Protein GB1." Biophysical Journal 96, no. 3 (February 2009): 47a. http://dx.doi.org/10.1016/j.bpj.2008.12.140.

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Vazdar, Mario, Erik Wernersson, Morteza Khabiri, Lukasz Cwiklik, Piotr Jurkiewicz, Martin Hof, Ella Mann, Sofiya Kolusheva, Raz Jelinek, and Pavel Jungwirth. "Aggregation of Oligoarginines at Phospholipid Membranes: Molecular Dynamics Simulations, Time-Dependent Fluorescence Shift, and Biomimetic Colorimetric Assays." Journal of Physical Chemistry B 117, no. 39 (September 24, 2013): 11530–40. http://dx.doi.org/10.1021/jp405451e.

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Allolio, Christoph, Mohsen Sajadi, Nikolaus P. Ernsting, and Daniel Sebastiani. "An Ab Initio Microscope: Molecular Contributions to the Femtosecond Time-Dependent Fluorescence Shift of a Reichardt-Type Dye." Angewandte Chemie International Edition 52, no. 6 (January 2, 2013): 1813–16. http://dx.doi.org/10.1002/anie.201204532.

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Khimich, M. N., N. I. Makarova, M. I. Knyazhansky, and B. M. Uzhinov. "Excited state structural relaxation relaxation of N-(1-anthryl)-2,4,6-trimethyl-pyridinium cation." International Journal of Photoenergy 6, no. 2 (2004): 69–72. http://dx.doi.org/10.1155/s1110662x04000108.

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The fluorescence spectrum of N-(1-anthryl)-2,4,6-trimethylpyridinium cation (1) has an anomalously high Stokes' shift. The fluorescence spectra of1in ethanol and butyronitrile are shifted to shortwavelength region and fluorescence quantum yield increases as the temperature decreases. The fluorescence rate constant of this compound changes considerably (6 times in ethanol and 15 times in butyronitrile) as the temperature decreases from 293 K (relaxed state) to 77 K (mainly nonrelaxed state). It points out that at these temperatures the fluorescence takes place from two species with different structures. It is concluded that anomalously high fluorescence Stokes' shift of1is caused by both solvent orientation relaxation and excited state structural relaxation consisting in the mutual rotation of anthracene and pyridinium fragments of the cation and resulting in the formation of a specie with different structure. The rates of these processes are determined by the temperature-dependent viscosity of the medium.

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Van der Zwan, G., and James T. Hynes. "Time-dependent fluorescence solvent shifts, dielectric friction, and nonequilibrium solvation in polar solvents." Journal of Physical Chemistry 89, no. 20 (September 1985): 4181–88. http://dx.doi.org/10.1021/j100266a008.

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Pokorna, Sarka, Piotr Jurkiewicz, Mario Vazdar, Lukasz Cwiklik, Pavel Jungwirth, and Martin Hof. "Does fluoride disrupt hydrogen bond network in cationic lipid bilayer? Time-dependent fluorescence shift of Laurdan and molecular dynamics simulations." Journal of Chemical Physics 141, no. 22 (December 14, 2014): 22D516. http://dx.doi.org/10.1063/1.4898798.

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Koutek, Bohumír, Lubomír Musil, Jiří Velek, and Milan Souček. "Fluorescence behaviour of some 4-substituted halobenzenes." Collection of Czechoslovak Chemical Communications 50, no. 8 (1985): 1753–63. http://dx.doi.org/10.1135/cccc19851753.

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The fluorescence characteristics of 4-substituted chloro and fluorobenzenes I and II were studied in isooctane and acetonitrile solutions. It was found that all compounds exhibit a weak (substituent and solvent dependent) fluorescence in the range 305-370 nm with quantum yields 1.2 . 10-2-2.3 . 10-1. The relation between the substituent nature and fluorescence band position may be quantified by log νf~ = ρσp + log νf~0, the magnitude of the shift paralleling the donor strength of the substituent. Fluorescence quantum yields are increased approximately by a factor 2 on going from isooctane to acetonitrile and solvent-induced shifts are proportional to the static dipole moment change Δμ which occurs upon excitation. Radiative decay rate varies only slightly around a mean value of 5 . 107 s-1 and shows no substantial difference between chloro (I) and fluoro (II) derivatives. The non-radiative decay rate (of the order ~ 109 s-1) was found to be about 5 times higher in the case of chloro compounds due to the more efficient S1 - Tn intersystem crossing.

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Shishkin, I., T. Alon, R. Dagan, and P. Ginzburg. "Temperature and Phase Transition Sensing in Liquids with Fluorescent Probes." MRS Advances 2, no. 44 (2017): 2391–99. http://dx.doi.org/10.1557/adv.2017.391.

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ABSTRACTLocal environment of fluorescent dyes could strongly affects emission dynamics of the latter. In particular, both signal intensities and emission lifetimes are highly sensitive to solvent temperatures. Here, temperature-dependent behavior Rhodamine B fluorescence in water and ethanol solutions was experimentally investigated. Phase transition point between liquid water and ice was shown to have a dramatic impact on both in intensity (30-fold drop) and in lifetime (from 2.68 ns down to 0.13 ns) of the dye luminescence along with the shift of spectral maxima from 590 to 625 nm. At the same time, use of ethanol as solvent does not lead to any similar behavior. The reported results and approaches enable further investigations of dye-solvent interactions and studies of physical properties at phase transition points.

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Declémy, A., C. Rulliére, and Ph Kottis. "Solvation Dynamics Studied by Picosecond Fluorescence: Microscopic Reorientation and Longitudinal Relaxation of the Solvent." Laser Chemistry 10, no. 5-6 (January 1, 1990): 413–29. http://dx.doi.org/10.1155/1990/86536.

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The dynamics of the Time-Dependent Fluorescence Shift (TDFS) of a rigid polar excited probe dissolved in alcohol solvents at different temperatures have been studied by picosecond time-resolved spectroscopy. The results are compared to previously published results on well characterized polar systems. These results show that solvation dynamics in such systems are strongly scaled by the microscopic (singleparticle) reorientation time τM of the solvent molecules and/or by the (macroscopic) longitudinal relaxation time τL of the solvent. The key point governing this scaling is the relative interaction between the solvent molecules and the probe compared to the interaction between the solvent molecules. It is also shown that specific interactions, such as hydrogen bonded-complex formation, may play an important role.

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Molchanov, Evgeniy E., Yuriy S. Marfin, Evgeniy V. Rumyantsev, and Aleksander A. Ksenofontov. "SYNTHESIS AND SPECTRAL PROPERTIES OF BODIPY LUMINOPHORE WITH EXTENDED π-ELECTRONIC SYSTEM." IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 62, no. 12 (December 7, 2019): 13–18. http://dx.doi.org/10.6060/ivkkt.20196212.6017.

