Synthesis and characterization of ferroelectric liquid crystalline organosiloxanes containing 4-(4-undecanyloxy bi-phenyl-1-carboxyloxy)phenyl (2S,3S)-2-chloro-3-methylvalerate and 4-(4-undecanyloxybenzoyloxy)biphenyl (2S,3S)-2-chloro-3-methylvalerate

A series of new organosiloxane ferroelectric liquid crystalline (FLC) materials have been synthesized, and their mesomorphic and physical properties have been characterized. Four new disiloxanes and trisiloxanes, containing biphenyl 4-hydroxybenzoate and phenyl 4-hydroxybiphenylcarboxylate as mesogenic units and eleven methylene unit as spacers and (2S,3S)-2-chloro-3-methylvalerate unit as chiral end groups. The molecule, using three phenyl ring as a mesogenic unit, formulates much wider liquid crystalline phase temperature ranges than that of a two phenyl ring unit. The phenyl arrangement differences of mesogenic unit result in the greater differences of the liquid crystal phase formation. The siloxane molecule induction is helpful to the more regular smectic phase formation and smectic phase stabilization, such as chiral SC (SC*) and SB phases. The siloxane molecule is helpful to reduce the phase transition temperature and broaden the liquid crystal temperature range of the SC* phase and, simultaneously, it will not induce chain crystallization phenomenon and dilute the Ps value. The synthesis and characterization of the new FLCs materials, which exhibit a room temperature SC* phase and higher spontaneous polarization are presented.

Spectroscopic, nonlinear optical and quantum chemical studies on Pyrrolidinium p-Hydroxybenzoate--a phase matchable organic NLO crystal

Good quality and bulk single crystals of Pyrrolidinium p-Hydroxybenzoate (PYPHB), a newly identified nonlinear optical material, were grown for the first time. It crystallizes in monoclinic system with an acentric space group Cc. The molecular structure including carbon, proton positions and functional groups has been confirmed through nuclear magnetic resonance and Fourier transform infrared spectra. Its transmission window has been observed for UV-VIS-NIR region along with its theoretical limit. The photoluminescence behavior has been observed by exciting the crystal at 310 nm. The principal refractive indices and second order NLO coefficient of PYPHB are determined by Mach-Zehnder interferometer and Maker-Fringe experiments respectively. The coherence length and phase-matchablility of PYPHB crystals are measured to explore its efficacy towards device fabrications. The dipole moment, polarizability and molecular orbital energy of an isolated PYPHB molecule have also been calculated theoretically and the results are found to corroborate the experimental values.

[Study on chemical constituents of Citrullus vulgaris Schrad vine (II)]

OBJECTIVE

To study the chemical constituents of ethyl acetate fraction of Citrullus vulgaris Schrad vine.

METHODS

Compounds were isolated and purified by polyamide column chromatography, silica gel column chromatography, thin layer chromatography and sephadex gel column chromatography. Their structures were elucidated on the basis of physicochemical properties and spectral data.

RESULTS

Ten compounds were isolated from Citrullus vulgaris Schrad vine and elucidated as: pentadecanoic acid (1), monopentadecanoin (2), 2, 3-dihydroxypropyl nonadecoate (3), lignoceric acid-2, 3-dihydroxy-propanenyl ester (4), lancerebroside 5 (5), salicylic acid (6), 4-hydroxybenzoic acid (7), hydroquinone (8), succinic acid (9) and vanillic acid (10).

CONCLUSION

Compounds 1 - 10 are obtained from Citrullus vulgaris Schrad vine for the first time.

