Efficient enrichment of phosphopeptides by magnetic TiO₂-coated carbon-encapsulated iron nanoparticles

Titanium dioxide (TiO₂) has been widely used for phosphopeptide enrichment. Several approaches have been reported to produce magnetic TiO₂ affinity probes. In this report, we present a facile approach to immobilize TiO₂ onto poly(acrylic acid)‐functionalized magnetic carbon‐encapsulated iron nanoparticles as affinity probes for efficient enrichment of phosphopeptides. By using the new magnetic TiO₂ affinity probes, denoted as TiO₂‐coated Fe@CNPs, rapid and effective MALDI‐TOF MS profiling of phosphopeptides was demonstrated in different model systems such as tryptic digests of β‐casein, and complex β‐casein/BSA mixture. The TiO₂‐coated Fe@CNPs out‐performed the commercial TiO₂‐coated magnetic beads for detection of phosphopeptides from tryptic digests of β‐casein/BSA mixture with a molar ratio of 1:100. The new TiO₂‐coated magnetic probes were also proven to be applicable for real life samples. The magnetic TiO₂‐coated Fe@CNPs were employed to selectively isolate phosphopeptides from tryptic digests of HeLa cell lysates and out‐performed the commercial magnetic TiO₂ beads in the number of identified phosphopeptides and phosphorylation sites. In a 200‐μg equivalent of HeLa cell lysates, we identified 1415 unique phosphopeptides and 1093 phosphorylation sites, indicating the good performance of the new approach.     

Intracellular chloride and calcium transients evoked by γ‐aminobutyric acid and glycine in neurons of the rat inferior colliculus

Microfluorometric recordings showed that the inhibitory neurotransmitters γ‐aminobutyric acid (GABA) and glycine activated transient increases in the intracellular Cl⁻ concentration in neurons of the inferior colliculus (IC) from acutely isolated slices of the rat auditory midbrain. Current recordings in gramicidin‐perforated patch mode disclosed that GABA and glycine mainly evoked inward or biphasic currents. These currents were dependent on HCO and characterized by a continuous shift of their reversal potential (E_GABA/gly) in the positive direction. In HCO‐buffered saline, GABA and glycine could also evoke an increase in the intracellular Ca²⁺ concentration. Ca²⁺ transients occurred only with large depolarizations and were blocked by Cd²⁺, suggesting an activation of voltage‐gated Ca²⁺ channels. However, in the absence of HCO, only a small rise, if any, in the intracellular Ca²⁺ concentration could be evoked by GABA or glycine. We suggest that the activation of GABA_A or glycine receptors results in an acute accumulation of Cl⁻ that is enhanced by the depolarization owing to HCO efflux, thus shifting E_GABA/gly to more positive values. A subsequent activation of these receptors would result in a strenghtened depolarization and an enlarged Ca²⁺ influx that might play a role in the stabilization of inhibitory synapses in the auditory pathway. © 1999 John Wiley & Sons, Inc. J Neurobiol 40: 386–396, 1999     

Importance of Manual Validation for the Identification of Phosphopeptides Using a Linear Ion Trap Mass Spectrometer

Accurate determination of protein phosphorylation is challenging, particularly for researchers who lack access to a high-accuracy mass spectrometer. In this study, multiple protocols were used to enrich phosphopeptides, and a rigorous filtering workflow was used to analyze the resulting samples. Phosphopeptides were enriched from cultured rat renal proximal tubule cells using three commonly used protocols and a dual method that combines separate immobilized metal affinity chromatography (IMAC) and titanium dioxide (TiO₂) chromatography, termed dual IMAC (DIMAC). Phosphopeptides from all four enrichment strategies were analyzed by liquid chromatography-multiple levels of mass spectrometry (LC-MSⁿ) neutral-loss scanning using a linear ion trap mass spectrometer. Initially, the resulting MS² and MS³ spectra were analyzed using PeptideProphet and database search engine thresholds that produced a false discovery rate (FDR) of <1.5% when searched against a reverse database. However, only 40% of the potential phosphopeptides were confirmed by manual validation. The combined analyses yielded 110 confidently identified phosphopeptides. Using less-stringent initial filtering thresholds (FDR of 7–9%), followed by rigorous manual validation, 262 unique phosphopeptides, including 111 novel phosphorylation sites, were identified confidently. Thus, traditional methods of data filtering within widely accepted FDRs were inadequate for the analysis of low-resolution phosphopeptide spectra. However, the combination of a streamlined front-end enrichment strategy and rigorous manual spectral validation allowed for confident phosphopeptide identifications from a complex sample using a low-resolution ion trap mass spectrometer.     