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We report the synthesis, purification and identification of a new derived class of BODIPY - of naphtho-fused BODIPY analogue, 8-(3,5-dimethylphenyl)-4,4-difluoro-4-bora-3a,4a-diaza-dinapht-[1,2b][1,2c]-s-indacene. A detailed method for obtaining the compound was given. The structure was confirmed by nuclear magnetic resonance spectroscopy, infrared spectroscopy and mass spectrometry. Electronic absorption and fluorescence spectra were obtained in solvents of different nature. The effect of solvent nature on the positions of absorption and fluorescence peaks and Stokes shift has been studied. It has been shown that the nature of the solvent has a significant effect on the fluorescence intensity and does not significantly effect the position of the absorption peaks. The photophysical characteristics of the compound were compared with known alkylated analogues. It is shown that the expansion of the electronic system leads to a bathochromic shift in the electronic absorption and fluorescence spectra. Quantum-chemical calculations of the electronic absorption and fluorescence spectra were carried out using the TDDFT (time dependent density functional theory) method. The influence of the extended π-electron system on the position and character of the absorption and fluorescence spectra was studied. It is shown that the presence of naphthalene fragments conjugated with the BODIPY core leads to a bathochromic shift of the absorption and fluorescence bands, as well as a partial change in the character of the spectra. The energy levels and electronic structure of the FMOs with the TDDFT method were calculated. The calculated data are in good agreement with the results obtained by experimental methods. The results obtained, in turn, are consistent with the results obtained earlier by our scientific group. Compounds that possess such properties are especially important and could be used in such practical applications as photovoltaics, photodynamic therapy of oncological diseases and as agents for visualization of biomolecules.

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Toptygin, Dmitri, Angela M. Gronenborn, and Ludwig Brand. "Nanosecond Relaxation Dynamics of Protein GB1 Identified by the Time-Dependent Red Shift in the Fluorescence of Tryptophan and 5-Fluorotryptophan." Journal of Physical Chemistry B 110, no. 51 (December 2006): 26292–302. http://dx.doi.org/10.1021/jp064528n.

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Lin, C. h., D. Zamzow, G. J. Small, and R. Jankowiak. "Time-Dependent Blue Shift of the Fluorescence Origin Band of Benzo[a]Pyrene (BP)-Derived BP-6-N7ADE Adducts in Glasses." Polycyclic Aromatic Compounds 14, no. 1-4 (December 1999): 43–52. http://dx.doi.org/10.1080/10406639908019110.

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20

Declémy, A., C. Rullière, and Ph Kottis. "Picosecond solvation of electronically excited solutes in alcoholic solvents: non-debye behaviour of the time-dependent fluorescence shift related to h." Chemical Physics Letters 133, no. 5 (January 1987): 448–54. http://dx.doi.org/10.1016/0009-2614(87)87100-2.

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21

Limosani, Francesca, Elvira Maria Bauer, Daniele Cecchetti, Stefano Biagioni, Viviana Orlando, Roberto Pizzoferrato, Paolo Prosposito, and Marilena Carbone. "Top-Down N-Doped Carbon Quantum Dots for Multiple Purposes: Heavy Metal Detection and Intracellular Fluorescence." Nanomaterials 11, no. 9 (August 31, 2021): 2249. http://dx.doi.org/10.3390/nano11092249.

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In the present study, we successfully synthesized N-doped carbon quantum dots (N-CQDs) using a top-down approach, i.e., hydroxyl radical opening of fullerene with hydrogen peroxide, in basic ambient using ammonia for two different reaction times. The ensuing characterization via dynamic light scattering, SEM, and IR spectroscopy revealed a size control that was dependent on the reaction time, as well as a more pronounced -NH2 functionalization. The N-CQDs were probed for metal ion detection in aqueous solutions and during bioimaging and displayed a Cr3+ and Cu2+ selectivity shift at a higher degree of -NH2 functionalization, as well as HEK-293 cell nuclei marking.

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Gottfried, J. A., and M. Chesler. "Temporal resolution of activity-dependent pH shifts in rat hippocampal slices." Journal of Neurophysiology 76, no. 4 (October 1, 1996): 2804–7. http://dx.doi.org/10.1152/jn.1996.76.4.2804.

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1. The rise time of activity-dependent extracellular pH shifts was measured in the CA1 stratum radiatum of rat hippocampal slices by recording pH-sensitive fluorescence of a fluorescein-conjugated dextran. Optical data were compared with simultaneous pH microelectrode recordings. 2. The pH shifts generated by CO2 or by stimulation of the Schaffer collaterals were paralleled by shifts in fluorescence emissions at 535 nm when the probe was excited with 490-nm light (delta F490). Emissions at 535 nm induced by 440-nm light were unchanged in these paradigms. 3. A train of three stimuli at 100 Hz was repeated at 30-s intervals and the stimulus-triggered delta F490 was averaged. The mean rise time of the delta F490 was 69 +/- 24 (SE) ms (range 20-200 ms, n = 6). The mean increase in emission was 0.75 +/- 0.22% of baseline, associated with a pH microelectrode response of +0.06 +/- 0.02 unit pH. 4. These data demonstrate that synaptically evoked alkaline transients develop within tens of milliseconds. The occurrence of the alkalinization in the same time frame as excitatory postsynaptic currents indicates that these pH shifts arise with sufficient speed to modulate synaptic transmission.

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Sai, Y., A. T. Nies, and I. M. Arias. "Bile acid secretion and direct targeting of mdr1-green fluorescent protein from Golgi to the canalicular membrane in polarized WIF-B cells." Journal of Cell Science 112, no. 24 (December 15, 1999): 4535–45. http://dx.doi.org/10.1242/jcs.112.24.4535.

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The bile canalicular membrane contains several ATP-dependent transporters that are involved in biliary secretion. Canalicular transporters are synthesized in ER, modified in Golgi and transported to the apical plasma membrane. However, the route and regulation of intracellular trafficking of ATP-dependent transporters have not been elucidated. In the present study, we generated a translational fusion of mdr1 and green fluorescent protein and investigated bile acid secretion and intracellular trafficking of mdr1 in WIF-B cells, a polarized liver derived cell line. Similar to hepatocytes, WIF-B cells secrete bile acids and organic cations (i.e. rhodamine-123) into the bile canaliculi. Canalicular secretion of fluorescein isothiocyanate-glycocholate was stimulated by taurocholate and a decapeptide activator of phosphoinositide 3-kinase and was decreased by wortmannin. WIF-B9 cells were transiently and stably transfected with a mdr1-GFP construct. Fluorescence was observed in the canalicular membrane, pericanalicular punctate structures and Golgi region. Time lapse microscopy revealed that mdr1-GFP is transferred from Golgi as tubular vesicular structures the majority of which traveled directly to the canalicular membrane. Recycling between the canalicular membrane and subapical region was also observed. At no time was mdr1-GFP detected in the basolateral plasma membrane. At 15 degrees C, mdr1-GFP accumulated in Golgi; after a shift to 37 degrees C, fluorescence moved directly to the canalicular membrane. This process was enhanced by taurocholate and blocked by wortmannin. In these studies as well, no mdr1-GFP fluorescence was observed at any time in basolateral membranes or other intracellular organelles. In conclusion, in WIF-B cells, there is a direct route from Golgi to the canalicular membrane for trafficking of mdr1, a bile canalicular ATP-dependent transporter of organic cations. As in normal hepatocytes, phosphoinositide 3-kinase regulates bile acid secretion and intracellular trafficking of mdr1 in WIF-B cells. WIF-B cells stably transfected with mdr1-GFP provide an important model in which to study trafficking and regulation of canalicular transporters. Movies available on-line: http://www.healthsci.tufts.edu/LABS/IMArias+++/Sai_F9.html

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Toptygin, Dmitri, Thomas B. Woolf, and Ludwig Brand. "Picosecond Protein Dynamics: The Origin of the Time-Dependent Spectral Shift in the Fluorescence of the Single Trp in the Protein GB1." Journal of Physical Chemistry B 114, no. 34 (September 2, 2010): 11323–37. http://dx.doi.org/10.1021/jp104425t.

