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Enhanced ‘Antenna effect’ of a suitably designed ternary complex of Eu(III), Tetracycline hydrochloride (TC) and globular proteins viz bovine serum albumin (BSA), human serum albumin (HSA) and β-lactoglobulin A (BLGA) in aqueous medium is employed to characterize the different partially unfolded states along with investigation of the micro- heterog...
A ternary system comprising of a Eu(III) complex of the drug Tetracycline hydrochloride (Eu3TC) bound to bovine β-lactoglobulin variant A (BLGA) in aqueous buffer at physiological pH (pH = 7.4) has been investigated to exploit the enhanced “antenna effect” to locate the bound drug and find the microenvironment of the binding site. Steady-state and...
The molecular charge transfer complexes using 9-methyl anthracene (9MA) and pyrene as donors and pyromellitic diimide (PMDI) as acceptor have been characterised by crystal structure analysis and photophysical studies. A π-π stacking interaction is observed in case of the 1:1 PMDI-Pyrene CT complex whereas the 1:1 PMDI-9MA CT complex exhibits select...
The present work demonstrates the photophysical characterization of the interaction of two antibacterial and antimicrobial compounds, thymol and its isomer, carvacrol with different biomimetic micellar nanocavities having varying surface charge characteristics. These types of molecules are reported to be photoacids and this behavior is remarkably e...
The reaction of a pentadentate compartmental ligand LH, namely 4-tert-Butyl-2,6-bis-[(2-pyridin-2-yl-ethylimino)-methyl]-phenol, with group 12 metal ions (ZnII, CdII, HgII) followed by addition of NaSCN afforded one discrete dinuclear complex [Zn2(L)(SCN)3](1), and two polymeric 1D species [Cd2.5(L)(SCN)3(AcO)]n (2) and [Hg2(L)(SCN)3]n (3). All the...
The role of intramolecular H-bonding within an excited state intramolecular proton transfer (ESIPT) probe, the intermolecular H-bonding ability of the microenvironment with the probe in different organized assemblies, the polarity of the medium after encapsulation and the motional restriction of the probe have been investigated by monitoring the ES...
The drug tetracycline hydrochloride (TC), which has cytotoxic and cytostatic effects on tumor cells, has been encapsulated within the nanocavity of apoferritin in the form of its EuIII complex (Eu3TC). The Eu3TC complex was encapsulated within apoferritin through disassembly followed by reassembly of the protein and exhibited significantly enhanced...
A combination of circular dichroism, steady-state and time-resolved fluorescence, and low temperature phosphorescence spectroscopy has been used to study guanidine hydrochloride (Gdn)-induced stepwise unfolding of MPT63, a small protein with immunoglobulin-like fold. A simple, rapid and inexpensive low temperature (77 K) phosphorescence (LTP) study...
The aggregation of phosphoprotein P of Chandipura virus (CHPV) and its interaction with viral leader (le) RNA in aqueous buffer and 40% ethylene glycol (EG)-buffer have been characterised using two single tryptophan (Trp/W) mutants W105F and W135F. The longer rotational correlation time [(θC)T] originating from overall motion observed at 300 nM con...
Three dinuclear zinc(ii) complexes with "end-off" compartmental ligands, namely 2,6-bis(N-ethylmorpholine-iminomethyl)-4-R-phenol (R = -CH3, Cl, (t)Bu) have been synthesized with the aim of exploring the role of the para substituent present in the ligand backbone in controlling the structural diversity, photophysical properties and different weak i...
A new family of pentanuclear 3d-4f heterometal complexes of general composition [Ln(III)2(M(II)L)3(μ3-O)3H](ClO4)·xH2O (1-5) [Ln = Nd, M = Zn, 1; Nd, Ni, 2; Nd, Cu, 3; Gd, Cu, 4; Tb, Cu, 5] have been synthesized in moderate yields (50-60%) following a self-assembly reaction involving the hexadentate phenol-based ligand, viz., N,N-bis(2-hydroxy-3-me...
We have designed a novel ternary system consisting of Tetracycline hydrochloride (TC), Eu(III) and unsaturated long chain fatty acid (Oleic acid, α-Linolenic acid) in aqueous buffer at physiological pH of 7.2. The systems exhibit highly efficient ‘antenna effect’ of Eu(III) compared to that observed in the binary system of TC and Eu(III) [Eu3TC]. T...