Interplay of reactive oxygen species,intracellular Ca2+ and mitochondrial homeostasis in the apoptosis of prostate cancer cells by deoxypodophyllotoxin

The limited treatment option for recurrent prostate cancer and the eventual resistance to conventional chemotherapy drugs has fueled continued interest in finding new anti‐neoplastic agents of natural product origin. We previously reported anti‐proliferative activity of deoxypodophyllotoxin (DPT) on human prostate cancer cells. Using the PC‐3 cell model of human prostate cancer, the present study reveals that DPT induced apoptosis via a caspase‐3‐dependent pathway that is activated due to dysregulated mitochondrial function. DPT‐treated cells showed accumulation of the reactive oxygen species (ROS), intracellular Ca surge, increased mitochondrial membrane potential (MMP, ΔΨ_m), Bax protein translocation to mitochondria and cytochrome c release to the cytoplasm. This resulted in caspase‐3 activation, which in turn induced apoptosis. The antioxidant N‐acetylcysteine (NAC) reduced ROS accumulation, MMP and Ca surge, on the other hand the Ca²⁺ chelator BAPTA inhibited the Ca overload and MMP without affecting the increase of ROS, indicating that the generation of ROS occurred prior to Ca²⁺ flux. This suggested that both ROS and Ca signaling play roles in the increased MMP via Ca‐dependent and/or ‐independent mechanisms, since ΔΨ_m elevation was reversed by NAC and BAPTA. This study provides the first evidence for the involvement of both ROS‐ and Ca‐activated signals in the disruption of mitochondrial homeostasis and the precedence of ROS production over the failure of Ca²⁺ flux homeostasis. J. Cell. Biochem. 114: 1124–1134, 2013. © 2012 Wiley Periodicals, Inc.     

Free‐energy profiles for ions in the influenza M2‐TMD channel

M₂ transmembrane domain channel (M₂‐TMD) permeation properties are studied using molecular dynamics simulations of M₂‐TMD (1NYJ) embedded in a lipid bilayer (DMPC) with 1 mol/kg NaCl or KCl saline solution. This study allows examination of spontaneous cation and anion entry into the selectivity filter. Three titration states of the M₂‐TMD tetramer are modeled for which the four His³⁷ residues, forming the selectivity filter, are net uncharged, +2 charged, or +3 charged. M₂‐TMD structural properties from our simulations are compared with the properties of other models extracted from NMR and X‐ray studies. During 10 ns simulations, chloride ions occasionally occupy the positively‐charged selectivity filter region, and from umbrella sampling simulations, Cl^? has a lower free‐energy barrier in the selectivity‐filter region than either Na⁺ or NH, and NH has a lower free‐energy barrier than Na⁺. For Na⁺ and Cl^?, the free‐energy barriers are less than 5 kcal/mol, suggesting that the 1NYJ conformation would probably not be exquisitely proton selective. We also point out a rotameric configuration of Trp⁴¹ that could fully occlude the channel. Proteins 2009. © 2009 Wiley‐Liss, Inc.     

