The present report describes an endeavor to follow the solubilization of DMPC and DMPG liposome membranes by a non-ionic detergent Triton X-100 on the lexicon of environment-sensitive intramolecular charge transfer (ICT) photophysics of an extrinsic molecular probe 5-(4-dimethylamino-phenyl)-penta-2, 4-dienoic acid methyl ester (DPDAME). The prospective applicability of the probe to function as a reporter for detergent-sequestered solubilization of liposome membranes is argued on the basis of comparison of the spectral properties of the probe in various environments. Fluorescence anisotropy study delineates the degree of motional restriction imposed on the probe in different microheterogeneous assemblies. The kinetics of association of the probe with the liposome membranes and the dissociation kinetics of TX-100-sequestered solubilization process of the liposomes have been monitored by the stopped-flow fluorescence technique and the results are rationalized in relevance to fluorescence anisotropy study. © 2012 Elsevier B.V. All rights reserved.

NIKHIL GUCHHAIT

Chemistry

B K PAUL

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy

The present study demonstrates the binding interaction of a drug, berberine (BR) with DMPG liposome membrane as a function of the phase state of the lipid. Our results display an apparently contradicting interaction behavior of BR with DMPG lipid in the sense that the drug:lipid binding constant is found to be higher with the more ordered and compact solid gel (Lβ) phase at T = 288 K (lower permeability) of the lipid compared to the liquid crystalline (Lα) phase at T = 310 K (greater permeability). This result is rationalized on the basis of the probable location of the cationic drug molecules at the interfacial region of the lipid membrane having anionic headgroup. The excited-state relaxation dynamics of the lipid-bound drug coupled with rotational relaxation studies further substantiate a stronger binding of BR with the solid gel (Lβ) phase. The BR:DMPG binding interaction is meticulously quantified by calorimetric studies which reveal that the interaction phenomenon is enthalpically (ΔH &lt; 0) as well as entropically (TΔS &gt; 0) favorable, and is accompanied with marked modulation of the hydration structure surrounding the interacting species as rationalized on the basis of release of structured water molecules following the interaction. The calorimetric results also quantify the differential binding constants and binding stoichiometries of BR with DMPG; Ka = (2.32 ± 0.09) × 105 M− 1 and 2:1 stoichiometry in the solid gel (Lβ) phase (T = 288 K) versus Ka = (5.00 ± 0.2) × 104 M− 1 and 1:1 stoichiometry in the liquid crystalline (Lα) phase (T = 310 K). In addition, our results of nonionic surfactant (Triton X-100)-induced solubilization of DMPG lipid reveal differential degrees of release of lipid-bound drug depending on the phase state of the lipid. Fluorescence anisotropy and excited-state relaxation studies of the lipid-bound BR following interaction with TX100 display a greater degree of release of the drug molecules from the liquid crystalline (Lα) phase of the liposome membrane. These results are further corroborated from fluorescence correlation spectroscopic (FCS) results. © 2017

Journal of Molecular Liquids

Differential interaction behaviors of an alkaloid drug with DMPG liposome membrane as a function of the phase state of the lipid: Nonionic surfactant-induced solubilization of the lipid

Photophysical properties of a potent intramolecular charge transfer probe viz.; 5-(4-dimethylamino-phenyl)-penta-2,4-dienoic acid methyl ester (DPDAME) have been investigated in aqueous micellar environments using spectroscopic techniques. The intramolecular charge transfer (ICT) fluorescence of DPDAME is found to display remarkable hypsochromic shift coupled with intensity enhancement within the microheterogeneous micellar environments. This is also associated with discernible increase in fluorescence anisotropy whereby indicating the impartation of considerable motional restrictions on the fluorophore within the micellar systems. The fluorescence anisotropy results are also processed to delve into an estimate of the microviscosity of the probe environment at the binding site on the micellar aggregates. Quantitative evaluation of the probe-micelle binding strength has been achieved from fluorescence data in terms of binding constant and free energy change of the interaction process. The extensive polarity-sensitive fluorescence behavior of DPDAME has been exploited to cast light on assessing the micropolarity at the interaction site of the probe within the micelles. This information has in turn been efficiently employed as the actuating avenue to argue on complex issues like probable location, distribution and orientation of the probe within the micellar aggregates. The pattern of variation of emission intensity of DPDAME as a function of surfactant concentrations is found to reveal the existence of multiple critical micellar concentration (CMC). Overall, the present results have been argued to reflect the commendable efficiency of DPDAME to function as a prospective molecular reporter for complex microheterogeneous micellar environments. © 2014 Elsevier B.V.