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Gabruk, Michal, Beata Mysliwa-Kurdziel, and Jerzy Kruk. "MGDG, PG and SQDG regulate the activity of light-dependent protochlorophyllide oxidoreductase." Biochemical Journal 474, no. 7 (March 23, 2017): 1307–20. http://dx.doi.org/10.1042/bcj20170047.

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Light-dependent protochlorophyllide oxidoreductase (POR) is a plant enzyme involved in the chlorophyll biosynthesis pathway. POR reduces one of the double bonds of the protochlorophyllide (Pchlide) using NADPH and light. In the present study, we found out that phosphatidylglycerol and sulfoquinovosyl diacylglycerol are allosteric regulators of the nucleotide binding, which increase the affinity towards NADPH a 100-fold. Moreover, we showed for the first time that NADH can, like NADPH, form active complexes with Pchlide and POR, however, at much higher concentrations. Additionally, monogalactosyldiacylglycerol (MGDG) was shown to be the main factor responsible for the red shift of the fluorescence emission maximum of Pchlide:POR:NADPH complexes. Importantly, the emission maximum at 654 nm was obtained only for the reaction mixtures supplemented with MGDG and at least one of the negatively charged plant lipids. Moreover, the site-directed mutagenesis allowed us to identify amino acid residues that may be responsible for lipid binding and Pchlide coordination. Our experiments allowed us to identify six different Pchlide:POR complexes that differ in the fluorescence emission maxima of the pigment. The results presented here reveal the contribution of thylakoid lipids in the regulation of the chlorophyll biosynthesis pathway; however, the molecular mechanisms of this process are to be clarified.

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Amaro, Mariana, Jan Brezovský, Silvia Kováčová, Lukáš Maier, Radka Chaloupková, Jan Sýkora, Kamil Paruch, Jiří Damborský, and Martin Hof. "Are Time-Dependent Fluorescence Shifts at the Tunnel Mouth of Haloalkane Dehalogenase Enzymes Dependent on the Choice of the Chromophore?" Journal of Physical Chemistry B 117, no. 26 (June 20, 2013): 7898–906. http://dx.doi.org/10.1021/jp403708c.

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Jin, Li, Ying Wang, Fengkai Yan, Jianpo Zhang, and Fangli Zhong. "The Synthesis and Application of Nitrogen-Doped Graphene Quantum Dots on Brilliant Blue Detection." Journal of Nanomaterials 2019 (May 7, 2019): 1–9. http://dx.doi.org/10.1155/2019/1471728.

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Nitrogen-doped graphene quantum dots had been successfully synthesized and characterized by using transmission electron microscope, X-ray photoelectron spectroscopy, absorbance spectrum, fluorescence emission spectrum, and fluorescence decay curve. TEM results indicated that the diameters of the as-prepared nitrogen-doped graphene quantum dots were in the range of 2 - 5 nm and the lattice space is about 0.276 nm; Raman spectrum result indicated that there were two characteristic peaks, generally named D (~1408 cm−1) and G (~1640 cm−1) bands; both TEM and Raman spectrum results indicated that the as-synthesized product was graphene quantum dots. Deconvoluted high resolution XPS spectra for C1s, O1s, and N1s results indicated that there are -NH-, -COOH, and -OH groups on the surface of nitrogen-doped graphene quantum dot. Fluorescence emission spectrum indicated that the maximum fluorescence emission spectrum of nitrogen-doped graphene quantum dots was blue shift about 30.1 nm and the average fluorescence decay time of nitrogen-doped graphene quantum dots increased about 2 ns, compared with graphene quantum dots without doping of nitrogen. Then, the as-prepared nitrogen-doped graphene quantum dots were used to quantitatively analyze brilliant blue based on the fluorescent quenching of graphene quantum dots, and the effect of pH and reaction time on this fluorescent quenching system was also obtained. Under selected condition, the linear regression equations were F0/F=0.0087 (brilliant blue) + 0.9553 and F0/F=0.01205 (brilliant blue) + 0.6695, and low detection limit was 3.776 μmol/L (3.776 nmol/mL). Once more diluted N-GQDs (0.05 mg/mL) were used, the low detection limit could reach 94.87 nmol/L. Then, temperature-dependent experiment, absorbance spectra, and dynamic fluorescence quenching rate constant were used to study the quenching mechanism; all results indicated that this quenching process was a static quenching process based on the formation of complex between nitrogen-doped graphene quantum dots and brilliant blue through hydrogen bond. Particularly, this method was used to quantitatively analyze the wine sample, of which results have a high consistence with the results of the spectrophotometric method; demonstrating this fluorescence quenching method could be used in practical sample application.

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Pan, Yu-Lu, Zhi-Bin Cai, Li Bai, Sheng-Li Li, and Yu-Peng Tian. "Preparation and Photophysical Properties of All-trans Acceptor–π-Donor (Acceptor) Compounds Possessing Obvious Solvatochromic Effects." Australian Journal of Chemistry 70, no. 9 (2017): 1048. http://dx.doi.org/10.1071/ch17021.

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A series of all-trans acceptor–π-donor (acceptor) compounds (BAQ, SFQ, BLQ, and XJQ) were conveniently synthesised and characterised by infrared, nuclear magnetic resonance, mass spectrometry, and elemental analysis. Their photophysical properties, including linear absorption, one-photon excited fluorescence, two-photon absorption, and two-photon excited fluorescence, were systematically investigated. All the compounds show obvious solvatochromic effects, such as significant bathochromic shifts of the emission spectra and larger Stokes shifts in more polar solvents. Under excitation from a femtosecond Ti : sapphire laser with a pulse width of 140 fs, they all exhibit strong two-photon excited fluorescence, and the two-photon absorption cross-sections in THF are 851 (BAQ), 216 (SFQ), 561 (BLQ), and 447 (XJQ) GM respectively. A combination of density functional theory (DFT) and time-dependent density functional theory (TDDFT) approaches was used to investigate the relationships between the structures and the photophysical properties of these compounds. The results show that they may have a potential application as polarity-sensitive two-photon fluorescent probes.

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Hu, Shanshan, Kun Liu, Yuanzuo Li, Qianqian Ding, Wei Peng, and Maodu Chen. "Investigation of excited-state intramolecular proton transfer coupled charge transfer reaction of paeonol." Canadian Journal of Chemistry 92, no. 4 (April 2014): 274–78. http://dx.doi.org/10.1139/cjc-2013-0286.

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An excited-state intramolecular proton transfer (ESIPT) coupled charge transfer reaction of paeonol was investigated both experimentally and theoretically. The ESIPT reaction of paeonol was predicted based on the large Stokes shift, which is observed in steady-state absorption and fluorescence spectra in an ethanol solution. The steady-state spectra in some solutions, such as methanol, ethanol, propanol, dichloromethane, and n-hexane, illustrate that the ESIPT reaction of paeonol has no dependence on the solvent properties. Therefore, the excited-state intermolecular proton transfer cannot be generated in protic solvents. Using the density functional theory and time-dependent density functional theory methods, we make a subsequent theoretical calculation that indicates that the ESIPT reaction of paeonol occurs through the intramolecular hydrogen bond O−H···O=C. The excited-state potential energy curve of paeonol indicates that the ESIPT reaction is a barrierless process, and the fluorescence emission of paeonol at 493 nm in the ethanol solution was assigned to the keto isomer fluorescence. Additionally, we also found an intramolecular charge transfer in the excited state by analysing the frontier molecular orbitals of paeonol.