Effects of hydrophobicity and anions on self‐assembly of the peptide EMK16‐II

Effects of hydrophobic and electrostatic interactions on the self‐assembling process of the ionic‐complementary peptide EMK16‐II are investigated by atomic force microscopy imaging, circular dichroism spectra, light scattering, and chromatography. It is found that the hydrophobicity of the peptide promotes the aggregation in pure water even at a very low concentration, resulting in a much lower critical aggregation concentration than that of another peptide, EAK16‐II. The effect of anions in solution with different valences on electrostatic interactions is also important. Monovalent anions (Cl^? and Ac^?) with a proper concentration can facilitate the formation of peptide fibrils, with Cl^? of smaller size being more effective than Ac^? of larger size. However, only small amounts of fibrils, but plenty of large amorphous aggregates, are found when the peptide solution is incubated with multivalent anions, such as SO, C₆H₅O, and HPO. More importantly, by gel filtration chromatography, the citrate anion, which induces a similar effect on the self‐assembling process of EMK16‐II as that of SO and HPO, can interact with two or more positively charged residues of the peptide and reside in the amorphous aggregates. This implies a “salt bridge” effect of multivalent anions on the peptide self‐assembling process, which can interpret a previous puzzle why divalent cations inhibit the formation of ordered nanofibrils of the ionic‐complementary peptides. Thus, our results clarify the important effects of hydrophobic and electrostatic interactions on the self‐assembling process of the ionic‐complementary peptides. These are greatly helpful for us to understand the mechanism of peptides' self‐assembling process and protein folding and aggregation. © 2009 Wiley Periodicals, Inc. Biopolymers 93: 318–329, 2010. This article was originally published online as an acceptedpreprint. The “Published Online” date corresponds to the preprintversion. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Scavenging of superoxide anion radical and hydroxyl radical by novel thiazolyl‐thiazolidine‐2,4‐dione compounds

The antioxidant behavior of a series of new synthesized substituted thiazolyl‐thiazolidine‐2,4‐dione compounds (TZDs) was examined using chemiluminescence and electron paramagnetic resonance spin trapping techniques. 5,5‐Dimethyl‐1‐pyrroline‐N‐oxide (DMPO) was used as the spin trap. The reactivity of TZDs with superoxide anion radical (O) and hydroxyl radical (HO^?) was evaluated using potassium superoxide/18‐crown‐6 ether dissolved in dimethylsulfoxide, and the Fenton‐like reaction (Fe²⁺ + H₂O₂), respectively. The results showed that TZDs efficiently inhibited light emission from the O generating system at a concentration of 0.05–1 mmol L^?1 (5–94% reductions were found at 1 mmol L^?1 concentration). The TZD compounds showed inhibition of HO^?‐dependent DMPO–OH spin adduct formation from DMPO (the amplitude decrease ranged from 8 to 82% at 1 mmol L^?1 concentration). The findings showed that examined TZDs had effective activities as radical scavengers. Copyright © 2009 John Wiley & Sons, Ltd.     

Phenotypic characterization of transgenic mice harboring Nf1+/- or Nf1-/- osteoclasts in otherwise Nf1+/+ background

Skeletal abnormalities in neurofibromatosis type 1 syndrome (NF1) are observed in ～50% of patients. Here, we describe the phenotype of Nf1_Ocl mouse model with Nf1‐deficient osteoclasts. Nf1_Ocl mice with Nf1^+/? or Nf1^?/? osteoclasts in otherwise Nf1^+/+ background were successfully generated by mating parental Nf1flox/flox and TRAP‐Cre mice. Contrary to our original hypothesis, osteoporotic or fragile bone phenotype was not observed. The µCT analysis revealed that tibial bone marrow cavity, trabecular tissue volume, and the perimeter of cortical bone were smaller in Nf1 mice compared to Nf1 control mice. Nf1 mice also a displayed narrowed growth plate in the proximal tibia. In vitro analysis showed increased bone resorption capacity and cytoskeletal changes including irregular cell shape and abnormal actin ring formation in Nf1^?/? osteoclasts. Surprisingly, the size of spleen in Nf1 mice was two times larger than in controls and histomorphometric analysis showed splenic megakaryocytosis. In summary, Nf1Ocl mouse model presented with a mild but specific bone phenotype. This study shows that NF1‐deficiency in osteoclasts may have a role in the development of NF1‐related skeletal abnormalities, but Nf1‐deficiency in osteoclasts in Nf1^+/+ background is not sufficient to induce skeletal abnormalities analogous to those observed in patients with NF1. J. Cell. Biochem. 113: 2136–2146, 2012. © 2012 Wiley Periodicals, Inc.     

