Specific Non-Reducing Ends in Heparins from Different Animal Origins: Building Blocks Analysis Using Reductive Amination Tagging by Sulfanilic Acid.

Heparins are linear sulfated polysaccharides widely used as anticoagulant drugs. Their nonreducing-end (NRE) has been little investigated due to challenges in their characterization, but is known to be partly generated by enzymatic cleavage with heparanases, resulting in N-sulfated glucosamines at the NRE. Uronic NRE (specifically glucuronic acids) have been isolated from porcine heparin, with GlcA-GlcNS,3S,6S identified as a porcine-specific NRE marker. To further characterize NRE in heparinoids, a building block analysis involving exhaustive heparinase digestion and subsequent reductive amination with sulfanilic acid was performed. This study describes a new method for identifying heparin classical building blocks and novel NRE building blocks using strong anion exchange chromatography on AS11 columns for the assay, and ion-pair liquid chromatography-mass spectrometry for building block identification. Porcine, ovine, and bovine intestine heparins were analyzed. Generally, NRE on these three heparins are highly sulfated moieties, particularly with 3-O sulfates, and the observed composition of the NRE is highly dependent on heparin origin. At the highest level of specificity, the isolated marker was only detected in porcine heparin. However, the proportion of glucosamines in the NRE and the proportion of glucuronic/iduronic configurations in the NRE uronic moieties greatly varied between heparin types.

Sulfonated glycosaminoglycan bioinspired carbon dots for effective cellular labelling and promotion of the differentiation of mesenchymal stem cells.

Although carbon dots (CDs) have been synthesized and applied in a variety of biological fields, such as disease diagnosis and gene/drug delivery, the exploration of facile bioinspired synthesis and applications of CDs is still of great significance. Particularly, recent increasing research has clearly confirmed that nanomaterials can affect a series of physiological behaviors and functions of mesenchymal stem cells (MSCs) (e.g., differentiation and pluripotency). Therefore, it is very important to develop multifunctional nanomaterials to simultaneously realize the cellular labelling and regulation of MSC behaviors in practical applications. Herein, sulfonated glycosaminoglycan-bioinspired CDs as bi-functional nanomaterials were ingeniously designed for cellular imaging and promoting the differentiation of rat bone MSCs (rBMSCs) in different culture media, which simultaneously met the two fundamental requirements in the field of MSC-based treatments (e.g., precisely directing the differentiation of MSCs and effective cellular labeling). These bifunctional CDs were successfully prepared via one-pot hydrothermal synthesis by using d-glucosamine hydrochloride (GA·HCl) and sodium p-styrenesulfonate (NaSS) as the reactants. The synthesized CDs with a uniform particle size (around 4 nm) dispersed well in aqueous solutions and exhibited remarkable fluorescence stability under different conditions. Additionally, cell viability and proliferation results demonstrated that the CDs possessed good biocompatibility, having negligible effects on the self-renewal potential of rBMSCs. The as-prepared CDs presented a cytoplasmatic distribution after being ingested by rBMSCs; thus, they are particularly suitable for cellular imaging. More importantly, the addition of CDs to osteogenic and chondrogenic induction media (OIM and CIM), respectively, was capable of effectively promoting the osteogenic and chondrogenic differentiation of rBMSCs due to the generation of reactive oxygen species (ROS) while having no influence on their pluripotency. In brief, this study not only implements a cellular labeling method based on CDs that were synthesized by a biomimicking strategy, but also paves a new way to regulate the differentiation of MSCs by designing multifunctional nanomaterials; this will enable the extensive development of facile synthesis methods and new applications of CDs and will also provide some research foundations for MSC-based fields.

Synthesis of sulfonated chitosan-derived carbon-based catalysts and their applications in the production of 5-hydroxymethylfurfural.

