7-amino Coumarin Research Articles

Interaction of a hydrophilic molecule with bovine serum albumin: A combined multi-spectroscopic, microscopic and isothermal calorimetric study in the presence of graphene oxide

One of the most widely studied plasma protein is bovine serum albumin (BSA), and it plays a crucial role in the binding and transportation of many exogenous and endogenous drugs. Coumarin derivatives play a crucial role as an analgesic, anticancer, and anticoagulant agent. Here in this report, we have studied the binding interaction between a 7-amino coumarin derivative, namely 7-(N, N′-diethylamino)coumarin-3-carboxylic acid (7-DCCA) with BSA and also have found out the effect of graphene oxide (GO) on the binding interaction. The binding interaction was probed by employing various spectroscopic, microscopic, isothermal titration calorimetric (ITC), and by using molecular docking studies. The change in absorption and emission maxima position of BSA and 7-DCCA in the absence and presence of GO along with the change in absorbance and emission intensity when we titrated by 7-DCCA or BSA respectively indicates the strong complexation between 7-DCCA and BSA. From the fluorescence resonance energy transfer study, the average distance between tryptophan 213 of the BSA (donor), and the 7-DCCA (acceptor) is found ~50 Ǻ. From excited-state lifetime and fluorescence lifetime imaging (FLIM) studies, we observed that the average lifetime of 7-DCCA is much higher in the presence of BSA compared to buffer medium and in the presence of BSA a heterogeneous environment was created around 7-DCCA. Again in the presence of GO, the formation of a complex of 7-DCCA with a low concentration of BSA shows greater binding interaction as compared to that in the absence of GO. Time-resolved fluorescence anisotropy measurement shows that the addition of GO provides a restricted environment surrounding the 7-DCCA molecule in the presence of both low and high concentrations of BSA. CD study demonstrates the same extent of reduction of α-helical content of BSA protein on binding with 7-DCCA in the absence and presence of GO. ITC study revealed that the interaction between 7-DCCA and BSA is favoured by negative enthalpy change and positive entropy change. Also, from the ITC study, we find out that GO doesn't inflict significant change in the overall global binding interaction pattern, rather it inflicts changes in the mechanistic pathways of binding between 7-DCCA and BSA. Step-scan FTIR studies show the modification of amide I and amide II bonds with time when complexation occurs between BSA and 7-DCCA in the absence and presence of GO. The docking result reveals that the deprotonated form of 7-DCCA has positioned at a distance of ~3.7 nm from Trp 213. Thus these interactions play a central role in the development of coumarin derivative based small molecules to be used for both academic and industrial purposes.

A photocleavable low molecular weight hydrogel for light-triggered drug delivery

A photocleavable low-molecular-weight hydrogelator (LMWG) was synthesized based on coumarin derivative. 1H NMR and UV spectroscopy study suggested that the gelator had good gelling ability, and the driving force for the gelation were hydrogen bonding and π-π stacking. This molecular hydrogel exhibited satisfied photocleavage at C-N bond in 7-amino coumarin with the light irradiation (365 nm, 77.5 mW/cm2). The promising photo-triggered drug release of antineoplastics cytarabine hydrochloride has been obtained, due to the photocleavage motived gel-sol transition.

Cosolubilization of Coumarin30 and Warfarin in Cationic, Anionic, and Nonionic Micelles: A Micelle-Water Interfacial Charge Dependent FRET.

Solubilization of structurally varied coumarins, viz., Warfarin (WF; a 4-hydroxy coumarin) and Coumarin30 (C30, a 7-amino coumarin) individually and in mixed states (cosolubilization) within the aqueous surfactant self-assemblies of varying architectures has been explored, exploiting steady-state, time-resolved fluorimetric, and spectrophotometric techniques. Cosolubilization studies within micelles, which have rarely been done in the literature, were specifically undertaken with the aim of understanding the effect of micelles on their photophysical phenomena when simultaneously present within these nanocarriers and assess their prospective use as an efficient FRET pair. WF solubilizes within CTAB micelles, whereas little or no solubilization is observed in Brij30 and SDS micelles. On the other hand, C30 solubilizes deep into the palisade layer of CTAB micelles, between negatively charged head groups in SDS micelles and between OE groups in Brij30 micelles. C30 and WF maintain their solubilization sites during cosolubilization. In SDS and Brij30 micelles, an increase in WF causes fluorescence quenching of C30 molecules, while in CTAB, an increase in WF causes an increase in fluorescence of C30 by excited WF molecules indicating FRET between the two molecules.

