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The effect of solvents and supramolecular hosts on the binding of metal ion with an excited state intramolecular proton transfer (ESIPT) active fluorophore 2-(2'-hydroxyphenyl)benzoxazole (HPBO) are investigated to scrutinize a possible metal ion carry and delivery system. The fluorophore forms strong fluorescent complex with Zn

To obtain proper insight into how structure develops during a protein folding reaction, it is necessary to understand the nature and mechanism of the polypeptide chain collapse reaction, which marks the initiation of folding. Here, the time-resolved fluorescence resonance energy transfer technique, in which the decay of the fluorescence light intensity with time is used to determine the time evolution of the distribution of intra-molecular distances, has been utilized to study the folding of the small protein, monellin. It is seen that when folding begins, about one-third of the protein molecules collapse into a molten globule state (IMG), from which they relax by continuous further contraction to transit to the native state. The larger fraction gets trapped into a metastable misfolded state. Exit from this metastable state occurs via collapse to the lower free energy IMG state. This exit is slow, on a time scale of seconds, because of activation energy barriers. The trapped misfolded molecules as well as the IMG molecules contract continuously and slowly as structure develops. A phenomenological model of Markovian evolution of the polymer chain undergoing folding, incorporating these features, has been developed, which fits well the experimentally observed time evolution of distance distributions. The observation that the "wrong turn" to the misfolded state has not been eliminated by evolution belies the common belief that the folding of functional protein sequences is very different from that of a random heteropolymer, and the former have been selected by evolution to fold quickly.

Chitosan was fabricated via gelation method using CaBr2.xH2O/methanol solution and was studied as a potential adsorbent (MCh) in adsorbing anionic synthetic dyes like Bromophenol blue (BB), Direct blue 6 (DB) and Congo red (CR) from single (one dye species at a time) and multi (having two dyes; binary and all three dyes; tertiary) adsorptive systems. Physico-chemical modifications of MCh surface prior and post modification and dye adsorption were evaluated using scanning electron microscopy, Energy-dispersive X-ray spectroscopy, powder X-ray diffraction analysis, surface area analysis and Fourier-transformed infrared spectroscopy. Influential parameters influencing the adsorption process viz. initial pH of dye solution, MCh dosage, adsorption temperature and initial concentration of dye species were optimised. Adsorptive studies involving single adsorptive setups verified formation of sorbate's (dye species) monolayer over the sorbent's (MCh) surface via chemisorption; as established by Langmuir isotherm and pseudo-second order kinetics model analysis. Theoretical maximum adsorption capacities of MCh for BB, DB and CR was found to be 81.301 mg/g, 163.934 mg/g and 75.758 mg/g, respectively. Meanwhile, for all multi-adsorptive systems, competitive Langmuir isotherm model verified antagonistic behaviour of an individual dye over other dye adsorption over MCh surface in their respective adsorptive systems. Thermodynamics of the sorbate-sorbent interaction was exothermic, spontaneous, with elevated degree of disorderedness; concluding the interaction as thermodynamically favourable. Co-existing metal cations and anionic salts had minimal effect on MCh's adsorption efficiency. Phytotoxicity assay via germination of Vigna mungo seeds verified the efficacy of the adsorbent in eliminating the dye species from single and multi-adsorptive systems.