A novel sulfonated chitosan-derived carbon-based catalyst was successfully prepared via isoamyl nitrite-assisted sulfanilic acid sulfonation, and its catalytic activity was examined using dehydration of fructose. The structural and chemical properties of sulfonated chitosan-derived carbon were characterized by SEM, FTIR, XRD, XPS, element analysis, N2 adsorption-desorption experiment, and acid-base titration experiment. KOH was used as activating agent in the synthesizing of carbon supports, and it was found that properly increasing the dose of KOH during activation stage had a positive effect on the subsequent sulfonation of prepared activated carbon. 4KSCC, with the highest sulfonation degree (2.04 mmol/g), exhibited high performance for the conversion of fructose to HMF in various solvent, and an optimal HMF yield of 80.9% was obtained at 140 °C in 40 min. In addition, the reusability of 4KSCC for fructose dehydration was fairly good.

A streamlined workflow for twoplexing of N-linked glycan analysis using light (12C6) and heavy (13C6) isotopologues of 3-aminobenzenesulfonic acid.

Comparative glycosylation analysis of biopharmaceuticals requires the development of methods that deliver the necessary throughput, support structural elucidation and relative quantitation of glycans released from therapeutics. The current study presents the development and applicability assessment of a twoplex approach using light and heavy isotopolouges of 3-aminobenzenesulfonic acid (3-ASA) under wet labeling conditions followed by UHPLC-MS analysis in data dependent acquisition mode. Excellent labelling efficiency, >90%, was achieved for both the light and heavy variants of the reagent. Glycan distributions of two human IgG lots labeled by light and heavy isotopolouges were identical, demonstrating no labeling bias introduced by either of the isotopologues. Peak area distributions of glycan profiles of two human IgG lots were compared to 2-aminobenzamide (2-AB) and RapiFluor-MS protocols. The comparison led to identical results in peak area distribution across the three dyes, but differences in chromatographic selectivity attributed to the different tags. MS1 based relative quantitation was further validated by releasing glycans from the same lot of human IgG, with glycan pools obtained labeled with light and heavy isotopologues separately, followed by mixing and clean-up of the same amount of light and heavy labeled glycan pools. MS analyses of each glycan resulted in a ratio of light and heavy XIC in the range of 0.97 ≤ x ≤ 1.05, demonstrating the method is amenable for the relative quantitation of glycans. Excellent correlation between the relative quantitation data of N-glycans from two human IgG N-glycan pools using the twoplex approach and ratios from peak area distribution calculated from the fluorescent chromatogram was observed (r = 0.986), further corroborating the reliability of the method and its potential applicability in the biopharmaceutical industry. Highly informative HCD-MS2 spectra dominated mostly by Y- and Z-type single and double glycosidic fragment ions facilitate structural interpretation of the oligosaccharides.

Sulfonated graphene oxide and titanium dioxide coated with nanostructured polyaniline nanocomposites as an efficient cathode catalyst in microbial fuel cells.

In this study, sulfonated graphene oxide (SGO) was synthesized as potential conducting matrix to improve the properties of catalyst for single chamber microbial fuel cells (SC-MFCs). Here, TiO2 and Polyaniline (PAni) nanoparticles were anchored over SGO and the resulting SGO-TiO2-PAni nanocomposites were used as a potential cathode catalyst in MFCs. We have also examined the performance of SGO-TiO2-PAni compared to GO-TiO2-PAni and TiO2-PAni catalyst. The structural and morphological analyses were examined using a variety of characterization techniques. TiO2 nanoparticles bridged PAni and SGO through hydrogen bonding/electrostatic interaction and improved the thermal stability of SGO-TiO2-PAni catalyst. The electrochemical characterizations of these nanocatalysts suggest that the SGO-TiO2-PAni showed higher reduction current value (-0.46 mA), enhanced stability, and lower internal resistance (46.2 Ω) in comparison to GO-TiO2-PAni and TiO2-PAni towards oxygen reduction reactions (ORR). Consequently, MFC using SGO-TiO2-PAni demonstrated a maximum power density of 904.18 mWm-2 than that of GO-TiO2-PAni (734.12 mWm-2), TiO2-PAni (561.5 mWm-2) and Pt/C (483.5 mWm-2). The enhanced catalytic activity of SGO-TiO2-PAni catalyst was ascribed to the high electronic conductivity and long-term permanence of the nanocomposite. These superior electrochemical results suggested that the SGO-TiO2-PAni catalyst could be applied as a potential alternative to the commercial Pt/C cathode catalyst for the application of MFCs.