The structural change of M. tuberculosis MPT63, which is predominantly a β-sheet protein having an immunoglobulin like fold, has been investigated in the pH range 7.5-1.5 using various biophysical techniques along with low-temperature phosphorescence (LTP) spectroscopy. MPT63 contains four Tryptophan (Trp) residues at 26, 48, 82, and 129. Although...
By using two potential tridentate ligands, HL1 [4-chloro-2-[(2-morpholin-4-yl-ethylimino)-methyl]-phenol] and 4-chloro-2-[(3-morpholin-4-yl-propylimino)-methyl]-phenol], which differ by one methylene group in the alkyl chain, four new Zn-II complexes, namely, [Zn((LH)-H-2)(2)](ClO4)(2) (1), [Zn(L-1))(H2O)(2)][Zn(L-1)(SCN)(2)] (2), [Zn(L-1))(dca)](n...
The crystal structures of synthesized d-f hybrid tetranuclear heterometal Zn-II Eu-2(III) (2) and Cd-II Eu-2(III) (2) complexes, involving a pair of carboxylate ligands in a rare mu(4)-eta(2):eta(2) bridging mode, reveal that the metal centers are arranged alternately in a rhombic plane within 4 angstrom from each other. The Zn-II Eu-2(III) (2) and...
The binding site and the binding mechanism of 3-Hydroxy-2-Naphthoic acid (3HNA) in Oleic acid (OA) bound serum albumins (bovine serum albumin (BSA) and human serum albumin (HSA)) have been determined using steady state and time resolved emission of tryptophan residues (Trp) in proteins and the ESIPT emission of 3HNA. Time resolved anisotropy of the...
Energy distribution between photosystems (PSI & PSII) under prolonged and continuous white light irradiance was assessed by monitoring the progress of their fluorescence emission (FPSI/FPSII) at 77 K. Our observations indicate FPSI/FPSII to oscillate with the progress of irradiance treatments at all intensities tested (100, 200, 500, and 800 μE m(-...
Reactions of benzoyl pyridine, o-phenylenediamine and anhydrous ZnX2 in methanol afford imine complexes [Zn(L1)X2] (X = Cl, ; X = Br, ) in good yields (L1 = (E)-N(1)-(phenyl(pyridin-2-yl)methylene)benzene-1,2-diamine). The reduction of with NaBH4 affords (E)-N(1)-(phenyl(pyridine-2-yl)methylene)benzene-1,2-diamine (L2H). The reaction of L2H with [R...
Reaction of α-pyridoin and N-phenyl-o-phenylenediamine affords 2-(2-(phenylamino)phenylimino)-1,2-di(pyridin-2-yl)ethanol () which undergoes cyclization to a chiral diimine, 2-methoxy-1-phenyl-2,3-di(pyridin-2-yl)-1,2-dihydroquinoxaline, (conjugated 14πe system) in the presence of zinc(ii), cadmium(ii) and mercury(ii) ions affording [Zn(L(OMe))Cl2]...
A comparative study of the interaction of an antibiotic Tetracycline hydrochloride (TC) with two albumins, Human serum albumin (HSA) and Bovine serum albumin (BSA) along with Escherichia Coli Alkaline Phosphatase (AP) has been presented exploiting the enhanced emission and anisotropy of the bound drug. The association constant at 298 K is found to...
A comparative study of the interaction of an antibiotic Tetracycline hydrochloride (TC) with two albumins, Human serum albumin (HSA) and Bovine serum albumin (BSA) along with Escherichia Coli Alkaline Phosphatase (AP) has been presented exploiting the enhanced emission and anisotropy of the bound drug. The association constant at 298 K is found to...
A complex of Tb(III) with (+) catechin (C) has been profitably encapsulated within the �-CD cavity at
physiological pH = 6.9 in aqueous medium. The ternary system exhibits a remarkable ‘antenna effect’
compared to the complex of Tb(III) with C. Time resolved measurement of Tb(III) emission in H2O and in
D2O directly proves the protection of Tb(III)...