Background The diagnosis of temporomandibular disorders (TMDs), specifically TMD myalgia, can be challenging. Although the anatomy of the jaw muscles has been extensively characterized, a structural difference in TMD-myalgia individuals has never been demonstrated. Tendons are a highly specialized tissue with a predominately mechanical function. Collagen fibrils, the main contributor to tendon mechanical properties, begin macroscopic failure at 8% to 10% strain. The characterization of tendon/muscle abnormalities in individuals with chronic, painful TMD myalgia will lay the groundwork for utilizing noninvasive magnetic resonance imaging (MRI) for screening and objective monitoring of patients with TMD myalgia. A structural marker unique to TMD myalgia will aid in its diagnosis and treatment. Objective(s) This study aimed to determine differences in the tendon/muscle volume ratio of the temporalis muscle in patients with TMD myalgia compared with age-/gender-matched controls without facial pain. Study Design This was a retrospective, observational study of the temporalis muscle and tendon on MRI images. The comparison between groups was based on a voxel-based morphometry of anatomic T1-weighted MRI images and analyzed for differences in the tendon/muscle volume ratio. The study included at least 14 patients per group to detect a 5% difference in tendon/muscle volume ratio. An intraclass correlation coefficient was used to evaluate the intrarater test–retest reliability. General linear models were used to test whether the outcome measures (muscle/tendon volume, muscle/tendon T1 signal intensity, tendon/muscle ratio) are different between groups. Results Our pilot data demonstrated similar muscle volumes but significantly smaller tendon volumes and signal intensity when comparing patients with TMD myalgia with healthy controls (P Discussion/Conclusions Preliminary data suggest that chronic TMD myalgia may be associated with structural abnormalities of the temporalis tendon. Should the temporalis tendon/muscle volume ratio prove to be a reliable marker, this metric may be used to evaluate different treatment modalities in a noninvasive manner.

The protective role of lycopene against various toxicants on various organs and its association with decreased oxidative stress seems to be well established. Sertoli cell function in the adult testis determines daily sperm production. Increasing evidence suggests that environmental pollutants including polychlorinated biphenyls (PCBs) are male infertility, which is associated with oxidative stress. Hence, the present study was designed to find out whether PCBs disrupt Sertoli cell function by inducing oxidative stress or endocrine disruption? Whether lycopene attenuates PCBs-induced disruption in Sertoli cells or not? Adult male rats were divided into four (vehicle control, lycopene, PCBs and PCBs + lycopene treated) groups. After the experimental period (30 days), the animals were decapitated for the blood collection and testes were removed for the isolation of Sertoli cells. In PCBs exposure, serum hormones (FSH, testosterone and estradiol), Sertoli cellular receptors (FSHR and AR) were significantly decreased whereas oxidative stress markers (H 2 O 2 and LPO) and ER-s expression in Sertoli cells were significantly increased. Sertoli cell functional proteins such as connexin 43, transferrin and androgen-binding protein expressions and the level of lactate were significantly decreased. However, simultaneous supplementation of lycopene to PCBs-exposed rats significantly decreased the endocrine disruption and oxidative stress in Sertoli cells. The findings point out that lycopene protects the Sertoli cell function by preventing PCBs-induced oxidative stress and endocrine disruption.

Inhibitory effect of green tea polyphenols viz., catechin and epigallocatechin gallate (EGCG) on the action of collagenase against collagen has been probed in this study. Catechin and EGCG treated collagen exhibited 56 and 95% resistance, respectively, against collagenolytic hydrolysis by collagenase. Whereas direct interaction of catechin and EGCG with collagenase exhibited 70 and 88% inhibition, respectively, to collagenolytic activity of collagenase against collagen and the inhibition was found to be concentration dependent. The kinetics of inhibition of collagenase by catechin and EGCG has been deduced from the extent of hydrolysis of (2-furanacryloyl-L-leucyl-glycyl-L-prolyl-L-alanine), FALGPA. Both catechin and EGCG exhibited competitive mode of inhibition against collagenase. The change in the secondary structure of collagenase on treatment with catechin and EGCG has been monitored using circular dichroism spectropolarimeter. CD spectral studies showed significant changes in the secondary structure of collagenase on treatment with higher concentration of catechin and EGCG. Higher inhibition of EGCG compared to catechin has been attributed to the ability of EGCG to exhibit better hydrogen bonding and hydrophobic interaction with collagenase.