Characterization of calcium signaling pathways in human preadipocytes

Intracellular free Ca²⁺ (Ca) is an important regulator of many cellular activities; however, Ca²⁺ signaling is not well studied in human preadipocytes. The purpose of the present study was to characterize Ca²⁺ signal pathways using a confocal scanning technique and RT‐PCR. It was found that spontaneous Ca oscillations were observed in 12.1% preadipocytes, and number of cells with Ca²⁺ oscillations was increased to 47.9% by 1% fetal bovine serum. Ca oscillations were dependent on Ca²⁺ entry mainly via stored‐operated Ca²⁺ (SOC) entry. They were suppressed by the SOC entry channel blocker La³⁺, the phospholipase C (PLC) inhibitor U73122, the inositol trisphosphate receptor (IP3R) blocker 2‐amino‐ethoxydiphenyl borate, or the sarcoplasmic/endoplasmic reticulum Ca²⁺ pump (SERCA) inhibitors thapsigargin and cyclopiazonic acid, but not by ryanodine. The IP3R activator thimerosal increased Ca oscillations. In addition, the plasma membrane Ca²⁺ pump (PMCA) inhibitor carboxyeosin and Na⁺–Ca²⁺ exchanger (NCX) inhibitor Ni²⁺ both suppressed Ca²⁺ oscillations. RT‐PCR revealed that the mRNAs for IP3R1‐3, SERCA1,2, NCX3 and PMCA1,3,4, Ca_V1.2, and TRPC1,4,6, STIM1 and Orai1 (for SOC entry channels) were significant in human preadipocytes. The present study demonstrates that multiple Ca²⁺ signal pathways are present in human preadipocytes, and provides a basis for investigating how Ca²⁺ signals regulate biological and physiological activities of human preadipocytes. J. Cell. Physiol. 220: 765–770, 2009. © 2009 Wiley‐Liss, Inc.     

Multiple Ca2+ signaling pathways regulate intracellular Ca2+ activity in human cardiac fibroblasts

Ca²⁺ signaling pathways are well studied in cardiac myocytes, but not in cardiac fibroblasts. The aim of the present study is to characterize Ca²⁺ signaling pathways in cultured human cardiac fibroblasts using confocal scanning microscope and RT‐PCR techniques. It was found that spontaneous intracellular Ca²⁺ (Ca) oscillations were present in about 29% of human cardiac fibroblasts, and the number of cells with Ca oscillations was increased to 57.3% by application of 3% fetal bovine serum. Ca oscillations were dependent on Ca²⁺ entry. Ca oscillations were abolished by the store‐operated Ca²⁺ (SOC) entry channel blocker La³⁺, the phospholipase C inhibitor U‐73122, and the inositol trisphosphate receptors (IP3Rs) inhibitor 2‐aminoethoxydiphenyl borate, but not by ryanodine. The IP3R agonist thimerosal enhanced Ca oscillations. Inhibition of plasma membrane Ca²⁺ pump (PMCA) and Na⁺–Ca²⁺ exchanger (NCX) also suppressed Ca oscillations. In addition, the frequency of Ca oscillations was reduced by nifedipine, and increased by Bay K8644 in cells with spontaneous Ca²⁺ oscillations. RT‐PCR revealed that mRNAs for IP3R1‐3, SERCA1‐3, Ca_V1.2, NCX3, PMCA1,3,4, TRPC1,3,4,6, STIM1, and Orai1‐3, were readily detectable, but not RyRs. Our results demonstrate for the first time that spontaneous Ca oscillations are present in cultured human cardiac fibroblasts and are regulated by multiple Ca²⁺ pathways, which are not identical to those of the well‐studied contractile cardiomyocytes. This study provides a base for future investigations into how Ca²⁺ signals regulate biological activity in human cardiac fibroblasts and cardiac remodeling under pathological conditions. J. Cell. Physiol. 223: 68–75, 2010. © 2009 Wiley‐Liss, Inc.     