Four tetranuclear complexes involving both homo- and hetero-metal combinations, viz. [Zn(II)(2)L(2)(μ(4)-PhCOO)(2)Zn(II)(2)(hfac)(2)] (), [Cd(II)(2)L(2)(μ(4)-PhCOO)(2)Cd(II)(2)(hfac)(2)] (), [Zn(II)(2)L(2)(μ(4)-PhCOO)(2)Tb(III)(2)(hfac)(4)] (), and [Cd(II)(2)L(2)(μ(4)-PhCOO)(2)Tb(III)(2)(hfac)(4)] () have been prepared following a single-pot synthe...
The phosphoprotein (P protein) of the chandipura virus (CHPV), a negative strand RNA virus, is involved in both transcription and replication of the viral life cycle. Interaction between the P protein and the viral leader (le) RNA under in vitro conditions has been previously reported for CHPV and other negative strand RNA viruses such as the rinde...
MPT63, a secreted protein of unknown function that is specific to Mycobacterium tuberculosis and a potential drug target, contains four Tryptophan (Trp/W) residues located at positions 26, 48, 82, and 129 in the amino acid sequence. All of the four Trp residues have been optically resolved by simple inexpensive phosphorescence spectroscopy at 77 K....
A ternary system consisting of a protein, catechin (either + or - epimer), and Tb(III) in suitable aqueous buffer medium at physiological pH (= 6.8) has been shown to exhibit highly efficient "antenna effect". Steady state and time-resolved emission studies of each component in the binary complexes (protein with Tb(III) and (+)- or (-)-catechin wit...
The interaction of antibiotic Tetracycline hydrochloride (TC) with Alkaline Phosphatase (AP) from Escherichia coli, an important target enzyme in medicinal chemistry, having tryptophan (Trp) residues at 109, 220 and 268 has been studied using the steady state and time resolved emission of the protein and the enhanced emission of the bound drug. The...
The interactions of two stereoisomeric antioxidant flavonoids, catechin (C) and epicatechin (EC) with bovine serum albumin (BSA) and human serum albumin (HSA), have been investigated by steady state and time resolved fluorescence, phosphorescence, circular dichroism (CD), FTIR and protein–ligand docking studies. The steady-state fluorescence studie...
Three types of atropisomeric unsymmetrical diimine complexes, tetrahedral (L(R)(Φ))MX(2) (M = Zn, Cd; X = Cl, Br; R = Me, CMe(3), OH, OMe, Cl; 1a-k, type-I), tetrahedral (L(Me2)(Φ))ZnBr(2) (2, type-II) and square planar (L(OH)(ϕ))PdCl(2) (3, type-III) with different photoluminescence properties, have been reported (L(R)(Φ) = (E)-4-R-N-(pyridine-2-y...
The enhancement of the excited state intramolecular proton transfer (ESIPT) emission of 3-hydroxy-2-naphthoic acid (3HNA) in presence of poly N-vinyl-2-pyrrolidone (PVP) has been investigated by time resolved fluorescence and anisotropy measurement. In other water soluble polymers and monomers there is no enhancement of the ESIPT emission of 3HNA....
To obtain a better understanding of the structural features characteristic of the equilibrated micelle a solubilized molecule acting as probe may be employed. A good probe is one whose selected physical properties are sensitive
Four multiring heterocyclic ligands with benzimidazole (L-1 and L-3) and benzothiazole nuclei (L-2 and L-4) are reported. Their silver(I) complexes involving it variety of anions (both organic and inorganic) have been prepared by the process of self-assembly and structurally characterized by single-crystal X-ray diffraction analyses. Discrete metal...
The phosphoprotein (P protein) of Chandipura virus (CHPV), a negative stranded RNA virus, is involved in both transcription and replication phases of the viral life cycle. The two Tryptophan (Trp) residues of CHPV, located at 105 and 135 respectively and two single Trp mutants W135F and W105F and a double Trp mutant W135F/W105F have been characteri...
Polystryne, Acetylene Black, Conductivity, Nanocomposites
We have investigated the organization and dynamics of tryptophan residues in tetrameric, monomeric and unfolded states of soybean agglutinin (SBA) by selective chemical modification, steady-state and time-resolved fluorescence, and phosphorescence. Oxidation with N-bromosuccinimide (NBS) modifies two tryptophans (Trp 60 and Trp 132) in tetramer, fo...
A conducting nanocomposite of polyacrylamide (PAA) with acetylene black was prepared via Na2AsO3-K2CrO4 redox initiated polymerization of acrylamide in water containing a suspension of acetylene black. FTIR analyses confirmed the presence of PAA in the nanocomposites. The composite possessed lower thermal stability than AB and exhibited three stage...