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Macháň, Radek, Piotr Jurkiewicz, Agnieszka Olżyńska, Marie Olšinová, Marek Cebecauer, Arnaud Marquette, Burkhard Bechinger, and Martin Hof. "Peripheral and Integral Membrane Binding of Peptides Characterized by Time-Dependent Fluorescence Shifts: Focus on Antimicrobial Peptide LAH4." Langmuir 30, no. 21 (May 20, 2014): 6171–79. http://dx.doi.org/10.1021/la5006314.

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Bączyński, A., T. Marszałek, D. Radomska, P. Targowski, and B. Ziętek. "Quasi-Molecule Model of the Spectra of Molecules in Polar Solution in Case of Time Dependent Fluorescence Shifts." Acta Physica Polonica A 82, no. 3 (September 1992): 413–20. http://dx.doi.org/10.12693/aphyspola.82.413.

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Först, Gesche, Lukasz Cwiklik, Piotr Jurkiewicz, Rolf Schubert, and Martin Hof. "Interactions of beta-blockers with model lipid membranes: Molecular view of the interaction of acebutolol, oxprenolol, and propranolol with phosphatidylcholine vesicles by time-dependent fluorescence shift and molecular dynamics simulations." European Journal of Pharmaceutics and Biopharmaceutics 87, no. 3 (August 2014): 559–69. http://dx.doi.org/10.1016/j.ejpb.2014.03.013.

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Vítek, Petr, Barbora Veselá, and Karel Klem. "Spatial and Temporal Variability of Plant Leaf Responses Cascade after PSII Inhibition: Raman, Chlorophyll Fluorescence and Infrared Thermal Imaging." Sensors 20, no. 4 (February 13, 2020): 1015. http://dx.doi.org/10.3390/s20041015.

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The use of photosystem II (PSII) inhibitors allows simulating cascade of defense and damage responses, including the oxidative stress. In our study, PSII inhibiting herbicide metribuzin was applied to the leaf of the model plant species Chenopodium album. The temporally and spatially resolved cascade of defense responses was studied noninvasively at the leaf level by combining three imaging approaches: Raman spectroscopy as a principal method, corroborated by chlorophyll a fluorescence (ChlF) and infrared thermal imaging. ChlF imaging show time-dependent transport in acropetal direction through veins and increase of area affected by metribuzin and demonstrated the ability to distinguish between fast processes at the level of electron transport (1 − Vj) from slow processes at the level of non-photochemical energy dissipation (NPQ) or maximum efficiency of PSII photochemistry (Fv/Fm). The high-resolution resonance Raman images show zones of local increase of carotenoid signal 72 h after the herbicide application, surrounding the damaged tissue, which points to the activation of defense mechanisms. The shift in the carotenoid band indicates structural changes in carotenoids. Finally, the increase of leaf temperature in the region surrounding the spot of herbicide application and expanding in the direction to the leaf tip proves the metribuzin effect on slow stomata closure.

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Havrdová, Markéta, Iztok Urbančič, Kateřina Bartoň Tománková, Lukáš Malina, Janez Štrancar, and Athanasios B. Bourlinos. "Self-Targeting of Carbon Dots into the Cell Nucleus: Diverse Mechanisms of Toxicity in NIH/3T3 and L929 Cells." International Journal of Molecular Sciences 22, no. 11 (May 25, 2021): 5608. http://dx.doi.org/10.3390/ijms22115608.

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It is important to understand the nanomaterials intracellular trafficking and distribution and investigate their targeting into the nuclear area in the living cells. In our previous study, we firstly observed penetration of nonmodified positively charged carbon dots decorated with quaternary ammonium groups (QCDs) into the nucleus of mouse NIH/3T3 fibroblasts. Thus, in this work, we focused on deeper study of QCDs distribution inside two healthy mouse NIH/3T3 and L929 cell lines by fluorescence microspectroscopy and performed a comprehensive cytotoxic and DNA damage measurements. Real-time penetration of QCDs across the plasma cell membrane was recorded, concentration dependent uptake was determined and endocytic pathways were characterized. We found out that the QCDs concentration of 200 µg/mL is close to saturation and subsequently, NIH/3T3 had a different cell cycle profile, however, no significant changes in viability (not even in the case with QCDs in the nuclei) and DNA damage. In the case of L929, the presence of QCDs in the nucleus evoked a cellular death. Intranuclear environment of NIH/3T3 cells affected fluorescent properties of QCDs and evoked fluorescence blue shifts. Studying the intracellular interactions with CDs is essential for development of future applications such as DNA sensing, because CDs as DNA probes have not yet been developed.

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Simon, V. R., T. C. Swayne, and L. A. Pon. "Actin-dependent mitochondrial motility in mitotic yeast and cell-free systems: identification of a motor activity on the mitochondrial surface." Journal of Cell Biology 130, no. 2 (July 15, 1995): 345–54. http://dx.doi.org/10.1083/jcb.130.2.345.

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Using fluorescent membrane potential sensing dyes to stain budding yeast, mitochondria are resolved as tubular organelles aligned in radial arrays that converge at the bud neck. Time-lapse fluorescence microscopy reveals region-specific, directed mitochondrial movement during polarized yeast cell growth and mitotic cell division. Mitochondria in the central region of the mother cell move linearly towards the bud, traverse the bud neck, and progress towards the bud tip at an average velocity of 49 +/- 21 nm/sec. In contrast, mitochondria in the peripheral region of the mother cell and at the bud tip display significantly less movement. Yeast strains containing temperature sensitive lethal mutations in the actin gene show abnormal mitochondrial distribution. No mitochondrial movement is evident in these mutants after short-term shift to semi-permissive temperatures. Thus, the actin cytoskeleton is important for normal mitochondrial movement during inheritance. To determine the possible role of known myosin genes in yeast mitochondrial motility, we investigated mitochondrial inheritance in myo1, myo2, myo3 and myo4 single mutants and in a myo2, myo4 double mutant. Mitochondrial spatial arrangement and motility are not significantly affected by these mutations. We used a microfilament sliding assay to examine motor activity on isolated yeast mitochondria. Rhodamine-phalloidin labeled yeast actin filaments bind to immobilized yeast mitochondria, as well as unilamellar, right-side-out, sealed mitochondrial outer membrane vesicles. In the presence of low levels of ATP (0.1-100 microM), we observed F-actin sliding on immobilized yeast mitochondria. In the presence of high levels of ATP (500 microM-2 mM), bound filaments are released from mitochondria and mitochondrial outer membranes. The maximum velocity of mitochondria-driven microfilament sliding (23 +/- 11 nm/sec) is similar to that of mitochondrial movement in living cells. This motor activity requires hydrolysis of ATP, does not require cytosolic extracts, is sensitive to protease treatment, and displays an ATP concentration dependence similar to that of members of the myosin family of actin-based motors. This is the first demonstration of an actin-based motor activity in a defined organelle population.