A multichannel system integrating molecularly imprinted conductive polymers for ultrasensitive voltammetric determination of four steroid hormones in urine.

This work reports on a modularized electrochemical method for the determination of the hormones cortisol, progesterone, testosterone and 17ß-estradiol in urine. These hormones were employed as templates when generating molecular imprints from aniline and metanilic acid by electropolymerization on the surface of screen-printed electrodes. The electrically conductive imprint was characterized by SEM, AFM and cyclic voltammetry. A four-channel system was then established to enable simultaneous determination of the hormones by cyclic voltammetry. The detection limits for cortisol, progesterone, testosterone and 17ß-estradiol are as low as 2, 2.5, 10 and 9 ag·mL-1 (for S/N = 3). Graphical abstract A four-channel system was established to enable simultaneous determination of 4 steroid hormones by cyclic voltammetry and by using moleculalry imprinted polymers.

Colorimetric detection of the ß-agonist ractopamine in animal feed, tissue and urine samples using gold-silver alloy nanoparticles modified with sulfanilic acid.

A highly sensitive, selective and simple method was proposed for colorimetric detection of ractopamine on the basis of the interaction between ractopamine and sulfanilic acid-modified gold-silver alloy nanoparticles (AuAgNPs). The AuAgNPs were prepared by the reduction of HAuCl4 and AgNO3 with sodium citrate in aqueous medium and further modified by sulfanilic acid. The interaction of ractopamine with sulfanilic acid induced rapid aggregation of sulfanilic acid-modified AuAgNPs along with an optical colour change, leading to precise quantification which could be detected by absorptiometry. Under the optimum conditions, the absorbance ratio (A600/A435) of sulfanilic acid-modified AuAgNPs exhibited a linear relationship with the concentration of ractopamine in the range of 4.5-31.6 ng/mL. The detection limit of ractopamine was 1.5 ng/mL. The established novel colorimetric detection method showed high selectivity towards ractopamine. The method was successfully applied to detect ractopamine in spiked pork, swine feed and swine urine samples with excellent recoveries from 94.4% to 112.5%. These results demonstrated that the proposed new method has a good potential for practical applications.

Degradation of textile dyes Remazol Yellow Gold and reactive Turquoise: optimization, toxicity and modeling by artificial neural networks.

In this work, the degradation of Remazol Yellow Gold RNL-150% and Reactive Turquoise Q-G125 were investigated using AOP: photolysis, UV/H2O2, Fenton and photo-Fenton. It was found that the photo-Fenton process employing sunlight radiation was the most efficient, obtaining percentages of degradation above 87%. The ideal conditions for the degradation of the dyes were determined from a factorial design 23 and study of the [H2O2] ([H2O2] equal to 100 mg·L-1); [Fe] equal to 1 mg·L-1 and pH between 3 and 4. In the kinetic study, a degradation of more than 97% was obtained after 150 min for the chromophoric groups and 91% for the aromatic compounds. The experimental data obtained presented a good fit to the nonlinear kinetic model. The model of artificial neural networks multilayer perceptron (MLP) (4-11-5) using the software Statistica 8.0 enabled the modeling of the degradation process and showed a better prediction of the data. The toxicity to the seeds of Lactuca sativa and the bacteria Escherichia coli and Salmonella enteritidis allowed to evaluate the effectiveness of the process. The results of this study suggest that the use of photo-Fenton process with sunlight radiation is an effective way to degrade the dyes under study.