The spectral characteristics of 2-(4'-N,N-dimethylaminophenyl)-pyrido[3,4-d]imidazole (DMAPPI) have been studied in a TritonX-100 (TX-100)/n-hexanol/water reverse micelle in cyclohexane as a function of water (w(0)), surfactant, cosurfactant, pH, and trifluoroacetic acid. Under the neutral conditions, dual fluorescence (normal and twiste intramolecular charge transfer) is observed, even at w(0)=0, suggesting that the TICT state is stabilized by the hydrogen bonding from n-hexanol. These studies indicate that DMAPPI molecules are present near the interface of the water pool and the micellar phase toward the micellar side, and the changes observed in the spectral characteristics with change of w(0) are due to the formation of the reverse micelles and the alignment of cosurfactant around DMAPPI. Variation of pH in the range 3-10 has no effect on the spectral characteristics of DMAPPI, suggesting that the protons do not penetrate the reverse micelles, whereas the trifluoroacetic acid protonates DMAPPI to form monocations (MCs). At w(0)=0, MC2 and MC3 (see Scheme 1) are the MCs present both in the S(0) and S(1) states, whereas with an increase in w(0), the MC2 shifts toward MC1. Biprotonic phototautomerism is observed in MC1, which leads to the formation of MC2 in the S(1) state. Copyright 2000 Academic Press.

The fluorescence quenching of 2-aminofluorene by cetylpyridinium chloride (CPy), iodide ion (I − ) and acrylamide (AC) has been studied in different concentrations of Tween-20, Tween-40, Tween-60 and Tween-80 surfactants. The results show that CPy and I − ion bind as well as get partitioned, whereas AC only gets partitioned. The high values of binding constants for CPy in comparison to I − ion are due to the long hydrocarbon chain length. The binding and partitioning coefficients of CPy increase, whereas those of I − ion decrease with the increase in the Tween number. The values of partitioning coefficient of AC also decrease with increase in the Tween number. On the other hand, quenching rate constants for each quencher in each Tween decrease in going from Tween-20 to Tween-80.

Splittings coming from the hyperfine interaction with the next neighbors 13C and 31P in the ESR spectra of a number of cupric and vanadyl mixed ligand complexes have been measured in chloroform solutions at 25°C. The ligands diethyldithiocarbamate (dtc−), didthyldithiophosphate (dtp−), diphenyldithiophosphinate (dtpi−), N-benzoyl-N-diethyl-thiocarbamide (btc−) and xanthate (X−) are used in the present study. Using isotopically enriched dtc it was observed that the spin density on the 13C atoms of dtc− is increased at the expense of the spin density on the 31P atoms of dtp− when the mixed ligand complex Cu(dtc)(dtp) is formed. The percentage changes in the 31P splitting in the mixed ligand complexes of dtp and dtpi are equal. It was concluded that the transfer of spin to the next neighbor in vanadyl complexes is due to the direct overlap of the dxy orbital on the metal with the orbital on the next neighbor and that in the cupric complexes is due to configuration interaction. The differences in the 31p splittings observed in M(dtp)2 and M(dtpi)2 (M = Cu2+, VO2+) have been attributed to the differences in the s character of the hybrid orbital on the phosphorus.

Spectrophotometric observations have been used to study equilibria and temperature jump relaxation associated with formation of Fe(III) complexes in aqueous DMSO in the presence of SCN − . The [SCN − ] dependent relaxation observed at 315 nm could be assigned to the formation of Fe DMSO 3+ , Fe DMSO OH 2+ , Fe DMSO SCN 2+ and Fe DMSO SCN OH + from Fe 2+ and Fe OH 2+ . The relaxation observed at 450 nm could be assigned to the formation of Fe SCN 2+ by paths similar to that in aqueous solutions and a pH dependent path in which the rate determining step is the displacement of DMSO from Fe DMSO SCN OH + by H 2 O. The rate constants suggest that coordination by a DMSO instead of a H 2 O has the effect of labilising the other H 2 O coordinated to Fe OH 2+ . The observed decrease in relaxation rates with increase in [DMSO] have been explained as dominantly due to the reduction in the acid dissociation constant K H associated with the aquocomplex of Fe(III).