The enhanced fluorescence and anisotropy of the ESIPT emission of 3-hydroxy-2-naphthoic acid (3HNA) in the complexes of 3HNA with bovine serum albumin (BSA) and human serum albumin (HSA) showed the formation of 1:1 complex [binding constant = 5.3 × 105 M−1 for BSA and = 2.2 × 105 M−1 for HSA]. The ESIPT emission of the probe in non-polar, polar pro...
A method exploring chemical oxidative polymerization (COP) to synthesize PF-13X zeolite composite thereafter reinforcing it by conductive polyaniline (PANI) moieties, was investigated. The analysis focused on demonstrating the detailed information regarding polymerization, composite formation, and evaluations of some distinctive bulk properties. A...
The paper reports time-resolved emission and energy transfer (ET) studies of metal ion complexes of a specially designed rigid macrocyclic naphthalene cryptand (L) under different conditions. Complex formation of L with Li+ and H+ causes an appreciable increase in singlet state quantum yield and lifetime of L implying photoinduced electron transfer...
The steady-state and time-resolved studies of the sensitized emission of the excited-state proton transfer (ESIPT) probe 3-hydroxy-2-naphthoic acid (3HNA) when bound to bovine serum albumin (BSA) and human serum albumin (HSA) indicate that the nonradiative dipole-dipole Förster type energy transfer from Trp singlet state of proteins to the ESIPT si...
The photoinduced energy transfer (ET) from naphthalene (N) to rare earth ions Eu/Tb has been studied in the lanthanide ion complexes of 1,4-naptho-22-crown-6 (system-I) using as counter ion. The ET efficiency and rate constants have been calculated and the values compared with the metal ion complexes of three other naptho-crown-6 systems (II to IV)...
Tubulin, a heterodimeric (alphabeta) protein, the main constituent of microtubules, binds efficiently with colchicine (consisting of a trimethoxybenzene ring, a seven-member ring and methoxy tropone moiety) and its analogues, viz., demecolcine and AC [2-methoxy-5-(2',3',4'-trimethoxyphenyl)tropone]. Tubulin contains eight tryptophan (Trp) residues...
A derivative of phenazine, dibenzo[a,c]phenazine (DBPZ), can be used as a very good hydrogen-bonding probe unlike its parent phenazine molecule. Steady-state absorption and fluorescence studies reveal that DBPZ is completely insensitive to polarity of the medium. However, DBPZ can form a hydrogen bond very efficiently in its first excited singlet s...
We report here the photophysical properties of a naphthalene derivative of a specially designed cryptand system (L). The system exhibits the unusual phenomenon of emission from T2 and T1 states of naphthalene which has been attributed to the inherent rigidity of the system. The results obtained have been analysed by comparison with two other model...
A poly(N-vinylcarbazole) (PNVC)–formalin (FO) resin (PNVC-FO) was prepared via copolycondensation between N-vinylcarbazole (NVC) and FO in the presence of dry HCl gas in toluene medium at 110°C. A highly conducting composite of PNVC-FO resin with nanodimensional acetylene black (AB) was prepared by carrying out the polycondensation reaction in pres...
From both steady state and fluorescence lifetime measurements it reveals that due to photoexcitation of benzotriazole (BZ) part of the bichromophore, 9(1-H-benzotriazole-lylmethyl)-9H-carbazole (BHC), singlet-singlet energy transfer takes place to populate the lowest excited singlet of carbazole (CZ). CZ, thus being excited indirectly via energy tr...
A comparative time-resolved emission studies of several naphtho-crown ethers I–V, where metal ions can be complexed in a predetermined orientation with respect to the naphthalene (Naph) π-plane and naphthalene-linked aza crown ethers (L1 and L2) have been presented. In both the systems, crown ethers and aza
crown ethers, naphthalene fluorescence ge...
Human placental ribonuclease inhibitor (hRI) containing six tryptophan (Trp) residues located at positions 19, 261, 263, 318, 375, and 438 and its complex with RNase A have been studied using steady-state and time-resolved fluorescence (298 K) as well as low-temperature phosphorescence (77 K). Two Trp residues in wild-type hRI and also in the prote...