Explicit spectral response of an intramolecular charge transfer molecule within microheterogeneous micellar environments

The present work demonstrates the interaction of an intramolecular charge transfer (ICT) probe 5-(4-dimethylamino-phenyl)-penta-2,4-dienoic acid methyl ester (DPDAME) with liposome membranes of dimyristoyl-l-α-phosphatidylcholine (DMPC) and dimyristoyl-l-α-phosphatidylglycerol (DMPG) studied by steady-state absorption, emission and time-resolved emission techniques. A huge hypsochromic shift together with remarkable enhancement of fluorescence quantum yield of the polarity sensitive ICT emission of DPDAME upon interaction with the lipids has been rationalized in terms of incorporation of the probe into hydrophobic interior of the lipids. Compelling evidences for penetration of the probe into the hydrocarbon interior of the lipids have been deduced from intertwining different experimental results e.g., micropolarity in the immediate vicinity of the probe in lipid environments, steady-state anisotropy, red-edge excitation shift (REES), fluorescence quenching experiments and time-resolved measurements. The rotational relaxation dynamics study of the membrane-bound probe unveils the impartation of high degree of motional rigidity. Wavelength-selective emission behaviour paves way for monitoring of solvent-relaxation in the membranes. Overall, the ICT probe DPDAME displays its commendable sensitivity in deciphering the microheterogeneous environments of liposomal membranes of DMPC and DMPG and promises a new membrane-polarity sensitizing probe. © 2011 Elsevier Inc.

Journal of Colloid and Interface Science

Spectroscopic probing of location and dynamics of an environment-sensitive intramolecular charge transfer probe within liposome membranes

The present work demonstrates the effect of β-cyclodextrin (β-CD) nanocaging on the photophysical properties of Excited-State Intramolecular Proton Transfer (ESIPT) probe 3,5,6-trichlorosalicylic acid (TCSA) through steady-state absorption, emission and time-resolved emission spectroscopy. The remarkable enhancement of tautomer (proton transferred form) emission of TCSA as a result of inclusion complex formation with β-CD has been argued to be principally due to retardation of radiationless decay channels within the encapsulated state. A quantitative assessment of the emission intensity data on Benesi-Hildebrand equation reveals a 1:1 stoichiometry for TCSA:β-CD complex. The steady-state anisotropy, REES, and time-resolved fluorescence decay measurements are consistent with other experimental findings. Additionally, chaotrope (urea)-induced perturbation of the phenomenon of host-guest inclusion complex formation has been elucidated for a series of urea concentration. The present findings have been interpreted on the basis of the hydrophobic interaction mechanism of urea, rather than water 3-D structure rupture. The data unravel that the perturbation of solvation of the β-CD receptor is not important in the presence of urea, while the hydrophobic interaction with free probe molecules could be instrumental behind the observed lowering of TCSA:β-CD binding strength in the presence of urea. © 2010 Elsevier Inc.

Constrained photophysics of an ESIPT probe within Î²-cyclodextrin nanocavity and chaotrope-induced perturbation of the binding phenomenon: Implication towards hydrophobic interaction mechanism between urea and the molecular probe