Electron transfer activities and steady state reduction levels of Fe-S centers of NADH-Q oxidoreductase were measured in mitochondria, submitochondrial particles (ETPH), and complex I after treatment with various reagents. p-Chloromercuribenzenesulfonate destroyed the signal from center N-4 (gx = 1.88) in ETPH but not in mitochondria, showing that N-4 is accessible only from the matrix side of the inner membrane. N-Bromosuccinimide also destroyed the signal from N-4 but without inhibiting rotenone-sensitive electron transfer to quinone, suggesting a branched pathway for electron transfer. Diethylpyrocarbonate caused oxidation of N-3 and N-4 in the steady state without changing N-1, suggesting N-1 is before N-3 and N-4. Difluorodinitrobenzene and dicyclohexylcarbodiimide inhibited oxidation of all Fe-S centers and tetranitromethane inhibited reduction of all Fe-S centers. Titrations of the rate of superoxide (O2-) generation in rotenone-treated submitochondrial particles were similar with the ratio [NADH]/[NAD] and that of 3-acetyl pyridine adenine nucleotide in spite of different midpoint potentials of the two couples. On reaction with inhibitors the inhibition of O2- formation was similar to that of ferricyanide reductase rather than quinone reductase. The rate of O2- formation during ATP-driven reverse electron transfer was 16% of the rate observed with NADH. The presence of NAD increased the rate to 83%. The results suggest that bound, reduced nucleotide, probably E-NAD., is the main source of O2- in NADH dehydrogenase. The effect of ATP on the reduction levels of Fe-S centers in well-coupled ETPH was measured by equilibrating with either NADH/NAD or succinate/fumarate redox couples. With NADH/NAD none of the Fe-S centers showed ATP induced changes, but with succinate/fumarate all centers showed ATP-driven reduction with or without NAD present. The effect on N-2 was smaller than that on N-1, N-3, and N-4. These observations indicate that the major coupling interaction is between N-2 and the low potential centers, N-1, N-3, and N-4. Possible schemes of coupling in this segment are discussed.

The g values of 1,4-benzosemiquinone and durosemiquinone anions in methanol, ethanol, and n -butanol have been measured at temperatures T , above the freezing point of the solvents. The rapid variation of g with T in the high-viscosity region has been assigned to slow tumbling effects. The gradual increase of g with an increase in T has been assigned to an equilibrium between the hydrogen-bonded and non-hydrogen-bonded semiquinones. This has been confirmed from a study of g of DSQ in ethanol-DME, ethanol-acetonitrile, and ethanol-DMSO mixtures. Combining the results of the earlier electron spin relaxation studies with the estimated fraction of the time for which the semiquinone is not hydrogen-bonded and the enthalpy change associated with the above-mentioned reaction (∼1 kcal mole −1 ), it was concluded that in alcohols (i) in the temperature range studied there is a greater probability of finding the semiquinone in the hydrogen-bonded state; (ii) it can go to a non-hydrogen-bonded state without requiring energies of the order of hydrogen-bonding energies; (iii) only a fraction of the non-hydrogen-bonded sate corresponds to a state of free rotation; (iv) this free rotation is different from the large-step motion associated with the reorientation; (v) the descriptions of the hindered rotation of the semiquinone in alcohols in the liquid state and the frozen state are likely to be similar. The value 1 kcal mole −1 corresponds to the energy difference between the two hydrogen-bonded states of an alcohol molecule in the neighborhood of the semiquinone. In the first hydrogen-bonded state it is bonded to the semiquinone, while in the second hydrogen-bonded state it is bonded to neighboring alcohol molecules, forming a polymer but leaving the semiquinone nonhydrogen-bonded.