The rice bacterial pathogen Xanthomonas oryzae pv. oryzae produces 3-hydroxybenzoic acid and 4-hydroxybenzoic acid via XanB2 for use in xanthomonadin, ubiquinone, and exopolysaccharide biosynthesis

Xanthomonas oryzae pv. oryzae, the causal agent of rice bacterial blight, produces membrane-bound yellow pigments, referred to as xanthomonadins. Xanthomonadins protect the pathogen from photodamage and host-induced perioxidation damage. They are also required for epiphytic survival and successful host plant infection. Here, we show that XanB2 encoded by PXO_3739 plays a key role in xanthomonadin and coenzyme Q8 biosynthesis in X. oryzae pv. oryzae PXO99A. A xanB2 deletion mutant exhibits a pleiotropic phenotype, including xanthomonadin deficiency, producing less exopolysaccharide (EPS), lower viability and H2O2 resistance, and lower virulence. We further demonstrate that X. oryzae pv. oryzae produces 3-hydroxybenzoic acid (3-HBA) and 4-hydroxybenzoic acid (4-HBA) via XanB2. 3-HBA is associated with xanthomonadin biosynthesis while 4-HBA is mainly used as a precursor for coenzyme Q (CoQ)8 biosynthesis. XanB2 is the alternative source of 4-HBA for CoQ8 biosynthesis in PXO99A. These findings suggest that the roles of XanB2 in PXO99A are generally consistent with those in X. campestris pv. campestris. The present study also demonstrated that X. oryzae pv. oryzae PXO99A has evolved several specific features in 3-HBA and 4-HBA signaling. First, our results showed that PXO99A produces less 3-HBA and 4-HBA than X. campestris pv. campestris and this is partially due to a degenerated 4-HBA efflux pump. Second, PXO99A has evolved unique xanthomonadin induction patterns via 3-HBA and 4-HBA. Third, our results showed that 3-HBA or 4-HBA positively regulates the expression of gum cluster to promote EPS production in PXO99A. Taken together, the results of this study indicate that XanB2 is a key metabolic enzyme linking xanthomonadin, CoQ, and EPS biosynthesis, which are collectively essential for X. oryzae pv. oryzae pathogenesis.

Antiproliferative and proapoptotic activities of 4-hydroxybenzoic acid-based inhibitors of histone deacetylases

Histone acetyltransferases (HATs) and histone deacetylases (HDACs) regulate cellular processes by modifying the acetylation status of many proteins. Pathologically altered HDAC activity contributes to cancer development and thus characterization of novel acetylation modulators is important for future anti-cancer therapies. In this study, we identified three novel 4-hydroxybenzoic acid derivatives as pan-HDAC inhibitors that increased protein acetylation levels, arrested cell cycle progression and triggered apoptotic cell death, without affecting viability of normal cells. Our data support the potential of 4-hydroxybenzoic acid derivatives as pan-HDAC inhibitors with anticancer properties.

Drug-excipient compatibility studies in binary mixtures of avobenzone

During preformulation studies of cosmetic/pharmaceutical products, thermal analysis techniques are very useful to detect physical or chemical incompatibilities between the active and the excipients of interest that might interfere with safety and/or efficacy of the final product. Differential scanning calorimetry (DSC) was used as a screening technique for assessing the compatibility of avobenzone with some currently used cosmetic excipients. In the first phase of the study, DSC was used as a tool to detect any interaction. Based on the DSC results alone, cetearyl alcohol, isopropyl myristate, propylparaben, diethylhexyl syringylidene malonate, caprylic capric triglyceride, butylated hydroxytoluene (BHT), glycerin, cetearyl alcohol/ceteareth 20, cetearyl alcohol/sodium lauryl sulfate/sodium cetearyl sulfate, and paraffinum liquidum exhibit interaction with avobenzone. Stressed binary mixtures (stored at 50°C for 15 days) of avobenzone and excipients were evaluated by high-performance liquid chromatography. Binary mixtures were further investigated by infrared (IR) spectroscopy. Based on DSC, isothermal stress testing, and fourier transform infrared results; avobenzone is incompatible with caprylic capric triglyceride, propylparaben, and BHT.