Photocleavable coumarin crosslinkers based polystyrene microgels: phototriggered swelling and release

Two types of photocleavable crosslinkers (CLA and CLB) based on 7-amino coumarin moieties have been synthesized. The ingenious design for the crosslinkers with different vinyl functionalities was aimed to investigate the influence of the crosslinker’s structure on the photodegradation and photoswelling behavior of the constructed microgels. Analysis of DLS, UV spectra and fluorescence spectra verified the original intention and the generated microgels revealed structure-dependent photo-regulated swelling and degradation behavior. The successive loading and release of the hydrophobic Nile Red (NR) dye of the microgel upon visible light irradiation further showed its ability to be used as an excellent nanocarrier for hydrophobic compounds.

7-Amino coumarin based fluorescent phototriggers coupled with nano/bio-conjugated bonds: Synthesis, labeling and photorelease

By several synthetic pathways, we designed and synthesized a new series of unsymmetrical substituted 7-amino coumarin-based phototriggers with various nano/bio-conjugated bonds. The photophysical properties of most of the substituted coumarin-based phototriggers, except for compound P9 with maleimide group, showed no significant change compared with that of 7-(diethylamino)-4-(hydroxylmethyl) coumarin (DEACM-OH, the reported symmetric substituted 7-amine coumarin based phototrigger). Four compounds (P2, P4, P9, 14) were successfully conjugated with typical carriers such as mesoporous silica nanoparticles, biocompatible polymer PEG and common protein BSA, respectively. The efficient photorelease of ibuprofen (IBU) in the model cargo delivery system of MD4 confirmed that our designed phototriggers could serve well as a photo-cage for bioactive molecules and the release can be regulated precisely by manipulating the external irradiation conditions. All the results hinted at the superiority of using these coumarin functional compounds for photo-regulated release in biotechnology and biomedical areas.

Photoionization and Time-Dependent Stokes Shift of Coumarin 307 in Soft Matter: Solvation and Radical-Ion Pair Recombination Dynamics

Photoionization, fluorescence time-dependent Stokes shift (TDSS), and rotational dynamics of coumarin 307 (C307) have been investigated in soft matter system such as micelles using time-resolved transient absorption and fluorescence spectroscopy. Photoionization of C307 leads to the formation of coumarin radical cation and hydrated electron, which were characterized by their respective transient absorption. The photoionization yields are significantly higher in anionic sodium dodecyl sulfate (SDS) micelle than in cationic cetyltrimethylammonium bromide (CTAB) and neutral Triton X-100 (TX-100) micelles, indicating the influence of micellar surface charge on the efficient separation of radical cation-hydrated electron pair. The CTAB micelle favors the recombination of radical cation and hydrated electron leading to the formation of triplet state of C307, which causes a decrease in the photoionization yield. C307 exhibits TDSS in all micelles; the time evolution and the magnitude of the TDSS depend on nature of the micelle. In TX-100 micelles, the decay of the TDSS exhibits ultraslow component (165 ns) and is affected by the presence of electron scavengers. The ultraslow component in TX-100 micelle originates from the recombination of radical cation-hydrated electron, which results in the formation of twisted intramolecular charge transfer (TICT) state; such formation of TICT state was not observed in SDS and CTAB micelles. To the best of our knowledge, this is the first report where the radical-ion pair recombination dynamics is probed using TDSS in combination with time-resolved transient absorption studies. The activation energy for the solvent relaxation and radical-ion pair (solvent separated) recombination process was found to be 6.1 and 3.0 kcal mol(-1), respectively. Temperature effect on TDSS in TX-100 micelles confirmed the increase in the water hydration, and size of the micelle influences the relative contribution of the solvation and radical-ion pair recombination dynamics toward the total TDSS. We propose that TDSS observed in neutral micelles and reported in other biomolecules such as proteins by the 7-amino coumarin probe is not only due to the solvation dynamics alone but also due to the radical-ion pair recombination dynamics.

