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  • 1.
    Berglund, Per
    et al.
    KTH, School of Biotechnology (BIO), Biochemistry.
    Park, S.
    Strategies for altering enzyme reaction specificity for applied biocatalysis2005In: Current organic chemistry, ISSN 1385-2728, E-ISSN 1875-5348, Vol. 9, no 4, p. 325-336Article in journal (Refereed)
    Abstract [en]

    The fact that many enzymes have broad substrate specificity has been a property, of fundamental importance for the widespread applications of enzymes in synthetic chemistry. Many enzymes can, in addition, catalyze completely different reactions compared to their natural ones. The possibility of using molecular biology techniques to control Such catalytic plasticity of enzymes in order to establish completely new reaction specificity in the active site is the topic for this review. The examples are subdivided according to six different approaches used (i - vi) for engineering of the reaction specificity. The first approach (i) is the random method of directed evolution to achieve new reaction specificity. Other approaches involve strategies where tire reaction specificity of a known enzyme is implemented into another, closely related, enzyme by substituting key amino acid residues selected either by (ii) sequence or (iii) structural overlap of the two enzymes. Yet other approaches involve substitution of key amino acid residues to introduce new reaction specificity without comparing with a template enzyme (iv) and the introduction of a complete catalytic machinery (v). The final approach is the introduction of an active site into a non-catalytic protein (vi). These six different approaches for altering the reaction chemistry of enzymes each represent a powerful tool for controlling the catalytic plasticity or enzymes. The prospect for these altered enzymes as catalysts in synthetic chemistry is very large although examples of practical use are rare and still challenging. The progress in the area of altering enzyme reaction specificity will result in a Continued development towards the goal of creating tailor-made enzymes for synthetic chemistry.

  • 2.
    Cetecioglu, Zeynep
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology. Istanbul Technical University, Turkey.
    Orhon, Derin
    Acute and Chronic Effects of Antibiotics on Deterioration of Anaerobic Substrate Utilization2017In: Current organic chemistry, ISSN 1385-2728, E-ISSN 1875-5348, Current Organic Chemistry, ISSN 1385-2728, Vol. 21, no 12, p. 1044-1053Article, review/survey (Refereed)
    Abstract [en]

    The paper essentially summarizes and provides a comprehensive evaluation of degeneration of substrate utilization in terms of short and long term effects and biodegradability of the selected antibiotics; sulfamethoxazole, erythromycin, and tetracycline; under different conditions. This review focuses on acute and chronic tests to evaluate the inhibitory effects of the antibiotics and to control them at the source. Acute impact based on batch tests was conducted using antibiotic dozing in the range of 1-1000 mg/L. Substrate removal was monitored by means of soluble COD and VFA measurements. At low antibiotic dosing VFA mixture was completely removed; at higher doses propionate utilization was impaired and butyrate was reduced. Higher doses induced total inactivation of microbial metabolism. For chronic impacts, the antibiotic dozing was gradually increased in lab-scale anaerobic reactors. COD, VFA, and methane generation were monitored during each phase. For each antibiotic, a threshold concentration level was determined, which did not impair substrate utilization. High concentration of antibiotics (3 mg/L<) caused toxic effects on the mixed microbial culture and affected substrate removal and biogas generation and finalized a total collapse of the reactors. Each antibiotic reflected a different impact and biodegradation pattern related to its specific mode of action. Complete removal of antibiotics could be achieved at low concentration levels. The main removal mechanism for all three antibiotics was biodegradation and not sorption. When the sorption increased in the system, the system collapsed.

  • 3. Li, S.
    et al.
    Xue, L.
    Fu, K.
    Xia, X.
    Zhao, Chengxin
    KTH, School of Information and Communication Technology (ICT).
    Zhang, X.
    High-performance Sn/carbon composite anodes derived from Sn(II) acetate/polyacrylonitrile precursors by electrospinning technology2013In: Current organic chemistry, ISSN 1385-2728, E-ISSN 1875-5348, Vol. 17, no 13, p. 1448-1454Article in journal (Refereed)
    Abstract [en]

    Sn/carbon composite nanofibers with various compositions were prepared from Sn(II) acetate/polyacrylonitrile (PAN) precursors by a combination of electrospinning and carbonization methods, and their potential use as anode materials for rechargeable lithiumion batteries was investigated. The composite electrode derived from 20 wt% Sn(II) acetate/PAN precursor showed excellent electrochemical properties, including a large reversible capacity of 699 mAh g-1 and a high capacity retention of 83% in 50 cycles. Sn/carbon composite nanofibers exhibited enhanced electrochemical performance ascribing to the combination of the properties of both Sn nanoparticles (large Li storage capability) and carbon matrices (long cycle life), and therefore could be potentially used in high-energy rechargeable lithium-ion batteries.