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Villalba-Galea, Carlos A., Walter Sandtner, Dorine M. Starace, and Francisco Bezanilla. "S4-based voltage sensors have three major conformations." Proceedings of the National Academy of Sciences 105, no. 46 (September 25, 2008): 17600–17607. http://dx.doi.org/10.1073/pnas.0807387105.

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Voltage sensors containing the charged S4 membrane segment display a gating charge vs. voltage (Q–V) curve that depends on the initial voltage. The voltage-dependent phosphatase (Ci-VSP), which does not have a conducting pore, shows the same phenomenon and the Q–V recorded with a depolarized initial voltage is more stable by at least 3RT. The leftward shift of the Q–V curve under prolonged depolarization was studied in the Ci-VSP by using electrophysiological and site-directed fluorescence measurements. The fluorescence shows two components: one that traces the time course of the charge movement between the resting and active states and a slower component that traces the transition between the active state and a more stable state we call the relaxed state. Temperature dependence shows a large negative enthalpic change when going from the active to the relaxed state that is almost compensated by a large negative entropic change. The Q–V curve midpoint measured for pulses that move the sensor between the resting and active states, but not long enough to evolve into the relaxed states, show a periodicity of 120°, indicating a 310 secondary structure of the S4 segment when determined under histidine scanning. We hypothesize that the S4 segment moves as a 310 helix between the resting and active states and that it converts to an α-helix when evolving into the relaxed state, which is most likely to be the state captured in the crystal structures.

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Sýkora, Jan, Petr Slavíček, Pavel Jungwirth, Justyna Barucha, and Martin Hof. "Time-Dependent Stokes Shifts of Fluorescent Dyes in the Hydrophobic Backbone Region of a Phospholipid Bilayer: Combination of Fluorescence Spectroscopy and Ab Initio Calculations." Journal of Physical Chemistry B 111, no. 21 (May 2007): 5869–77. http://dx.doi.org/10.1021/jp0719255.

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Kubheka, Gugu, John Mack, Tebello Nyokong, and Zhen Shen. "NIR Absorbing AzaBODIPY Dyes for pH Sensing." Molecules 25, no. 16 (August 13, 2020): 3689. http://dx.doi.org/10.3390/molecules25163689.

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Two near-infrared (NIR) absorbing di(thien-2-nyl)-di(dimethylanilino)azaBODIPY dyes 2a and 2b were synthesized and characterized that differ depending on whether the dimethylaniline substituents are introduced at the 3,5- or 1,7-positions of the azaBODIPY core. The main spectral bands lie at 824 and 790 nm, respectively, in CH2Cl2. The effect of substituent position on the photophysical and pH sensing properties was analyzed through a comparison of the optical properties with the results of time-dependent density functional theory (TD-DFT) calculations. Protonation of the dimethylamino nitrogen atoms eliminates the intramolecular charge transfer properties of these compounds, and this results in a marked blue-shift of the main absorption bands to 696 and 730 nm, respectively, in CH2Cl2, and a fluorescence “turn-on” effect in the NIR region. The pH dependence studies reveal that the pKa values of the non-protonated 2a and 2b molecules are ca. 6.9 (±0.05) and 7.3 (±0.05), respectively, while that of the monoprotonated species for both dyes is ca. 1.4 (±0.05) making them potentially suitable for use as colorimetric pH indicators under highly acidic conditions.

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Casals, C., E. Miguel, and J. Perez-Gil. "Tryptophan fluorescence study on the interaction of pulmonary surfactant protein A with phospholipid vesicles." Biochemical Journal 296, no. 3 (December 15, 1993): 585–93. http://dx.doi.org/10.1042/bj2960585.

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The fluorescence characteristics of surfactant protein A (SP-A) from porcine and human bronchoalveolar lavage were determined in the presence and absence of lipids. After excitation at either 275 or 295 nm, the fluorescence emission spectrum of both proteins was characterized by two maxima at about 326 and 337 nm, indicating heterogeneity in the emission of the two tryptophan residues of SP-A, and also revealing a partially buried character for these fluorophores. Interaction of both human and porcine SP-A with various phospholipid vesicles resulted in an increase in the fluorescence emission of tryptophan without any shift in the emission wavelength maxima. This change in intrinsic fluorescence was found to be more pronounced in the presence of dipalmitoyl phosphatidylcholine (DPPC) than with dipalmitoyl phosphatidylglycerol (DPPG), DPPC/DPPG (7:3, w/w) and 1-palmitoyl-sn-glycerol-3-phosphocholine (LPC). Intrinsic fluorescence of SP-A was almost completely unaffected in the presence of egg phosphatidylcholine (egg-PC). In addition, we demonstrated a shielding of the tryptophan fluorescence from quenching by acrylamide on interaction of porcine SP-A with DPPC, DPPG or LPC. This shielding was most pronounced in the presence of DPPC. In the case of human SP-A, shielding was only observed on interaction with DPPC. From the intrinsic fluorescence measurements as well as from the quenching experiments, we concluded that the interaction of some phospholipid vesicles with SP-A produces a conformational change on the protein molecule and that the interaction of SP-A with DPPC is stronger than with other phospholipids. This interaction appeared to be independent of Ca2+ ions. Physiological ionic strength was found to be required for the interaction of SP-A with negatively charged vesicles of either DPPG or DPPC/DPPG (7:3, w/w). Intrinsic fluorescence of SP-A was sensitive to the physical state of the DPPC vesicles. The increase in intrinsic fluorescence of SP-A in the presence of DPPC vesicles was much stronger when the vesicles were in the gel state than when they were in the liquid-crystalline state. The effect produced by SP-A on the lipid vesicles was also dependent on temperature. The aggregation of DPPC, DPPC/DPPG (7:3, w/w) or dimyristoyl phosphatidylglycerol (DMPG) was many times higher below the phase-transition temperature of the corresponding phospholipids. These results strongly indicate that the interaction of SP-A with phospholipid vesicles requires the lipids to be in the gel phase.

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Deden, Tobias, Lars May, Guido J. Reiss, and Thomas J. J. Müller. "Rapid Sequentially Palladium Catalyzed Four-Component Synthesis of Novel Fluorescent Biaryl-Substituted Isoxazoles." Catalysts 10, no. 12 (December 3, 2020): 1412. http://dx.doi.org/10.3390/catal10121412.

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A series of novel 3- and 5-biaryl-substituted isoxazoles was prepared by a rapid microwave-assisted four-component three-step synthesis: concatenating Sonogashira coupling, cyclocondensation, and Suzuki coupling in a one-pot fashion. The Pd-catalyst was successfully employed in the sense of a sequentially catalyzed process, i.e., without the addition of further catalyst loading. Biaryl-substituted isoxazoles with donor–acceptor decoration possess remarkable photophysical properties, such as high fluorescence quantum yields in solution up to ΦF = 0.86 and large Stokes shifts up to 10,000 cm−1. The experimental absorption and emission characteristics can be reproduced and rationalized by computations on the DFT (density functional theory) and TDDFT (time-dependent density functional theory) level of theory.