An overview of parabens and allergic contact dermatitis

Esters of p-hydroxybenzoic acid (parabens) are the most widely used preservatives in cosmetic, pharmaceutical, and industrial products. However, since the 1960s, controversy has surrounded its use and safety as a potential cause of allergic contact dermatitis. Despite the cloud of suspicion that has hovered over parabens ever since, these ubiquitous compounds have withstood four decades of extensive skin testing conducted by a variety of organizations, both North American and European, and now, it seems parabens have shown to be one of the least sensitizing preservatives in commercial use. Of the very limited reports of paraben-induced allergic contact dermatitis, these cases are often attributable to the application of parabens on damaged skin.

Sonochemical effects on free phenolic acids under ultrasound treatment in a model system

Sonochemical effects on seven free phenolic acids under ultrasound treatment in a model system have been investigated. The degradation products have also been tentatively identified by FTIR and HPLC-UV-ESIMS. Five phenolic acids (protocatechuic acid, p-hydroxybenzoic acid, vanillic acid, p-coumaric acid, and ferulic acid) proved to be stable, while two others (caffeic acid and sinapic acid) were degraded under ultrasound treatment. The nature of the solvent and the temperature has been identified as important factors in determining the degradation reaction. Liquid height, ultrasonic intensity, and duty cycle of the ultrasound exposure affected only the degradation rate and did not change the nature of the degradation. The degradation rates of caffeic acid and sinapic acid decreased with increasing temperature. The degradation kinetics of these two acids under ultrasound conformed to zeroth-order reactions at -5 to 25 °C. Both decomposition and polymerization reactions occurred when caffeic acid and sinapic acid were subjected to ultrasound. Degradation products, such as the corresponding decarboxylation products and their dimers, have been tentatively identified.

(Fe3O4)-graphene oxide-SO3H as a new magnetic nanocatalyst for electro-oxidation and determination of selected parabens

For the first time magnetic graphene oxide functionalized by chlorosulfonic acid Fe3O4-GO-SO3H was used for electrode modification and electrocatalytic oxidation of three selected parabens. Scanning electron microscopy (SEM) and X-ray diffraction techniques are utilized in order to study the surface morphology of the modified electrode. The modified electrode was applied for parabens detection using cyclic voltammetry (CV), chronoamperometry, and amperometry methods. The modified electrode shows many advantages as a parabens sensor such as simple preparation method without using any specific electron transfer mediator or specific reagent, excellent catalytic activity, short response time, long-term stability and remarkable antifouling property toward parabens.

Two new glycosides from the florets of Carthamus tinctorius

Two new glycoside compounds, named saffloquinoside C (1) and (-)-4-hydroxybenzoic acid-4-O-[6'-O-(2″-methylbutyryl)-β-D-glucopyranoside] (2), were isolated from the florets of Carthamus tinctorius. Their structures were elucidated by detailed spectroscopic means including UV, IR, HR-ESI-MS, 1D and 2D NMR, and CD data. Compound 1 was a rare quinochalcone glycoside with six five-membered dioxaspirocycle.

Spectroscopic, quantum-chemical and X-ray diffraction studies of Piperidinium p-Hydroxybenzoate-combined experimental and theoretical studies on a novel NLO crystal

Large size and high quality single crystals of organic nonlinear optical material Piperidinium p-Hydroxybenzoate (PDPHB) have been grown by solution growth method. This crystal belongs to monoclinic system with a noncentrosymmetric space group of Cc. To confirm its structure and compositions this material was subjected to single and powder X-ray diffraction and microanalysis studies. Fourier transform infrared (FTIR), UV-VIS-NIR, photoluminescence and nuclear magnetic resonance spectra have been recorded and extensive spectroscopic investigations have been carried out. Frequency conversion property of the crystal was tested by using Kurtz and Perry powder technique and the relative conversion efficiency was about 19 times greater than that of KDP. Static and dynamic hyperpolarizability values were calculated to confirm the suitability of the crystal for nonlinear optical applications. In addition, frontier molecular orbital (FMO), Mulliken charge and molecular electrostatic potential (MEP) analyses were performed by density functional theory (DFT) at the B3LYP/6-31G (d) basis set.