Structural basis of malodour precursor transport in the human axilla.

Mammals produce volatile odours that convey different types of societal information. In Homo sapiens, this is now recognised as body odour, a key chemical component of which is the sulphurous thioalcohol, 3-methyl-3-sulfanylhexan-1-ol (3M3SH). Volatile 3M3SH is produced in the underarm as a result of specific microbial activity, which act on the odourless dipeptide-containing malodour precursor molecule, S-Cys-Gly-3M3SH, secreted in the axilla (underarm) during colonisation. The mechanism by which these bacteria recognise S-Cys-Gly-3M3SH and produce body odour is still poorly understood. Here we report the structural and biochemical basis of bacterial transport of S-Cys-Gly-3M3SH by Staphylococcus hominis, which is converted to the sulphurous thioalcohol component 3M3SH in the bacterial cytoplasm, before being released into the environment. Knowledge of the molecular basis of precursor transport, essential for body odour formation, provides a novel opportunity to design specific inhibitors of malodour production in humans.

The Utility of [18F]DASA-23 for Molecular Imaging of Prostate Cancer with Positron Emission Tomography.

PURPOSE: There is a strong, unmet need for superior positron emission tomography (PET) imaging agents that are able to measure biochemical processes specific to prostate cancer. Pyruvate kinase M2 (PKM2) catalyzes the concluding step in glycolysis and is a key regulator of tumor growth and metabolism. Elevation of PKM2 expression was detected in Gleason 8-10 tumors compared to Gleason 6-7 carcinomas, indicating that PKM2 may potentially be a marker of aggressive prostate cancer. We have recently reported the development of a PKM2-specific radiopharmaceutical [18F]DASA-23 and herein describe its evaluation in cell culture and preclinical models of prostate cancer. PROCEDURE: The cellular uptake of [18F]DASA-23 was evaluated in a panel of prostate cancer cell lines and compared to that of [18F]FDG. The specificity of [18F]DASA-23 to measure PKM2 levels in cell culture was additionally confirmed through the use of PKM2-specific siRNA. PET imaging studies were then completed utilizing subcutaneous prostate cancer xenografts using either PC3 or DU145 cells in mice. RESULTS: [18F]DASA-23 uptake values over 60-min incubation period in PC3, LnCAP, and DU145 respectively were 23.4 ± 4.5, 18.0 ± 2.1, and 53.1 ± 4.6 % tracer/mg protein. Transient reduction in PKM2 protein expression with siRNA resulted in a 50.1 % reduction in radiotracer uptake in DU145 cells. Small animal PET imaging revealed 0.86 ± 0.13 and 1.6 ± 0.2 % ID/g at 30 min post injection of radioactivity in DU145 and PC3 subcutaneous tumor bearing mice respectively. CONCLUSION: Herein, we evaluated a F-18-labeled PKM2-specific radiotracer, [18F]DASA-23, for the molecular imaging of prostate cancer with PET. [18F]DASA-23 revealed rapid and extensive uptake levels in cellular uptake studies of prostate cancer cells; however, there was only modest tumor uptake when evaluated in mouse subcutaneous tumor models.

Enzymatic Synthesis of Lignin-Based Concrete Dispersing Agents.

Lignin is the most abundant aromatic biopolymer, functioning as an integral component of woody materials. In its unmodified form it shows limited water solubility and is relatively unreactive, so biotechnological lignin valorisation for high-performance applications is greatly underexploited. Lignin can be obtained from the pulp and paper industry as a by-product. To expand its application, a new synthesis route to new dispersing agents for use as concrete additives was developed. The route is based on lignin functionalisation by enzymatic transformation. Screening of lignin-modifying systems resulted in functionalised lignin polymers with improved solubility in aqueous systems. Through grafting of sulfanilic acid or p-aminobenzoic acid by fungal laccases, lignin became soluble in water at pH≤4 or pH≤7, respectively. Products were analysed and evaluated in miniaturised application tests in cement paste and mortar. Their dispersing properties match the performance criteria of commercially available lignosulfonates. The study provides examples of new perspectives for the use of lignin.