  • 4.
    Yang, Huaiyu
    et al.
    Imperial Coll London, Dept Chem Engn, London, England..
    Zhang, Fan
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    We, Han
    UCL, Dept Chem Engn, London, England..
    Review on Life Cycle of Parabens, Synthesis, Degradation, Characterization and Safety Analysis2018In: Current organic chemistry, ISSN 1385-2728, E-ISSN 1875-5348, Vol. 22, no 8, p. 769-779Article, review/survey (Refereed)
    Abstract [en]

    In this review, we show the life cycle of parabens, commonly used preservatives that exist in nature and commercial products. Typical synthetic methods to produce parabens, and a set of complimentary characterization techniques to monitor the composition of parabens are also highlighted. This includes solid state analysis using Scanning Electron Microscope (SEM), Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD), in-situ monitoring of crystallization process using Focused Beam Reflectance Measurement (FBRM), Particle Vision Measurement (PVM), quantitative detection via High Performance Liquid Chromatography (HPLC), and Gas Chromatography (GC). An improved understanding of the overall physical, biophysical and chemical properties of parabens and their life cycle, summarized in this article, are vital for the safety control and extensive applications of relevant products in food, cosmetic and pharmaceutical industries.

  • 5. Zhang, Meiling
    et al.
    Song, Ce
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Yao, Zhi
    Ji, Qiang
    Theoretical Studies of the Structure and Properties of Anticancer Drug Taxol2012In: Current organic chemistry, ISSN 1385-2728, E-ISSN 1875-5348, Vol. 16, no 19, p. 2321-2331Article in journal (Refereed)
    Abstract [en]

    In the present study, prior MD investigation or Monte-Carlo search, our step-by-step search for the real lowest energy conformers and the properties of taxol (Also called paclitaxel) is presented theoretically. The paper completes the old paper of Ballone and Marchi (JPC A 1999) which carried out LDA calculations on taxol. A total of 216 initial trial structures were generated by all combinations of internal single-bond rotamers and optimized at the B3LYP/3-21G* level and further optimized at the B3LYP/6-311G* level. A total of 12 unique conformers are found, and their relative energies, dipole moments, rotational constants, zero point vibrational energy, and harmonic frequencies are determined. Their relative electronic energies were determined at the M06L/6-311G(2df,p) level. Combined with statistical mechanics principles, conformational distributions at various temperatures are computed. Characteristic H-bonding types are classified and demonstrated in the taxol structure. It is found that various hydrogen bonds (red shift H-bonding, blue-shifted H-bonding and dihydrogen bond) coexist in the title compound. The NBO analysis was performed showing the change of the charge and stereoelectronic effect of different radicals. The UV spectra of the lowest-lying conformer of taxol in methanol are investigated with the TD CAM-B3LYP/6-311+G(2df,p)calculations. The S0-S1, S0-S2, and S0-S3 excitations of taxol are mixed pi pi*/pi sigma*/n pi* transitions at 4.32, 5.02, and 5.13 eV, respectively. The theoretical IR spectrum and UV absorption spectrum of the taxol agree with the available experimental data of taxol very well. Calculations in the solution using SCRF/CPCM method at the M06L/6-311G(2df,p) level showing the hydrophobic nature of taxol.

  • 6.
    Zhu, Hongli
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Areskogh, Dimitri
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Helander, Mikaela
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Investigation on enzymatic oxidative polymerization of technical soda lignin2012In: Current organic chemistry, ISSN 1385-2728, E-ISSN 1875-5348, Vol. 16, no 16, p. 1850-1854Article in journal (Refereed)
    Abstract [en]

    Enzyme, including laccase and peroxidase, catalyzed oxidative polymerization of technical bagasse soda lignin and low molecular weight ultra-filtrated kraft pulp lignin in methanol-water solution were studied. The weight average molecular weight of original macromonomer and polymerized lignin were characterized with alkaline size exclusion chromatograph system. Laccase treatment increased the molecular weight of both technical bagasse lignin and ultra-filtrated lignin up to 20 times in 24h. Compared to the low molecular weight ultra filtrated lignin, the reaction rate of bagasse lignin was consistant during the whole procedure. The reaction time and the laccase dosage were investigated to obtain the maximal molecular weight. The horseradish peroxidase treatment was a potential method for low molecular weight ultra filtrated lignin.

  • 7.
    Zhu, Hongli
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Helander, Mikaela
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Moser, Carl
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Ståhlkranz, Adam
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Söderberg, Daniel
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lindström, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    A novel nano cellulose preparation method and size fraction by cross flow ultra- filtration2012In: Current organic chemistry, ISSN 1385-2728, E-ISSN 1875-5348, Vol. 16, no 16, p. 1871-1875Article in journal (Refereed)
    Abstract [en]

    A novel energy-efficient method called nanopulping (patent pending) to produce nanocellulose from chemical pulp, and a novel cross-flow ultra-filtration method to separate nanofibrils fractions of different size were applied in this study. Pretreatment with endoglucanase or 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidation seems to enhance the nanopulping process. Results were evaluated with atomic force microscope and ultrafiltration. The nanopulping produced a relatively inhomogeneous material with larger particles/ fibers in addition to nanofibers. However, by ultrafiltration of the material it was possible to obtain more homogeneous material in different dimensions with methods industrially acceptable.

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