Photoinduced electron transfer (PET) from N, N-dimethylaniline to 7-amino Coumarin dyes in a room temperature ionic liquid (RTIL): Slowing down of electron transfer rate compared to conventional solvent

In this Letter we have investigated the photoinduced electron transfer (PET) in a protic room temperature ionic liquid (PRTIL) comprised of non-aromatic cation and anion, N, N-dimethyl ethanol ammonium formate (DAF) to investigate how the dynamics of PET is affected in RTIL compared to other solvents. The photoinduced electron transfer rate in the ionic liquid DAF decreases by an order of magnitude upon going from the conventional solvent acetonitrile. We have observed saturation, i.e., a Rehm–Weller type of behaviour in the electron transfer rate. The ET rate ( k q ) vs. −ΔG 0 plot shows saturation to a diffusion-controlled value at the higher exergonicity region.

Photoinduced electron transfer reaction in polymer-surfactant aggregates: Photoinduced electron transfer between N,N-dimethylaniline and 7-amino coumarin dyes

Photoinduced electron transfer between coumarin dyes and N,N-dimethylaniline has been investigated by using steady state and picosecond time resolved fluorescence spectroscopy in sodium dodecyl sulphate (SDS) micelles and PVP-polyvinyl pyrrolidone (SDS) polymer-surfactant aggregates. A slower rate of electron transfer is observed in PVP-SDS aggregates than in polymer-free SDS micelles. A Marcus type inversion is observed in the correlation of free energy change in comparison with the electron transfer rate. The careful investigation reveals that C-151 deviates from the normal Marcus inverted region compared to its analogs C-152 and C-481 due to slower rotational relaxation and smaller translational diffusion coefficient.

Photoinduced Electron Transfer in a Protein−Surfactant Complex: Probing the Interaction of SDS with BSA

Photoinduced fluorescence quenching electron transfer from N,N-dimethyl aniline to different 7-amino coumarin dyes has been investigated in sodium dodecyl sulfate (SDS) micelles and in bovine serum albumin (BSA)-SDS protein-surfactant complexes using steady state and picosecond time resolved fluorescence spectroscopy. The electron transfer rate has been found to be slower in BSA-SDS protein-surfactant complexes compared to that in SDS micelles. This observation has been explained with the help of the "necklace-and-bead" structure formed by the protein-surfactant complex due to coiling of protein molecules around the micelles. In the correlation of free energy change to the fluorescence quenching electron transfer rate, we have observed that coumarin 151 deviates from the normal Marcus region, showing retardation in the electron transfer rate at higher negative free energy region. We endeavored to establish that the retardation in the fluorescence quenching electron transfer rate for coumarin 151 at higher free energy region is a result of slower rotational relaxation and slower translational diffusion of coumarin 151 (C-151) compared to its analogues coumarin 152 and coumarin 481 in micelles and in protein-surfactant complexes. The slower rotational relaxation and translational diffusion of C-151 are supposed to be arising from the different location of coumarin 151 compared to coumarin 152 and coumarin 481.

Photoinduced intermolecular electron transfer from dimethyl aniline to 7-amino Coumarin dyes in the surface of β-cyclodextrin

The photoinduced electron-transfer reaction between Coumarin dyes and N, N-dimethylaniline has been investigated using steady-state and Time-resolved fluorescence spectroscopy in the surface of β-cyclodextrin in dimethyl formamide (DMF) solvent. The electron-transfer rate constant has been correlated with the free-energy change during the process. We have observed a diffusion-controlled ET process in pure DMF by showing a normal Marcus region. However, the picture is different in presence of cyclodextrin. Here the ET is retarded at higher free-energy region. This unusual feature in bimolecular electron-transfer reaction is assumed to be arising from the different binding possibility of the Coumarin molecules to the cyclodextrin moity.

Study of Energy Transfer from 7-Amino Coumarin Donors to the Rhodamine 6G Acceptor in Lecithin Vesicles and Sodium Taurocholate−Lecithin Mixed Aggregates

The energy transfer using 7-amino coumarin dyes as the donor and rhodamine 590 (Rh6G) as the acceptor was investigated in lecithin vesicles and sodium taurocholate (NaTC)-lecithin mixed aggregates using steady-state and time-resolved fluorescence spectroscopy. All energy transfer parameters were calculated. The coumarin 153-Rh6G pair is the most efficient donor-acceptor pair as reflected by the value of k(ET). With addition of NaTC in lecithin, in the case of the coumarin 153-Rh6G pair, the energy transfer rate or efficiency does not change very much, whereas in the case of the coumarin 151-Rh6G pair, the energy transfer rate decreases 2-fold upon going from lecithin vesicles to NaTC-lecithin mixed aggregates where the molar ratio is 2.5. It is mainly due to the deeper location of coumarin 153 in the lipid bilayer or in mixed aggregates. Rotational relaxation data also support this idea.