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Fuchs, Bernhard Maximilian, Günter Wallner, Wolfgang Beisker, Ines Schwippl, Wolfgang Ludwig, and Rudolf Amann. "Flow Cytometric Analysis of the In Situ Accessibility of Escherichia coli 16S rRNA for Fluorescently Labeled Oligonucleotide Probes." Applied and Environmental Microbiology 64, no. 12 (December 1, 1998): 4973–82. http://dx.doi.org/10.1128/aem.64.12.4973-4982.1998.

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ABSTRACT In situ identification of whole fixed bacterial cells by hybridization with fluorescently labeled, rRNA-targeted oligonucleotide probes is often limited by low signal intensities. In addition to an impermeability of the cell periphery and a low cellular rRNA content, the three-dimensional structure of the ribosome may hinder the access of oligonucleotides to their target sites. Until now, a systematic study on the accessibility of 16S rRNA target sites had not been done. Here, we report fluorescence intensities obtained with more than 200 oligonucleotide probes (mostly 18-mers) used with whole fixed cells ofEscherichia coli DSM 30083T. Two overlapping sets of adjacent oligonucleotides, 171 in total, were designed to cover the full length of the 16S rRNA. The two sets are shifted by 5 to 13 nucleotides. The probes were labeled with carboxyfluorescein, and signal intensities of hybridized cells were quantified by flow cytometry. Care was taken that the signal intensity of cells was dependent solely on the in situ accessibility of probe target sites. The brightest signal resulted from probe Eco1482, complementary to positions 1482 to 1499. With this probe, the fluorescence was 1.7 times brighter than that of the standard bacterial probe EUB338 and 44 times brighter than that of the worst probe, Eco468. The distribution of probe-conferred cell fluorescence in six arbitrarily set brightness classes (classes I to VI; 100 to 81%, 80 to 61%, 60 to 41%, 40 to 21%, 20 to 6%, and 5 to 0% of the brightness with Eco1482, respectively) was as follows: I, 4%; II, 14%; III, 21%; IV, 29%, V, 19%; and VI, 13%. A more detailed analysis of helices 6, 18, and 23 with additional probes demonstrated that a shift of the target region by only a few bases could result in a decline of cell fluorescence from >80 to <10%. Considering the high evolutionary conservation of 16S rRNA, the in situ accessibility map of E. coli should facilitate a more rational selection of probe target sites for other species as well.

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Michán, Carmen, Manuel Manchado, Gabriel Dorado, and Carmen Pueyo. "In Vivo Transcription of the Escherichia coli oxyRRegulon as a Function of Growth Phase and in Response to Oxidative Stress." Journal of Bacteriology 181, no. 9 (May 1, 1999): 2759–64. http://dx.doi.org/10.1128/jb.181.9.2759-2764.1999.

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ABSTRACT Simultaneous expression of seven genes in Escherichia coli was measured by a reverse transcription-multiplex PCR fluorescence procedure. Genes studied were (i) oxyR(transcriptional regulator); (ii) katG, dps,gorA, and ahpCF (controlled by OxyR); (iii) sodA (controlled by SoxRS); and (iv) trxA(not related to OxyR or SoxRS). Except for trxA, transcription of all genes was activated during the course of growth of wild-type bacteria, though notable variations were observed with respect to both the time and extent of activation. WhereasoxyR, katG, dps, andgorA were activated during exponential growth,ahpCF and sodA were stimulated in stationary phase. Maximal induction ranged from 4.6- to 86.5-fold, forgorA and dps, respectively. Treatment with H2O2 stimulated expression of the genes (katG, dps, ahpCF, andgorA) previously identified as members of the OxyR regulon, except for oxyR itself. Induction by H2O2 was a remarkably rapid and reversible process that took place in an OxyR-dependent and ςS-independent manner. NaCl induced expression of the genes controlled by OxyR, including the oxyR locus. This transcriptional up-regulation was preserved in a strain with the ΔoxyR::kan mutation, but it was abolished (ahpCF) or significantly reduced (oxyR and dps) in a strain with therpoS::Tn10 mutation, potentially reflecting positive transcriptional regulation of the oxyRregulon by ςS. Expression of trxA was not increased either by H2O2 stress or by a shift to high-osmolarity conditions.

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Kanaya, Noriaki, Paul A. Murray, and Derek S. Damron. "Propofol and Ketamine Only Inhibit Intracellular Ca2+Transients and Contraction in Rat Ventricular Myocytes at Supraclinical Concentrations." Anesthesiology 88, no. 3 (March 1, 1998): 781–91. http://dx.doi.org/10.1097/00000542-199803000-00031.

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Background The cellular mechanisms that mediate the cardiodepressant effects of intravenous anesthetic agents remain undefined. The objective of this study was to elucidate the direct effects of propofol and ketamine on cardiac excitation-contraction coupling by simultaneously measuring intracellular calcium concentration ([Ca2+]i) and shortening in individual, field-stimulated ventricular myocytes. Methods Freshly isolated rat ventricular myocytes were loaded with the Ca2+ indicator, fura-2, and placed on the stage of an inverted fluorescence microscope in a temperature-regulated bath. [Ca2+]i and myocyte shortening (video edge detection) were monitored simultaneously in individual cells that were field-stimulated at 0.3 Hz. Results Baseline [Ca2+]i (mean +/- SEM) was 80 +/- 12 nM, and resting cell length was 112 +/- 2 microm. Field stimulation increased [Ca2+]i to 350 +/- 23 nM, and the myocytes shortened by 10% of diastolic cell length. Both intravenous anesthetic agents caused dose-dependent decreases in peak [Ca2+]i and shortening. At 300 microM, propofol prolonged time to peak concentration and time to 50% recovery for [Ca2+]i and shortening. In contrast, changes in time to peak concentration and time to 50% recovery in response to ketamine were observed only at the highest concentrations. Neither agent altered the amount of Ca2+ released from intracellular stores in response to caffeine. Propofol but not ketamine, however, caused a leftward shift in the dose-response curve to extracellular Ca2+ for shortening, with no concomitant effect on peak [Ca2+]i. Conclusions These results indicate that both intravenous anesthetic agents have a direct negative inotropic effect, which is mediated by a decrease in the availability of [Ca2+]i. Propofol but not ketamine may also alter sarcoplasmic reticulum Ca2+ handling and increase myofilament Ca2+ sensitivity. The effects of propofol and ketamine are primarily apparent at supraclinical concentrations, however.

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Barták, Miloš, and Peter Váczi. "Long-term fluorometric measurements of photosynthetic processes in Antarctic moss Bryum sp. during austral summer season." Czech Polar Reports 4, no. 1 (January 1, 2014): 63–72. http://dx.doi.org/10.5817/cpr2014-1-7.