The paper reports time resolved emission studies in different solvents of the dual emission observed in the macrotricyclic cryptand (L) where the three secondary amino nitrogen have been derivatized with methoxy coumarin at room temperature and at 77 K. The emission from the ‘locally excited monomer state’ has a lifetime less than 1 ns while the ot...
Nanocomposites of polyfuran (PF) and polythiophene (PTP) with montmorillonite clay (MMT) were prepared and modified by loading
of polyaniline (PANI) and polypyrrole (PPY) moieties via polymerization of aniline (ANI) and pyrrole (PY) in aqueous dispersions
of PF-MMT and PTP-MMT nanocomposites. Formation of PANI and PPY and their subsequent incorpora...
The photoinduced energy transfer (ET) from naphthalene (N) to Tb3+ has been studied in the complexes of Tb3+ ion with 2,3-naphtho-17-crown-5 ether(I), 2,3-naphtho-20-crown-6 ether(II), 1,8-naphtho-21-crown-6 ether(III) and 1,5-naphtho-22-crown-6 ether(IV), respectively, using nitrate (NO3−) ion as the counter anion in EtOH glass at 77 K. The ligand...
We report here the photophysical properties of two derivatives of N-(β-methylnaphthalene) aza-crown systems having different cavity dimensions. The aza-crown moiety is attached to β-position of naphthalene moiety by one >CH2 unit in both the derivatives. The cavity size is found to have a pronounced effect on exciplex formation as well as energy tr...
Low-temperature phosphorescence (LTP) decay measurements have been carried out in wild-type Escherichia coli alkaline phosphatase (AP), metal-depleted AP (apoAP), and terbium-substituted AP (TbAP) at 77, 4.2, and 1.2 K. Over this temperature range, Tb emission monitored at 542.4 nm decays with two apparent lifetime components of 16−20 ms and 130−17...
Odmr measurements of photoexcited triplet state traps were carried out at 1.2 K on polycrystalline donor-acceptor complexes of naphthalene (N) with the acceptors pyromellitic dianhydride (PMDA), 1,2,4,5-tetracyanobenzene (TCNB), and 1,3,5-trinitrobenzene (TNB). The zero field splittings (zfs) are consistent with a locally excited N triplet state wi...
The paper reports the photophysical studies of a macrobicyclic cryptand where the three secondary amino nitrogen have been derivatized with methoxy coumarin in various solvents at room temperature and at 77K. The system having (F–S)3–R configuration (where F is fluorophore, S is CH2 spacer and R is receptor unit) shows intramolecular PET from the r...
Spin−lattice relaxation (SLR) has been studied at 1.2 K in the photoexcited triplet state of tryptophan (Trp) in a number of protein sites in zero applied magnetic field. We find that there is a distribution of SLR rate constants in every case that indicates the partitioning into two populations, ns0 and nf0, with differing behavior. ns0 undergoes...
The three secondary amino nitrogens of a heteroditopic cryptand have been derivatized with naphthyl groups and different spacer units to have a (fluorophore–spacer)3–receptor configuration. The length and the nature of the spacer units have been varied in the systems to study the effect on the photophysical behavior and the photoinduced electron tr...
The phosphorescence and zero field optically detected magnetic resonance (ODMR) of the tryptophan (Trp) residues of alkaline phosphatase from Escherechia coli are examined. Each Trp is resolved optically and identified with the aid of the W220Y mutant and the terbium complex of the apoenzyme. Trp(109), known from earlier work to be the source of ro...
Gramicidin A (gr A), a linear pentadecapeptide containing four trp residues has been studied using steady state and time resolved fluorescence (at 298 K) and phosphorescence (at 77 K) in methanol (CH3OH), ethanol (C2H5OH), dimethyl sulfoxide (DMSO), 1,4-dioxane, 2-methyl tetrahydrofuran (2-MeTHF), ethanol/benzene (C2H5OH/C6H6) mixed solvent. Simila...
Gramicidin A (gr A), a linear pentadecapeptide containing four trp residues has been studied using steady state and time resolved fluorescence (at 298 K) and phosphorescence (at 77 K) in methanol (CH3OH), ethanol (C2H5OH), dimethyl sulfoxide (DMSO), 1,4-dioxane, 2-methyl tetrahydrofuran (2-MeTHF), ethanol/benzene (C2H5OH/C6H6) mixed solvent. Simila...