Thermodynamics of stabilization of RNA pseudoknots by cobalt(III) hexaammine

Equilibrium unfolding (folding) studies reveal that the autoregulatory RNA pseudoknots derived from the bacteriophage T2 and T4 gene 32 mRNAs exhibit significant stabilization by increasing concentrations of divalent metal ions in solution. In this report, the apparent affinities of exchange inert trivalent Co(NH₃) have been determined, relative to divalent Mg²⁺, for the folded, partially folded (K_f), and fully unfolded (K_u) conformations of these molecules. A general nonspecific, delocalized ion binding model was developed and applied to the analysis of the metal ion concentration dependence of individual two‐state unfolding transitions. Trivalent Co(NH₃) was found to associate with the fully folded and partially unfolded pseudoknotted forms of these RNAs with a K_f of 5–8 × 10⁴ M⁻¹ in a background of 0.10 M K⁺, or 3‐ to 5‐fold larger than the K_f obtained for two model RNA hairpins and hairpin unfolding intermediates, and ≈ 40–50‐fold larger than K_f for Mg²⁺. The magnitude of K_f was found to be strongly dependent on the monovalent salt concentration in a manner qualitatively consistent with polyelectrolyte theory, with K_f reaching 1.2 × 10⁵ M⁻¹ in 50 mM K⁺. Two RNA hairpins were found to have affinities for Co(NH₃) and Ru(NH₃) of 1–2 ×10⁴ M⁻¹, or ≈ 15‐fold larger than the K_f of ∼ 1000 M⁻¹ observed for Mg²⁺. Additionally, the K_u of 4,800 M⁻¹ for the trivalent ligands is ≈ 8‐fold larger than the K_u of 600 M⁻¹ observed for Mg²⁺. These findings suggest that the T2 and T4 gene 32 mRNA pseudoknots possess a site(s) for Mg²⁺ and Co(NH₃) binding of significantly higher affinity than a “duplexlike” delocalized ion binding site that is strongly linked to the thermodynamic stability of these molecules. Imino proton perturbation nmr spectroscopy suggests that this site(s) lies near the base of the pseudoknot stem S2, near a patch of high negative electrostatic potential associated with the region where the single loop L1 adenosine crosses the major groove of stem S2. © 1999 John Wiley & Sons, Inc. Biopoly 50: 443–458, 1999     

Regulation of changes in cytosolic Ca2+ and Na+ concentrations in rat submandibular gland acini exposed to carbachol and ATP