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Photosynthetic activity pattern of Bryum sp. was monitored for 28days using a chlorophyll a fluorescence measuring system installed in the field. For the study, long-term research plot, a moss-dominated vegetaiton oasis at seashore located close to the J.G. Mendel station (James Ross Island, Antarctica) was selected. In this study, two measuring sites were used: (1) control plot with moss cover and (2) moss located inside open top chamber (OTC). At both sites, effective quantum yield of photosynthetic processes in photosyntem II (FPSII) was measured and relative photosynthetic electron transport rate (ETRrel) evaluated each 15 min. Simultaneously, microclimate of the sites was measured including air and moss surface temperature, relative air humidity and photosynthetically active radiation. The length of photosyntetically active period depended mainly on hydration of moss cushion. Water availability, however, was not limiting in the measuring period (Jan 8 - Feb 18, 2009), because the sites were well suplied by melt water from neighbouring snowfield. Thus, daily courses of ETRrel were dependent on incident PAR. On sunny days, ETRrel reached values over 400. Inhibition of primary photosynthetic processes due to below-zero temperature and resulting freezing of moss cushions appeared two times within the measuring periods thanks to rapid decreases in air temperature. The effect of low air temperature on ETRrel was less apparent in OTC site since moss cushion freezing period was shorter and less pronounced than in control site thanks to OTC-induced shift in air temperature. For future photosynthetic studies in Antarctic mosses, simultaneous measurements of gas exchange- and chlorophyll fluorescence-related parameters is recommended so that the effects of particular limiting factors for photosynthesis and photosynthetic productivity can be distinguished and evaluated.

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Tsang, John Y. C., Wayne J. E. Lamm, and Erik R. Swenson. "Regional CO2 tension quantitatively mediates homeostatic redistribution of ventilation following acute pulmonary thromboembolism in pigs." Journal of Applied Physiology 107, no. 3 (September 2009): 755–62. http://dx.doi.org/10.1152/japplphysiol.00245.2009.

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Previous studies reported that regional CO2 tension might affect regional ventilation (V̇) following acute pulmonary thromboembolism (APTE). We investigated the pathophysiology and magnitude of these changes. Eight anesthetized and ventilated piglets received autologous clots at time = 0 min until mean pulmonary artery pressure was 2.5 times baseline. The distribution of V̇ and perfusion (Q̇) at four different times (−5, 30, 60, 120 min) was mapped by fluorescent microspheres. Regional V̇ and Q̇ were examined postmortem by sectioning the air-dried lung into 900–1,000 samples of ∼2 cm3 each. After the redistribution of regional Q̇ by APTE, but in the scenario assuming that no V̇ shift had yet occurred, CO2 tension in different lung regions at 30 min post-APTE (PXCO2) was estimated from the V̇/Q̇ data and divided into four distinct clusters: i.e., PXCO2 < 10 Torr; 10 < PXCO2 < 25 Torr; 25 < PXCO2 < 50 Torr; PXCO2 > 50 Torr. Our data showed that the clusters in higher V̇/Q̇ regions (with a PXCO2 < 25 Torr) received ∼35% less V̇ when measured within 30 min of APTE, whereas, in contrast, the lower V̇/Q̇ regions showed no statistically significant increases in their V̇. However, after 30 min, there was minimal further redistribution of V̇. We conclude that there are significant compensatory V̇ shifts out of regions of low CO2 tension soon following APTE, and that these variations in regional CO2 tension, which initiate CO2-dependent changes in airway resistance and lung parenchymal compliance, can lead to improved gas exchange.

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Razem, Fawzi A., and Robert D. Hill. "Hydrogen peroxide affects abscisic acid binding to ABAP1 in barley aleurones." Biochemistry and Cell Biology 85, no. 5 (October 2007): 628–37. http://dx.doi.org/10.1139/o07-107.

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Dramatic increases in H2O2 levels have been observed following abscisic acid (ABA) treatment of plant tissues. Following ABA treatment in aleurone cells, H2O2 reached transient levels of approximately 115 µmol/L H2O2. To determine whether ABA perception was modified by such changes, the effect of H2O2 on a recently characterized ABA-binding protein (ABAP1), cloned from barley aleurone layers, was examined. ABA binding to the protein was weakened by H2O2 in a concentration-dependent manner. A concentration of 75 µmol/L H2O2 gave a 50% decline in ABA binding in a reaction following first-order kinetics, indicative of binding-site susceptibility to its microenvironment. We monitored the unfolding of ABAP1 using steady-state and time-resolved tryptophan fluorescence, while following the capacity of ABAP1 to bind ABA. ABA binding decreased by 50% following ABAP1 denaturation with 1 mol/L guanidine hydrochloride or 2 mol/L urea, while the maximum emission spectra (λemi) red shifted from 338 to 347 nm at 3.5 mol/L guanidine hydrochloride and 5 mol/L urea. However, only a slight blue shift of λemi was observed following either ABAP1 incubation with H2O2 or binding to (+)-ABA (physiologically active ABA). The equilibrium ABA dissociation rate accelerated in the presence of 250 µmol/L H2O2, with the half-time dissociation reduced to 8 min. A comparison of inactivation kinetics and conformational changes shows that inactivation of ABAP1 occurs before any noticeable conformational change. This suggests that the ABA binding site is highly responsive to its microenvironment and is situated in a region that is more flexible than the protein molecule as a whole. The results demonstrate that H2O2, generated by ABA treatment of aleurone layers, is sufficient to affect the ABA-binding capacity of ABAP1, suggesting that this may be another level of control of ABA signal transduction.

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Knisley, Stephen B., Robert K. Justice, Wei Kong, and Philip L. Johnson. "Ratiometry of transmembrane voltage-sensitive fluorescent dye emission in hearts." American Journal of Physiology-Heart and Circulatory Physiology 279, no. 3 (September 1, 2000): H1421—H1433. http://dx.doi.org/10.1152/ajpheart.2000.279.3.h1421.

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Transmembrane voltage-sensitive fluorescence measurements are limited by baseline drift that can obscure changes in resting membrane potential and by motion artifacts that can obscure repolarization. Voltage-dependent shift of emission wavelengths may allow reduction of drift and motion artifacts by emission ratiometry. We have tested this for action potentials and potassium-induced changes in resting membrane potential in rabbit hearts stained with di-4-ANEPPS [Pyridinium, 4-(2-(6-(dibutylamino)-2-naphthalenyl) ethenyl)-1-(3-sulfopropyl)-, hydroxide, inner salt] using laser excitation (488 nm) and a two-photomultiplier tube system or spectrofluorometer (resolution of 500–1,000 Hz and <1 mm). Green and red emissions produced upright and inverted action potentials, respectively. Ratios of green emission to red emission followed action potential contours and exhibited larger fractional changes than either emission alone ( P < 0.001). The largest changes and signal-to-noise ratio (signal/noise) were obtained with numerator wavelengths of 525–550 nm and denominator wavelengths of 650–700 nm. Ratiometry lessened drift 56–66% ( P < 0.015) and indicated decreases in resting membrane potential. Ratiometry lessened motion artifacts and increased magnitudes of deflections representing phase-zero depolarizations relative to total deflections by 123–188% in intact hearts ( P < 0.02). Durations of action potentials at different pacing rates, temperatures, and potassium concentrations were independent of whether they were measured ratiometrically or with microelectrodes ( P ≥ 0.65). The ratiometric calibration slope was 0.017/100 mV and decreased with time. Thus emission ratiometry lessens the effects of motion and drift and indicates resting membrane potential changes and repolarization.

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Kiefmann, Martina, Sascha Tank, Marc-Oliver Tritt, Paula Keller, Kai Heckel, Leonie Schulte-Uentrop, Cynthia Olotu, Sonja Schrepfer, Alwin E. Goetz, and Rainer Kiefmann. "Dead space ventilation promotes alveolar hypocapnia reducing surfactant secretion by altering mitochondrial function." Thorax 74, no. 3 (January 12, 2019): 219–28. http://dx.doi.org/10.1136/thoraxjnl-2018-211864.