Modular design of optically controlled protein affinity reagents.

Photopharmaceuticals can, in principle, be created by linking photoswitchable moieties to bioactive molecules. However, a general strategy for converting a therapeutic agent into its photoswitchable version is not currently available. Herein we propose a generalizable, modular approach for obtaining light controllable bioactive agents by modifying the scaffold of a protein affinity reagent using an azobenzene photoswitch.

Ultrasensitive electrochemiluminescence immunoassay for simultaneous determination of CA125 and CA15-3 tumor markers based on PAMAM-sulfanilic acid-Ru(bpy)32+ and PAMAM-CdTe@CdS nanocomposite.

A multiplex ultrasensitive electrochemiluminescence (ECL) immunoassay was developed for the simultaneous determination of two different tumor markers, cancer antigen 153 (CA 15-3) and cancer antigen 125 (CA 125) using polyamidoamine dendrimer-quantum dots (PAMAM-QDs) and PAMAM-sulfanilic acid-Ru(bpy)32+ as the signal probes and Fe3O4-SiO2 as a magnetic bead. The CdTe@CdS- QDs and Ru(bpy)32+ at the presence of tripropyl amine (TPA) as coreactant generate ECL at an applied voltage of + 1.2V (vs Ag/AgCl) in two different wavelengths 500 and 620nm, respectively. Based on this strategy, the simultaneous detection of two tumor markers in single run carried out. This dual signal amplification technique was achieved by employing Fe3O4@SiO2-dendrimer as immunosensing platform and PAMAM as the carrier for immobilizing CdTe@CdS and Ru(bpy)32+ probes. Experimental results illustrated that the designed immunosensor can be used to sequentially detection of CA 125 and CA 15-3 markers with the wide linear ranges of 1µU/mL to 1U/mL and 0.1mU/mL to 100U/mL with very low detection limits of 0.1µU/mL and 10µU/mL, respectively. The application of the immunosensor for simultaneous detection of CA125 and CA15-3 in human serum samples was evaluated and the obtained results were found to be in acceptable agreement with the those obtained with an ELISA assay as reference method. The proposed ECL immunosensor can provide a simple, sensitive and reliable approach for the simultaneous detection of tumor markers in clinical samples.

Sulfanilic acid-modified chitosan mini-spheres and their application for lysozyme purification from egg white.

A cation exchange matrix with zwitterionic and multimodal properties was synthesized by a simple reaction sequence coupling sulfanilic acid to a chitosan based support. The novel chromatographic matrix was physico-chemically characterized by ss-NMR and ζ potential, and its chromatographic performance was evaluated for lysozyme purification from diluted egg white. The maximum adsorption capacity, calculated according to Langmuir adsorption isotherm, was 50.07 ± 1.47 mg g-1 while the dissociation constant was 0.074 ± 0.012 mg mL-1 . The process for lysozyme purification from egg white was optimized, with 81.9% yield and a purity degree of 86.5%, according to RP-HPLC analysis. This work shows novel possible applications of chitosan based materials. The simple synthesis reactions combined with the simple mode of use of the chitosan matrix represents a novel method to purify proteins from raw starting materials. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:387-396, 2018.

Structural Basis for the Inhibitory Effects of Ubistatins in the Ubiquitin-Proteasome Pathway.

