Isomerization and fluorescence depolarization of merocyanine 540 in polyacrylic acid. Effect of pH

Dynamics of isomerization and fluorescence depolarization of merocyanine 540 (MC540) in an aqueous solution of polyacrylic acid (PAA) have been studied using picosecond time resolved fluorescence spectroscopy. It is observed that the dynamics of isomerization and depolarization are sensitive enough to monitor the uncoiling of PAA at high pH (> 6). At low pH (< 3), when the polymer remains in a hypercoiled form, polymer bound MC540 experiences very high microscopic friction and, hence, the isomerization and depolarization processes are very slow. At high pH (> 6) a polyanion is formed and the polymer assumes an extended configuration due to electrostatic repulsion. At high pH(> 6), the anionic probe MC540 is expelled from the polyanion to bulk water and the dynamics of isomerization and fluorescence depolarization become faster by 12 and 5 times respectively, compared to those at low pH

Photoisomerization of merocyanine 540 in polymer-surfactant aggregate

Photoisomerization of merocyanine 540 (MC540) in a polymer-surfactant aggregate is studied using picosecond time resolved emission spectroscopy. The aggregate consists of the polymer, poly(vinylpyrrolidone) (PVP) and the surfactant, sodium dodecyl sulphate (SDS). With increase in the concentration of SDS in an aqueous solution of MC540 containing PVP, the emission quantum yield and lifetime of MC540 increase markedly. This indicates marked retardation in the nonradiative photoisomerization process of MC540, when it binds to the polymer-surfactant aggregate. The critical association concentration of SDS for binding to PVP has been found to be 0.5 mM. This is about 16 times lower than the CMC of SDS in pure water (8 mM)

Transmission Map and Atmospheric Light Guided Iterative Updater Network for Single Image Dehazing

Hazy images obscure content visibility and hinder several subsequent computer vision tasks. For dehazing in a wide variety of hazy conditions, an end-to-end deep network jointly estimating the dehazed image along with suitable transmission map and atmospheric light for guidance could prove effective. To this end, we propose an Iterative Prior Updated Dehazing Network (IPUDN) based on a novel iterative update framework. We present a novel convolutional architecture to estimate channel-wise atmospheric light, which along with an estimated transmission map are used as priors for the dehazing network. Use of channel-wise atmospheric light allows our network to handle color casts in hazy images. In our IPUDN, the transmission map and atmospheric light estimates are updated iteratively using corresponding novel updater networks. The iterative mechanism is leveraged to gradually modify the estimates toward those appropriately representing the hazy condition. These updates occur jointly with the iterative estimation of the dehazed image using a convolutional neural network with LSTM driven recurrence, which introduces inter-iteration dependencies. Our approach is qualitatively and quantitatively found effective for synthetic and real-world hazy images depicting varied hazy conditions, and it outperforms the state-of-the-art. Thorough analyses of IPUDN through additional experiments and detailed ablation studies are also presented.Comment: First two authors contributed equally. This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessible. Project Website: https://aupendu.github.io/iterative-dehaz

Isomerization and fluorescence depolarization of merocyanine 540 in polyacrylic acid. Effect of pH

Abstract. Dynamics of isomerization and fluorescence depolarization of merocyanine 540 (MC540) in an aqueous solution of polyacrylic acid (PAA) have been studied using picosecond time resolved fluorescence spectroscopy. It is observed that the dynamics of isomerization and depolarization are sensitive enough to monitor the uncoiling of PAA at high pH (> 6). At low pH (< 3), when the polymer remains in a hypercoiled form, polymer bound MC540 experiences very high microscopic friction and, hence, the isomerization and depolarization processes are very slow. At high pH (> 6) a polyanion is formed and the polymer assumes an extended configuration due to electrostatic repulsion. At high pH (> 6), the anionic probe MC540 is expelled from the polyanion to bulk water and the dynamics of isomerization and fluorescence depolarization become faster by 12 and 5 times respectively, compared to those at low pH

Ras hyperactivation versus overexpression : Lessons from Ras dynamics in Candida albicans