Intramolecular charge transfer (ICT) reaction has been investigated in 5-(4-dimethylamino-phenyl)-penta-2,4-dienoic acid methyl ester (DPDAME) using spectroscopic techniques. The molecule DPDAME shows local emission in non-polar solvent and dual emission in polar solvents. Solvatochromic effects on the Stokes shifted emission band clearly demonstrate the charge transfer character of the excited state. Quantum chemical calculations have been performed at Hartree-Fock (HF) and density functional theoretical (DFT) levels to correlate the experimental findings. Potential energy curves (PECs) for the ICT reaction have been evaluated along the donor twist angle at DFT and time dependent density functional theory (TDDFT) levels for the ground and excited states, respectively, using B3LYP hybrid functional and 6-31G** basis set. The solvent effects on the spectral properties have been explored theoretically at the same level with time dependent density functional theory-polarized continuum model (TDDFT-PCM) and the theoretical results are found to well substantiate the solvent polarity dependent Stokes shifted emission of DPDAME. Huge enhancement of dipole moment (Δμ=16.42 D) of the molecule following photoexcitation dictates the highly polar character of the excited state. Although elucidation of PECs does not exactly predict the operation of ICT according to twisted intramolecular charge transfer (TICT) model in DPDAME, lowering of vertical transition energy as a function of the donor twist coordinate scripts the occurrence of red shifted emission as observed experimentally. © 2010 Elsevier B.V. All rights reserved.

Journal of Luminescence

Evidence for excited state intramolecular charge transfer reaction in donor-acceptor molecule 5-(4-dimethylamino-phenyl)-penta-2,4-dienoic acid methyl ester: Experimental and quantum chemical approach

The excited-state intramolecular proton transfer (ESIPT) reaction of l-hydroxy-2-naphthaldehyde (HN12) has been studied within the interior of the supramolecular assemblies of α-, β-, and γ-cyclodextrins (CD) and biomimicking environments of ionic (SDS) and non-ionic (TW-20) micelles. Fluorescence measurements are used to investigate the effect of various supramolecular assemblies on the ESIPT reaction by monitoring the large Stokes-shifted tautomer emission of HN12. Enhanced tautomer emission in the microencapsulated state predicts favorable ESIPT reaction in the supramoleuclar assemblies. Benesi-Hildebrand plots have been employed to ascertain that the stoichiometric ratios of the complexes formed between HN12 and CDs are 1:2, 1:1, and 1:1 for α-, β-, and γ-CD, respectively. The binding constants (K1) and free-energy change (ΔG) for inclusion complexation are also determined from the linearized Benesi-Hildebrand plots. Steady-state fluorescence anisotropy, REES, excitation anisotropy, and fluorescence lifetime measurements are in line with other experimental findings. Differential action of urea on SDS and TW-20-bound probe has also been investigated. © 2009 American Chemical Society.

Langmuir

Modulation of excited-state intramolecular proton transfer reaction of 1-hydroxy-2-naphthaldehyde in different supramolecular assemblies

A simple intramolecular charge transfer (ICT) compound, 5-(4-dimethylamino-phenyl)-penta-2,4-dienoic acid methyl ester (DPDAME), has been documented to be a potential molecular reporter for probing microheterogeneous environments of a model transport protein bovine serum albumin (BSA) using spectroscopic techniques. Meteoric modifications to the emission profile of DPDAME upon addition of BSA come out to be a result of its binding to hydrophobic subdomain IIA. The highly polarity-sensitive ICT emission of DPDAME is found to be a proficient extrinsic molecular reporter for efficient mapping of native, intermediate, unfolded, and refolded states of the protein. Experimental data coupled with a reinforcing support from theoretical simulation using CHARMM22 software confirm the binding site of the probe to be the subdomain IIA of BSA, while FRET study reveals a remarkably close approach of our extrinsic molecular reporter to Trp-212 (in domain IIA): the distance between DPDAME and Trp-212 is 1.437 nm. The caliber of DPDAME as an external fluorescence marker also extends to the depiction of protein-surfactant (BSA-SDS) interaction to commendable fruition. Additionally, the protective action of small amounts of SDS on urea-denatured protein is documented by polarity-sensitive ICT emission of the probe. The present study also reflects the enhancement of the stability of BSA with respect to chemically induced denaturation by urea as a result of binding to the probe DPDAME. © 2010 American Chemical Society.

Journal of Physical Chemistry B

Exploring hydrophobic subdomain iia of the protein bovine serum albumin in the native, intermediate, unfolded, and refolded states by a small fluorescence molecular reporter

Response of an environment-sensitive intramolecular charge transfer probe towards solubilization of liposome membranes by a non-ionic detergent: Association and dissociation kinetics

Journal	Data powered by TypesetSpectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
Publisher	Data powered by TypesetPERGAMON-ELSEVIER SCIENCE LTD
ISSN	1386-1425
Open Access	No