The discovery of ubistatins, small molecules that impair proteasomal degradation of proteins by directly binding to polyubiquitin, makes ubiquitin itself a potential therapeutic target. Although ubistatins have the potential for drug development and clinical applications, the lack of structural details of ubiquitin-ubistatin interactions has impeded their development. Here, we characterized a panel of new ubistatin derivatives using functional and binding assays. The structures of ubiquitin complexes with ubistatin B and hemi-ubistatin revealed direct interactions with ubiquitin's hydrophobic surface patch and the basic/polar residues surrounding it. Ubistatin B binds ubiquitin and diubiquitin tighter than a high-affinity ubiquitin receptor and shows strong preference for K48 linkages over K11 and K63. Furthermore, ubistatin B shields ubiquitin conjugates from disassembly by a range of deubiquitinases and by the 26S proteasome. Finally, ubistatin B penetrates cancer cells and alters the cellular ubiquitin landscape. These findings highlight versatile properties of ubistatins and have implications for their future development and use in targeting ubiquitin-signaling pathways.

Photocatalytic degradation of Direct yellow 86 diazo dye using sulfanilic acid-modified TiO2 in aqueous suspensions.

This study synthesized sulfanilic acid (SA)-modified TiO2 nanocomposites and used them as an effective photocatalyst for Direct yellow 86 diazo dye removal from aqueous solution. This novel nanocomposite (SA/TiO2) was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy and X-ray diffraction. The results showed the formation of SA/TiO2 nanocatalyst. The photocatalytic activity of the modified photocatalyst was examined by degradation of Direct yellow 86 (GE) under UV and visible light. The effects of five parameters, the concentration of GE, dosage of SA/TiO2 nanocomposite, UV light irradiation intensity, pH and visible light illumination, on the removal of GE using SA/TiO2 nanocomposite were studied. The highest GE removal was determined at pH of 9, nanocomposite dosage of 0.15 g/l and initial GE concentration of 50 mg/l at the constant temperature of 25 °C. However, the results showed that the GE removal rate increased as the UV light intensity increased. In addition, an enhancement in the photodegradation rate was observed with visible light illumination. The adsorption trends of GE at various initial concentrations followed the Langmuir isotherm model.

Hydrophobic Patch of Ubiquitin is Important for its Optimal Activation by Ubiquitin Activating Enzyme E1.

Protein ubiquitination plays a role in essentially every process in eukaryotic cells. The attachment of ubiquitin (Ub) or Ub-like (UBL) proteins to target proteins is achieved by parallel but distinct cascades of enzymatic reactions involving three enzymes: E1, E2, and E3. The E1 enzyme functions at the apex of this pathway and plays a critical role in activating the C-terminus of ubiquitin or UBL, which is an essential step that triggers subsequent downstream transfer to their cognate E2s resulting in the fidelity of the Ub/UBL conjugation machinery. Despite the central role of the E1 enzyme in protein modification, a quantitative method to measure Ub/UBL activation by E1 is lacking. Here, we present a mass spectrometry-based assay to accurately measure the activation of Ub/UBL by E1 independent of the E2/E3 enzymes. Our method does not require radiolabeling of any components and therefore can be used in any biochemical laboratory having access to a mass spectrometer. This method allowed us to dissect the concerted process of E1-E2-catalyzed Ub conjugation in order to separately characterize the process of Ub activation and how it is affected by select mutations and other factors. We found that the hydrophobic patch of Ub is important for the optimal activation of Ub by E1. We further show that the blockers of the Ub-proteasome system such as ubistatin and fullerenol inhibit Ub activation by E1. Interestingly, our data indicate that the phosphorylation of Ub at the S65 position augments its activation by the E1 enzyme.

Novel derivative of aminobenzenesulfonamide (3c) induces apoptosis in colorectal cancer cells through ROS generation and inhibits cell migration.