Advanced oxidation kinetics and mechanism of preservative propylparaben degradation in aqueous suspension of TiO2 and risk assessment of its degradation products

The absolute kinetic rate constants of propylparaben (PPB) in water with different free radicals were investigated, and it was found that both hydroxyl radicals (HO(•)) and hydrated electrons could rapidly react with PPB. The advanced oxidation kinetics and mechanisms of PPB were investigated using photocatalytic process as a model technology, and the degradation was found to be a pseudo-first-order model. Oxidative species, particularly HO(•), were the most important reactive oxygen species mediating photocatalytic degradation of PPB, and PPB degradation was found to be significantly affected by pH because it was controlled by the radical reaction mechanism and was postulated to occur primarily via HO(•)-addition or H-abstraction reactions on the basis of pulse radiolysis measurements and observed reaction products. To investigate potential risk of PPB to humans and aqueous organisms, the estrogenic assays and bioassays were performed using 100 μM PPB solution degraded by photocatalysis at specific intervals. The estrogenic activity decreased as PPB was degraded, while the acute toxicity at three trophic levels first increased slowly and then decreased rapidly as the total organic carbon decreased during photocatalytic degradation.

Spectral characterization of the binding and conformational changes of bovine serum albumin upon interaction with an anti-fungal drug, methylparaben

The binding of methylparaben with bovine serum albumin (BSA) was investigated by spectroscopic methods viz., fluorescence, FT-IR and UV-vis absorption techniques under physiological conditions i.e., pH 7.4. Spectroscopic analysis of the emission quenching at different temperatures revealed that the quenching mechanism of bovine serum albumin by methylparaben shows a dynamic quenching. The binding sites number n and binding constants, K were obtained at various temperatures. The distance, r between methylparaben and BSA was evaluated according to the theory of Förster energy transfer. The result of FT-IR spectra and UV-vis absorption spectra showed that the conformation of bovine serum albumin has been changed in the presence of methylparaben. The thermodynamic parameters, enthalpy change (ΔH(0)) and entropy change (ΔS(0)) were calculated according to van't Hoff equation, which indicated that the hydrophobic interaction was the predominant intermolecular force stabilizing the complex. The effect of common ions and site probes were also carried on the binding of methylparaben to BSA.

Surfactant and temperature effects on paraben transport through silicone membranes

This study investigates the effects of two surfactants (one anionic and one non-ionic) and controlled modifications in temperature (298-323K) on the permeation of two structurally similar compounds through a silicone membrane using a Franz diffusion cell system. In all cases the presence of an anionic surfactant, namely sodium dodecyl sulphate (SDS), reduced the permeation of both compounds (methylparaben and ethylparaben) over a period of 24h. The degree of permeation reduction was proportional to the concentration of surfactant with a maximum effect observed, with an average reduction of approximately 50%, at the highest surfactant concentration of 20mM. Differences were seen around the critical micelle concentration (CMC) of SDS implying the effect was partially connected with the favoured formation of micelles. In contrast, the presence of non-ionic surfactant (Brij 35) had no effect on the permeation of methylparaben or ethylparaben at any of the concentrations investigated, both above and below the CMC of the surfactant. From these findings the authors conclude that the specific effects of SDS are a consequence of ionic surfactant-silicone interactions retarding the movement of paraben through the membrane through indirect modifications to the surface of the membrane. As expected, an increase in experimental temperature appeared to enhance the permeation of both model compounds, a finding that is in agreement with previously reported data. Interestingly, in the majority of cases this effect was optimum at the second highest temperature studied (45°C) which suggests that permeation is a temperature-dependent phenomenon.

New nervogenic acid derivatives from Liparis nervosa

Ten new nervogenic acid derivatives (1-4, 6-11) and one known compound (5) have been isolated from Liparis nervosa. Their structures were determined using extensive spectroscopic analysis, including 1D and 2D NMR experiments. Compounds 3, 4, 9, 10, and 11 were evaluated for their cytotoxicity against A549, H460, Hela, MCF-7, Caco2, and HepG2 human cancer cell lines.