We thank Prof. Neta Dean for the CIp10ADH1-Cherry plasmid and Prof. Aaron Mitchell for the BWP17 strain. We gratefully acknowledge Prof. Sudipta Maiti, TIFR, Mumbai, India for providing the data acquisition software. We also appreciate the feedback and discussions with Dr. Rohini Muthuswami, SLS, JNU as well as from the Protein Society group, New Delhi while this study was taking shape. We thank Prof. Alok Bhattacharya for Cytochalasin D. The GC-MS and fluorescence lifetime measurements were carried out at the Advanced Instrumentation Research Facility (AIRF), JNU. Confocal images were recorded either at the central instrumentation facility (CIF), SLS, JNU or at AIRF, JNU. This work was supported by project grants from Department of Biotechnology (DBT, Project grant no. BT/PR20410/BRB/10/1542/2016) and Department of Science and Technology (DST, Project grant no. SB/SO/BB-011/2014), India to S.S.K; and project grants from Department of Information Technology, (DIT, Project grant no. 12(4)/2007-PDD), India to S.S. for FCS setup. In addition, both S.S. and S.S.K. thank DBT-BUILDER for funding support (Project grant no. BT/PR5006/INF/153/2012). S.S.K. also acknowledges funding support from UGC Resource Networking grant to the School of Life Sciences. We thank DST-PURSE and JNU for assistance with funding for publication. G.S.V. and S.C.S. received a fellowship from UGC; V.A.P., B.Y., P.J., N.P., M.F.K. acknowledge CSIR for fellowships. S.L.S. received a fellowship from ICMR. D.T.H. and M.F.K. thank DBT-BUILDER for funding.Peer reviewedPublisher PD

Solvation dynamics in bile salt aggregates

The solvation dynamics inside an aggregate of a bile salt, sodium deoxycholate (NaDC), in aqueous solution has been studied using picosecond time-resolved emission spectroscopy and two fluorescent probes, 4-(dicyanomethylene)-2-methyl-(p-dimethylaminostyryl)-4H-pyran (DCM) and 2,6-p-toluidinonaphthalenesulfonate (TNS). Addition of NaDC to an aqueous solution causes a nearly 110-fold increase in the emission quantum yield (ff) of TNS. From the variation of ff of TNS, two critical micellar concentrations of NaDC have been detected at around 7 and 60 mM, respectively. The solvation dynamics of TNS in 100 mM NaDC solution is described by three components, 95 ps (17%), 380 ps (16%), and 1.9 ns (67%). The solvation dynamics of DCM bound to 100 mM NaDC is also found to be triexponential with components of 110 ps (19%), 700 ps (17%), and 2.75 ns (64%). The substantially slow solvation dynamics of water in the vicinity of NaDC indicates restricted solvation dynamics of water inside the bile salt aggregate

Slow solvation dynamics of dimethylformamide in a nanocavity. 4-aminophthalimide in β -cyclodextrin

Solvation dynamics of a nonaqueous solvent, N,N-dimethylformamide (DMF) has been studied for the first time in a β -cyclodextrin (β -CD) cavity using picosecond time dependent fluorescence Stokes' shift and 4-aminophthalimide (4-AP) as a probe. Solvation dynamics of confined DMF molecules within the β -CD cavity is found to be described by a component of 400 ± 50 ps (25%) and a slow component of 8 ± 1 ns (75%). This is substantially slower than the solvation time (1 ps) in bulk DMF

Solvation dynamics in a protein-surfactant complex

Solvation dynamics in the denatured state of a protein, lysozyme (denatured by sodium dodecyl sulfate, SDS) is markedly slower than that in the native state. For coumarin 153 bound to lysozyme, the average solvation time, <τs> is 330 ps. In the lysozyme-SDS complex, the solvation dynamics is markedly slower with <τs>=7250 ps. On addition of dithiothreitol (DTT) to the lysozyme-SDS complex, when the di-sulfide bonds are destroyed, <τs> is found to be 1140 ps. The slow dynamics in the denatured protein is attributed to the polymer chain dynamics and the exchange of bound and free water molecules

Femtosecond study of solvation dynamics of DCM in micelles

Solvation dynamics of 4-(dicyanomethylene)-2-methyl-6-(p-dimethylamino-styryl) 4H-pyran (DCM) has been studied in neutral (triton X-100, TX) and cationic (cetyl trimethyl ammonium bromide, CTAB) micelles using femtosecond upconversion. Since DCM is insoluble in bulk water the observed solvation dynamics reports the relaxation dynamics exclusively at the micellar interface. It is observed that the solvation dynamics in TX is slower than that in CTAB. The solvation dynamics is described by components of 2.1, 165 and 2050 ps for TX and 0.23, 6.5 (average 1.75 ps) and 350 ps for CTAB