BACKGROUND: Colorectal cancer (CRC) is the 3rd most common type of cancer worldwide. New anti-cancer agents are needed for treating late stage colorectal cancer as most of the deaths occur due to cancer metastasis. A recently developed compound, 3c has shown to have potent antitumor effect; however the mechanism underlying the antitumor effect remains unknown. METHODS: 3c-induced inhibition of proliferation was measured in the absence and presence NAC using MTT in HT-29 and SW620 cells and xCELLigence RTCA DP instrument. 3c-induced apoptotic studies were performed using flow cytometry. 3c-induced redox alterations were measured by ROS production using fluorescence plate reader and flow cytometry and mitochondrial membrane potential by flow cytometry; NADPH and GSH levels were determined by colorimetric assays. Bcl2 family protein expression and cytochrome c release and PARP activation was done by western blotting. Caspase activation was measured by ELISA. Cell migration assay was done using the real time xCELLigence RTCA DP system in SW620 cells and wound healing assay in HT-29. RESULTS: Many anticancer therapeutics exert their effects by inducing reactive oxygen species (ROS). In this study, we demonstrate that 3c-induced inhibition of cell proliferation is reversed by the antioxidant, N-acetylcysteine, suggesting that 3c acts via increased production of ROS in HT-29 cells. This was confirmed by the direct measurement of ROS in 3c-treated colorectal cancer cells. Additionally, treatment with 3c resulted in decreased NADPH and glutathione levels in HT-29 cells. Further, investigation of the apoptotic pathway showed increased release of cytochrome c resulting in the activation of caspase-9, which in turn activated caspase-3 and -6. 3c also (i) increased p53 and Bax expression, (ii) decreased Bcl2 and BclxL expression and (iii) induced PARP cleavage in human colorectal cancer cells. Confirming our observations, NAC significantly inhibited induction of apoptosis, ROS production, cytochrome c release and PARP cleavage. The results further demonstrate that 3c inhibits cell migration by modulating EMT markers and inhibiting TGFß-induced phosphorylation of Smad2 and Samd3. CONCLUSIONS: Our findings thus demonstrate that 3c disrupts redox balance in colorectal cancer cells and support the notion that this agent may be effective for the treatment of colorectal cancer.

Accelerating biodegradation of a monoazo dye Acid Orange 7 by using its endogenous electron donors.

Biodegradation of a monoazo dye - Acid Orange 7 (AO7) was investigated by using an internal circulation baffled biofilm reactor. For accelerating AO7 biodegradation, endogenous electron donors produced from AO7 by UV photolysis were added into the reactor. The result shows that AO7 removal rate can be accelerated by using its endogenous electron donors, such as sulfanilic and aniline. When initial AO7 concentration was 13.6mg/L, electron donors generated by 8h UV photolysis were added into the same system. The biodegradation rate 0.4mg0.05h-1 was enhanced 60% than that without adding electron donor. Furthermore, sulfanilic and aniline were found to be the main endogenous electron carriers, which could accelerate the steps of the azo dye biodegradation.

Physicochemical aspects of the energetics of binding of sulphanilic acid with bovine serum albumin.

The thermodynamic study of the binding of sulphanilic acid with model transport protein bovine serum albumin is a promising approach in the area of synthesizing new sulfa drugs with improved therapeutic effect. Thus, such binding studies play an important role in the rational drug design process. The binding between sulphanilic acid and bovine serum albumin has been studied using calorimetry, light scattering in combination with spectroscopic and microscopic techniques. The calorimetric data reveals the presence of two sequential nature of binding sites where the first binding site has stronger affinity (~10(4)M(-1)) and second binding site has weaker affinity (~10(3)M(-1)). However, the spectroscopic (absorption and fluorescence) results suggest the presence of single low affinity binding site (~10(3)M(-1)) on protein. The contribution of polar and non-polar interactions to the binding process has been explored in the presence of various additives. It is found that sulphanilic acid binds with high affinity at Sudlow site II and with low affinity at Sudlow site I of protein. Light scattering and circular dichroism measurements have been used to study the effect on the molecular topology and conformation of protein, respectively. Thus these studies provide important insights into the binding of sulphanilic acid with bovine serum albumin both quantitatively and qualitatively.