The health controversies of parabens

Parabens are preservatives used in a variety of personal care, cosmetic, pharmaceutical and food products. Studies have confirmed the ubiquitous presence of parabens, with levels detected in wastewater, rivers, soil and house dust. Parabens have also been detected in human tissues and bodily fluids, but it is the discovery of these chemical compounds in the breast tissue of patients with breast cancer that has raised public concern over their use. It is hypothesized that the estrogenic properties of parabens may play a role in breast cancer development. However, studies investigating the health effects of parabens are conflicting. At this point, there is an insufficient amount of data suggesting serious consequences from paraben use and exposure to warrant drastic avoidance measures or government regulations.

Investigation of parabens in commercial cosmetics for children in Beijing, China

Parabens are one of the most common preservatives in cosmetics. Because allergenicity and cytotoxicity potential values are major aspects of preservative safety and parabens are xenoestrogens, safety levels of parabens have been restricted in "Hygienic Standard for Cosmetics" (2007 edition) by the Ministry of Public Health of China, and a high-performance liquid chromatography (HPLC) for the simultaneous determination of parabens is recommended. To investigate whether the commonly used parabens in children's cosmetics were at a safety level, 105 cosmetics for children were randomly purchased from the local market in Beijing and analyzed by the proposed HPLC method. The detection rate of methylparaben was the highest and the next was propylparaben. Among the 105 samples, two or more kinds of parabens were detected in 72 samples with concentrations ranging from 0.02% to 0.75%; 18 samples contained one kind of paraben with concentrations ranging from 0.002% to 0.06%. In this study, the contents of parabens in the 105 samples were all below the restricted levels.

Photo-degradation of butyl parahydroxybenzoate by using TiO2-supported catalyst

The present work evaluates the potential of the photocatalysis (PC) process for the degradation of butylparaben (BPB). Relatively high treatment efficiency was achieved by comparison to photochemical process. Prior to photocatalytic degradation, adsorption (AD) of BPB occurred on the titanium dioxide (TiO2)-supported catalyst. AD was described by Langmuir isotherm (KL = 0.085 L g(-1), qm = 4.77 mg g(-1)). The influence of angle of inclination of the reactor, pH, recirculation flow rate and initial concentration of BPB were investigated. The PC process applied under optimal operating conditions (recirculation flow rate of 0.15 L min(-1), angle of inclination of 15°, pH = 7 and 5 mg L(-1) of BPB) is able to oxidize 84.9-96.6% of BPB and to ensure around 38.7% of mineralization. The Langmuir-Hinshelwood kinetic model described well the photocatalytic oxidation of BPB (k = 7.02 mg L(-1) h(-1), K = 0.364 L mg(-1)).

UPLC-PDA-ESI-MS/MS analysis of compounds extracted by cardiac h9c2 cell from Polygonum orientale

INTRODUCTION

A flavonoid-enriched extract (FEE) of Polygonum orientale was reported to show cardioprotective effect but only very few compounds were reported to contribute to the effect. Identification of compounds interacting with the target cardiac cell is important for the understanding of active compounds.

OBJECTIVE

To develop an efficient method for the screening of potential active compounds directly acting on the target cardiac cell in FEE and to structurally characterise these compounds.

METHODOLOGY

Flavonoid-enriched extract was prepared by extraction of the plant with water, addition of ethanol to the solution to remove polysaccharides and proteins, and removal of tannins by a polyamide column chromatography. Cell extraction was conducted on a cardiac h9c2 cell and the solution containing compounds released from the cell were desalted by solid phase extraction. Compounds present in the cell extract were detected by ultra-performance liquid chromatography (UPLC) and targeted multi-reaction monitoring (MRM), while their structures were characterised by UPLC-photodiodide array (PDA)-electrospray ion source (ESI)-MS/MS investigations of the FEE.

RESULTS

Twenty-three potentially active phenolics including ten flavonoid C-glycosides and six flavonoid O-glycosides have been identified from the 40 compounds screened in the cell extract. Among these compounds, three were new and nine were identified from this plant for the first time. Strategies for the structural characterisation of flavonoid glycosides were also discussed.