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BackgroundIn acute respiratory distress syndrome (ARDS), pulmonary perfusion failure increases physiologic dead space ventilation (VD/VT), leading to a decline of the alveolar CO2 concentration [CO2]iA. Although it has been shown that alveolar hypocapnia contributes to formation of atelectasis and surfactant depletion, a typical complication in ARDS, the underlying mechanism has not been elucidated so far.MethodsIn isolated perfused rat lungs, cytosolic or mitochondrial Ca2+ concentrations ([Ca2+]cyt or [Ca2+]mito, respectively) of alveolar epithelial cells (AECs), surfactant secretion and the projected area of alveoli were quantified by real-time fluorescence or bright-field imaging (n=3–7 per group). In ventilated White New Zealand rabbits, the left pulmonary artery was ligated and the size of subpleural alveoli was measured by intravital microscopy (n=4 per group). Surfactant secretion was determined in the bronchoalveolar lavage (BAL) by western blot.ResultsLow [CO2]iA decreased [Ca2+]cyt and increased [Ca2+]mito in AECs, leading to reduction of Ca2+-dependent surfactant secretion, and alveolar ventilation in situ. Mitochondrial inhibition by ruthenium red or rotenone blocked these responses indicating that mitochondria are key players in CO2 sensing. Furthermore, ligature of the pulmonary artery of rabbits decreased alveolar ventilation, surfactant secretion and lung compliance in vivo. Addition of 5% CO2 to the inspiratory gas inhibited these responses.ConclusionsAccordingly, we provide evidence that alveolar hypocapnia leads to a Ca2+ shift from the cytosol into mitochondria. The subsequent decline of [Ca2+]cyt reduces surfactant secretion and thus regional ventilation in lung regions with high VD/VT. Additionally, the regional hypoventilation provoked by perfusion failure can be inhibited by inspiratory CO2 application.

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Kanaya, Noriaki, Daniel R. Zakhary, Paul A. Murray, and Derek S. Damron. "Thiopental Alters Contraction, Intracellular Ca2+, and pH in Rat Ventricular Myocytes." Anesthesiology 89, no. 1 (July 1, 1998): 202–14. http://dx.doi.org/10.1097/00000542-199807000-00027.

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Background Myocardial contractility is regulated by intracellular concentration of free Ca2+ ([Ca2'],) and myofilament Ca2+ sensitivity. The objective of this study was to elucidate the direct effects of thiopental on cardiac excitation-contraction coupling using individual, field-stimulated ventricular myocytes. Methods Freshly isolated rat ventricular myocytes were loaded with the Ca2+ indicator, fura-2, and placed on the stage of an inverted fluorescence microscope in a temperature-regulated bath. [Ca2+], (340/380 ratio) and myocyte shortening (video-edge detection) were monitored simultaneously in individual cells field-stimulated at 0.3 Hz. Amplitude and timing of myocyte shortening and [Ca2+l, were compared before and after addition of thiopental. Intracellular pH was measured with the pH indicator, BCECF (500/440 ratio). Real-time uptake of Ca2+ into isolated sarcoplasmic reticulum vesicles was measured using fura-2 free acid in the extravesicular compartment. One hundred thirty-two cells were studied. Results Field stimulation increased [Ca2+]i from 85 + 10 nM to 355 + 22 nM (mean + SEM). Myocytes shortened by 10% of resting cell length (127 + 5 tlm). Times to peak [Ca2+], and shortening were 139 + 6 and 173 + 7 msec, respectively. Times to 50% recovery for [Ca2+], and shortening were 296 + 6 and 290 + 6 ms, respectively. Addition of thiopental (30-1,000 /lM) resulted in dose-dependent decreases in peak [Ca2+]i and myocyte shortening. Thiopental altered time to peak and time to 50% recovery for [Ca2+], and myocyte shortening and inhibited the rate of uptake of Ca2+ into isolated sarcoplasmic reticulum vesicles. Thiopental did not, however, alter the amount of Ca2+ released in response to caffeine in sarcoplasmic reticulum vesicles or intact cells. Thiopental (100 uM) increased intracellular pH and caused an upward shift in the dose-response curve to extracellular Ca2+ for shortening, with no concomitant effect on peak [Ca2+],. These effects were abolished by ethylisopropyl amiloride, an inhibitor of Na+-H+ exchange. Conclusion Thiopental has a direct negative inotropic effect on cardiac excitation-contraction coupling at the cellular level, which is mediated by a decrease in [Ca2+],. Thiopental also increases myofilament Ca2+ sensitivity via alkalinization of the cell, which may partially offset its negative inotropic effect.

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Cui, Y., KA Harvey, RA Siddiqui, J. Jansen, LP Akard, JM Thompson, JG Garcia, and D. English. "Cytosolic inactivation of translocated neutrophil plasma membrane protein tyrosine phosphatase." Blood 87, no. 1 (January 1, 1996): 341–49. http://dx.doi.org/10.1182/blood.v87.1.341.341.

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Abstract Phosphotyrosine phosphatases (PTPases) regulate cellular metabolic activation by reversing the effects of tyrosine kinases activated earlier in intracellular signaling pathways. We coupled fluorescence-activated cell sorter analysis using anti-CD45 monoclonal antibody with direct measurements of enzyme activity in resolved subcellular fractions to define mechanisms that potentially regulate the availability and activity of CD45-PTPase on neutrophil plasma membranes. Neutrophils in freshly obtained blood as well as neutrophils freshly isolated from blood were found to possess detectable levels of plasma membrane CD45 as assessed by immunofluorescence. However, plasma membranes from these cells were essentially devoid of PTPase catalytic activity, which was largely confined to the specific granules. Granulocyte-macrophage colony-stimulating factor (GM-CSF) upregulated both the catalytic and antigenic components of CD45-PTPase on the plasma membrane of these cells. Upregulation was associated with a shift in the particulate subcellular PTPase catalytic activity from the specific granule fraction to the plasma membrane fraction. The tyrosine kinase inhibitor genistein abrogated GM-CSF-promoted upregulation of plasma membrane CD45 PTPase but did not prevent the GM-CSF-dependent decrease in specific granule catalytic activity. Anti-CD45 antibody immunoprecipitated PTPase activity from both specific granules of resting cells and plasma membranes of GM-CSF-treated cells. However, antiphosphotyrosine immunoprecipitated only activity that had translocated to the plasma membrane, suggesting a role for CD45 phosphorylation in translocation. Western analysis confirmed the tyrosine phosphorylation of CD45 in plasma membranes of GM-CSF-treated neutrophils. Preincubation of plasma membranes of GM-CSF-stimulated neutrophils with cytosol from resting cells resulted in a time- and temperature-dependent loss in membrane PTPase as a consequence of the effects of a cytosolic inactivator. Cytosol obtained from stimulated neutrophils possessed substantially reduced levels of this PTPase inactivator. We conclude that activity of the catalytic component of membrane PTPase in circulating neutrophils is regulated by a cytosolic inactivator. Upon stimulation, intact CD45 PTPase is incorporated into the plasma membrane by a process that requires tyrosine phosphorylation. As a result of inhibition of the cytosolic inactivator, the translocated PTPase expresses full activity, thereby amplifying the potential regulatory influence of the enzyme on the cells' functional response.

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Journal articles on the topic 'Time dependent fluorescence shift'

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