The relationship between cytosolic concentrations of Ca²⁺ (Ca) and Na⁺ (Na) were studied in preparations of rat submandibular and pancreatic acini loaded with the Ca²⁺-sensitive dye Fura-2 or the Na⁺-sensitive dye SBFI. Pancreatic acini showed no changes in Na during either transient or persistent changes in Ca. Increases in Ca produced by exposure of submandibular gland acini to carbachol, a muscarinic cholinergic agonist, were followed by an increase in Na after a delay of 5–10 s. When Ca²⁺ stores were mobilized without Ca²⁺ influx Na also increased, but in acini loaded with BAPTA, a nonfluorescent Ca²⁺ chelator, the transient increase in Ca²⁺ caused by mobilization of stored Ca²⁺ was virtually abolished, as was the increase in Na. In the presence of ionomycin, increases in Ca were followed by increases in Na. Ca²⁺-dependent increases in Na were abolished in Na⁺-free buffer and by the presence of furosemide, a blocker of Na⁺-K⁺-2Cl⁻ cotransport. In other studies, extracellular ATP (ATP_o) produced an increase in Ca and Na. The steady-state increase in Ca was reduced by increasing extracellular Na⁺ concentrations (Na) in dose-dependent fashion (IC₅₀ = 16.4 ± 4.7 mM Na⁺). Likewise, increasing Na reduced ATP_o-stimulated ⁴⁵Ca²⁺ uptake at steady state (IC₅₀ = 15.8 ± 9.2 mM Na⁺). Changing Na had no effect on carbachol-stimulated increases in Ca. We conclude that, in rat submandibular gland acini, ATP_o promotes an increase in Ca and Na via a common influx pathway and that, under physiologic conditions, Na⁺ significantly limits the ATP_o-stimulated increase in Ca. In the presence of carbachol, however, Na rises in Ca-dependent fashion in submandibular gland acini via stimulation of Na⁺-K⁺-2Cl⁻ cotransport. © 1996 Wiley-Liss, Inc.     

Hydroxyl and superoxide radical scavenging abilities of chromonyl‐thiazolidine‐2,4‐dione compounds

The oxygen free radical scavenging activities of 15 chromonyl‐thiazolidine‐2,4‐dione compounds (CTDs) were examined in chemical systems producing superoxide anion radicals, O (potasium superoxide–18‐crown‐6 ether–DMSO), and hydroxyl radicals, HO^? (a Fenton reaction: Fe(II)–H₂O₂–sodium trifluoroacetate, pH 6.15). Chemiluminescence and electron spin resonance (ESR) spectroscopy using 5,5‐dimethyl‐1‐pyrroline‐1‐oxide (DMPO) as spin trap were applied to evaluate antioxidant behaviour of CTDs towards the oxygen radicals. The results indicated that 11 of the 15 tested compounds showed a significant inhibitory effect on the chemiluminescence generated from the O‐generating system, ranging from 41 to 86%, and 13 CTDs quenched the ESR signal of the DMPO–OH spin adduct by 33–86%, at a concentration of 1 mmol L^?1. Our findings demonstrate that CTDs could be good free radical scavengers. Copyright © 2008 John Wiley & Sons, Ltd.     

Regulation of the Na+-K+(NH)-2Cl− cotransporter of rat submandibular glands

A cellular suspension from rat submandibular glands was exposed to different concentrations of NH₄Cl, and the variations of the intracellular concentration of calcium ([Ca²⁺]_i) and the intracellular pH (pH_i) were measured using fura-2 and 2′,7′-bis-(2-carboxy-ethyl)-5(6)-carboxyfluorescein. More than 5 mmol/l NH₄Cl significantly increased the [Ca²⁺]_i without affecting the response to 100 µmol/l carbachol. When exposed to 1 and 5 mmol/l NH₄Cl, the cells acidified immediately. At 30 mmol/l, NH₄Cl first alkalinized the cells and the pH_i subsequently dropped. This drop reflects the uptake of NH ions that dissociate to NH₃ and H⁺ in the cytosol. These protons are exchanged for extracellular sodium by the Na⁺/H⁺ exchanger because the presence of an inhibitor of the exchanger in the medium increased the acidification induced by 1 mmol/l NH₄Cl. Ouabain partly blocked the uptake of NH. In the combined presence of ouabain and bumetanide (an inhibitor of the Na⁺-K⁺-2Cl⁻ cotransporter), 1 mmol/l NH₄Cl alkalinized the cells. The contribution of the Na/K ATPase and the Na⁺-K⁺-2Cl⁻ cotransporter in the uptake of NH was independent of the presence of calcium in the medium. Isoproterenol increased the uptake of NH by the cotransporter. Conversely, 1 mmol/l extracellular ATP blocked the basal uptake of NH by the cotransporter. This inhibition was reversed by extracellular magnesium or Coomassie Blue. It was mimicked by benzoyl-ATP but not by CTP, GTP, UTP, ADP, or ADPβS. ATP only slightly inhibited the increase of cyclic AMP (−22%) by isoproterenol but fully blocked the stimulation of the cotransporter by the β-adrenergic agonist. ATP increased the release of ³H-arachidonic acid from prelabeled cells but SK&F 96365, an imidazole-based cytochrome P450 inhibitor, did not affect the inhibition by ATP. It is concluded that the activation of a purinoceptor inhibits the basal and the cyclic AMP-stimulated activity of the Na⁺-K⁺-2Cl⁻ cotransporter. J. Cell. Physiol. 180:422–430, 1999. © 1999 Wiley-Liss, Inc.     