CONCLUSION

The study has shown that FEE contains the flavonoid as its major principles and the coupling of UPLC-PDA-ESI-MS/MS and targeted UPLC-MRM with target cell extraction is an efficient method for the screening and structural characterisation of potential active compounds.

Comparison of segmented flow analysis and ion chromatography for the quantitative characterization of carbohydrates in tobacco products

Segmented flow analysis (SFA) and ion chromatography with pulsed amperometric detection (IC-PAD) are widely used analytical techniques for the analysis of glucose, fructose, and sucrose in tobacco. In the work presented here, 27 cured tobacco leaves and 21 tobacco products were analyzed for sugars using SFA and IC. The results of these analyses demonstrated that both techniques identified the same trends in sugar content across tobacco leaf and tobacco product types. However, comparison of results between techniques was limited by the selectivity of the SFA method, which relies on the specificity of the reaction of p-hydroxybenzoic acid hydrazide (PAHBAH) with glucose and fructose to generate a detectable derivative. Sugar amines and chlorogenic acid, which are found in tobacco, are also known to react with PAHBAH to form a reaction product that interferes with the analysis of fructose and glucose. To mitigate this problem, solid phase extraction (SPE) was used to remove interferences such as sugar amines and chlorogenic acid from sample matrices prior to SFA. A combination of C18 and cation exchange solid phase extraction cartridges was used, and the results from SFA and IC analyses showed significant convergence in the results of both analytical methods. For example, the average difference between the results from the SFA and IC analyses for flue-cured tobacco samples dropped by 73% when the two-step C18/cation exchange resin sample cleanup was used.

Effect of compression pressure, preservative, and storage with potassium chloride on the microbiological quality of tablets formulated with Terminalia randii Gum (Combretaceae)

Gums are used as binders in tablets and also as emulsion stabilisers, suspending agents and thickeners in syrups. The need for other natural gums apart from the conventional gums to be employed as binding agents in tablets formulation led to this study. A gum obtained from the incised trunk of Terminalia randii (Combretaceae) was evaluated for the effect of compression pressure, methyl paraben preservative and storage with potassium chloride, on the microbial load of tablets formulated with the gum. The microbial load was determined by surface spread method on the processed gum at suitable dilutions, and tablets formulated from the gum at different compression pressures. The formulated tablets were evaluated for microbial load, also when stored in potassium chloride for 8 and 12 weeks with and without preservation with 1% Methyl Paraben. In each case the compressed tablets were incubated in 0.1% peptone water as control. The microbial load recorded reflected generally, reduction in microbial counts in tablets formulated with the gum as a binder both in terms of compression at different pressures and when the different compression pressures were associated with or without 1% methyl paraben in the presence of potassium chloride. Comparatively, the processed gum showed higher microbial load than the pressure compressed tablets. Besides the different compression pressures, duration of storage was also found to cause reduction of microbial load, particularly in the formulated tablets compressed with methyl paraben stored in potassium chloride such that after 8 weeks, the microbial load was zero. The studies showed that compression pressures and duration of storage caused marked reduction in microbial load of the tablets formulated with the processed gum of Terminalia randii as a binder.

[Study on chemical constituents of Carthamus tinctorius]

OBJECTIVE

To investigate the chemical constituents in water-soluble fraction of Carthamus tinctorius.

METHODS

Compounds were isolated and purified by macroporus resin, silica gel, Sephadex LH-20 column chromatography and preparative HPLC. The structures were identified by spectral analysis.

RESULTS

Twelve compounds were isolated and identified as 4-Hydroxybenzaldehyde (1); E-1-(4'-hydroxypheny) -but-1-en-3-one (2); 3-Formylindole (3); 2-Acetyl-5-hydroxymethylfuran (4); p-Hydroxycinnamic acid (5); (6R, 7E, 9R) -9-hydroxy-4,7-megastigmandien-3-one (6); 4-hydroxyacetophenone (7); 5-(hydroxymethyl) -2-furaldehyde (8); 4-Hydroxybenzoic acid (9); Stigmasterol-3-O-beta-D-glucopyranoside (10); Daucosterol (11); beta-sitosterol (12).