Study of energy transfer from 7-amino coumarin donors to rhodamine 6G acceptor in non-aqueous reverse micelles

The energy transfer using 7-amino coumarin dyes as donor and rhodamine 590 (Rh6G) as acceptor were investigated in methanol and acetonitrile solubilized non-aqueous reverse micelles using steady state and time resolved fluorescence spectroscopy. For all donors and acceptor we have obtained higher value of overlap integral ( J( λ)) and higher value of Förster distance ( R 0). Although we have got higher value of J( λ) but the rate constant of energy transfer ( k ET) in almost all systems are small. Coumarin153–Rh6G pair is the most efficient donor acceptor pair as reflected by the value of k ET. The different value of energy transfer rate constant in case of different donors indicate the dependence of energy transfer on the structure of donors.

Use of Tandem Cuvettes to Determine Whether Radiative (Trivial) Energy Transfer Can Contaminate Steady-State Measurements of Fluorescence Resonance Energy Transfer

The energy transfer using 7-amino coumarin dyes as donor and rhodamine 590 (Rh6G) as acceptor were investigated in methanol and acetonitrile solubilized non-aqueous reverse micelles using steady state and time resolved fluorescence spectroscopy. For all donors and acceptor we have obtained higher value of overlap integral (J(λ)) and higher value of Förster distance (R0). Although we have got higher value of J(λ) but the rate constant of energy transfer (kET) in almost all systems are small. Coumarin153–Rh6G pair is the most efficient donor acceptor pair as reflected by the value of kET. The different value of energy transfer rate constant in case of different donors indicate the dependence of energy transfer on the structure of donors.

Effect of 1,4-diazabicyclo-[2,2,2]-octane on the laser properties of 7-amino coumarin dyes

1,4-Diazabicyclo-[2,2,2]-octane (Dabco), a tertiary amine, was found to quench the fluorescence of two 7-amino coumarin dyes C1 and C102. The quenching was monitored in solvents of varying polarity. In non-polar and polar aprotic solvents the quenching is very efficient and the rate constants for quenching are within diffusion-controlled limits, whereas in protic solvents the quenching efficiency is very low. An attempt has also been made to delineate the mechanism for the stabilization of a dye laser by Dabco, following the reactions of the triplets of C1 with Dabco and also by monitoring the photodegradation of C1 in the presence of Dabco.

A study of the triplet state of 7-amino coumarin laser dyes by the nanosecond pulse radiolysis technique

The triplet characteristics of two 7-amino coumarin laser dyes (7-diethylamino 4-methyl coumarin (C 1) and 7-diethylamino 4-trifluoromethyl coumarin (C 1F)) were studied in benzene solution using the nanosecond pulse radiolysis technique. Their T—T absorption spectra, rate constants for triplet to ground state transition and triplet—triplet annihilation and G values were determined. The energy transfers from coumarin triplets to various acceptor molecules such as pyrene, t-stilbene and anthracene and from benzene, biphenyl and naphthalene triplets to these dyes as acceptors were studied. Estimates of their energy levels were made.

Nonradiative energy transfer from 7-amino coumarin dyes to thiazine dyes in methanolic solutions

Nonradiative energy-transfer processes between 7-amino coumarin and thiazine dyes in methanolic solutions have been studied using a single-photon counting technique. The critical transfer distances calculated from the experimantal rate constants are in the range 30–70 Å and exhibit the same trend as the values calculated from Förster's formula.

Triplet state of coumarin 153 studied by nanosecond pulse radiolysis

The triplet—triplet absorption spectrum of the rigidized 7-amino coumarin dye C 153 has been investigatd in benzene solution in the region 450 – 750 nm by the pulse radiolysis technique. The triplet decay was first order with a half-life of 5 μs. Its formation was confirmed by energy transfer from the pulse radiolytically generated biphenyl triplet. The extinction coefficient of C 153 triplet in benzene was calculated to be 10 000 ± 500 dm 3 mol −1 cm −1. Using various triplet donors and acceptors its energy level was estimated to be 50 ± 2 kcal mol −1. The energy transfer rate constants from benzene, biphenyl and naphthalene triplets to C 153 and from C 153 triplet to anthracene were found to be diffusion controlled.

New laser dyes with blue-green emission

Several new derivatives of 7-amino coumarin and 7-amino-(2)-quinolone were synthesized and tested for lasing performance. Relative output, stability and lasing wavelength for these dyes are reported.