Biopolymer–surfactant interaction. I. Kinetics of binding of cetyltrimethyl ammonium bromide with carboxymethyl cellulose (Na Salt)

The kinetics of binding of the cationic surfactant cetyltrimethyl ammonium bromide with the Na salt of carboxymethyl cellulose was studied by the electrometric method using cetyltrimetlyl ammonium⁺ (CTA⁺) ion-selective polyvinyl chloride membrane electrode. The binding process followed the first-order kinetics and occurred in three stages. Its affinity increased with increasing CTA bromide concentration and decreased with ionic strength. The activation process comprised moderate E and ΔH^≠ and negative ΔS^≠ for all three stages with a ΔH^≠ < TδS^≠ trend proving it to be entropy controlled. The ΔG^≠ values followed the trend ΔG < ΔG < ΔG (in accordance with k₁ > k₂ > k₃). The enthalpies (ΔH^≠) and entropies (ΔS^≠) of activation followed a systematic and interdependent trend. The multiple-stage binding kinetics is grossly comparable with the kinetics of binding of proteins to solid surfaces. © 1995 John Wiley & Sons, Inc.     

On the blue color of triiodide ions in starch and starch fractions. I. Characterization and assignment of absorption and circular dichroism spectra of triiodide ions in amylose

Four fundamental Raman lines were observed at 159, 111, 55 and 27 cm^-1 corresponding to the I bound (I) in amyloses with DP from 20 to 100, regardless of the degree of polymerization of I and the excitation wavelength. The spectral resolution was based on the molar extinction coefficient and molar ellipticity spectra of I. Eight bands, named, S₁, S₂, ?, S₈ from long to short wavelength, were isolated. These were found regardless of the DP. By a resonance excitation Raman study, the characteristics of S₃ and S₄, comprising the shoulder around 480 nm, were found to be different from those of S₁ and S₂, comprising the blue band. The assignment of the spectra was based on the electronic states of the monomeric I in the exciton-coupled dimeric unit. It was concluded that the blue band (S₁,S₂) belonged to the long-axis transitions and the shoulder band (S₃,S₄) to the short-axis ones on the monmeric coordinate system.     

Scavenging capacities of some thiazolyl thiazolidine‐2,4‐dione compounds on superoxide radical,hydroxyl radical,and DPPH radical

The scavenging effects of eighteen thiazolyl thiazolidine‐2,4‐dione compounds (TTCs) on superoxide radical , hydroxyl radical HO^?, and 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH^?) radical were evaluated by the chemiluminescence technique, electron spin resonance spectrometry (ESR) and visible spectrophotometry, respectively. The examined compounds were shown to have 27–59% scavenging ability, 19–69% HO^? scavenging activity and 2–32% DPPH^? scavenging ability. This property of the tested compound seems to be important in the prevention of various diseases of free radicals etiology. Copyright © 2009 John Wiley & Sons, Ltd.