CONCLUSION

Compounds 1 - 4, 6, 7, 10 are isolated from this plant for the first time.

(6R,9S)-6"-(4"-hydroxybenzoyl)-roseoside, a new megastigmane derivative from Ouratea polyantha and its effect on hepatic glucose-6-phosphatase

A new megastigmane derivative, (6R,9S)-6'-(4"-hydroxybenzoyl)-roseoside (1) and two known compounds, the biflavoneagathisflavone (2) and 4-hydroxybenzoic acid (3) were isolated and purified from leaves and stems of Ouratea polyantha Engl. Agathisflavone was isolated in a single high-speed countercurrent chromatography run, while the megastigmane was purified in two steps, by using a combination of high-speed countercurrent chromatography and analytical column chromatography. All structures were elucidated on the basis of spectral evidence and comparison with literature data. Compound 1 was characterized by [alpha]D20, UV-Vis, IR, MS, 1H NMR, 13C NMR, HMQC, HMBC, COSY and NOESY. Compounds 1 and 2 showed an inhibitory effect of 63.6 and 13.7% on the G-6-Pase intact microsomes, respectively.

Biophysical and structural characterization of a sequence-diverse set of solute-binding proteins for aromatic compounds

Rhodopseudomonas palustris metabolizes aromatic compounds derived from lignin degradation products and has the potential for bioremediation of xenobiotic compounds. We recently identified four possible solute-binding proteins in R. palustris that demonstrated binding to aromatic lignin monomers. Characterization of these proteins in the absence and presence of the aromatic ligands will provide unprecedented insights into the specificity and mode of aromatic ligand binding in solute-binding proteins. Here, we report the thermodynamic and structural properties of the proteins with aromatic ligands using isothermal titration calorimetry, small/wide angle x-ray scattering, and theoretical predictions. The proteins exhibit high affinity for the aromatic substrates with dissociation constants in the low micromolar to nanomolar range. The global shapes of the proteins are characterized by flexible ellipsoid-like structures with maximum dimensions in the 80-90-Å range. The data demonstrate that the global shapes remained unaltered in the presence of the aromatic ligands. However, local structural changes were detected in the presence of some ligands, as judged by the observed features in the wide angle x-ray scattering regime at q ~0.20-0.40 Å(-1). The theoretical models confirmed the elongated nature of the proteins and showed that they consist of two domains linked by a hinge. Evaluation of the protein-binding sites showed that the ligands were found in the hinge region and that ligand stabilization was primarily driven by hydrophobic interactions. Taken together, this study shows the capability of identifying solute-binding proteins that interact with lignin degradation products using high throughput genomic and biophysical approaches, which can be extended to other organisms.

Formation of organic nanoparticles by electrospinning of volatile microemulsions

This study presents a method for one-step formation of poly(ethylene oxide) nanofibers incorporating nanoparticles of a poorly water-soluble compound. Using the new method reported here, nanofiber-nanoparticle composites are fabricated in one step by electrospinning of an oil-in-water microemulsion, in which a model material, propylparaben, has been dissolved within the volatile dispersed phase in the presence of a high-molecular-weight polymer. The approach is based on nanoscale confinement to the dispersed phase of an oil-in-water microemulsion with a volatile oil phase, in which the poorly water-soluble materials are dissolved. Thus, when the thermodynamically stable oil-in-water microemulsion is combined with the rapid evaporation of solvent inherent in the electrospinning process, the droplets are converted into organic nanoparticles embedded within a polymeric nanofiber. In addition to possessing process simplicity, this method exhibits a very high percentage of nanoparticle loading with desirable active material properties. Specifically, the diameter of the nanofibers is in the range of 60-185 nm, and propylparaben exists within the nanofiber as nanocrystals of 30-120 nm. These dimensions suggest that the nanofiber-nanocrystal composites could serve as a delivery system for water-insoluble materials.