The nature of an unusual specific interaction between aromatic cyclic cis-vicinal triketone (I, II, III in Fig. 1) and cyclic saturated ethers (tetrahydrofuran and 2-methyl tetrahydrofuran) in the ground state has been explored using detailed AM1 calculation. The experimental values of ΔH for such interaction, determined by the temperature variatio...
The tris-acetylpyrene derivative of a heteroditopic cryptand is found to be a rare supramolecular system exhibiting three emissions due to localised monomer, intramolecular exciplex and excimer emissions in different environments. The lifetime for the monomer emission is much shorter compared to that of free pyrene indicating PET from cryptand moie...
The three secondary nitrogens in a heteroditopic cryptand are derivatized with anthroyl groups to have a cryptand based system in the ‘(fluorophore)3-spacer-receptor’ format. This supramolecular system shows enhancement of fluorescence in presence of metal ions like Cu(II), Co(II), Zn(II). The quantum yields of fluorescence enhancement as well as t...
The three secondary amino nitrogens of a heteroditopic cryptand have been derivatized with acetylpyrene to have a fluorophore–spacer–receptor configuration. The localized monomer fluorescence intensity is reduced in this system due to quenching via photoinduced intramolecular electron transfer from nitrogen atoms in the receptor cryptand moiety to...
The energy transfer (ET) from naphthalene (N) to Eu3+ has been studied in complexes of the Eu3+ ion with 2,3-naphtho-17-crown-5, 2,3-naphtho-20-crown-6, 1,8-naphtho-21-crown-6 and 1,5-naphtho-22-crown-6, respectively, using the NO3− ion as the counter anion in EtOH glass at 77 K. Both the ET efficiency and the N-phosphorescence quenching show a str...
Three heteroditopic cryptands with different cavity dimensions have been synthesized in high yields at 278 K without employing any templating metal ion. The three secondary amino nitrogens in each cryptand could be derivatized with anthryl groups to have a fluorophore−spacer−receptor configuration. The fluorophores in these systems do not show any...
A comparative study of the low lying electronic states and photophysical aspects of the compounds anhydrous benz (f) ninhydrin (I), indanetrione (anhydrous ninhydrin) (II) and 5-methoxy indanetrione (anhydrous 5-methoxy ninhydrin) (III) having a cis vicinal cyclic triketo system (three adjacent carbonyl groups in the same plane) has been carried ou...
2,3-naphtho-17-crown-5 ether (I) shows an unusual dual phosphorescence in EtOH and MeOH glass at 77 K as a function of concentration of I. Compound I exhibits, however, single phosphorescence in 2-methyl tetrahydrofuran glass at 77 K in the same concentration range. Crown ethers containing six oxygen atoms do not show any dual phosphorescence at 77...
Indanetrione, a cis vicinal cyclic triketone, is found to exhibit room temperature (nπ∗) phosphorescence (RTP) in a phthalic anhydride matrix in addition to (nπ∗) fluorescence. The compound does not show RTP in benzophenone mixed crystals or in any other solvent studied. A rigid binding of the cyclic triketone in the phthalic anhydride matrix, lowe...
Interaction of ketocyanine dyes with cationic (CTAB), anionic (SDS) and neutral (Triton X-100) micelles has been studied by monitoring the polarity-sensitive absorption and fluorescence band of the solute. The position of equilibrium between the bare form of the dye (S0 state) and its hydrogen-bonded complex with water is modified by the micellar m...
The fluorescence characteristics of two ketocyanine dyes have been studied in six mixed binary solvents. Several parameters such as the maximum energy E(12)(F) of fluorescence, the quantum yield Phi(12) of fluorescence and the normalized intensity of the fluorescence have been investigated as functions of solvent composition. In protic + aprotic bi...
The lowestS
1(n, π*) transition (absorption) of indanetrione having acis-vicinal triketo group exhibits a large blue-shift in cyclic saturated ethers compared to that in an open-chain saturated ether. This transition of indanetrione in mixed solvents containing a cyclic saturated ether (tetrahydrofuran, dioxane and tetrahydropyran) as one of the co...
The three tryptophan (trp) residues located at positions 126, 138, and 158 in wild‐type bacteriophage T4 lysozyme have been investigated by low temperature phosphorescence and ODMR spectroscopy. Assignment of spectral properties to individual trp residues was facilitated by measurements on mutant proteins containing one or two trp→tyr (tyrosine) su...
Triplet state sublevel spectroscopy using optical detection of magnetic resonance (ODMR) in zero magnetic field can be successfully
employed to study (i) the environment of tryptophan (Trp) residues in a protein by observing the position and structure of
phosphorescence spectra, zero field ODMR transitions and triplet state sublevel kinetics, (ii)...
We have investigated perturbations of the triplet-state properties of Trp residues in bacteriophage T4 lysozyme caused by point mutations using low-temperature phosphorescence and optical detection of triplet-state magnetic resonance (ODMR) spectroscopy. Five temperature-sensitive mutants have been studied in detail. These include lysozymes with th...
Two spectroscopically distinct types of tyrosine (Tyr) residues in triply point mutated bacteriophage T4 lysozyme, which contains no tryptophan (Trp), have been detected by optical detection of triplet-state magnetic resonance (ODMR) spectroscopy. Their triplet states are characterized by similar E but different D values. The Tyr site which exhibit...
Triplet-state energies, zero-field splittings (ZFS), and total decay rate constants of the individual triplet-state sublevels of the tryptophan (Trp) residues located at positions 126, 138, and 158 in bacteriophage T4 lysozyme have been determined by using low-temperature phosphorescence and optical detection of magnetic resonance spectroscopy in z...
The lowest triplet state energy and the zero‐field splitting parameters ‖D‖ and ‖E‖ have been determined for 1,5‐naphtho‐22‐crown‐6, 1,8‐naphtho‐21‐crown‐6, 2,3‐naphtho‐20‐crown‐6, and 2,3‐naphtho‐17‐crown‐5, and their complexes with various metal ions (Na+, K+, Cs+, Ba+2, Hg+2, Ag+, Tl+) by low temperature phosphorescence and optical detection of...
The phosphorescent triplet states of a series of aromatic thioketones exhibiting unusually large zero-field splittings (ZFSs) have been investigated by optically detected magnetic resonance spectroscopy (ODMR) in zero applied magnetic field at 1.2 K. Molecules examined include 4H-pyran-4-thione (PT), 2,6-dimethyl-4H-pyran-4-thione (DMPT), chromthio...
The lowest excited triplet state and the sublevel dynamics have been studied in 1, 5-naphtho-22-crown-6 (I), 1,8-naphtho-21-crown-6 (II), and 2, 3-naphtho-20-crown-6 (III) and their complexes with various metal ions (Na+, K+,Cs+, Tl+) using optical detection of magnetic resonance at 1.2 K in zero applied magnetic field. The results indicate that th...
The individual spin-lattice relaxation (SLR) rate constants (Wij) between the sublevels of the lowest triplet state of quinoxaline in n-pentane and in n-hexane Sphol’skii hosts over the temperature range of 1.2 to 4.2 K have been measured in zero applied magnetic field. The anisotropy pattern for the Wij for quinoxaline in these n-alkane hosts diff...
Phosphorescence and optical detection of triplet-state magnetic resonance (ODMR) in zero applied magnetic field have been utilized to probe subtle changes in the microenvironment of solubilized naphthalene (N) in frozen anionic sodium n-alkyl sulfate micelles as a function of chain length and in sodium dodecyl sulfate micelles as a function of Na+...
Optical detection of triplet-state magnetic resonance (ODMR) is used to study the phosphorescent state of naphthalene (N) solubilized into trimethyl-n-alkylammonium bromide (CnTABr) micelles. The results are compared with those found for N solubilized by sodium n-alkyl sulfate (NaCnS) micelles. In NaCnS the 0,0 phosphorescence band of N shifts to t...
The nature of the phosphorescence emission, optically detected magnetic resonance (ODMR) transitions and triplet state lifetime data of naphthalene (N) solubilized in frozen mixed micelles containing sodium dodecyi sulfate (NaDS) and either silver dodecyi sulfate (AgDS) or thallium dodecyi sulfate (T1DS) suggest stronger perturbation of the N tripl...
The individual spin-lattice relaxation (SLR) rate constants (Wij) between the lowest triplet sublevels of the lone tryptophan residue buried in the interior of the globular protein ribonuclease T1 have been reported in the temperature range 1.2 to 3.0 K in zero applied magnetic field. The SLR rate constants between spin sublevels exhibit marked ani...